CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63/375,318 filed on September 12, 2022, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

[0002] The following generally relates to temperature measurement and monitoring systems and, in particular, to temperature measurement using Fiber Bragg Grating sensors.

BACKGROUND

[0003] In many semiconductor manufacturing operations, the manufacturing processes are temperature dependent. For example, in plasma etching, small variations in temperature can cause considerable changes in etching rates or critical dimension (“CD”) uniformity. Thus, the inability to precisely measure and control wafer temperature can lead to process yield loss. Additionally, accurate temperature measurement and control is becoming of increasing importance as features produced using such semiconductor manufacturing processes continue to decrease in size.

[0004] A common technique for measuring wafer temperature is phosphor thermometry, which is often carried out using contact phosphor-based temperature sensors. These sensors operate by remote, optical excitation of the phosphor and subsequent analysis of the re-emitted, temperature dependent optical signal. A single, point-based measurement can be implemented using, for example, a fiber optic delivery system with a single photodetector. Multiple single point measurements can be used to build a temperature profile across the wafer chuck and thus the water itself. However, the need for physical installation of such probes can result in space constraints, limiting the number of accessible measurement points on the chuck. Moreover, it can be burdensome to manage the multiple optical cables necessitated by using multiple probes in such a configuration.

[0005] Other methods for monitoring wafer temperature include the use of thermocouples or resistance temperature detectors (“RTDs”). However, thermocouples and RTDs are electrical devices and thus are prone to electromagnetic interference. This electromagnetic interference can arise from ambient electromagnetic fields and/or radio frequency energy which is used in some processes to ignite or strike a plasma. Additionally, acquiring multiple single point temperature measurements with these devices can necessitate a plurality of cables, which can be difficult to manage. Moreover, since RTDs need to be physically wired to the wafer, a feedthrough system is required, increasing the complexity of the chamber. Should one of the RTDs fail, the entire temperature sensing system would need to be changed. Furthermore, by increasing the number of RTDs used, the number of wires also increases, thus increasing the complexity further. All of these issues make the setup of the temperature sensing system fragile, complex, and difficult to scale.

SUMMARY

[0006] To address at least some of the above challenges, the following provides a temperature measurement system that uses Fiber Bragg Grating (FBG) sensors installed, set, or embedded on or within an electrostatic chuck (ESC) or ceramic plate used in etch or deposition equipment.

[0007] In one aspect, there is provided a temperature sensing system including an electrostatic chuck including a capillary in the shape of a pattern associated with a surface of the electrostatic chuck, and an optical fiber. The optical fiber is passed through the capillary. The optical fiber includes a Fiber Bragg Grating (FBG) sensing point along its length, wherein at least one optical property of the FBG sensing point changes depending on temperatures operating thereon.

[0008] In example embodiments, the electrostatic chuck comprises a plurality of capillaries, each capillary including at least one optical fiber passed therethrough, each of the at least one optical fibers including respective Fiber Bragg Grating (FBG) sensing points.

[0009] In example embodiments, the optical fiber comprises a plurality of FBG sensing points. The plurality of FBG sensing points can be uniformly spaced apart from one another along the length of the optical fiber.

[0010] In example embodiments, the pattern comprises a plurality of curves. The pattern can be a spiral pattern.

[0011] In example embodiments, the pattern is defined in part by a through passage in the electrostatic chuck. The through passage can extend away from an anticipated position of a wafer.

[0012] In example embodiments, the pattern is defined by a groove on the surface.

[0013] In example embodiments, the pattern is defined by one or more passages on the surface. [0014] In another aspect, a temperature sensing system is disclosed that includes a ceramic plate including a capillary following a pattern associated with a surface of the ceramic plate. The ceramic plate can be supported atop an electrostatic chuck. The ceramic plate includes an optical fiber passed through the capillary and including a Fiber Bragg Grating (FBG) sensing point along its length, wherein at least one optical property of the FBG sensing point changes depending on temperatures operating thereon.

[0015] In example embodiments, the ceramic plate comprises a plurality of capillaries, each capillary including at least one optical fiber passing therethrough, each of the at least one optical fibers including respective Fiber Bragg Grating (FBG) sensing points.

[0016] In example embodiments, the optical fiber comprises a plurality of FBG sensing points. The plurality of FBG sensing points can be uniformly spaced apart from one another along the length of the optical fiber.

[0017] In example embodiments, the pattern comprises a plurality of curves. The pattern can include concentric rings.

[0018] In example embodiments, the pattern is defined in part by a through passage of the electrostatic chuck. The through passage can extend towards a complimentary passage in a complimentary electrostatic chuck, or the through passage can extend radially towards a radial edge of the ceramic plate .

[0019] In example embodiments, the capillary is embedded within the ceramic plate.

[0020] In example embodiments, the capillary can be embedded within the ceramic plate between an upper surface and a heating coil. The capillary can be embedded within the ceramic plate between a lower surface and the heating coil.

[0021] In example embodiments, the pattern is at least in part defined by a heating coil of the ceramic plate.

[0022] In another aspect, a method for manufacturing temperature sensing systems is disclosed. The method includes entrapping a capillary in an electrostatic chuck or a ceramic plate, the capillary being in thermal communication with the electrostatic chuck or the ceramic plate. The method includes passing an optical fiber through the capillary, the optical fiber including a Fiber Bragg Grating (FBG) sensing point along its length.

[0023] In example embodiments, the optical fiber comprises a plurality of FBG sensing points, and the method further includes passing the optical fiber through the capillary to position the FBG sensing points in a first configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Embodiments will now be described with reference to the appended drawings wherein:

[0025] FIG. 1 is a plan view of an ESC.

[0026] FIG. 2 is a plan view of a rendering of an ESC with a groove pattern formed in an upper surface of the ESC.

[0027] FIG. 3 is a plan view of an ESC with a completed groove.

[0028] FIG. 4 is an enlarged close-up view of an entry point for a capillary set in the groove.

[0029] FIG. 5 is a partial cross-sectional schematic view showing an FBG optical fiber fed into a capillary.

[0030] FIG. 6 is a perspective view of a ceramic plate and ESC.

[0031] FIG. 7 is a plan view of the ceramic plate.

[0032] FIG. 8 is a partial cross-sectional schematic view showing a capillary embedded in a ceramic plate in one example.

[0033] FIG. 9 is a partial cross-sectional schematic view showing a capillary embedded in a ceramic plate in another example.

[0034] FIGS. 10 and 11 are examples of other groove/embedding patterns for the capillary.

DETAILED DESCRIPTION

[0035] The following provides a temperature measurement system that uses Fiber Bragg Grating (FBG) structures in an optical fiber installed, set, or embedded in an electrostatic chuck (ESC) or ceramic plate used in etch or deposition equipment. The use of FBG sensor technology allows for many temperature measurement points in various patterns throughout or on the substrate with which the FBG sensor(s) is/are integrated.

[0036] An FBG structure is an optical filtering device that reflects light of a specific wavelength and is present within the core of an optical fiber. The wavelength of light that is reflected depends on the spacing of a periodic variation or modulation of the refractive index that is present within the fiber core. This grating structure acts as a band-rejection optical filter which reflects light within a narrow wavelength range. Changes in temperature experienced by FBG structures can result in a change in the periodic variation or modulation of the FBG structure, causing a shift of the wavelengths that the FBG structure reflects. Being a completely optical device, a temperature sensor that relies on FBG structures can be immune to electromagnetic interference. Moreover, FBG technology provides the ability to form many FBG sensors in a single optical fiber. The FBG sensors may enable 2D temperature mapping of test wafers and ESCs based on detected temperatures at various points of the test wafers and/or the ESCs and/or ceramic plates (hereinafter these point(s) shall be referred to as FBG temperature sensing point(s)), and thus can be used to, e.g., analyze the impact of a temperature gradient within the ESC on process uniformity.

[0037] In one implementation, described below, an optical fiber(s) that incorporates a number of FBG temperature sensors, is fed through a capillary or other tubular structure that is seated or otherwise embedded or installed, or along a surface of an ESC. The disclosure contemplates a single fiber having a one or more FBG temperature sensors, or a plurality of fibers providing the plurality of FBG temperature sensors.

[0038] In another implementation, also described below, an optical fiber that incorporates a number of FBG sensors is fed through such a capillary that is embedded in a ceramic plate that is supported on the ESC to bring the FBG temperature sensors closer to the heat source in the ceramic plate that supports a wafter thereon.

[0039] In current solutions, thermocouples or single point fiber optical temperature sensors are used, and those cables are fed through the “umbilical cord” of electrical cables, cooling lines, and optical fibers to operate the ESC. Adding multiple points in this fashion occupies valuable space within the conduit. These multi-point approaches also add cost, with additional complexity and cost associated with adding additional ports to install multiple sensors. In contrast, with the FBG approach described herein, a single optical fiber (or fiber bundle passing through a single capillary) can measure temperature at multiple FBG temperature sensing points and can reduce the volume of space needed within the ESC umbilical conduit. As a result, the FBG approach described herein can provide for implementations with more sensor points, thereby allowing a greater understanding and control of the distributed temperature pattern.

[0040] The FBG temperature sensor implementations described herein can address a desire to segregate different zones having different temperatures with an ESC to allow users to control processes and improve yields. An advantage of FBG sensors over traditional methods (such as Fiber Optic Temperature Sensors) is that a single optical fiber could measure temperature at multiple points across the surface of the ESC. The embodiments described herein address this by installing the FBG temperature sensors within an ESC or ceramic plate to measure multiple FBG temperature sensing points as close as possible to a heater coil or surface of the wafer.

[0041] Turning now to the figures, FIG. 1 illustrates a plan view of an ESC 10 having an upper surface 12 that is positioned in a semiconductor processing chamber, for example. The ESC 10 includes a number of passages 14, such as holes or apertures to permit a ceramic plate 40 (see FIG. 5) to be attached to the ESC 10 (via bolts, pins, etc.) and/or to permit temperature probes to pass through the ESC 10 to make contact with the underside of such a ceramic plate 40. In the shown implementation, the pattern of passages 14 and other surface features is scanned or otherwise mapped to enable a rendering of the upper surface 12 of the ESC 10 to be generated as shown in FIG. 2.

[0042] Referring now to FIG. 2, the scanned or mapped ESC 10 can be used to enable a temperature sensing pattern or path 18 to be created within the ESC 10. A through- passage 16 in this example is used as a starting point for the temperature sensing path 18, which, in this embodiment, generally spirals towards the central (radially) portion of the ESC 10 and terminates at an endpoint 20. A capillary 30 can be fed at least in part through the passage 16, which capillary can include an optical fiber 32. The optical fiber 32 can incorporate FBG structures to measure temperature at different points along its length, and therefore along the path 18. These different points shall hereafter be referred to as FBG temperature sensing point(s), where one FGB temperature sensing point is illustratively shown as sensing point 34, and the portion of the optical fiber 32 responsible for measuring the temperature at the sensing point may hereinafter be referred to as an FBG temperature sensor(s).

[0043] The temperature sensing path 18 can be applied to or formed in the upper surface 12 of the ESC 10 by machining, etching, forming, or otherwise creating a groove or channel, e.g., using a CNC machine (not shown). The temperature sensing path 18 can be applied to or formed within the ESC 10. In embodiments where the path 18 is defined on the surface of the ESC 10, the groove can be machined along the path 18 and, hereinafter, may also be referred to as the “groove 18”. The groove 18 is machined beginning at the through- passage 16 and continues to the endpoint 20 as shown in FIG. 3 (the sensing point(s) 34 are intentionally omitted from FIG. 3 to enhance visual clarity).

[0044] Referring now to the close-up view of the ESC 10 in FIG. 4, the capillary 30 can be fed through the passage 16 and be laid along and within the groove 18 such that the capillary 30 is substantially flush or slightly below the upper surface 12 so as to not disrupt the seating of the ceramic plate 40 atop the ESC 10. When the capillary 30 is placed as such, each of the sensing points 34 formed in the optical fiber 32 are in thermal communication with the ESC 10. The capillary 30 can be stainless-steel or another material that provides suitable heat transfer properties to enable accurate temperature measurement from within the capillary 30. The capillary 30 can be placed, entrapped or otherwise secured in the groove 18 using any suitable method such as staking, adhesive, etc.

[0045] FIG. 5 provides a partial cross-sectional schematic view of the through-passage 16 (exaggerated) and installation of the capillary 30 and/or optical fiber 32. As seen in FIG.

5, the capillary 30 is placed within the groove 18 to permit the ceramic plate 40, which supports a wafer 50, to be seated atop the surface 12 of the ESC 10. The capillary 30 provides a conduit through which the optical fiber 32 with FBG structures can be fed through the ESC 10 along the path 18. The optical fiber 32 can be manufactured and positioned within the capillary 30 to position the FBG temperature sensors of the optical fiber 32 in desired sensing points along the groove 18. In this way, numerous temperature sensing points can be spread across the ESC 10 in a way that is difficult using multiple separate temperature probes that would each require their own passage 16 to make thermal contact with the underside of the ceramic plate 40. This disclosure contemplates various distribution of FBG temperature sensing points, including a uniform or relatively uniform distribution, a scattered distribution, etc. With the optical fiber 32 in the capillary 30 being positioned adjacent to or against the underside of the ceramic plate 40 (and, thereby in thermal communication therewith), the implementation shown in FIGS. 2-5 replicates current methodologies that measure the temperature of the bottom surface of the ceramic plate 40 (e.g., the same contact surface of such temperature probes) and thus can facilitate at least in part retrofitting or repurposing existing methods which rely on already-determined offset temperatures (used to estimate temperatures at the upper surface of the ceramic plate 40 on which the wafer 50 sits) based on existing models associated with these offsets.

[0046] Referring now to FIG. 6, in another implementation, the FBG optical fiber 32 can be positioned within the ceramic plate 40 so as to place the FBG temperature sensing points closer to the surface being monitored. FIG. 6 illustrates the underside of the ceramic plate 40 that includes a number of pins 42 that fit within passages 14 of the ESC 10 to position the ceramic plate 40 atop the surface 12 of the ESC 10. In the view shown in FIG. 7, a heating element 44 with visibility exaggerated for clarity, is visible through the upper surface of the ceramic plate 40. In one example, in order to embed the optical fiber 32 in the ceramic plate 40, the capillary 30 used in the implementation shown in FIG. 5 can be embedded in a pattern that follows or generally aligns with the pattern of the heating element 44. FIG. 8 provides a partial cross-sectional schematic view in which the capillary 30 is embedded within the ceramic plate 40 in a spiral pattern, the capillary 30 being positioned between the upper surface of the ceramic plate 40 which interfaces with the wafer 50 and the heating elements 44. Similar to FIG. 5, the optical fiber 32 can be fed through the capillary 30 from an entry point (in this example shown to the right in the image) to an endpoint 46, in this example near the center (radially), of the ceramic plate 40. Alternatively, as shown in FIG. 9, the capillary 30 can be embedded between the heating element(s) 44 and the lower surface of the ceramic plate 40. The optical fiber 32 can be fed up through the passage 16, similar to the implementation shown in FIG. 5. The capillary 30 can be embedded in a spiral pattern towards a central (radially) endpoint 46 as in FIG. 8.

[0047] It can be appreciated that the capillary 30 can be embedded in the ceramic plate 40 at the same time as the heating coil(s) 44 such that the capillary 30 is added before the ceramic plate 40 is baked and cured. In this way, the capillary 30 and its pattern are effectively cast into the ceramic plate 40 and provide a conduit through which the optical fiber 32 can be fed at a later time when set up in the processing chamber atop the ESC 10.

[0048] While the examples shown and described herein refer to a generally spiral pattern for laying the capillary 30 and the FBG optical fiber 32, it can be appreciated that other patterns are possible. For example, a zig-zag pattern could be used as shown in FIG. 10. Similarly, multiple capillaries 30 and multiple FBG optical fibers 32 could be used, as shown in FIG. 11 , which includes a fingering pattern throughout the surface 12 of the ESC or embedded within the ceramic plate 40 (i.e., other patterns are applicable to all implementations described herein). Similarly, as alluded to above, various positionings of the sensing points 34 relative to one another are contemplated. As shown in FIG. 11 , the sensing points 34 can be a uniform distance from one another, or the distance(s) can be other than uniform, periodic along the length of the optical fiber 32, different for different optical fibers 32, etc.

[0049] For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the examples described herein. However, it will be understood by those of ordinary skill in the art that the examples described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the examples described herein. Also, the description is not to be considered as limiting the scope of the examples described herein. [0050] It will be appreciated that the examples and corresponding diagrams used herein are for illustrative purposes only. Different configurations and terminology can be used without departing from the principles expressed herein. For instance, components and modules can be added, deleted, modified, or arranged with differing connections without departing from these principles.

[0051] Although the above principles have been described with reference to certain specific examples, various modifications thereof will be apparent to those skilled in the art as having regard to the appended claims in view of the specification as a whole.