Method and apparatus for measuring erosion and calibrating position for moving process kits

Abstract

Embodiments disclosed herein include a method of calibrating a processing chamber. In an embodiment, the method includes placing a sensor wafer onto a support surface in a processing chamber with a process kit displaceable in a Z-direction positioned around the support surface. In an embodiment, the method further includes measuring a first gap distance between the sensor wafer and the process kit with a sensor on an edge surface of the sensor wafer. In an embodiment, the method further includes the step of displacing the process kit in the Z-direction. In an embodiment, the method further includes measuring an additional gap distance between the sensor wafer and the process kit.

Description

[0001] This application is a divisional application with the application date of "August 23, 2019", application number "201980048811.X", and titled "Method and device for measuring erosion and calibrating position for a moving process kit".

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Non-Provisional Application No. 16 / 545,827, filed on August 20, 2019, which claims the benefit of U.S. Provisional Application No. 62 / 726,892, filed on September 4, 2018, the entire contents of which are hereby incorporated by reference into this document. Technical Field

[0004] Embodiments relate to the field of semiconductor manufacturing, and more particularly to methods and apparatus for measuring position and erosion of a moving process kit. Background Art

[0005] In processing of substrates, such as semiconductor wafers, the substrate is placed on a support surface, such as an electrostatic chuck (ESC), in a processing chamber. Generally, a process kit is placed around the support surface to provide desired processing characteristics during processing of the substrate. For example, a process kit can be used to help shape the plasma in a plasma chamber to provide a more uniform process across the wafer. As such, it is often necessary to control the positioning of the top surface of the process kit relative to the top surface of the substrate being processed to achieve the desired processing results.

[0006] After the process kit is installed, various tests (such as etch rate tests or particle tests) can be implemented to confirm that the process kit is properly positioned relative to the processed substrate. However, such tests are expensive and may take hours to complete. Also, the process kit may be eroded during processing of the substrate. As such, the process kit may need to be adjusted to reset the relationship between the substrate surface and the top surface of the process kit. Currently, the erosion rate is not properly defined and adjustments may be made until an observable defect is found on the processed substrate. Summary of the invention

[0007] Embodiments disclosed herein include a method of calibrating a process chamber. In an embodiment, the method includes the steps of placing a sensor wafer onto a support surface in the process chamber, wherein a process kit displaceable in the Z direction is positioned around the support surface. In an embodiment, the method further includes the steps of measuring a first gap distance between the sensor wafer and the process kit with a sensor on an edge surface of the sensor wafer. In an embodiment, the method further includes the steps of displacing the process kit in the Z direction. In an embodiment, the method further includes the steps of measuring an additional gap distance between the sensor wafer and the process kit.

[0008] Embodiments disclosed herein include a method for measuring erosion of a process kit. In an embodiment, the method includes the steps of placing a sensor wafer on a support surface in a processing tool. In an embodiment, the method further includes the steps of aligning a top surface of a process kit surrounding the support surface with a top surface of the sensor wafer using a sensor on the sensor wafer. In an embodiment, the method further includes the steps of removing the sensor wafer from the support surface. In an embodiment, the method further includes the steps of processing one or more device substrates in the processing tool. In an embodiment, the method further includes the steps of placing a sensor wafer on a support surface. In an embodiment, the method further includes the steps of measuring a gap distance between the sensor wafer and the process kit with a sensor on an edge surface of the sensor wafer. In an embodiment, the method further includes the steps of shifting the process kit in the Z direction. In an embodiment, the method further includes the steps of measuring the gap distance between the sensor wafer and the process kit again. In an embodiment, the method further includes the steps of repeating the operations of shifting the process kit and measuring the gap distance until consecutive gap distance measurements are equal to each other.

[0009] Embodiments disclosed herein include a sensor wafer. In an embodiment, the sensor wafer includes: a substrate having a first surface and a second surface opposite to the first surface, the first surface and the second surface being connected by an edge surface. In an embodiment, the sensor wafer further includes: a plurality of sensors located around the periphery of the substrate, wherein each of the sensors is an outward-facing position sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A is a plan view of a sensor wafer with edge sensors according to an embodiment.

[0011] Figure 1B is a perspective view of a sensor wafer with edge sensors according to an embodiment.

[0012] Figure 2Ais a partial cross-sectional view of a sensor wafer having edge sensors according to an embodiment.

[0013] Figure 2B is a partial cross-sectional view of a sensor wafer with edge sensors and an electric field protection shield according to an embodiment.

[0014] Figure 2C is a partial cross-sectional view of a sensor wafer having edge sensors and a top surface notch according to an embodiment.

[0015] Figure 2D is a partial cross-sectional view of a sensor wafer having an edge sensor formed over a top surface of the sensor wafer in accordance with an embodiment.

[0016] Figure 3A is a cross-sectional view of a sensor wafer measuring a gap distance between the sensor wafer and a fully recessed process kit according to an embodiment.

[0017] Figure 3B According to the embodiment Figure 3A A cross-sectional view of a sensor wafer and a process kit after the process kit is vertically displaced a first distance by lift pins.

[0018] Figure 3C According to the embodiment Figure 3B A cross-sectional view of the sensor wafer and the process kit after the process kit is vertically displaced a second distance such that a top surface of the process kit and a top surface of the sensor wafer are substantially coplanar.

[0019] Figure 4 is a graph illustrating gap distance measured relative to vertical displacement of a process kit according to an embodiment.

[0020] Figure 5 is a cross-sectional view of a sensor wafer having an edge sensor above a top surface of the sensor wafer and a process kit elevated above the sensor wafer according to an embodiment.

[0021] Figure 6 is a process flow diagram of a process for positioning a process kit relative to a sensor wafer according to an embodiment.

[0022] Figure 7 is a process flow diagram of a process for determining an erosion rate of a process kit for a given processing operation in accordance with an embodiment.

[0023] Figure 8 A block diagram is shown of an exemplary computer system that may be used in conjunction with a process including the step of measuring a relationship of a sensor wafer relative to a process kit in accordance with an embodiment. DETAILED DESCRIPTION

[0024] Systems including sensor wafers with edge sensors and methods of using such sensor wafers to measure positioning of a process kit relative to the sensor wafer are described according to various embodiments. In the following description, numerous specific details are set forth to provide a thorough understanding of the embodiments. It will be apparent to those skilled in the art that the embodiments may be practiced without these specific details. In other instances, well-known aspects are not described in detail to avoid unnecessarily obscuring the embodiments. Also, it is to be understood that the various embodiments shown in the drawings are illustrative representations and are not necessarily drawn to scale.

[0025] As described above, in order to confirm that the process kit is properly positioned relative to the substrate, multiple substrates are processed in the processing tool to monitor the etch rate and / or run particle tests. Only after processing many substrates is it possible to confirm that the process kit is properly aligned to provide the desired processing results. This process requires hours of downtime of the processing tool and is expensive.

[0026] Thus, embodiments disclosed herein include sensor wafers that can directly measure a process kit. In embodiments, the sensor wafer can be used to confirm that the top surface of the process kit is substantially coplanar with the top surface of the sensor wafer. Because the sensor wafer can have substantially the same form factor as the wafer being processed in the chamber, the measurement of the process kit relative to the sensor wafer provides a sufficiently close approximation of the position of the production wafer relative to the process kit. In this way, a single test procedure can be implemented after evacuating the process tool to confirm that the process kit is positioned to a desired tolerance relative to the production wafer. Thus, the time to calibrate the process tool is reduced, and the throughput capacity of the process tool can be increased.

[0027] Because process kits are used to manufacture semiconductor devices, the processing environment may cause erosion of the process kit, and the desired relationship between the process kit and the device wafer may drift. Therefore, embodiments include a sensor wafer that can also be used to detect the erosion rate of the process kit. After using the sensor wafer to determine the erosion rate, the process kit can then be adjusted to account for the predicted erosion without the need to recalibrate the process tool. In this way, the throughput capacity of the process tool can be increased.

[0028] Now refer to Figure 1A , according to an embodiment, a plurality of edge sensor regions 1351-135 nFIG. 1 is a plan view of a sensor wafer 110 of FIG. 1. In an embodiment, edge sensor regions 135 are distributed around the perimeter of the sensor wafer 110. Each sensor region 135 includes one or more sensors facing outward. In an embodiment, the sensors in the sensor region 135 can be used to measure the gap between the edge of the sensor wafer 110 and a process kit (not shown) surrounding the sensor wafer 110. One or more sensors in the edge sensor region 135 can be capacitive sensors. In a specific embodiment, the edge sensor region 135 can include a self-referencing capacitive sensor.

[0029] In the illustrated embodiment, three edge sensor regions 135 are shown. However, it is understood that one or more edge sensor regions 135 may be used to determine when the top surface of the process kit is substantially coplanar with the top surface of the sensor wafer 110, as will be described in more detail below.

[0030] In an embodiment, each of the edge sensor regions 135 may be communicatively coupled to a computing module 138 on the sensor wafer 110 using traces 137. In an embodiment, the computing module 138 may include one or more of the following: a power source 132 (e.g., a battery), a processor / memory 134 (e.g., circuitry, memory, etc. for implementing and / or storing measurements made with the edge sensor regions 135), and a wireless communication module 133 (e.g., Bluetooth, WiFi, etc.). In an embodiment, the computing module 138 may be embedded in the sensor wafer 110. Furthermore, while shown as being in the center of the sensor wafer 110, it is to be understood that the computing module 138 may be located at any convenient location in the sensor wafer 110.

[0031] Now refer to Figure 1B , a perspective view of a sensor wafer 110 is shown emphasizing details of an exemplary edge sensor region 135 according to an embodiment. In an embodiment, the sensor wafer 110 may include a first surface 111 (e.g., a top surface), a second surface 113 (e.g., a bottom surface), and an edge surface 112 connecting the first surface 111 to the second surface 113. In an embodiment, the edge sensor region 135 may be formed along the edge surface 112.

[0032] In a particular embodiment, the edge sensor region 135 may include a probe 141. The probe 141 (i.e., the probe in each edge sensor region) may be a self-referenced capacitive probe. That is, the output phase of the current supplied to the first probe 141 in the first edge sensor region 135 may be offset by 180 degrees relative to the output phase of the current supplied to the second probe 141 in the adjacent second edge sensor region 135. In this way, a distance measurement from the edge surface 112 to the surface of the process kit (not shown) may be performed without grounding the process kit. In the illustrated embodiment, the edge sensor region 135 is shown as having a single probe. However, in some embodiments, each edge sensor region 135 may include more than one probe 141. Although self-referenced capacitive sensors are specifically referred to herein, it is to be understood that the embodiments disclosed herein include any suitable sensor technology (e.g., laser sensors, optical sensors, etc.).

[0033] Now refer to Figures 2A-2D , an exemplary partial cross-sectional view of a sensor wafer 210 is shown according to various embodiments. Figure 2A , a partial cross-sectional view depicts a sensor region 235 that is substantially coplanar with the edge surface 212. In an embodiment, the sensor region 235 emits an electric field 249 from the edge surface 212 such that the sensor can measure a gap between the edge surface 212 and a surface of the process kit.

[0034] Now refer to Figure 2B , a partial cross-sectional view of a sensor wafer 210 having an electric field protection shield 247 is shown according to an embodiment. In an embodiment, the electric field protection shield 247 can be a conductive layer formed between the bottom surface 213 of the sensor wafer 210 and the edge sensor region 235. The electric field 249 of the edge sensor region 235 can be modified by the electric field protection shield 247. Specifically, the electric field protection shield 247 can modify the electric field 249 of the edge sensor region 235 so that the electric field extends laterally from the edge surface 212 toward the process kit. Therefore, the electric field protection shield 247 prevents the sensors in the edge sensor region 235 from detecting objects under the sensor wafer 210 that may provide erroneous readings.

[0035] Now refer to Figure 2C, a partial cross-sectional view of a sensor wafer 210 having a top surface notch 248 is shown according to an embodiment. In an embodiment, the top surface notch 248 can be formed into the first surface 211 adjacent to the sensor region 235. The top surface notch 248 can be made to prevent the sensor of the sensor region 235 from sensing the top surface 211 and providing erroneous readings. In an embodiment, the top surface notch 248 can extend back a distance R. For example, the distance R can be approximately equal to the maximum sensing distance of the edge sensing region 235. In an embodiment, the distance R can be 2.0 mm or less, or 1.0 mm or less.

[0036] Now refer to Figure 2D , a partial cross-sectional view of a sensor wafer 210 having a sensor region 235 formed above a first surface 211 of the sensor wafer 210 is shown according to an embodiment. Positioning the sensor region 235 above the sensor wafer 210 may be beneficial when it is desired to position the top surface of the process kit above the top surface of the device wafer. In an embodiment, the sensor region 235 may have a thickness T that does not significantly alter the form factor of the sensor wafer 210. For example, the thickness T may be less than 5 mm, less than 2 mm, less than 1 mm, or less than 0.5 mm. Thus, the sensor wafer 210 may still pass through any load lock chamber in a processing tool.

[0037] Now refer to Figures 3A-3C , a series of cross-sectional views depict a process for calibrating a processing tool so that a top surface 361 of a process kit 360 is substantially coplanar with a first (ie, top) surface 311 of a sensor wafer 310 .

[0038] Now refer to Figure 3A , according to an embodiment, a cross-sectional view of a portion of a sensor wafer 310 supported by a support surface 322 is shown. In an embodiment, the sensor wafer 310 can be any sensor wafer having one or more edge sensor regions 335. For example, the sensor wafer 310 can be used according to various embodiments. Figure 1A-1B Any of the sensor wafers described. Figure 3A In the particular embodiment illustrated in , the sensor wafer 310 includes an edge sensor region 335 and an electric field protection shield 347, however embodiments are not limited to such configurations. In embodiments, the sensor wafer 310 may have a form factor substantially similar to the form factor of a wafer to be processed in a processing tool. For example, the sensor wafer 310 may have a diameter of 300 mm and a thickness of less than 1 mm. In embodiments, the support surface 322 may be an electrostatic chuck (ESC) or any other suitable surface for supporting and securing the sensor wafer 310.

[0039] In an embodiment, the support surface 322 may be surrounded by a process kit support 350 on which the process kit 360 rests. The support surface 322 may include a plurality of lift pins 352 disposed into openings 353 in the process kit support 350. In an embodiment, the lift pins 352 may be below the process kit 360. When the lift pins 352 are extended with an actuator (not shown), the process kit is displaced in the Z direction.

[0040] exist Figure 3A 3, the lift pins 352 are fully retracted so that the process kit is completely resting on the process kit support surface 350. In such embodiments, the top surface 361 of the process kit 360 can be below the top surface 311 of the sensor wafer 310. Thus, when the edge sensor region 335 senses outward toward the process kit 360, the edge sensor region detects a first point 371 on the top surface 361 of the process kit 360. In embodiments, the first point 371 can be a first distance V1 from the inner surface 362 of the process kit 360.

[0041] Now refer to Figure 3B , according to an embodiment, shows a partial cross-sectional view after the lift pins are extended and the process kit 360 is raised a distance D1 in the Z direction. As shown, the edge sensor area 335 now senses a second point 372 on the top surface 361 of the process kit 360. In an embodiment, the second point 372 can be a second distance V2 from the inner edge of the process kit 360. As will be appreciated by those skilled in the art, the process kit 360 is displaced a distance D1 in the Z direction such that the second distance V2 is less than Figure 3A That is, the second point 372 is closer to the inner surface 362 of the process kit 360 than the first point 371 .

[0042] Now refer to Figure 3C , according to an embodiment, shows a partial cross-sectional view after the process kit is displaced a second distance D2 in the Z direction. As shown, the displacement D2 causes the top surface 361 of the process kit 360 to be substantially coplanar with the top surface 311 of the sensor wafer. At this point, the edge sensor region 335 begins to measure the true gap G between the edge surface 312 of the sensor wafer 310 and the edge surface 362 of the process kit 360. Since the field of view of the edge sensor region 335 is completely blocked by the process kit 360, subsequent readings from the edge sensor region 335 will be substantially consistent as the process kit is further displaced in the Z direction.

[0043] For example, Figure 4 Graph showing gap measurements relative to process kit displacement in the Z direction. As shown, when the process kit 360 is at D0 (i.e., when the process kit 360 is resting on the process kit support surface 350), as shown in FIG. Figure 3A ), the measured gap is equal to the actual gap G plus the first distance V1. When the process kit 360 is shifted by a distance D1 (ie, as shown in Figure 3B When the process kit 360 is shifted by a distance D2 (ie, as shown in FIG. Figure 3C ), the measured gap is equal to the true gap G. Subsequent measurements (e.g., D n ) will be maintained at the true gap G because the inner surface 362 of the process kit 360 is substantially vertical and the edge sensor "sees" an unchanged surface as the process kit is further advanced in the Z direction. As used herein, it is to be understood that the sensor may not literally "see" a surface. For example, in the case of utilizing a capacitive sensor (such as, those described herein), the voltage measurement of the sensor's conductive pad can be related to the distance between the "seen" surface and the sensor. Once consecutive gap measurements return the same value (i.e., when the slope of the line of gap measurement distance versus process kit displacement is zero), it can be inferred that the displacement (D) of the first instance of the repeated measurement is the displacement where the top surface of the sensor wafer 310 is substantially coplanar with the top surface 361 of the process kit 360.

[0044] When the top surface of the process kit needs to be above the top surface of the device wafer, the edge sensor region can be placed above the first (i.e., top) surface of the sensor wafer. Such an embodiment is shown in Figure 5 As shown, the sensor region 535 is placed above the first surface 511 of the sensor wafer 510. Therefore, the sensor region 535 does not "see" the inner surface 562 of the process kit 560 until the process kit 560 is shifted so that the top surface 561 of the process kit 560 is a distance D above the top surface 511 of the sensor wafer.

[0045] Now refer to Figure 6 , a process flow diagram of a process 680 for aligning a top surface of a process kit with a top surface of a sensor wafer is shown in accordance with an embodiment.

[0046] In an embodiment, process 680 may begin with operation 681, which includes the following steps: placing a sensor wafer on a support surface, wherein a displaceable process kit surrounds the support surface. In an embodiment, the sensor wafer may be any sensor wafer, such as those described herein that include one or more edge sensor regions. In an embodiment, the sensor wafer may have a substantially identical form factor to a wafer processed in a processing tool. In this manner, the sensor wafer may be placed on a support surface (e.g., an electrostatic chuck) using a wafer handling robot. In an embodiment, the process kit may rest on a process kit support surface. The process kit support surface may include a plurality of lift pins for displacing the process kit in the Z direction.

[0047] In an embodiment, process 680 may continue with operation 682, which includes the following steps: obtaining a first gap distance between the sensor wafer and the process kit with an edge sensor of the sensor wafer. In an embodiment, the edge sensor may be a self-referencing capacitive sensor. In an embodiment, a top surface of the process kit may be below a top surface of the sensor wafer. Thus, the first gap distance may be obtained by sensing a first point along the top surface of the process kit rather than sensing an inner edge of the process kit.

[0048] In an embodiment, process 680 may continue with operation 683, which includes the step of displacing the process kit a distance in the Z direction. In an embodiment, the process kit may be displaced in the Z direction using lift pins in a process kit support surface.

[0049] In an embodiment, process 680 may continue with operation 684 which includes the step of obtaining an additional standoff distance between the sensor wafer and the process kit with the edge sensor.

[0050] In an embodiment, process 680 may proceed to operation 685, which includes the following steps: comparing the last two measured gap distances. In embodiments where the last two measured gap distances are different, process 680 may repeat operations 683-685. For example, process 680 may repeat the following operations: shifting the process kit in the Z direction; obtaining additional gap distances; and comparing the last two measured gap distances (e.g., comparing the third gap distance to the second gap distance, comparing the fourth gap distance to the third gap distance, etc.). In embodiments where the last two measured gap distances are the same, process 680 may end because the top surface of the process kit is now substantially coplanar with the top surface of the sensor wafer.

[0051] Now refer to Figure 7 , a process flow diagram of a process 780 for determining an erosion amount for a process kit is shown according to an embodiment.

[0052] In an embodiment, process 780 begins with operation 781, which includes the steps of placing a sensor wafer on a support surface and aligning a top surface of a process kit with a top surface of the sensor wafer using an edge sensor of the sensor wafer. The process for aligning the top surface of the process kit with the top surface of the sensor wafer can be the same as described above for Figure 6 The process 680 described is substantially similar.

[0053] In an embodiment, process 780 may continue with operation 782, which includes the step of removing the sensor wafer from the support surface. In an embodiment, the sensor wafer may be removed using a wafer handling robot or the like.

[0054] In an embodiment, process 780 may continue with operation 783, which includes the following steps: processing a plurality of wafers on a support surface. In an embodiment, the step of processing the plurality of wafers may include any semiconductor manufacturing process. For example, the process may include an etching process. In an embodiment, the processing may cause an erosion process kit. In an embodiment, the plurality of wafers may include tens of wafers, hundreds of wafers, or thousands of wafers.

[0055] In an embodiment, process 780 may continue with operation 784, which includes the following steps: placing a sensor wafer on a support surface. In an embodiment, the sensor wafer may be the same sensor wafer used in operation 781. However, it is understood that different sensor wafers may also be used in some embodiments.

[0056] In an embodiment, process 780 may continue with operation 785, which includes the following steps: obtaining a first gap distance between the sensor wafer and the process kit with an edge sensor of the sensor wafer. In an embodiment, the erosion may cause the top surface of the process kit to be below the top surface of the sensor wafer. Therefore, the first gap distance may sense the top surface of the process kit instead of the inner surface of the process kit.

[0057] In an embodiment, process 780 may continue with operation 786 which includes the step of displacing the process kit a distance in the Z direction. In an embodiment, the process kit may be displaced using lift pins in a process kit support surface.

[0058] In an embodiment, process 780 may continue with operation 787 which includes the step of obtaining an additional standoff distance between the sensor wafer and the process kit with the edge sensor.

[0059] In an embodiment, process 780 may continue with operation 788, which includes the following steps: comparing the last two measured gap distances. In embodiments where the last two measured gap distances are different, process 780 may repeat operations 786-688. For example, process 780 may repeat the following operations: shifting the process kit in the Z direction; obtaining additional gap distances; and comparing the last two measured gap distances (e.g., comparing the third gap distance to the second gap distance, comparing the fourth gap distance to the third gap distance, etc.).

[0060] In embodiments where the last two measured gap distances are the same, process 780 may proceed to operation 789, which includes the following steps: calculating an erosion rate. In embodiments, the erosion rate may be calculated by determining the total displacement of the process kit in the Z direction and dividing by the number of wafers in the plurality of wafers processed in operation 783. Thus, the erosion rate may be expressed in terms of erosion distance per unit number of processed wafers. In additional embodiments, the erosion rate may be calculated by determining the total displacement of the process kit and dividing by the time taken to process the plurality of wafers. In such embodiments, the erosion rate may be expressed as an erosion rate per processing minute.

[0061] In an embodiment, the erosion rates may be stored in a database for future use. For example, the erosion rates may be stored and subsequent processing may automatically shift the process kit to account for the expected erosion. In this way, further measurements of the sensor wafer may not be necessary and processing tool throughput capacity may be increased.

[0062] Now refer to Figure 8, a block diagram of an exemplary computer system 860 of a processing tool is illustrated according to an embodiment. In an embodiment, a computer system 860 can be used to implement one or more processes, such as, processes 680 and 780. In an embodiment, a computer system 860 is coupled to a processing tool and controls the processing in the processing tool. The computer system 860 can be connected (e.g., networked) to other machines in a network 861 (e.g., a local area network (LAN), an intranet, an extranet, or the Internet). The computer system 860 can operate with the identity of a server or client machine in a client-server network environment, or operate as a peer-to-peer machine in a point-to-point (or distributed) network environment. The computer system 860 can be a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a cellular phone, a web device, a server, a network router, a switch or a bridge, or any machine capable of executing a set of instructions (sequential or otherwise), which specifies the action to be taken by the machine. Further, while a single machine is illustrated with respect to computer system 860, the term "machine" shall also be taken to include any series of machines (e.g., computers) that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies described herein.

[0063] The computer system 860 may include a computer program product or software 822 having a non-transitory machine-readable medium having instructions stored thereon, which instructions can be used to program the computer system 860 (or other electronic device) to perform a process according to an embodiment. The machine-readable medium includes any mechanism for storing or transmitting information in a form that can be read by a machine (e.g., a computer). For example, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., computer) readable storage medium (e.g., read-only memory ("ROM"), random access memory ("RAM"), disk storage medium, optical storage medium, flash memory device, etc.), a machine (e.g., computer) readable transmission medium (electrical, optical, acoustic, or other forms of propagation signals (e.g., infrared signals, digital signals, etc.)), etc.

[0064] In an embodiment, the computer system 860 includes a system processor 802, a main memory 804 (e.g., read-only memory (ROM), flash memory, dynamic random access memory (DRAM) (e.g., synchronous DRAM (SDRAM) or Rambus DRAM (RDRAM)), etc.), a static memory 806 (e.g., flash memory, static random access memory (SRAM), etc.), and a secondary memory 818 (e.g., a data storage device) that communicate with each other via a bus 830.

[0065] The system processor 802 represents one or more general-purpose processing devices, such as a microsystem processor, a central processing unit, and the like. More specifically, the system processor may be a complex instruction set computing (CISC) microsystem processor, a reduced instruction set computing (RISC) microsystem processor, a very long instruction word (VLIW) microsystem processor, a system processor implementing other instruction sets, or a system processor implementing a combination of instruction sets. The system processor 802 may also be one or more special-purpose processing devices, such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal system processor (DSP), a network system processor, and the like. The system processor 802 is configured to execute processing logic 826 for performing the operations described herein.

[0066] The computer system 860 may further include a system network interface device 808 for communicating with other devices or machines. The computer system 860 may also include a video display unit 810 (e.g., a liquid crystal display (LCD), a light emitting diode display (LED), or a cathode ray tube (CRT)), an alphanumeric input device 812 (e.g., a keyboard), a cursor control device 814 (e.g., a mouse), and a signal generating device 816 (e.g., a speaker).

[0067] The secondary memory 818 may include a machine-accessible storage medium 831 (or more specifically, a computer-readable storage medium) on which is stored one or more sets of instructions (e.g., software 822) embodying any one or more of the methods or functions described herein. The software 822 may also reside completely or at least partially within the main memory 804 and / or within the system processor 802 during execution of the software by the computer system 860, the main memory 804 and the system processor 802 also constituting machine-readable storage media. The software 822 may further be transmitted or received over a network 861 via a system network interface device 808.

[0068] Although the machine-accessible storage medium 831 is shown as a single medium in the exemplary embodiment, the term "machine-readable storage medium" should also be considered to include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) that store the one or more sets of instructions. The term "machine-readable storage medium" should also be considered to include any medium that is capable of storing or encoding a set of instructions for execution by a machine and causing the machine to perform any one or more of the methodologies. The term "machine-readable storage medium" should therefore be considered to include, but is not limited to, solid-state memory and optical and magnetic media.

[0069] In the foregoing description, specific exemplary embodiments have been described. Obviously, various modifications may be made to these embodiments without departing from the scope of the appended claims. Therefore, the description and drawings should be viewed in an illustrative rather than a restrictive sense.

Claims

1. A sensor wafer, comprising: a substrate having a first surface and a second surface opposite to the first surface, wherein the first surface and the second surface are connected by an edge surface; as well as A plurality of sensors are positioned around a periphery of the substrate, wherein each of the sensors is an outwardly facing position sensor, wherein each of the plurality of sensors includes a first pad and a second pad, and wherein a current supplied to the first pad has an output phase that is 180 degrees different from an output phase of a current supplied to the second pad.

2. The sensor wafer of claim 1, wherein the plurality of sensors are located on the edge surface.

3. The sensor wafer of claim 1, wherein the plurality of sensors extend above the first surface.

4. The sensor wafer of claim 1, wherein each of the plurality of sensors is a self-referenced capacitive sensor.

5. The sensor wafer of claim 1, wherein each of the plurality of sensors is a capacitive sensor.

6. The sensor wafer of claim 1, wherein the sensor wafer is used to perform a method of calibrating a process chamber, the method comprising: placing the sensor wafer onto a support surface in the processing chamber, wherein a process kit displaceable in the Z direction is positioned around the support surface; measuring a first gap distance between the sensor wafer and the process kit; displacing the process kit in the Z direction; and An additional standoff distance is measured between the sensor wafer and the process kit.

7. A sensor wafer, comprising: a substrate having a first surface and a second surface opposite to the first surface, wherein the first surface and the second surface are connected by an edge surface; as well as a plurality of sensors located around a perimeter of the substrate, wherein each of the sensors is an outwardly facing position sensor, wherein the sensor wafer is used to perform a method of calibrating a process chamber, the method comprising: placing the sensor wafer onto a support surface in the processing chamber, wherein a process kit displaceable in the Z direction is positioned around the support surface; measuring a first gap distance between the sensor wafer and the process kit; displacing the process kit in the Z direction; and An additional standoff distance is measured between the sensor wafer and the process kit.

8. The sensor wafer of claim 7, wherein the plurality of sensors are located on the edge surface.

9. The sensor wafer of claim 7, wherein the plurality of sensors extend above the first surface.

10. The sensor wafer of claim 7, wherein each of the plurality of sensors is a self-referenced capacitive sensor.

11. The sensor wafer of claim 7, wherein each of the plurality of sensors is a capacitive sensor.

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