CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Application No. 62/925,811, filed October 25, 2019 and titled SMART GAS TEMPERATURE CONTROL IN A LASER SOURCE, which is incorporated herein in its entirety by reference.

FIELD

[0002] The present disclosure relates to systems and methods for controlling gas temperature in a laser source for use in, for example, lithographic apparatuses and systems.

BACKGROUND

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC being formed. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Known lithographic apparatus includes so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the target portions parallel or anti-parallel to this scanning direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004] A laser source can be used with the lithographic apparatus for, for example, generating illumination radiation for illuminating the patterning device. The laser source can use gas for generating the laser for use in the lithographic apparatus. Accordingly, there is a need for a system and a method for controlling the temperature and other aspects of the gas in the laser source that affect the radiation produced by the laser. SUMMARY

[0005] Embodiments of gas temperature control systems and methods are described in the present disclosure.

[0006] One aspect of the present disclosure provides a laser source that includes a first laser chamber configured to generate a first laser beam and a second laser chamber configured to receive the first laser beam and amplify the first laser beam to generate a second laser beam. The laser source further includes a first temperature actuator configured to control a first temperature of a gas in the first laser chamber and a second temperature actuator configured to control a second temperature of a gas in the second laser chamber. The laser source also includes a temperature control system configured to receive data from the first and second temperature actuators and determine a threshold associated with the first and second temperature actuators based on the received data. The threshold is used by the first and second temperature actuators in controlling the first and second temperatures.

[0007] In some embodiments, each of the first and second temperature actuators includes a cooling system and a heating system and the data from the first and second temperature actuators includes data associated with the corresponding cooling system and the threshold includes a threshold associated with the heating systems.

[0008] In some embodiments, the cooling system include a water cooling system and the data associated with the cooling system includes position data associated with one or more valves of the water cooling system. In some embodiments, the threshold associated with the heating system includes a lower threshold for turning on the heating system and an upper threshold for turning off the heating system.

[0009] In some embodiments, the temperature control system is configured to monitor the position data associated with the one or more valves of the water cooling system during a first time period, determine a status of the laser source during the first time period and determine a first filtered data by filtering out a portion of the position data associated with the one or more valves of the water cooling system when the status of the laser source indicates that the laser source was not in on state.

[0010] In some embodiments, the temperature control system is further configured to determine a second filtered data by filtering out an outlier portion of the first filtered data.

The outlier portion is determined based on one or more data thresholds. The temperature control system is further configured to determine envelope data based on the second filtered data, determine filtered envelope data by applying a low pass moving average filter to the envelope data, and determine the lower and upper thresholds based on the filtered envelope data.

[0011] In some embodiments, the first temperature actuator includes a first cooling system and a first heating system associated with the first laser chamber. The second temperature actuator includes a second cooling system and a second heating system associated with the second laser chamber. The data from the first and second temperature actuators includes data associated with the first and second cooling systems, respectively. The threshold includes a first threshold associated with the first heating system and a second threshold associated with the second heating system. The first threshold is used by the first temperature actuator in controlling the first temperature and the second threshold is used by the second temperature actuator in controlling the second temperature.

[0012] In some embodiments, the temperature control system is configured to determine a chamber shot count associated with the first laser chamber. In response to a determination that the chamber shot count is greater than a first count threshold, the temperature control system is configured to communicate, to the first and second temperature actuators, the threshold associated with the first and second temperature actuators. In response to a determination that the chamber shot count is greater than a second count threshold and less than or equal to the first count threshold, the temperature control system is configured to modulate the threshold associated with the first and second temperature actuators to determine a modulated threshold, where the modulated threshold achieves a desired duty cycle. The temperature control system is configured to communicate, to the first temperature actuator, the modulated threshold. In response to a determination that the chamber shot count is less than or equal to the second count threshold, the temperature control system is configured to communicate with the first and second temperature actuators to use a default threshold associated with the first and second temperature actuators.

[0013] In some embodiments, to determine the threshold the temperature control system is configured to determine a first lower threshold and a first upper threshold associated with the first temperature actuator based on the received data. The temperature control system is further configured to determine a second lower threshold and a second upper threshold associated with the second temperature actuator based on the received data. The first lower threshold and first upper threshold are used by the first temperature actuator in controlling the first temperature. The second lower threshold and second upper threshold are used by the second temperature actuator in controlling the second temperature. [0014] Another aspect of the present disclosure provides a lithographic apparatus that includes an illumination system configured to condition a radiation beam and a projection system configured to project a pattern imparted to the radiation beam onto a substrate. The illumination system includes a laser source. The laser source includes a first laser chamber configured to generate a first laser beam and a second laser chamber configured to receive the first laser beam and amplify the first laser beam to generate a second laser beam. The laser source further includes a first temperature actuator configured to control a first temperature of a gas in the first laser chamber and a second temperature actuator configured to control a second temperature of a gas in the second laser chamber. The laser source also includes a temperature control system configured to receive data from the first and second temperature actuators and determine a threshold associated with the first and second temperature actuators based on the received data. The threshold is used by the first and second temperature actuators in controlling the first and second temperatures.

[0015] Another aspect of the present disclosure provides a method including generating, at a first laser chamber, a first laser beam and amplifying, at a second laser chamber, the first laser beam to generate a second laser beam. The method further includes controlling, using a first temperature actuator, a first temperature of a gas in the first laser chamber and controlling, using a second temperature actuator, a second temperature of a gas in the second laser chamber. The method also includes receiving, at a temperature control system, data from the first and second temperature actuators and determining, using the temperature control system, a threshold associated with the first and second temperature actuators based on the received data. The threshold is used by the first and second temperature actuators in controlling the first and second temperatures.

[0016] Another aspect of the present disclosure provides a non-transitory computer- readable medium storing instructions that, when executed by a processor, cause the processor to perform operations. The operations include receiving position data associated with one or more valves of a water cooling system of a laser source during a first time period. The operations further include determining a status of the laser source during the first time period and generating a first filtered data by filtering out a portion of the position data associated with the one or more valves of the water cooling system when the status of the laser source indicates that the laser source was not in on state. The method also includes generating a second filtered data by filtering out an outlier portion of the first filtered data and determining envelope data based on the second filtered data. The method also includes determining filtered envelope data by applying a low pass filter to the envelope data and determining, based on the filtered envelope data, first and second thresholds associated with a heating system of the laser source. The first and second thresholds are used for controlling gas temperature in at least one laser chamber.

[0017] Another aspect of the present disclosure provides an apparatus. The apparatus includes a first temperature actuator configured to control a first temperature of a gas in a first laser chamber and a second temperature actuator configured to control a second temperature of a gas in a second laser chamber. The apparatus further includes a temperature control system configured to receive data from the first and second temperature actuators and determine a threshold associated with the first and second temperature actuators based on the received data. The threshold is used by the first and second temperature actuators in controlling the first and second temperatures.

[0018] In some embodiments, the first laser chamber is configured to generate a first laser beam and the second laser chamber is configured to receive the first laser beam and amplify the first laser beam to generate a second laser beam.

[0019] Another aspect of the present disclosure provides a laser source that includes a first laser chamber configured to generate a first laser beam and a second laser chamber configured to receive the first laser beam and amplify the first laser beam to generate a second laser beam. The laser source further includes a first temperature actuator configured to control a first temperature of a gas in the first laser chamber and a second temperature actuator configured to control a second temperature of a gas in the second laser chamber. The laser source also includes a temperature control system. The temperature control system is configured to receive data from the first and second temperature actuators and determine a first lower threshold and a first upper threshold associated with the first temperature actuator based on the received data. The temperature control system is further configured to determine a second lower threshold and a second upper threshold associated with the second temperature actuator based on the received data. The first lower threshold and the first upper threshold are used by the first temperature actuator in controlling the first temperature and the second lower threshold and the second upper threshold are used by the second temperature actuator in controlling the second temperature.

[0020] Another aspect of the present disclosure provides an apparatus that includes a first temperature actuator configured to control a first temperature of a gas in a first chamber and a second temperature actuator configured to control a second temperature of a gas in a second chamber. The apparatus also includes a temperature control system. The temperature control system is configured to receive data from the first and second temperature actuators and determine a first threshold associated with the first temperature actuator based on the received data. The first threshold is used by the first temperature actuator in controlling the first temperature. The temperature control system is further configured to determine a second threshold associated with the second temperature actuator based on the received data. The second threshold is used by the second temperature actuator in controlling the second temperature.

[0021] Further features, as well as the structure and operation of various embodiments, are described in detail below with reference to the accompanying drawings. It is noted that the disclosure is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0022] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the embodiments of this disclosure and to enable a person skilled in the relevant art(s) to make and use the embodiments of this disclosure.

[0023] FIG. 1 is a schematic illustration of a reflective lithographic apparatus, according to an exemplary embodiment.

[0024] FIG. 2 is a schematic illustration of a transmissive lithographic apparatus, according to an exemplary embodiment.

[0025] FIG. 3 is a schematic illustration of a lithographic cell, according to an exemplary embodiment.

[0026] FIG. 4A illustrates a schematic of a laser source having a temperature control system, according to some embodiments of the present disclosure.

[0027] FIG. 4B illustrates the heating system status based on position data associated with one or more valves of a cooling system, according to some embodiments of the present disclosure

[0028] FIG. 5 illustrates an exemplary graph depicting position data associated with one or more valves of cooling system during a time period and an associated filtered envelope data, according to some embodiments of this disclosure.

[0029] FIGS. 6 A and 6B illustrate exemplary graphs depicting position data associated with one or more valves of cooling system during a time period and the lower and upper valve position thresholds associated with heating system, according to some embodiments of this disclosure.

[0030] FIG. 7 is a flow chart that illustrates an example of a method for determining lower and upper valve position thresholds associated with heating systems, according to some embodiments of the disclosure.

[0031] FIG. 8 is a flow chart that illustrates an example of a method for determining the lower and upper valve position thresholds associated with heating systems, according to some embodiments of the disclosure.

[0032] FIG. 9 is a flow chart that illustrates an example of a method for communicating the lower and upper valve position thresholds associated with heating systems, according to some embodiments of the disclosure.

[0033] FIG. 10A illustrates an exemplary graph depicting the status of a laser source during a time period, according to some embodiments of this disclosure.

[0034] FIG. 10B illustrates an exemplary graph depicting the status of heating systems during the time period, according to some embodiments of this disclosure.

[0035] FIG. 11 is an example computer system for implementing some embodiments or portion(s) thereof.

[0036] The features the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, unless otherwise indicated, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. Unless otherwise indicated, the drawings provided throughout the disclosure should not be interpreted as to-scale drawings.

DETAILED DESCRIPTION

[0037] This specification discloses one or more embodiments that incorporate the features of this invention. The disclosed embodiment(s) merely exemplify the invention. The scope of the disclosure is not limited to the disclosed embodiment(s). The breadth and scope of the disclosure are defined by the claims appended hereto and their equivalents.

[0038] The embodiment(s) described, and references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” “an exemplary embodiment,” etc., indicate that the embodiment(s) described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is understood that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0039] Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “on,” “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0040] The term “about” as used herein indicates the value of a given quantity that can vary based on a particular technology. Based on the particular technology, the term “about” can indicate a value of a given quantity that varies within, for example, 10-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0041] Embodiments of the disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, and/or instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc.

[0042] Before describing such embodiments in more detail, however, it is instructive to present an example environment in which embodiments of the present disclosure may be implemented.

[0043] Example Lithographic Systems [0044] FIGS. 1 and 2 are schematic illustrations of a lithographic apparatus 100 and lithographic apparatus 100’, respectively, in which embodiments of the present disclosure may be implemented. Lithographic apparatus 100 and lithographic apparatus 100’ each include the following: an illumination system (illuminator) IL configured to condition a radiation beam B (for example, deep ultra violet (DUV) radiation); a support structure (for example, a mask table) MT configured to support a patterning device (for example, a mask, a reticle, or a dynamic patterning device) MA and connected to a first positioner PM configured to accurately position the patterning device MA; and, a substrate holder such as a table (for example, a wafer table) WT configured to hold a substrate (for example, a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. Lithographic apparatus 100 and 100’ also have a projection system PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion (for example, comprising one or more dies) C of the substrate W. In lithographic apparatus 100, the patterning device MA and the projection system PS are reflective. In lithographic apparatus 100’, the patterning device MA and the projection system PS are transmissive.

[0045] The illumination system IL may include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for directing, shaping, or controlling the radiation beam B.

[0046] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA with respect to a reference frame, the design of at least one of the lithographic apparatus 100 and 100’, and other conditions, such as whether or not the patterning device MA is held in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT can be a frame or a table, for example, which can be fixed or movable, as required. By using sensors, the support structure MT can ensure that the patterning device MA is at a desired position, for example, with respect to the projection system PS.

[0047] The term “patterning device” MA should be broadly interpreted as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section, such as to create a pattern in the target portion C of the substrate W. The pattern imparted to the radiation beam B can correspond to a particular functional layer in a device being created in the target portion C to form an integrated circuit. [0048] The patterning device MA may be transmissive (as in lithographic apparatus 100’ of FIG. 2) or reflective (as in lithographic apparatus 100 of FIG. 1). Examples of patterning devices MA include reticles, masks, programmable mirror arrays, or programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase shift, or attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B, which is reflected by a matrix of small mirrors.

[0049] The term “projection system” PS can encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors, such as the use of an immersion liquid on the substrate W or the use of a vacuum. A vacuum environment can therefore be provided to the whole beam path with the aid of a vacuum wall and vacuum pumps.

[0050] Lithographic apparatus 100 and/or lithographic apparatus 100’ can be of a type having two (dual stage) or more substrate tables WT (and/or two or more mask tables). In such “multiple stage” machines, the additional substrate tables WT can be used in parallel, or preparatory steps can be carried out on one or more tables while one or more other substrate tables WT are being used for exposure. In some situations, the additional table may not be a substrate table WT.

[0051] The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g., water, so as to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.

[0052] Referring to FIGS. 1 and 2, the illuminator IL receives a radiation beam from a radiation source SO. The source SO and the lithographic apparatus 100, 100’ can be separate physical entities, for example, when the source SO is an excimer laser. In such cases, the source SO is not considered to form part of the lithographic apparatus 100 or 100’, and the radiation beam B passes from the source SO to the illuminator IL with the aid of a beam delivery system BD (in FIG. 2) including, for example, suitable directing mirrors and/or a beam expander. In other cases, the source SO can be an integral part of the lithographic apparatus 100, 100’, for example, when the source SO is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD, if required, can be referred to as a radiation system.

[0053] The illuminator IL can include an adjuster AD (in FIG. 2) for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as “s-outer” and “s-inner,” respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL can comprise various other components (in FIG. 2), such as an integrator IN and a condenser CO. The illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross section.

[0054] Referring to FIG. 1 , the radiation beam B is incident on the patterning device (for example, mask) MA, which is held on the support structure (for example, mask table) MT, and is patterned by the patterning device MA. In lithographic apparatus 100, the radiation beam B is reflected from the patterning device (for example, mask) MA. After being reflected from the patterning device (for example, mask) MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF2 (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT can be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor IF1 can be used to accurately position the patterning device (for example, mask) MA with respect to the path of the radiation beam B. Patterning device (for example, mask) MA and substrate W can be aligned using mask alignment marks Ml, M2 and substrate alignment marks PI, P2.

[0055] Referring to FIG. 2, the radiation beam B is incident on the patterning device (for example, mask MA), which is held on the support structure (for example, mask table MT), and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil conjugate PPU to an illumination system pupil IPU. Portions of radiation emanate from the intensity distribution at the illumination system pupil IPU and traverse a mask pattern without being affected by diffraction at the mask pattern and create an image of the intensity distribution at the illumination system pupil IPU.

[0056] The projection system PS projects an image MP’ of the mask pattern MP, where image MP’ is formed by diffracted beams produced from the mark pattern MP by radiation from the intensity distribution, onto a photoresist layer coated on the substrate W. For example, the mask pattern MP may include an array of lines and spaces. A diffraction of radiation at the array and different from zeroth order diffraction generates diverted diffracted beams with a change of direction in a direction perpendicular to the lines. Undiffracted beams (i.e., so-called zeroth order diffracted beams) traverse the pattern without any change in propagation direction. The zeroth order diffracted beams traverse an upper lens or upper lens group of the projection system PS, upstream of the pupil conjugate PPU of the projection system PS, to reach the pupil conjugate PPU. The portion of the intensity distribution in the plane of the pupil conjugate PPU and associated with the zeroth order diffracted beams is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. The aperture device PD, for example, is disposed at or substantially at a plane that includes the pupil conjugate PPU of the projection system PS.

[0057] The projection system PS is arranged to capture, by means of a lens or lens group L, not only the zeroth order diffracted beams, but also first-order or first- and higher-order diffracted beams (not shown). In some embodiments, dipole illumination for imaging line patterns extending in a direction perpendicular to a line may be used to utilize the resolution enhancement effect of dipole illumination. For example, first-order diffracted beams interfere with corresponding zeroth-order diffracted beams at the level of the wafer W to create an image of the line pattern MP at highest possible resolution and process window (i.e., usable depth of focus in combination with tolerable exposure dose deviations).

[0058] With the aid of the second positioner PW and position sensor IF (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT can be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor (not shown in FIG. 2) can be used to accurately position the mask MA with respect to the path of the radiation beam B (for example, after mechanical retrieval from a mask library or during a scan).

[0059] In general, movement of the mask table MT can be realized with the aid of a long- stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT can be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT can be connected to a short-stroke actuator only or can be fixed. Mask MA and substrate W can be aligned using mask alignment marks Ml, M2, and substrate alignment marks PI, P2. Although the substrate alignment marks (as illustrated) occupy dedicated target portions, they can be located in spaces between target portions (known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask MA, the mask alignment marks can be located between the dies.

[0060] Mask table MT and patterning device MA can be in a vacuum chamber V, where an in- vacuum robot IVR can be used to move patterning devices such as a mask in and out of vacuum chamber. Alternatively, when mask table MT and patterning device MA are outside of the vacuum chamber, an out-of- vacuum robot can be used for various transportation operations, similar to the in- vacuum robot IVR. Both the in- vacuum and out-of- vacuum robots need to be calibrated for a smooth transfer of any payload (e.g., mask) to a fixed kinematic mount of a transfer station.

[0061] The lithographic apparatus 100 and 100’ can be used in at least one of the following modes:

[0062] l.In step mode, the support structure (for example, mask table) MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam B is projected onto a target portion C at one time (i.e., a single static exposure). The substrate table WT is then shifted in the X and/or Y direction so that a different target portion C can be exposed.

[0063] 2. In scan mode, the support structure (for example, mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B is projected onto a target portion C (i.e., a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (for example, mask table) MT can be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0064] 3. In another mode, the support structure (for example, mask table) MT is kept substantially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO can be employed and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes a programmable patterning device, such as a programmable mirror array.

[0065] Combinations and/or variations on the described modes of use or entirely different modes of use can also be employed.

[0066] Exemplary Lithographic Cell

[0067] FIG. 3 shows a lithographic cell 300, also sometimes referred to a lithocell or cluster. Lithographic apparatus 100 or 100’ may form part of lithographic cell 300. Lithographic cell 300 may also include one or more apparatuses to perform pre- and post exposure processes on a substrate. Conventionally these include spin coaters SC to deposit resist layers, developers DE to develop exposed resist, chill plates CH, and bake plates BK. A substrate handler, or robot, RO picks up substrates from input/output ports I/O 1 , 1/02, moves them between the different process apparatuses and delivers them to the loading bay LB of the lithographic apparatus 100 or 100’. These devices, which are often collectively referred to as the track, are under the control of a track control unit TCU, which is itself controlled by a supervisory control system SCS, which also controls the lithographic apparatus via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0068] Exemplary Temperature Control System and Method

[0069] FIG. 4A illustrates a schematic of a laser source 400 having a temperature control system 430, according to some embodiments of the present disclosure. In some embodiments, laser source 400 can be used as part of, or in addition to, source SO of lithographic apparatus 100 or 100’. Additionally, or alternatively, laser source 400 can be used in generating DUV radiation to be used in lithographic apparatus 100 or 100’ or other DUV lithographic apparatuses.

[0070] As illustrated in FIG. 4A, laser source 400 can include a dual-chamber laser source. For example, laser source 400 can include a first laser chamber 403 a and a second lase chamber 403b. In one exemplary embodiment, first laser chamber 403a can include or be part of a master oscillator. For example, laser source 400 can include the master oscillator where the maser source contains first laser chamber 403 a. In this example, second laser chamber 403b can include or be part of a power amplifier. For example, the laser source can include the power amplifier where the power amplifier contains second laser chamber 403b. Although some embodiments are discussed with respect to a dual-chamber laser source, the embodiments of this disclosure are not limited to these examples. The embodiments of this disclosure can be applied to laser sources with one chamber or to laser sources with multiple laser chambers.

[0071] According to some embodiments, first chamber 403a generates a first laser beam 409, which is directed to second laser chamber 403b where first laser beam 409 is amplified to produce a second laser beam 411. Second laser beam 411 is output to the lithographic apparatus (e.g., lithographic apparatus 100 and/or 110’).

[0072] According to some embodiments, each laser chamber 403a and 403b contains a mixture of gases. For example, in an excimer laser source, first laser chamber 403a and second laser chamber 403b can contain a halogen, for example, fluorine, along with other gases such as argon, neon, and possibly others in different partial pressures that add up to a total pressure. Laser chambers 403 a and 403b can include other gases used in producing and amplifying laser beams. Laser chambers 403a and 403b can include the same or different mixtures of gases.

[0073] In some embodiments, laser source 400 can include (or can be coupled) to gas sources (for example, gas bottles) 420a and 420b. For example, gas source 420a can be coupled to first laser chamber 403a to provide the gas mixture used for generating first laser beam 409. Additionally, gas source 420b can be coupled to second laser chamber 403b to provide the gas mixture used for generating second laser beam 411. In some examples, gas sources 420a and 420b can be coupled to laser chambers 403a and 403b, respectively, through valves (not shown). A control system (for example, control system 410) can be used to control the valves for sending gas from gas sources 420a and 420b to laser chambers 403 a and 403b.

[0074] In some embodiments, gas source 420a can contain a mixture of gases including, but not limited to, fluorine, argon and neon. According to some embodiments, gas source 420b can contain a mixture of argon, neon and/or other gases, but no fluorine. However, other gas mixtures can be used in gas sources 420a and 420b.

[0075] According to some embodiments, the temperature of the gas in the laser chambers 403a and 403b can be controlled using one or more temperature actuators. In some examples, the one or more temperature actuators can include heating systems 405 a and 405b (collectively, heating system 405) and cooling systems 407a and 407b (collectively, cooling system 407). In the embodiment illustrated in FIG. 4A, first laser chamber 403a includes a first temperature actuator including heating system 405a and cooling system 407a. The first temperature actuator including heating system 405 a and cooling system 407a can control the temperature of the gas in first laser chamber 403a. Similarly, second laser chamber 403b includes a second temperatures actuator including heating system 405b and cooling system 407b. The second temperature actuator including heating system 405b and cooling system 407b can control the temperature of the gas in first laser chamber 403b.

[0076] In some embodiments, the temperature actuators (for example, heating system 405 and cooling system 407) can control the gas temperature in first laser chamber 403a based on the gas temperature in the first laser chamber 403 a and independent of the gas temperature in second laser chamber 403b. Alternatively, the temperature actuators (for example, heating system 405 and cooling system 407) can control the gas temperature in first laser chamber 403a based on the gas temperatures in second laser chamber 403b, or vice versa. In some embodiments, the temperature actuators can control the gas temperature in one of the laser chambers based on the gas temperatures in both of the laser chambers.

[0077] According to some embodiments, heating system 405 can include one or more coils configured to heat the gas in corresponding laser chamber. In some examples, the one or more coils can be resistive loads, which can generate heat proportional to square of the voltage applied to the coil(s). However, other heating systems can also be used. According to some embodiments, cooling system 407 can include water cooling system to cool the gas in corresponding laser chamber. In some examples, the water cooling system can include a pipe or series of pipes, which can transport cold water across the corresponding laser chamber, such that conductive heat transfer occurs, simultaneously (or substantially simultaneously) heating the water and cooling the laser chamber. Then, the heated water is exhausted out of the system and replaced with fresh cold water. The amount of cooling can be proportional to the flowrate of water into the pipe(s), which is controlled by a valve or set of valves.

[0078] According to some embodiments, control system 410 is used to control the gas temperatures in laser chambers 403a and 403b (collectively, laser chamber 403). For example, control system 410 can be connected to one or more temperature sensors in laser chamber 403 to detect the gas temperatures. Depending on, for example, set points set for the gas temperatures in laser chamber 403 and also the sensed temperatures; control system 410 is configured to control heating system 405 and/or cooling system 407.

[0079] In some examples, cooling system 407a, 407b is the primary actuator in the temperature actuators. In these examples, cooling system 407 maintains the gas temperature in its corresponding laser chamber (e.g., cooling system 407a for first laser chamber 403 a and cooling system 407b for first laser chamber 403b) within a threshold of the set points. In a non- limiting example, cooling system 407 maintains the gas temperature in its corresponding laser chamber within around 1°C of the set point. However, other thresholds of the set points can also be used. In some examples, cooling system 407 is controlled to gradually increase or decrease. Additionally, heating system 405 can be a course actuator in the temperature actuators, in some example. In these examples, heating system 405 can be configured to keep its corresponding laser chamber warm enough so that cooling system 407 has enough margins to function properly. In some examples, heating system 405 is either on (e.g., to its maximum capacity) or is off.

[0080] In some examples, the on/off state of each of heating systems 405 is determined based on the state of its corresponding cooling system 407. In some embodiments, cooling system 407 can include a water cooling system. When cooling system 407 includes a water cooling system, the state of cooling system 407 (for example, data associated with cooling system 407) can include position data associated with one or more valves of cooling system 407. The valves of cooling system 407 can be monitored and controlled by control system 410. For example, valves of cooling system 407 can be monitored and controlled by control system 410 to gradually open or close. According to some embodiments, the position data associated with one or more valves of cooling system 407 can indicate how open the one or more valves are. For example, position data associated with one or more valves of cooling system 407 can indicate the valve opening (for example, in percentage) of the one or more valves.

[0081] As noted above, the on/off state of each of heating systems 405 is determined based on the state of its corresponding cooling system 407 (for example, position data associated with one or more valves of cooling system 407). For example, if the state of cooling system 407a is close to one of its limits, heating system 405a may change state to compensate. For example, if control system 410 determines that the monitored position data associated with one or more valves of cooling system 407a is less than a lower valve position threshold (the one or more valves are nearly completely closed), then control system 410 can instruct heating system 405a to turn on. This is because control system 410 has determined that first laser chamber 403 a is relatively cold.

[0082] This is illustrated in, for example, FIG. 4B. FIG. 4B illustrates the heating system status based on position data associated with one or more valves of a cooling system, according to some embodiments of the present disclosure. Graph 450 includes the x-axis as valve opening 451 (in percentage - e.g., position data associated with one or more valves of a cooling system) and the y-axis as the status of the heating system 453 (e.g., on or off). In one example, if control system 410 determines that the monitored position data associated with one or more valves of cooling system 407 (e.g., valve opening 451) is less than lower valve position threshold 455, then control system 410 can instruct heating system 405 to turn on. [0083] In another example, if control system 410 determines that the monitored position data associated with one or more valves of cooling system 407a is more than an upper valve position threshold (the one or more valves are nearly completely open), then control system 410 can instruct heating system 405a to turn off. This is because control system 410 has determined that first laser chamber 403a is relatively hot. In some examples, control system 410 provides this hysteresis control for controlling heating system 405 and/or cooling system 407. For example, as illustrated in FIG. 4B, if control system 410 determines that the monitored position data associated with one or more valves of cooling system 407 (e.g., valve opening 451) is more than upper valve position threshold 457, then control system 410 can instruct heating system 405 to turn off.

[0084] In some examples, the lower and upper valve position thresholds 455 and 457 can be fixed default values. For example, the lower valve position threshold can be around 30% valve opening and the upper valve position threshold can around 70% valve opening. However, these are exemplary thresholds and other values can be used for these lower and upper valve position thresholds. In some examples, using fixed default lower and upper valve position thresholds can result in wasted energy. For example, laser chambers 403 may be heated more than necessary to provide enough margins to cooling system 407. In some systems (for example, high utilization systems), because the chamber blowers (not shown) and high firing rates can create enough heat inside laser chambers 403, the wasted energy is even higher.

[0085] According to some embodiments, temperature control system 430 in association with control system 410 is configured to dynamically adjust the lower and upper valve position thresholds 455 and 457. In these embodiments, temperature control system 430 is configured to monitor the gas temperatures of laser chambers 403, the performance of cooling systems 407, the status of laser source 400, and/or performance of laser source 400 to dynamically control one or more thresholds associated with heating systems 405 (for example, the lower and upper valve position thresholds). According to some embodiments, by dynamically controlling one or more thresholds associated with heating systems 405, heating systems 405 can be turned off when they are unnecessary, therefore, conserving energy and power consumption of laser source 400.

[0086] According to some embodiments, temperature control system 430 is configured to receive data from the temperature actuators (e.g., the first and second temperature actuators discussed above). As discussed above, the first temperature actuator can include heating system 405 a and cooling system 407a and the second temperature actuator can include heating system 405b and cooling system 407b. In some embodiments, temperature control system 430 is configured to receive the data from the temperature actuators through control system 410 (e.g., through connection 433). Additionally, or alternatively, temperature control system 430 can receive the data directly from the temperature actuators.

[0087] In some embodiments, the data received from the temperature actuators can include data associated with cooling system 407. For example, the data associated with cooling system 407 can include position data (for example, valve opening data) associated with one or more valves of cooling system 407. In some embodiments, the position data associated with one or more valves of cooling system 407 includes position data monitored by temperature control system 430 (and/or control system 410) over a time period. The time period can include approximately a few hours, approximately one day, around 10 days, approximately one month, approximately one year, etc. However, the embodiments of this disclosure are not limited to these examples and other time periods can be used to monitor the position data associated with one or more valves of cooling system 407.

[0088] According to some embodiments, using the data received from the temperature actuators (for example, the position data associated with one or more valves of cooling system 407), temperature control system 430 is configured to determine one or more thresholds associated with the temperature actuators. The temperature actuators can use the determined threshold to control the gas temperature in laser chambers 403. For example, temperature control system 430 is configured to determine the one or more thresholds associated with heating system 405 of the temperature actuators. The one or more threshold can include the lower and upper valve position thresholds discussed above. For example, a lower threshold includes a threshold for turning on heating system 405 (e.g., the lower valve position threshold discussed above). An upper threshold can include a threshold for turning off heating system 405 (e.g., the upper valve position threshold discussed above).

[0089] In some exemplary embodiments, both heating systems 405a and 405b use the same lower threshold (e.g., the lower valve position threshold discussed above) and the same upper threshold (e.g., the upper valve position threshold discussed above). In other words, although first laser chamber 403a/cooling system 405a may have different requirements, measurement, and performance than second laser chamber 403b/cooling system 407b, the heating systems 405a and 405b use the same thresholds. Alternatively, heating systems 405a and 405b can use different first and second thresholds. In some embodiments, there is a first threshold associated with the first heating system and a second threshold associated with the second heating system, wherein the first threshold is used by the first temperature actuator in controlling the first temperature and the second threshold is used by the second temperature actuator in controlling the second temperature. In some embodiments, the first threshold includes lower and upper thresholds associated with heating system 405a and the second threshold includes lower and upper thresholds associated with the heating system 405b.

[0090] According to some embodiments, in addition to the data received from the temperature actuators (for example, the position data associated with one or more valves of cooling system 407), temperature control system 430 is configured to use a status of laser source 400 to determine the one or more thresholds associated with heating system 405 of the temperature actuators. In this example, temperature control system 430 is configured to determine (e.g., generate) a first filtered data by filtering out a portion of the received data (for example, a portion of the position data associated with one or more valves of cooling system 407) when the status of laser source 400 indicates that laser source 400 was not in on state. In other words, temperature control system 430 does not consider the position data associated with one or more valves of cooling system 407 when laser source 400 was in off or standby state, according to some embodiments. According to some embodiments, laser source 400 can have many states. For example, laser source 400 can be in on state (e.g.,

“laser ON”), standby state, or off state (e.g., “laser OFF”). In some embodiments, during the standby state and/or the off state, first chamber 403a does not generate first laser beam 409 and/or second laser chamber 403b does not produce second laser beam 411. Temperature control system 430 can filter out data associated with both off and standby states.

[0091] FIG. 5 illustrates an exemplary graph depicting position data associated with one or more valves of cooling system 407 during a time period and an associated filtered envelope data, according to some embodiments of this disclosure. Graph 500 includes a y- axis 501 indicating valve opening in percentage and an x-axis 503 indicating time. Graph 500 illustrates the position data 509 associated with one or more valves of cooling system 407. [0092] In this exemplary embodiment, as discussed above, temperature control system 430 does not consider the position data associated with one or more valves of cooling system 407 when laser source 400 was not in on state (e.g., was in off or standby state), according to some embodiments. This position data is illustrated as data point 513 on graph 500.

[0093] According to some embodiments, after temperature control system 430 determines (e.g., generates) the first filtered data by filtering out a portion of the received data for when laser source 400 was not in on state, temperature control system 430 further determines (e.g., generates) a second filtered data by filtering out an outlier portion of the first filtered data. In some examples, temperature control system 430 is configured to determine the outlier portion based on one or more data thresholds. Additionally, or alternatively, temperature control system 430 is configured to perform one or more outlier filtering methods to filter out the outlier portion of the first filtered data. In some examples, determining the outlier portion can include ignoring values above a data threshold, ignoring values which lie outside a certain number of standard deviations from a mean value, using an average of several data points to reduce the impact of a single outlier, ignoring values that represent an unrealistic or physically impossible event (for example, a percentage not between 0 and 100), etc. For example, as illustrated in graph 500 of FIG. 5, temperature control system 430 is configured to filter out the outlier data points 511.

[0094] According to some embodiments, after determining the second filtered data, temperature control system 430 is configured to determine envelope data based on the second filtered data. In some example, the envelope data is data that outlines the second filtered data and can generalize the concept of amplitude of the second filtered data. For example, the envelope data is determined (by temperature control system 430) to span from the bottom of the second filtered data to just beneath the top of the second filtered data. Since temperature control system 430 is determining the envelope data based on the second filtered data, the envelope data exclude the portion of data received from the temperature actuator (e.g., the position data associated with one or more valves of cooling system 407) when laser source was off or in standby state and also excludes outlier data, according to some embodiments. [0095] In some embodiments, after determining the envelope data, temperature control system 430 further determines filtered envelope data by applying a filter to the envelope data. For example, temperature control system 430 applies the filter to the envelope data such that the filtered envelope data can be robust and not sensitive to temporary shifts in performance and the filtered envelope data can be robust and not sensitive to noise on data within the filtered envelope data. In some examples, temperature control system 430 applies a low pass moving average filter to the envelope data. However, the embodiments of this disclosure can include other filters applied to the envelope data to make the filtered envelope data more robust to noise and to performance fluctuations. For example, temperature control system 430 is configured to generate the filtered envelope data 505 and 507 as illustrated in FIG. 5. In this example, the filtered envelope data includes a lower value (e.g., edge) 505 and an upper value (e.g., edge) 507. [0096] Using the determined filtered envelope data, temperature control system 430 is configured to determine the one or more thresholds of the temperature actuators (e.g., the lower and upper valve position thresholds associated with heating systems 405), according to some embodiments.

[0097] As discussed above, the upper valve position threshold associated with heating system 405 can be the heating system off threshold. In other words, when the valve position associated with cooling system 407 is greater than the upper valve position threshold, heating system 405 is turned off. In one embodiment, temperature control system 430 is configured to determine (e.g., set) the upper valve position threshold associated with heating system 405 (e.g., the heating system off threshold) to be just below the lower value (e.g., edge) of the filtered envelope data. This is illustrated in, for example, FIGS. 6 A and/or 6B.

[0098] FIGS. 6 A and 6B illustrate exemplary graphs depicting position data associated with one or more valves of cooling system 407 during a time period and the lower and upper valve position thresholds associated with heating system 405, according to some embodiments of this disclosure. Graph 600 (or 620) includes a y-axis 601 (or 621) indicating valve opening in percentage and an x-axis 603 (or 623) indicating time. Graph 600 (or 620) illustrates position data 609 (or 629) associated with one or more valves of cooling system 407.

[0099] In this example, graph 600 (or 620) also illustrates upper valve position threshold (e.g., heating system off threshold) 607 (or 627) associated with heating systems 405. Also, graph 600 (or 620) also illustrates lower valve position threshold (e.g., heating system on threshold) 605 (or 625) associated with heating system 405. In one embodiment, temperature control system 430 is configured to determine (e.g., set) the upper valve position threshold 607 (or 627) associated with heating system 405 to be just below the lower value (e.g., edge) of the filtered envelope data (e.g., lower value 505 of FIG. 5).

[0100] It can be seen that in FIGS. 6 A and 6B, the lower valve position thresholds 605, 625 are the same and also the upper valve position thresholds 607, 627 are the same. As noted above, in some embodiments, the lower valve position thresholds 605, 625 may differ and in some embodiments, the upper valve position thresholds 607, 627 may differ. As such, there may be a lower and upper threshold associated with the first laser chamber 403 a and first heating system 405a, and a separate lower and upper threshold associated with the second laser chamber 403b and second heating system 405b.

[0101] Additionally, or alternatively, temperature control system 430 is configured to determine (e.g., set) the lower valve position threshold 605 (or 625) associated with heating system 405 such that heating system 405 turns on when laser source 400 transitions to off or standby state. As discussed above, the lower valve position threshold associated with heating systems 405 can be the heating system on threshold. In other words, when the valve position associated with cooling system 407 is less than the lower valve position threshold, heating system 405 is turned on.

[0102] It is noted that this disclosure is not limited to this method and other methods can be used by temperature control system 430 is configured to determine the one or more thresholds of the temperature actuators based on the determined filtered envelope data. For example, temperature control system 430 can use the upper value (e.g., edge) of the filtered data envelope (e.g., 507 of FIG. 5) to determine the upper valve position threshold associated with heating system 405 (e.g., heating system off threshold). For example, temperature control system 430 can determine (e.g., set) the upper valve position threshold associated with heating system 405 to be equal to or greater than the upper value (e.g., edge) of the filtered data envelope.

[0103] As illustrated in FIGS. 6A and 6B, temperature control system 430 can receive two sets of data from the temperature actuators - a first set of data (e.g., position data 609) associated with cooling system 407a of first laser chamber 403a and a second set of data (e.g., position data 629) associated with cooling system 407b of second laser chamber 403b). In some embodiments, temperature control system 430 can determine first lower and upper valve position thresholds for first laser chamber 403a and second lower and upper valve position thresholds for second laser chamber 403b. In these examples, temperature control system 430 can determine the lower and upper valve position thresholds using the first and second sets of thresholds. For example, temperature control system 430 can determine the upper valve position threshold as the minimum of the first and second upper valve position thresholds. Also, as one example, temperature control system 430 can determine the lower valve position threshold as the minimum of the first and second lower valve position thresholds. Additionally, or alternatively, the first lower and upper valve position thresholds are used for controlling the gas temperature in first laser chamber 403a and the second lower and upper valve position thresholds are used for controlling the gas temperature in second laser chamber 403a. In some examples, the first lower and upper valve position thresholds are the same as the second lower and upper valve position thresholds. Alternatively, the first lower and upper valve position thresholds are different than the second lower and upper valve position thresholds. [0104] After determining the lower and upper valve position thresholds associated with heating systems 405, temperature control system 430 can communicate these thresholds to control system 410 (e.g., through connection 431). Control system 410 uses these thresholds in controlling the gas temperatures in first and second laser chambers 403 a and 403b. Alternatively or additionally, temperature control system 430 can directly communicate with the temperature actuators (including heating systems 405 and cooling systems 407) to monitor (e.g., receive) data and send control data/instructions. According to some embodiments, by dynamically controlling one or more thresholds associated with heating systems 405, energy and power consumption can be conserved in laser source 400.

[0105] According to some embodiments, temperature control system 430 is configured to determine the lower and upper valve position thresholds associated with heating systems 405 periodically. In one example, the period for determining the lower and upper valve position thresholds associated with heating systems 405 can be set by a user at temperature control system 430. In another example, temperature control system 430 can analyze the data associated with the temperature actuators and depending on the changes in the data, temperature control system 430 can set or change the period for determining the lower and upper valve position thresholds associated with heating systems 405. In other embodiments, the period for determining the lower and upper valve position thresholds associated with heating systems 405 can be a fixed period or a varying period. In some embodiments, temperature control system 430 can determine the lower and upper valve position thresholds associated with heating systems 405 based on instructions received from a user, from control system 401, and/or other parts of lithographic apparatus 100 and/or 100’.

[0106] FIG. 7 illustrates an example method 700 for determining the lower and upper valve position thresholds associated with heating systems 405, according to some embodiments of the disclosure. As a convenience and not a limitation, FIG. 7 may be described with regard to elements of FIG. 1-6. Method 700 may represent the operation of temperature control system 403 for determining the lower and upper valve position thresholds associated with heating systems 405. Method 700 may be performed by temperature control system 403 of FIG. 4A and/or computer system 1100 of FIG. 11. But method 700 is not limited to the specific embodiments depicted in those figures and other systems may be used to perform the method as will be understood by those skilled in the art. It is to be appreciated that not all operations may be needed, and the operations may not be performed in the same order as shown in FIG. 7. [0107] At 702, data associated with a first cooling system of a first laser chamber of a laser source is monitored during a first time period. For example, temperature control system 430 (directly and/or through control system 410) monitors valve position data associated with cooling system 407a (e.g., a water cooling system) of first laser chamber 403a of laser source 400 during the first time period.

[0108] At 704, data associated with a second cooling system of a second laser chamber of the laser source is monitored during the first time period. For example, temperature control system 430 (directly and/or through control system 410) monitors valve position data associated with cooling system 407b (e.g., a water cooling system) of second laser chamber 403b of laser source 400 during the first time period.

[0109] At 706, a status of the laser source during the first time period is determined. For example, temperature control system 430 (directly and/or through control system 410) determines whether and/or when laser source 400 was in an on state, off state, or standby state during the first time period.

[0110] At 708, one or more thresholds associated with a first heating system of the first laser chamber and with a second heating system of the second laser chamber are determined based on the monitored data and the status of the laser source. For example, temperature control system 430 uses the monitored valve position data associated with cooling systems 405 and also the status of laser source 400 to determine the lower valve position threshold for heating systems 407 (e.g., heating system on threshold) and to determine the upper valve position threshold for heating systems 407 (e.g., heating system off threshold).

[0111] According to some embodiments, temperature control system 430 uses the monitored valve position data associated with cooling system 405 a and also the status of laser source 400 to determine a first lower valve position threshold and a first upper valve position threshold for heating system 407a. In this example, temperature control system 430 uses the monitored valve position data associated with cooling system 405b and also the status of laser source 400 to determine a second lower valve position threshold and a second upper valve position threshold for heating system 407b. Then, temperature control system 430 uses the first and second lower and upper valve position thresholds to determine the lower and upper valve position thresholds for both heating systems 407a and 407b. However, other methods discussed in this disclosure for determining the lower and upper valve position thresholds can also be used.

[0112] According to some embodiments, after determining the one or more thresholds (e.g., the lower and upper valve position thresholds), these thresholds are communicated to control system 410 and are used to control heating systems 407 for controlling the gas temperatures in laser chambers 403. There may be different thresholds for the respective laser systems or a single set of upper and lower thresholds for both of the laser systems.

[0113] FIG. 8 illustrates an example method 800 for determining the lower and upper valve position thresholds associated with heating systems 405, according to some embodiments of the disclosure. As a convenience and not a limitation, FIG. 8 may be described with regard to elements of FIGS. 1-7. Method 800 may represent the operation of temperature control system 403 for determining the lower and upper valve position thresholds associated with heating systems 405. Method 800 may be performed by temperature control system 403 of FIG. 4A and/or computer system 1100 of FIG. 11. But method 800 is not limited to the specific embodiments depicted in those figures and other systems may be used to perform the method as will be understood by those skilled in the art. It is to be appreciated that not all operations may be needed, and the operations may not be performed in the same order as shown in FIG. 8.

[0114] According to some embodiments, method 800 can be part of step 708 of method 700 of FIG. 7. In some embodiments, at 802, a first filtered data is determined by filtering out a portion of the data associated with the first and/or second cooling system when the status of the laser source indicates that the laser source was not in on state (e.g., it was in off state or in standby state). As discussed above, in one example, the data associated with the first and/or second cooling system comprises valve position data associated with cooling systems 407. At 802, for example, temperature control system 430 determines (e.g., generate) the first filtered data by filtering out a portion of the received data (for example, a portion of the valve position data associated with one or more valves of cooling system 407) when the status of laser source 400 indicates that laser source 400 was not in on state. In other words, temperature control system 430 does not consider the valve position data associated with one or more valves of cooling system 407 when laser source 400 was in off state or in standby state, according to some embodiments.

[0115] At 804, second filtered data is determined by filtering out an outlier portion of the first filtered data. For example, temperature control system 430 further determines (e.g., generates) the second filtered data by filtering out an outlier portion of the first filtered data.

In some examples, temperature control system 430 is configured to determine the outlier portion based on one or more data thresholds. Additionally, or alternatively, temperature control system 430 is configured to perform one or more outlier filtering methods to filter out the outlier portion of the first filtered data. [0116] At 806, envelope data based on the second filtered data is determined. For example, temperature control system 430 determines the envelope data based, at least in part, on the second filtered data. In some example, the envelope data is data that outlines the second filtered data and can generalize the concept of amplitude of the second filtered data. For example, the envelope data is determined (by temperature control system 430) to span from the bottom of the second filtered data to just beneath the top of the second filtered data. [0117] At 808, filtered envelope data is determined by applying a low pass moving average filter to the envelope data. For example, temperature control system 430 applies a low pass moving average filter to the envelope data. Although some embodiments are discussed with a low pass moving average filter, the embodiments of this disclosure can include other filters applied to the envelope data to make the filtered envelope data more robust to noise and to performance fluctuations.

[0118] At 810, the one or more thresholds are determined based, at least in part, on the filtered envelope data. For example, temperature control system 430 determines the one or more thresholds based, at least in part, on the filtered envelope data. In on example, the one or more thresholds include the lower and upper valve position thresholds associated with heating system 405. In one embodiment, temperature control system 430 determines (e.g., sets) the upper valve position threshold associated with heating system 405 (e.g., the heating system off threshold) to be just below a lower value (e.g., edge) of the filtered envelope data. Additionally, or alternatively, temperature control system 430 determines (e.g., sets) the lower valve position threshold associated with heating system 405 such that heating system 405 turns on when laser source 400 transitions to off or standby mode.

[0119] FIG. 9 illustrates an example method 900 for communicating the lower and upper valve position thresholds associated with heating systems 405, according to some embodiments of the disclosure. As a convenience and not a limitation, FIG. 9 may be described with regard to elements of FIGS. 1-8. Method 900 may represent the operation of temperature control system 403 for communicating the lower and upper valve position thresholds associated with heating systems 405. Method 900 may be performed by temperature control system 403 of FIG. 4A and/or computer system 1100 of FIG. 11. But method 900 is not limited to the specific embodiments depicted in those figures and other systems may be used to perform the method as will be understood by those skilled in the art. It is to be appreciated that not all operations may be needed, and the operations may not be performed in the same order as shown in FIG. 9. [0120] According to some embodiments, in addition to determining the lower and upper valve position thresholds associated with heating systems 405, temperature control system 430 can be further configured to control heating system 405 (through control system 410) based on an age of laser chamber 403. In some embodiments, the age of laser chamber 403 can be determined based on a chamber shot count associated with that laser chamber.

[0121] For example, for a laser chamber in early chamber life, temperature control system 430 can instruct control system 410 to use the default lower and upper valve position thresholds instead of the lower and upper valve position thresholds determined by temperature control system 430.

[0122] For a laser chamber in mid chamber life, temperature control system 430 can instruct control system 410 to use modulated lower and upper valve position thresholds determined by temperature control system 430. Temperature control system 430 is configured to modulate the lower and upper valve position thresholds to generate the modulated thresholds to achieve a desired duty cycle, according to some examples.

[0123] For a laser chamber in after mid chamber life, temperature control system 430 can instruct control system 410 to use the lower and upper valve position thresholds determined by temperature control system 430, according to some embodiments.

[0124] According to some embodiments, at 902, a chamber shot count associated with the first and/or second laser cambers of the laser source is determined. For example, temperature control system 430 can determine a first chamber shot count associated with first laser camber 403 a of laser source 400 and a second chamber shot count associated with second laser camber 403b of laser source 400. In some example, the chamber shot count can indicate the number of laser shots generated in a chamber since the chamber’s installation into the laser source.

[0125] At 904, the determined chamber shot count is compared with a first count threshold. For example, temperature control system 430 compares the determined chamber shot count with the first count threshold. A separate first count threshold may be associated with each of the laser chambers or there may be a first count threshold associated with the two laser chambers combined. If the determined chamber shot count is greater than the first count threshold, temperature control system 430 can determine that the laser chamber is at after mid-life cycle. In this example, the method can continue to 906, where temperature control system 430 communicates with control system 410 one or more of the lower and upper valve position thresholds determined by temperature control system 430. Additionally, or alternatively, temperature control system 430 instructs control system 410 to use one or more of the lower and upper valve position thresholds. In some examples, the first count threshold can be a value around or more than 10 billion pulses (Bps). In some examples, the first count threshold can be a value around or more than 15 Bps. In some examples, the first count threshold can be a value around or more than 18 Bps. In some examples, the first count threshold can be a value around 20 Bps. However, these values for the first count threshold are provided as examples and other values can be used.

[0126] If at 908 a determination is made that the determined chamber shot count is not greater than the first count threshold, then method 900 moves to 908. At 908, a determination is made whether the determined chamber shot count is greater than a second count threshold. For example, temperature control system 430 determines whether the determined chamber shot count is more than the second count threshold. If temperature control system 430 determines that the determined chamber shot count is less than the second count threshold, temperature control system 430 can determine that the laser chamber is at early life cycle. In this example, method 900 moves to 910.

[0127] At 910, temperature control system 430 communicates to control system 410 so that control system 410 to use default/original thresholds(s) instead of the lower and upper valve position thresholds determined by temperature control system 430. In one example, temperature control system 430 may communicate to control system 410 one or more of the lower and upper valve position thresholds determined by temperature control system 430, but may instruct control system 410 to not use them and instead use the default/original thresholds(s). Alternatively, temperature control system 430 does not communicate to control system 410 the one or more of the lower and upper valve position thresholds determined by temperature control system 430 and control system 410 uses the default/original thresholds(s).

[0128] According to some embodiments, by using the default/original thresholds instead of the lower and upper valve position thresholds determined by temperature control system 430, temperature control system 430 can avoid or improve cold-start risks. Cold-start risks can refer to a temporary loss of system efficiency following a long period of laser idle time, which can be related to laser chamber gas temperature and/or laser chamber age. In some examples, the second count threshold can be a value around or more than 0.5 Bps. In some examples, the second count threshold can be a value around or more than 1 Bps. In some examples, the second count threshold can be a value around 2 Bps. However, these values for the second count threshold are provided as examples and other values can be used. [0129] If at 908 a determination is made that the determined chamber shot count is between the second count threshold and the first count threshold, temperature control system 430 can determine that the laser chamber is at mid-life cycle. In this example, method 900 moves to 912. At 912, temperature control system 430 is configured to modulate the lower valve position threshold to generate a modulated lower valve position threshold. Temperature control system 430 is configured to modulate the upper valve position threshold to generate modulated upper valve position threshold. Temperature control system 430 is configured to generate the modulated lower and upper valve position thresholds to achieve a desired duty cycle. At 914, temperature control system 430 communicates to control system 410 one or more of the modulated lower and upper valve position thresholds determined by temperature control system 430.

[0130] According to some embodiments, control system 410 uses the modulated lower and upper valve position thresholds to switch the control of heating system 405 between the default/original threshold(s) and the threshold(s) determined by temperature control system 430 (e.g., thresholds before modulation. In other words, temperature control system 430 is configured to communicate a new set of thresholds at a frequency to achieve the duty cycle. For example, the set of thresholds include (1) the determined lower and upper valve position thresholds and (2) the default/original lower and upper valve position threshold(s). Temperature control system 430 switches between (1) the determined lower and upper valve position thresholds and (2) the default/original lower and upper valve position threshold(s) at the frequency to achieve the duty cycle. For example, for a duty cycle value of 50%, control system 410 can use the default/original threshold(s) 50% of time and use the threshold(s) determined by temperature control system 430 the other 50% of time for controlling heating system 405. In this example, temperature control system 430 and/or control system 410 can modulate the threshold(s) determined by temperature control system 430 to maintain an effective duty cycle.

[0131] As another example, and to achieve a duty cycle of 40%, temperature control system 430 and/or control system 410 can modulate the threshold(s) determined by temperature control system 430 such that heating system 405 is on for 10 minutes, then off for 15 minutes, on for 10 minutes, and so on. This example is illustrated in FIGS. 10A and 10B.

[0132] FIG. 10A illustrates an exemplary graph depicting the status of a laser source 400 during a time period, according to some embodiments of this disclosure. FIG. 10B illustrates an exemplary graph depicting the status of heating systems 405 during the time period, according to some embodiments of this disclosure. Graph 1000 includes a y-axis indicating the laser status 1001 of laser source 400 and an x-axis 1003 indicating time. Graph 1000 illustrates a time period 1005 where laser source 400 is off or in standby state. Similarly, graph 1020 includes a y-axis indicating the heating system status 1021 of heating systems 405 and an x-axis 1023 indicating time.

[0133] Graph 1020 illustrates heating system status 1021 for heating system 405a (e.g., heating system associated with first laser chamber 403a associated with, for example, main oscillator (MO)) and for heating system 405b (e.g., heating system associated with second laser chamber 403b associated with, for example, power amplifier (PA)). Graph 1020 illustrates a time period 1025 where the heating systems are on. Time period 1025 correspond to time period 1005 of FIG. 10A where laser source 400 is off or in standby state. Other than time period 1025, the threshold(s) determined by temperature control system 430 are modulated to achieve a duty cycle of 40%, where heating systems 405 are on for 10 minutes, then off for 15 minutes, on for 10 minutes, and so on.

[0134] According to some embodiments, the duty cycle value is provided to temperature control system 430 by a user. Additionally, or alternatively, temperature control system 430 determines the duty cycle value based on, for example, the chamber shot count of the laser chamber. By modulating the threshold(s) determined by temperature control system 430, temperature control system 430 can avoid or improve cold-start risks.

[0135] According to some embodiments, method 900 is performed for both first laser chamber 403a and second laser chamber 403b. In some examples, first laser chamber 403a and second laser chamber 403b can be at same life cycle. For example, both are at early life cycle, both are at mid-life cycle, or both are after mid-life cycle. In other examples, first laser chamber 403a and second laser chamber 403b can be at different life cycles. If first laser chamber 403a and second laser chamber 403b are at different life cycles, method 900 can be performed conservatively, according to some embodiments. For example, method 900 can be performed based on the laser chamber that has lower chamber shot count. Alternatively, method 900 can be performed based on the laser chamber that has higher chamber shot count, in some examples.

[0136] Embodiments of the disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical, or other forms of propagated signals, and others. Further, firmware, software, routines, and/or instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, and/or instructions.

[0137] Various embodiments can be implemented, for example, using one or more computer systems, such as computer system 1100 shown in FIG. 11. Computer system 1100 can be any well-known computer capable of performing the functions described herein such as control system 410 or temperature control system 430 of FIG. 4A. Computer system 1100 includes one or more processors (also called central processing units, or CPUs), such as a processor 1104. Processor 1104 is connected to a communication infrastructure 1106 (e.g., a bus.) Computer system 1100 also includes user input/output device(s) 1103, such as monitors, keyboards, pointing devices, etc., that communicate with communication infrastructure 1106 through user input/output interface(s) 1102. Computer system 1100 also includes a main or primary memory 1108, such as random access memory (RAM). Main memory 1108 may include one or more levels of cache. Main memory 1108 has stored therein control logic (e.g., computer software) and/or data.

[0138] Computer system 1100 may also include one or more secondary storage devices or memory 1110. Secondary memory 1110 may include, for example, a hard disk drive 1112 and/or a removable storage device or drive 1114. Removable storage drive 1114 may be a floppy disk drive, a magnetic tape drive, a compact disk drive, an optical storage device, tape backup device, and/or any other storage device/drive.

[0139] Removable storage drive 1114 may interact with a removable storage unit 1118. Removable storage unit 1118 includes a computer usable or readable storage device having stored thereon computer software (control logic) and/or data. Removable storage unit 1118 may be a floppy disk, magnetic tape, compact disk, DVD, optical storage disk, and/ any other computer data storage device. Removable storage drive 1114 reads from and/or writes to removable storage unit 1118 in a well-known manner.

[0140] According to some embodiments, secondary memory 1110 may include other means, instrumentalities or other approaches for allowing computer programs and/or other instructions and/or data to be accessed by computer system 1100. Such means, instrumentalities or other approaches may include, for example, a removable storage unit 1122 and an interface 1120. Examples of the removable storage unit 1122 and the interface 1120 may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and/or any other removable storage unit and associated interface.

[0141] Computer system 1100 may further include a communication or network interface 1124. Communication interface 1124 enables computer system 1100 to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (individually and collectively referenced by reference number 1128). For example, communication interface 1124 may allow computer system 1100 to communicate with remote devices 1128 over communications path 1126, which may be wired and/or wireless, and which may include any combination of LANs, WANs, the Internet, etc. Control logic and/or data may be transmitted to and from computer system 1100 via communication path 1126.

[0142] The operations in the preceding embodiments can be implemented in a wide variety of configurations and architectures. Therefore, some or all of the operations in the preceding embodiments may be performed in hardware, in software or both. In some embodiments, a tangible, non-transitory apparatus or article of manufacture includes a tangible, non-transitory computer useable or readable medium having control logic (software) stored thereon is also referred to herein as a computer program product or program storage device. This includes, but is not limited to, computer system 1100, main memory 1108, secondary memory 1110 and removable storage units 1118 and 1122, as well as tangible articles of manufacture embodying any combination of the foregoing. Such control logic, when executed by one or more data processing devices (such as computer system 1100), causes such data processing devices to operate as described herein.

[0143] Based on the teachings contained in this disclosure, it will be apparent to persons skilled in the relevant art(s) how to make and use embodiments of the disclosure using data processing devices, computer systems and/or computer architectures other than that shown in FIG. 11. In particular, embodiments may operate with software, hardware, and/or operating system implementations other than those described herein.

[0144] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, LCDs, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion”, respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track unit (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology unit and/or an inspection unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[0145] It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by those skilled in relevant art(s) in light of the teachings herein.

[0146] The term “substrate” as used herein describes a material onto which material layers are added. In some embodiments, the substrate itself may be patterned and materials added on top of it may also be patterned, or may remain without patterning.

[0147] The following examples are illustrative, but not limiting, of the embodiments of this disclosure. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in the field, and which would be apparent to those skilled in the relevant art(s), are within the spirit and scope of the disclosure.

[0148] Although specific reference may be made in this text to the use of the apparatus and/or system according to the embodiments in the manufacture of ICs, it should be explicitly understood that such an apparatus and/or system has many other possible applications. For example, it can be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, LCD panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle,” “wafer,” or “die” in this text should be considered as being replaced by the more general terms “mask,” “substrate,” and “target portion,” respectively.

[0149] While specific embodiments of the disclosure have been described above, it will be appreciated that the embodiments may be practiced otherwise than as described. The description is not intended to limit the embodiments. [0150] It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments as contemplated by the inventor(s), and thus, are not intended to limit the present embodiments and the appended claims in any way.

[0151] Some embodiments have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.

[0152] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0153] Other aspects of the invention are set out in the following numbered clauses.

1. A laser source, comprising: a first laser chamber configured to generate a first laser beam; a second laser chamber configured to receive the first laser beam and amplify the first laser beam to generate a second laser beam; a first temperature actuator configured to control a first temperature of a gas in the first laser chamber; a second temperature actuator configured to control a second temperature of a gas in the second laser chamber; and a temperature control system configured to receive data from the first and second temperature actuators and determine a threshold associated with the first and second temperature actuators based on the received data, wherein the threshold is used by the first and second temperature actuators in controlling the first and second temperatures.

2. The laser source of clause 1, wherein each of the first and second temperature actuators comprises a cooling system and a heating system. 3. The laser source of clause 2, wherein the data from the first and second temperature actuators comprises data associated with the corresponding cooling system and the threshold comprises a threshold associated with the heating systems.

4. The laser source of clause 3, wherein: each of the cooling systems comprises a water cooling system, the data associated with the corresponding cooling system comprises position data associated with one or more valves of the corresponding water cooling system, and the threshold associated with the heating systems comprises a lower threshold for turning on the heating systems and an upper threshold for turning off the heating systems.

5. The laser source of clause 4, wherein the temperature control system is configured to: monitor the position data associated with the one or more valves of the corresponding water cooling system during a first time period; determine a status of the laser source during the first time period; and determine a first filtered data by filtering out a portion of the position data associated with the one or more valves of the water cooling system when the status of the laser source indicates that the laser source was not in an on state.

6. The laser source of clause 5, wherein the temperature control system is further configured to: determine a second filtered data by filtering out an outlier portion of the first filtered data, wherein the outlier portion is determined based on one or more data thresholds; determine envelope data based on the second filtered data; determine filtered envelope data by applying a low pass moving average filter to the envelope data; and determine the lower and upper thresholds based on the filtered envelope data.

7. The laser source of clause 6, wherein the temperature control system is configured to determine the upper threshold to be equal to or less than a lower value of the filtered envelope data.

8. The laser source of clause 6, wherein the temperature control system is configured to determine the upper threshold to be equal to or greater than an upper value of the filtered envelope data.

9. The laser source of clause 6, wherein the temperature control system is configured to determine the lower threshold such that the heating system turns on in response to the first and second laser chambers not generating the first and second laser beams, respectively.

10. The laser source of clause 1, wherein: the first temperature actuator comprises a first cooling system and a first heating system associated with the first laser chamber, the second temperature actuator comprises a second cooling system and a second heating system associated with the second laser chamber, the data from the first and second temperature actuators comprises data associated with the first and second cooling systems, respectively, and the threshold comprises a first threshold associated with the first heating system and a second threshold associated with the second heating system, wherein the first threshold is used by the first temperature actuator in controlling the first temperature and the second threshold is used by the second temperature actuator in controlling the second temperature.

11. The laser source of clause 1, wherein the temperature control system is configured to: determine a chamber shot count associated with the first laser chamber; in response to a determination that the chamber shot count is greater than a first count threshold, communicate, to the first and second temperature actuators, the threshold associated with the first and second temperature actuators; in response to a determination that the chamber shot count is greater than a second count threshold and less than or equal to the first count threshold: modulate the threshold associated with the first and second temperature actuators to determine a modulated threshold, wherein the modulated threshold achieves a desired duty cycle; and communicate, to the first temperature actuator, the modulated threshold; and in response to a determination that the chamber shot count is less than or equal to the second count threshold, communicate with the first and second temperature actuators to use a default threshold associated with the first and second temperature actuators.

12. The laser source of clause 1, wherein to determine the threshold the temperature control system is configured to: determine a first lower threshold and a first upper threshold associated with the first temperature actuator based on the received data, wherein the first lower threshold and first upper threshold are used by the first temperature actuator in controlling the first temperature; and determine a second lower threshold and a second upper threshold associated with the second temperature actuator based on the received data, wherein the second lower threshold and second upper threshold are used by the second temperature actuator in controlling the second temperature. 13. A lithographic apparatus, comprising: an illumination system configured to condition a radiation beam; a projection system configured to project a pattern imparted to the radiation beam onto a substrate, wherein the illumination system comprises a laser source, the laser source comprising: a first laser chamber configured to generate a first laser beam; a second laser chamber configured to receive the first laser beam and amplify the first laser beam to generate a second laser beam; a first temperature actuator configured to control a first temperature of a gas in the first laser chamber; a second temperature actuator configured to control a second temperature of a gas in the second laser chamber; and a temperature control system configured to receive data from the first and second temperature actuators and determine a threshold associated with the first and second temperature actuators based on the received data, wherein the threshold is used by the first and second temperature actuators in controlling the first and second temperatures.

14. The lithographic apparatus of clause 13, wherein: each of the first and second temperature actuators comprises a water cooling system and a heating system; the data from the first and second temperature actuators comprises position data associated with one or more valves of the corresponding water cooling system; and the threshold comprises a lower threshold for turning on the heating systems and an upper threshold for turning off the heating systems.

15. The lithographic apparatus of clause 14, wherein the temperature control system is configured to, for each of the laser chambers: monitor the position data associated with the one or more valves of the corresponding water cooling system during a first time period; determine a status of the laser source during the first time period; determine a first filtered data by filtering out a portion of the position data associated with the one or more valves of the corresponding water cooling system when the status of the laser source indicates that the laser source was not in on state; and determine a second filtered data by filtering out an outlier portion of the first filtered data, wherein the outlier portion is determined based on one or more data thresholds. 16. The lithographic apparatus of clause 15, wherein the temperature control system is further configured to, for each of the first and second laser chambers: determine envelope data based on the second filtered data; determine filtered envelope data by applying a low pass moving average filter to the envelope data; and determine the lower and upper thresholds based on the filtered envelope data.

17. The lithographic apparatus of clause 15, wherein the temperature control system is configured to, for each of the first and second laser chambers: determine the lower threshold such that the heating system turns on in response to the laser source turning off or transitioning to standby state; and determine the upper threshold to be equal to or less than a lower value of the filtered envelope data.

18. The lithographic apparatus of clause 13, wherein the temperature control system is configured to: determine a chamber shot count associated with the first laser chamber; in response to a determination that the chamber shot count is greater than a first count threshold, communicate, to the first and second temperature actuators, the threshold associated with the first and second temperature actuators; in response to a determination that the chamber shot count is greater than a second count threshold and less than or equal to the first count threshold: modulate the threshold associated with the first and second temperature actuators to determine a modulated threshold, wherein the modulated threshold achieves a desired duty cycle; and communicate, to the first temperature actuator, the modulated threshold; and in response to a determination that the chamber shot count is less than or equal to the second count threshold, communicate with the first and second temperature actuators to use a default threshold associated with the first and second temperature actuators.

19. The lithographic apparatus of clause 13, wherein: the first temperature actuator comprises a first cooling system and a first heating system associated with the first laser chamber, the second temperature actuator comprises a second cooling system and a second heating system associated with the second laser chamber, the data from the first and second temperature actuators comprises data associated with the first and second cooling systems, respectively, and the threshold comprises a first threshold associated with the first heating system and a second threshold associated with the second heating system, wherein the first threshold is used by the first temperature actuator in controlling the first temperature and the second threshold is used by the second temperature actuator in controlling the second temperature.

20. A method, comprising: generating, at a first laser chamber, a first laser beam; amplifying, at a second laser chamber, the first laser beam to generate a second laser beam; controlling, using a first temperature actuator, a first temperature of a gas in the first laser chamber; controlling, using a second temperature actuator, a second temperature of a gas in the second laser chamber; receiving, at a temperature control system, data from the first and second temperature actuators; and determining, using the temperature control system, a threshold associated with the first and second temperature actuators based on the received data, wherein the threshold is used by the first and second temperature actuators in controlling the first and second temperatures.

21. The method of clause 20, wherein: each of the first and second temperature actuators comprises a water cooling system and a heating system; the data from the first and second temperature actuators comprises position data associated with one or more valves of the corresponding water cooling system; the threshold comprises a lower threshold for turning on the heating systems and an upper threshold for turning off the heating systems; the receiving data from the first and second temperature actuators comprises monitoring the position data associated with the one or more valves of the corresponding water cooling system during a first time period; and the determining the threshold comprises: determining a status of the laser source during the first time period; determining a first filtered data by filtering out a portion of the position data associated with the one or more valves of the water cooling system when the status of the laser source indicates that the laser source was not in on state; and determining a second filtered data by filtering out an outlier portion of the first filtered data, wherein the outlier portion is determined based on one or more data thresholds.

22. The method of clause 21, wherein the determining the threshold further comprises: determining envelope data based on the second filtered data; determining filtered envelope data by applying a low pass moving average filter to the envelope data; and determining the lower and upper thresholds based on the filtered envelope data.

23. The method of clause 20, wherein: the first temperature actuator comprises a first cooling system and a first heating system associated with the first laser chamber, the second temperature actuator comprises a second cooling system and a second heating system associated with the second laser chamber, the data from the first and second temperature actuators comprises data associated with the first and second cooling systems, respectively, and the determining the threshold comprises: determining a first threshold associated with the first heating system; and determining a second threshold associated with the second heating system, wherein the first threshold is used by the first temperature actuator in controlling the first temperature and the second threshold is used by the second temperature actuator in controlling the second temperature.

24. A non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform operations, the operations comprising: receiving position data associated with one or more valves of a water cooling system of a laser source during a first time period; determining a status of the laser source during the first time period; generating a first filtered data by filtering out a portion of the position data associated with the one or more valves of the water cooling system when the status of the laser source indicates that the laser source was not in on state; generating a second filtered data by filtering out an outlier portion of the first filtered data; determining envelope data based on the second filtered data; determining filtered envelope data by applying a low pass filter to the envelope data; and determining, based on the filtered envelope data, first and second thresholds associated with a heating system of the laser source, wherein the first and second thresholds are used for controlling gas temperature in at least one laser chamber.

25. An apparatus, comprising: a first temperature actuator configured to control a first temperature of a gas in a first laser chamber; a second temperature actuator configured to control a second temperature of a gas in a second laser chamber; and a temperature control system configured to receive data from the first and second temperature actuators and determine a threshold associated with the first and second temperature actuators based on the received data, wherein the threshold is used by the first and second temperature actuators in controlling the first and second temperatures.

26. The apparatus of clause 25, wherein: the first laser chamber is configured to generate a first laser beam, and the second laser chamber is configured to generate a second laser beam, wherein the second laser chamber is configured to receive the first laser beam and amplify the first laser beam to generate the second laser beam.

27. The apparatus of clause 25, wherein each of the first and second temperature actuators comprises a cooling system and a heating system.

28. The apparatus of clause 27, wherein the data from the first and second temperature actuators comprises data associated with the corresponding cooling system and the threshold comprises a threshold associated with the heating systems.

29. The apparatus of clause 28, wherein: each of the cooling systems comprises a water cooling system, the data associated with the corresponding cooling system comprises position data associated with one or more valves of the corresponding water cooling system, and the threshold associated with the heating systems comprises a lower threshold for turning on the heating systems and an upper threshold for turning off the heating systems.

30. The apparatus of clause 29, wherein the temperature control system is configured to: monitor the position data associated with the one or more valves of the corresponding water cooling system during a first time period; determine a status of the apparatus during the first time period; and determine a first filtered data by filtering out a portion of the position data associated with the one or more valves of the water cooling system when the status of the apparatus indicates that the apparatus was not in an on state.

31. The apparatus of clause 30, wherein the temperature control system is further configured to: determine a second filtered data by filtering out an outlier portion of the first filtered data, wherein the outlier portion is determined based on one or more data thresholds; determine envelope data based on the second filtered data; determine filtered envelope data by applying a low pass moving average filter to the envelope data; and determine the lower and upper thresholds based on the filtered envelope data.

32. The apparatus of clause 25, wherein: the first temperature actuator comprises a first cooling system and a first heating system associated with the first chamber, the second temperature actuator comprises a second cooling system and a second heating system associated with the second chamber, the data from the first and second temperature actuators comprises data associated with the first and second cooling systems, respectively, and the threshold comprises a first threshold associated with the first heating system and a second threshold associated with the second heating system, wherein the first threshold is used by the first temperature actuator in controlling the first temperature and the second threshold is used by the second temperature actuator in controlling the second temperature.

33. A laser source, comprising: a first laser chamber configured to generate a first laser beam; a second laser chamber configured to receive the first laser beam and amplify the first laser beam to generate a second laser beam; a first temperature actuator configured to control a first temperature of a gas in the first laser chamber; a second temperature actuator configured to control a second temperature of a gas in the second laser chamber; and a temperature control system configured to: receive data from the first and second temperature actuators; determine a first lower threshold and a first upper threshold associated with the first temperature actuator based on the received data, wherein the first lower threshold and the first upper threshold are used by the first temperature actuator in controlling the first temperature; and determine a second lower threshold and a second upper threshold associated with the second temperature actuator based on the received data, wherein the second lower threshold and the second upper threshold are used by the second temperature actuator in controlling the second temperature.

34. An apparatus, comprising: a first temperature actuator configured to control a first temperature of a gas in a first chamber; a second temperature actuator configured to control a second temperature of a gas in a second chamber; and a temperature control system configured to: receive data from the first and second temperature actuators; determine a first threshold associated with the first temperature actuator based on the received data, wherein the first threshold is used by the first temperature actuator in controlling the first temperature; and determine a second threshold associated with the second temperature actuator based on the received data, wherein the second threshold is used by the second temperature actuator in controlling the second temperature.

35. The apparatus of clause 34, wherein: the first chamber comprises a first laser chamber configured to generate a first laser beam, and the second chamber comprises a second laser chamber configured to receive the first laser beam and amplify the first laser beam to generate a second laser beam.

[0154] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.