CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims priority of US provisional application 62/408,880, which was filed on October 17, 2016, and US provisional application 62/570,625, which was filed on October 10, 2017, both of which are incorporated herein in its entirety by reference.

TECHNICAL FIELD

[002] The present disclosure generally relates to a vent valve vacuum system, and more particularly, to systems and methods for speedy venting of a chamber while minimizing the generating and spreading of particles and the causing of air turbulence within the chamber.

BACKGROUND

[003] In manufacturing processes of integrated circuits (ICs), unfinished or finished circuit components are inspected to ensure that they are manufactured according to design and are free of defects. An inspection system utilizing an optical microscope typically has resolution down to a few hundred nanometers; and the resolution is limited by the wavelength of light. As the physical sizes of IC components continue to reduce down to a sub- 100 or even sub- 10 nanometers, inspection systems capable of higher resolution than those utilizing optical microscopes are needed.

[004] A charged particle (for example, an electron) beam microscope, such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM), capable of resolution down to less than a nanometer, serves as a practicable tool for inspecting IC components having a feature size that is sub- 100 nanometers. With an SEM, electrons of a single primary electron beam, or electrons of a plurality of primary electron beams, can be focused at one or more scan locations of a wafer under inspection.

[005] When the imaging inspection is complete, the wafer sample needs to be transferred from a vacuum environment to an atmospheric environment. The transition from a vacuum to atmospheric environment— a vacuum-to-atmosphere transition process— is typically carried out by the following steps. A wafer sample is first transferred from a wafer stage by an automation arm to a closed space of a main chamber. Then an inert gas is slowly vented into the closed space until the pressure inside the main chamber reaches a desired value (e.g., close to ambient air pressure). When the gas venting process is complete, the main chamber is opened to allow the wafer sample to be moved out and into an atmospheric environment (i.e., to the load/lock chamber). The vacuum-to- atmosphere transition process is thus completed.

[006] During the vacuum-to-atmosphere transition process, particle contamination on the surface of a wafer sample can often occur. During the gas venting process, a strong gas stream can cause the wafer sample to deform or shift, thereby producing tiny particles. In addition, the gas stream can also lift particles present in the chamber. These particles can cause serious issues, such as contaminating the wafer sample.

[007] On the other hand, the long venting time of existing inert gas venting system prolongs the vacuum-to-atmosphere transition process, and thus limits the throughput of the manufacturing process. The size of the venting opening sets the constraint of the venting speed.

SUMMARY

[008] Embodiments of the present disclosure provide systems and methods for venting gas into a chamber. In some embodiments, a vent valve vacuum system is provided. The system comprises a first gas flow and a second gas flow. The first gas flow is formed by a first vent valve and optionally a third vent valve. The second gas flow is formed by a second vent valve. The vent valve vacuum system is configured to connect a gas source reservoir and a chamber for gas to be vented into. The vent valve vacuum system is further configured to couple to a controller. The controller is configured to instruct the vent valve vacuum system to turn on the second vent valve to form a second gas flow at a point of time later than the point of time at when the first gas flow is formed.

[009] In some embodiments, venting methods are provided. The method comprises first venting a chamber with a first flow, and further venting the chamber with a second flow until the pressure of the closed space of the chamber reaches a desirable pressure. The method can further comprises opening the second flow after the first flow is opened for a predefined period of time.

[010] Embodiments of the present disclosure of systems and methods provide speedy venting of a chamber without generating particles or causing turbulence during sample transfer from a vacuum to atmospheric environment. The accelerated venting process improves the throughput of manufacturing processes of semiconductors.

[011] Additional objects and advantages of the disclosed embodiments will be set forth in part in the following description, and in part will be apparent from the description, or may be learned by practice of the embodiments. The objects and advantages of the disclosed embodiments may be realized and attained by the elements and combinations set forth in the claims.

[012] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed embodiments, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[013] FIG. 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system, consistent with embodiments of the present disclosure.

[014] FIG. 2 is a schematic diagram illustrating an exemplary electron beam tool that can be a part of the exemplary electron beam inspection system of FIG. 1, consistent with embodiments of the present disclosure.

[015] FIG. 3 is a block diagram illustrating an exemplary vent valve vacuum system for venting a gas into a chamber, consistent with embodiments of the present disclosure.

[016] FIG. 4 is a diagram illustrating operations of vacuum system, consistent with embodiments of the present disclosure.

[017] FIG. 5 is a flowchart illustrating an exemplary method for venting a gas into a chamber, consistent with embodiments of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

[018] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations consistent with the invention. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the invention as recited in the appended claims.

[019] Reference is now made to FIG. 1, which illustrates an exemplary electron beam inspection (EBI) system 10 consistent with embodiments of the present disclosure. As shown in FIG. 1, EBI system 10 includes a main chamber 100, a load/lock chamber 102, an electron beam tool 104, and an equipment front end module (EFEM) 106. Electron beam tool 104 is located within main chamber 100.

[020] EFEM 106 includes a first loading port 106a and a second loading port 106b. EFEM

106 may include additional loading port(s). First loading port 106a and second loading port 106b receive wafer front opening unified pods (FOUPs) that contain wafers (e.g., semiconductor wafers or wafers made of other material(s)) or samples to be inspected (wafers and samples are collectively referred to as "wafers" hereafter). One or more robot arms (not shown) in EFEM 106 transport the wafers to load/lock chamber 102.

[021] Load/lock chamber 102 is connected to a load/lock vent valve vacuum system (not shown), which vents clean gas into load/lock chamber 102 to reach a first pressure above the vacuum pressure. Main chamber 100 is connected to a main chamber vent valve vacuum system (not shown), which vents clean gas into main chamber 100 to reach a second pressure above ambient air pressure. The volume of load/lock chamber 102 is significantly smaller than the volume of main chamber 100.

[022] While the present disclosure provides examples of main chamber 100 housing an electron beam inspection tool 104 to form an electron beam inspection system, it should be noted that aspects of the disclosure in their broadest sense, are not limited to a chamber housing an electron beam inspection system. Rather, it is appreciated that the forgoing principles may be applied to other chambers as well. For example, the main chamber 100 can encompass a critical dimension scanning electron microscopy or a review scanning electron microscopy for electron beam inspection applications, or an electron beam direct write lithography system for semiconductor manufacturing process.

[023] Reference is now made to FIG. 2, which illustrates exemplary components of electron beam tool 104 consistent with embodiments of the present disclosure. As shown in FIG. 2, electron beam tool 104 includes a wafer stage 200, and a wafer holder 202 supported by wafer stage 200 to hold a wafer 203 to be inspected. Electron beam tool 104 further includes an objective lens assembly 204, electron detector 206, an objective aperture 208, a condenser lens 210, a beam limit aperture 212, a gun aperture 214, an anode 216, and a cathode 218. Objective lens assembly 204, in some embodiments, can include a modified swing objective retarding immersion lens (SORIL), which includes a pole piece 204a, a control electrode 204b, a deflector 204c, and an exciting coil 204d. Electron beam tool 104 may additionally include an energy dispersive X-ray spectrometer (EDS) detector (not shown) to characterize the materials on the wafer.

[024] A primary electron beam 220 is emitted from cathode 218 by applying a voltage between anode 216 and cathode 218. Primary electron beam 220 passes through gun aperture 214 and beam limit aperture 212, both of which can determine the size of electron beam entering condenser lens 210, which resides below beam limit aperture 212. Condenser lens 210 focuses primary electron beam 220 before the beam enters objective aperture 208 to set the size of the electron beam before entering objective lens assembly 204. Deflector 204c deflects primary electron beam 220 to facilitate beam scanning on the wafer. For example, in a scanning process, deflector 204c can be controlled to deflect primary electron beam 220 sequentially onto different locations of top surface of wafer 203 at different time points, to provide data for image reconstruction for different parts of wafer 203.

Further, in some embodiments, anode 216 and cathode 218 can be configured to generate multiple primary electron beams 220, and electron beam tool 104 can include a plurality of deflectors 204c to project the multiple primary electron beams 220 to different portions of the wafer at the same time, to provide data for image reconstruction for different portions of wafer 203.

[025] Exciting coil 204d and pole piece 204a generate a magnetic field that begins at one end of pole piece 204a and terminates at the other end of pole piece 204a. A part of wafer 203 being scanned by primary electron beam 220 can be immersed in the magnetic field and can be electrically charged, which, in turn, creates an electric field. The electric field reduces the energy of impinging primary electron beam 220 near the surface of the wafer before it collides with the wafer. Control electrode 204b, being electrically isolated from pole piece 204a, controls an electric field on the wafer to prevent micro-arching of the wafer and to ensure proper beam focus.

[026] A secondary electron beam 222 can be emitted from the part of wafer 203 upon receiving primary electron beam 220. Secondary electron beam 222 can form a beam spot on sensor surfaces of electron detector 206. Electron detector 206 can generate a signal (e.g., a voltage, a current, etc.) that represents an intensity of the beam spot, and provide the signal to a processing system (not shown in FIG. 2). The intensity of secondary electron beam 222, and the resultant beam spot, can vary according to the external and/or internal structure of wafer 203. Moreover, as discussed above, primary electron beam 220 can be projected onto different locations of the surface of the wafer, to generate secondary electron beams 222 (and the resultant beam spot) of different intensities. Therefore, by mapping the intensities of the beam spots with the locations of wafer 203, the processing system can reconstruct an image that reflects the internal and/or external structures of wafer 203.

[027] Reference is now made to FIG. 3, which is a block diagram illustrating an exemplary vacuum system for venting a gas into a chamber, consistent with embodiments of the present disclosure. While the exemplary vacuum system 300 comprises a clean gas reservoir 301, a controller 302, a vent valve vacuum system 310, and a chamber 304 with an attached gas filter 303, it is appreciated that the configuration of a vacuum system 300 can be designed to incorporate other parts. For example, a gas regulator can be configured to connect between clean gas reservoir 301 and vent valve vacuum system 310 for regulating of clean gas flow coming into vent valve vacuum system 310.

[028] Clean gas reservoir 301 stores clean gas at a predefined pressure for providing a clean gas to vent valve vacuum system 310 at the predefined pressure. In one example, the pressure inside of clean gas reservoir 301 is a pressure over atmospheric pressure, e.g. 1.1 atmospheric pressure or 760+40/50 Torr. In some examples, clean gases utilized in semiconductor manufacturing processes are high purity inert gases. For example, the clean gas can be nitrogen trifluoride in lithography process.

[029] Vent valve vacuum system 310 comprises a first vent valve 312, a second vent valve 314, and a third vent valve 316. Vent valve vacuum system 310 provides a first gas flow and a second gas flow in parallel with the first gas flow. Vent valve vacuum system 310 provides the gas flow rate of the clean gas of clean gas reservoir 301 to chamber 304.

[030] A first vent valve 312 and a third vent valve 316 are configured to connect in series, forming and providing the first gas flow to filter. It is appreciated that in some examples, third vent valve 316 can be removed and first vent valve 312 becomes the only valve in the first gas flow. In some examples, third vent valve 316 can be a solenoid soft vent valve, which is primarily an electro- magnetic valve. Solenoid soft vent valve can be configured to open differentially by connecting and be controlled by electronic amplifier boards residing in controller 302. In practice, the control valve may comprise, for example, a direct current coil and a valve assembly sitting on an orifice. Flow is regulated by varying the valve drive voltage to the direct current coil, thereby creating a magnetic field lifting the valve assembly from the orifice to allow gas flow control. Proportional control valves are commonly seen in many different applications; varying details of their mechanical design and working principals should not be used to limit the scope of the present disclosures.

[031] A second vent valve 314 is configured to provide the second gas flow to filter 303, which can provide a conjunctive gas flow to chamber 304. In some examples, the size of second vent valve 314 is greater than the size of first vent valve 312 and the size of third vent valve 316. Hence, the speed of the second gas flow can be configured to be higher than the speed of the first gas flow. Further, the speed of the conjunctive gas flow combining the first gas flow and the second gas flow is higher than the speed of the second gas flow. The first gas flow rejoins the second gas flow before the conjunctive gas flow goes into chamber 304 via filter 303. While filter 303 provides a conjunctive gas flow combining the first gas flow and the second gas flow, it is appreciated that the first gas flow can be turned off and filter 303 provides the second gas flow to chamber 304.

[032] Controller 302 is coupled to vent valve vacuum system 310 and chamber 304. In some embodiments, controller 302 connects with a pressure gauge which can be set within chamber 304, so that controller 302 can collect instant information of pressure inside the closed space of chamber 304 through the pressure gauge and operates vent valve vacuum system 310 in real time based on the collected pressure information. In some embodiments, controller 302 comprises a timer. The timer is configured to start ticking once vent valve vacuum system 310 is turned on and forms a first gas flow from clean gas reservoir 301 to chamber 304. When the predefined time lapses, controller 302 is configured to instruct vent valve vacuum system 310 to turn on a second gas flow from clean gas reservoir 301 to chamber 304 so that the combined volume of the first gas flow and second gas flow is greater than that of the first gas flow. It is appreciated that controller 302 can shut off the second gas flow and the first gas flow after a predefined time period.

[033] Controller 302 can be implemented using one or more modules, which can be a packaged functional hardware unit designed for use with other components (e.g., portions of an integrated circuit) and/or a part of a program (stored on a computer readable medium) that performs a particular function of related functions. The one or more modules can have entry and exit points and can be written in a programming language, such as, for example, Java, Lua, C, or C++. A software module can be compiled and linked into an executable program, installed in a dynamic link library, or written in an interpreted programming language such as, for example, BASIC, Perl, or Python. It will be appreciated that software modules can be callable from other modules or from themselves, and/or can be invoked in response to detected events or interrupts. Software modules configured for execution on computing devices can be provided on a non-transitory computer readable medium, such as a compact disc, digital video disc, RAM, ROM, flash drive, or any other non-transitory medium, or as a digital download (and can be originally stored in a compressed or installable format that requires installation, decompression, or decryption prior to execution). Such software code can be stored, partially or fully, on a memory device of the executing computing device, for execution by controller 302. Software instructions can be embedded in firmware, such as an EPROM. It will be further appreciated that hardware modules can be comprised of connected logic units, such as gates and flip- flops, and/or can be comprised of programmable units, such as programmable gate arrays or processors.

[034] It is appreciated that timer can be an electronic or mechanical component embedded in controller 302, or can be part of a software module stored in a computer readable medium, which can be a memory part of controller 302.

[035] One or more software modules stored in the computer readable medium is read by controller 302, which can instruct vent valve vacuum system 310 to turn on first vent valve 312 and adjust the speed of the first gas flow by using third vent valve 316. Controller 302 can receive an input regarding the pressure of chamber 304 and/or can use the timer to determine when to send instructions to vent valve vacuum system 310 to turn on second vent valve 314. It is appreciated that controller 302 can communicate directly with the first, second, and third vent valves 312, 314, 316.

[036] Filter 303 is used to filter off hazardous particles carried in the gas stream from vent valve vacuum system 310 and thereby improve the effectiveness of particle contamination control. In some examples, filter 303 can be an artificial membrane that is made from metal or ceramic, homogenous films (polymers), heterogeneous solids (polymeric mixes, mixed glasses), or liquids. In some other examples, filter 303 can be a micro-electro-mechanical system (MEMS) comprising a plurality of zigzag channels with artificial membranes. Filter 303 is configured to attach to chamber 304. Gas passed through the plurality of zigzag channels can be evenly spread and enters chamber 304 at a lower flow speed. By providing even spreading and low speed of gas flow, filter 303 can reduce the possibility of forming of turbulence flow in chamber 304.

[037] Chamber 304 can be a load/lock chamber 102 or a main chamber 100 of FIG. 1. In some examples, a vacuum system 300 connects to a load/lock chamber 102 and vents gas to load/lock chamber 102 so that the gas pressure of load/lock chamber 102 reaches a first pressure above a vacuum pressure. In some examples, a vacuum system 300 connects to a main chamber 100 and vents gas to main chamber 100 so that the gas pressure of main chamber 100 reaches a second pressure above ambient air pressure.

[038] Reference is now made to FIG. 4, which is a diagram illustrating operations of vacuum system 300, consistent with embodiments of the present disclosure.

[039] In some embodiments, vent valve vacuum system 310 couples with a load/lock chamber 102 for venting a clean gas into the closed space formed within load/lock chamber 102. The starting pressure in the load/lock chamber is close to vacuum pressure. Controller 302 can cause first vent valve 312 alone or in combination with third vent valve 314 to introduce clean gas into chamber 304. The clean gas can be first vented into the load/lock chamber at a first gas flow rate, which increases at a substantially differential incremental rate, until a predefined time is reached and/or the pressure inside the load/lock chamber changes from the vacuum pressure to a first pressure level Pi. The first gas flow rate is preferably to start from zero. The first pressure level may be substantially equal to or greater than a saturation pressure inside the load/lock chamber at which the incoming clean gas no longer induces disturbance and/or convection in the load/lock chamber.

[040] At this point, controller 302 initiates second vent valve 314 to vent clean gas into chamber 304 at a second flow rate. While second vent valve 314 can work with first vent valve 312 to provide clean gas at a conjunctive rate, it is appreciated that second vent valve 314 can work by itself to provide clean gas to provide clean gas to chamber 304. The clean gas continues to vent into the load/lock chamber at the second flow rate until a predefined time is reached and/or the pressure inside the load/lock chamber reaches a second pressure level. The second pressure level may be set to be close to ambient air pressure.

[041] For example, with reference to FIG. 4, the first vent valve is set to turn on at to to form the first gas flow. At to, the pressure in chamber 304 is 1.0*10 ^~5 Torr. The clean gas starts to vent from a first gas flow rate. In response to the changes of valve drive voltage to the direct current coil, the gas flow rate of the first gas flow increases at a differential incremental rate until ti. At ti, the gas flow rate can include a second gas flow rate to form a conjunctive gas flow. In some examples, at ti, the opening areas of the first, second, and third vent valves are maximized so that the gas flow rate of the conjunctive gas flow reaches its saturation stage. On the contrary, when the vacuum system is configured that the second gas flow is not turned on at ti, the gas flow rate of the first gas flow continues to increase at a differential incremental rate until 13. At 13, the pressure of chamber 304 reaches the ambient air pressure, e.g., 760 Torr.

[042] In some embodiments, vent valve vacuum system 310 couples with a main chamber

100 for venting a clean gas into the closed space formed within the main chamber. The starting pressure in the load/lock chamber is close to vacuum pressure. The clean gas can be first vented into the main chamber at a first gas flow rate, which increases at a substantially differential incremental rate. However, the volume of main chamber 100 is much larger than that of load/lock chamber 102. After the predefined time of the timer of the controller 302 lapses, the controller 302 is configured to construct vent valve vacuum system 310 to turn on second vent valve 314 for forming a second gas flow.

[043] For example, with reference to FIG. 4, first vent valve 312 is set to turn on at to to form the first gas flow. At to, the pressure in chamber 304 is 1.0*10 ^"5 Torr. The clean gas starts to vent from a first gas flow rate. In response to the changes of valve drive voltage to the direct current coil, the gas flow rate of the first gas flow increases at a differential incremental rate until ti. At ti, the gas flow rate can change to a conjunctive gas flow rate when second vent valve 314 is turned on, and the first gas flow and the second gas flow provide a conjunctive gas flow. Therefore, the pressure of chamber 304 increases to a pressure near to the ambient air pressure, e.g. 720 Torr, in a very short period of time. In some examples, at ti, the opening areas of the first vent valve and the solenoid soft vent valve are maximized so that the gas flow rate of the first gas flow reaches its saturation stage. In some other examples, the gas flow rate of the first gas flow continues to increase at a differential incremental rate until t2. At t2, the pressure of chamber 304 reaches the ambient air pressure, e.g., 760 Torr. As the conjunctive gas flow rate of the first gas flow and the second gas flow is much greater than the gas flow rate of the first gas flow, so t ₂ is smaller than t ₃ . Comparing to the time of reaching ambient air pressure via the first gas flow only, the saved venting time of reaching ambient air pressure is At = t ₃ — t ₂ .

[044] For purpose of illustration, the diagram may not be drawn to reflect the dimensional relationships in practice and the dimensional relationships disclosed are not limited to the scale pictured. For example, the rate of the pressure change of the first gas flow LI, the rate of the pressure change of the conjunctive gas flow of the first gas flow and the second gas flow L(l+2), and the substantially differential incremental rate at which the speed of the gas flow changes may be different than what are shown in FIG. 4.

[045] Reference is now made to FIG. 5, which is a flowchart illustrating an exemplary method for venting a gas into a chamber, consistent with embodiments of the present disclosure. In some embodiments, controller 302 is configured to couple with vent valve vacuum system 310 in the way that at the point of time when first vent valve 312 is turned on, the timer in the controller can start to count down from a predefined period of time. For example, the predefined period of time can be 10 seconds. As the timer counts down the time, the first gas flow vents the clean gas at a speed of gas flow which increases at a substantially differential incremental rate. When the predefined time lapses, controller 302 is configured to instruct vent valve vacuum system 310 to turn on the second vent valve for forming a second gas flow.

[046] In another embodiment, vent valve vacuum system 310 turns on the first gas valve and the third vent valve to form the first gas flow. Controller 302 can be configured to couple with vent valve vacuum system 310 and chamber 304 in the way when the pressure of the closed space of chamber 304 reaches a predefined value, controller 302 instructs vent valve vacuum system 310 to turn on the second vent valve for forming a second gas flow.

[047] It will be appreciated that the present invention is not limited to the exact construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes can be made without departing from the scope thereof. It is intended that the scope of the invention should only be limited by the appended claims.