Integrated adaptive positioning system and routine for education of automatic wafer handling robot and health-check

Abstract

To provide a system and a method for determining and using a plurality of types of offsets to provide a wafer to a wafer support body of a wafer station as a semiconductor processing tool.SOLUTION: An active wafer centering (AWC) system uses an automatic calibration wafer. An automatic calibration wafer 200 may include a plurality of sensors (image sensors 222 and 224, a vibration sensor 230, a direction / inclination sensor 232, a proximity sensor 234, for example) including image sensors 222 in an edge. The image sensors are used to take images of a reference part related to two different structures in a selected wafer station.SELECTED DRAWING: Figure 2

Description

Background Art

[0001] [Related Application Data] As part of this application, a PCT application is filed simultaneously with this specification. As confirmed in the simultaneously filed PCT application, each of the applications for which this application claims benefit or priority is hereby incorporated by reference in its entirety for all purposes.

[0002] Semiconductor processing tools use wafer handling robots to move semiconductor wafers between various wafer stations. Wafer handling robots typically use blade-type or spatula-type end effectors to pick up semiconductor wafers from below, and since the semiconductor wafers are not securely fixed to the end effectors of the wafer handling robots, there is often some variation in relative positioning between the end effectors and the semiconductor wafers disposed thereon. Due to the sensitivity of semiconductor processing operations, when placing semiconductor wafers using a wafer handling robot, it is typical to correct such variations so that the semiconductor wafers are placed at a desired location within the corresponding processing station within the allowable tolerance range, for example, usually centered within the processing station. Modern semiconductor processing tools utilize an Active Wafer Centering (AWC) system to assist with such wafer placement.

Summary of the Invention

[0003] Details of one or more implementations of the subject matter described herein are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will be apparent from the description, drawings, and claims herein. The following non-limiting implementations are considered part of the present disclosure. Other implementations will be apparent from the entire present disclosure and the accompanying drawings.

[0004] In some embodiments, a system for assisting in the calibration of a wafer handling robot for a semiconductor processing tool may be provided. The system may include, for example, an auto-calibration wafer, which is a substrate sized to be carried by the wafer handling robot and having a first surface configured to contact the end effector of the wafer handling robot when carried by the wafer handling robot, and a plurality of first image sensors supported by the substrate and positioned at locations offset from a common point of the substrate, each of the first image sensors having a downward field of view when the substrate is oriented with the first surface facing downward, and a first controller communicatively connected to each of the first image sensors.

[0005] In some embodiments of the system, the first image sensors may be configured in a circular array around a common point.

[0006] In some embodiments of the system, the substrate may be nominally circular and may have the same diameter as a semiconductor wafer configured to be processed by the semiconductor processing tool.

[0007] In some embodiments of the system, the substrate may be nominally circular and may have the same diameter as an edge ring configured to be used by the semiconductor processing tool.

[0008] In some embodiments of the system, the substrate may be nominally circular and may have a diameter between the outer diameter and the inner diameter of an edge ring configured to be used by the semiconductor processing tool.

[0009] In some embodiments of the system, the substrate may be nominally circular and may have a diameter within ±10% of the average between the outer diameter and the inner diameter of an edge ring configured to be used by the semiconductor processing tool.

[0010] In some embodiments of the system, the substrate may be a nominally circular disk having a diameter selected from the group consisting of 200 mm, 300 mm, and 450 mm.

[0011] In some embodiments of the system, the auto-calibration wafer may further include a power source configured to supply power to at least a first controller and a first image sensor.

[0012] In some embodiments of the system, the power source may be a rechargeable battery, and the auto-calibration wafer may further include a wireless charging function configured to charge the rechargeable battery when interfacing with an electromagnetic field.

[0013] In some embodiments of the system, the auto-calibration wafer may further include a first wireless communication interface, and the first wireless communication interface may be communicatively connected to the first controller.

[0014] In some embodiments of the system, the first wireless communication interface may include one or more wireless communication interfaces such as a Bluetooth (registered trademark. The same applies hereinafter) transceiver or a WiFi transceiver.

[0015] In some embodiments of the system, the auto-calibration wafer may further include one or more orientation sensors, and the one or more orientation sensors may be communicatively connected to the first controller.

[0016] In some embodiments of the system, each orientation sensor may be an inclinometer or an accelerometer.

[0017] In some embodiments of the system, the auto-calibration wafer may further include one or more vibration sensors, and the one or more vibration sensors may be communicatively connected to the first controller.

[0018] In some embodiments of the system, each vibration sensor may be an accelerometer, a laser microphone, or an optical distance measurement sensor.

[0019] In some embodiments of the system, the auto - calibration wafer may further include one or more proximity sensors, each proximity sensor being configured to measure the distance between the first surface and an object located below the proximity sensor when the first surface is facing downward, and the one or more proximity sensors may be communicatively connected to the first controller.

[0020] In some embodiments of the system, each proximity sensor may be an optical proximity sensor, an inductive proximity sensor, or a capacitive proximity sensor.

[0021] In some embodiments of the system, the first image sensor may be configured in a circular array around a common point, the substrate may nominally be circular, may have the same diameter as a semiconductor wafer configured to be processed by a semiconductor processing tool, the substrate may be a nominally circular disk having a diameter selected from the group consisting of 200 mm, 300 mm, and 450 mm, and the auto - calibration wafer may further include a rechargeable battery configured to supply power to at least the first controller and the first image sensor, a wireless charging function configured to charge the rechargeable battery when interfacing with an electromagnetic field, a first wireless communication interface that may be communicatively connected to the first controller and may include one or more wireless communication interfaces such as a Bluetooth transceiver or a WiFi transceiver, one or more vibration sensors that may be communicatively connected to the first controller, and one or more proximity sensors, each of the proximity sensors being communicatively connected to the first controller and configured to measure the distance between the first surface and an object located below the proximity sensor when the first surface is facing downward.

[0022] In some embodiments of the system, the system may further include a semiconductor processing tool, which may include a wafer handling robot, one or more wafer stations, and a second controller. In such embodiments, each wafer station may include one or more corresponding wafer supports, the wafer handling robot and the second controller may be communicatively connected, and the second controller and the first controller as a whole may be configured to: a) select a first wafer support among the one or more wafer supports of a first wafer station among the one or more wafer stations; b) cause the wafer handling robot to position a calibration wafer on the first wafer station; and c) cause each of the first image sensors to obtain a corresponding first image of a reference portion of the first wafer support while the calibration wafer is positioned on the first wafer support.

[0023] In some embodiments of the system, the second controller and the first controller as a whole may be further configured to determine location information of the center point of the first wafer support based on the first image.

[0024] In some such embodiments of the system, the second controller and the first controller as a whole may be further configured to: d) cause the wafer handling robot to remove the calibration wafer; and e) cause the wafer handling robot to transfer the calibration wafer to the first wafer support such that the center point of the calibration wafer is nominally centered on the center point of the first wafer support when viewed along the vertical axis.

[0025] In some embodiments of the system, the second controller and the first controller as a whole: f) position the auto-calibration wafer on the first wafer support and the calibration wafer by the wafer handling robot; g) while the auto-calibration wafer is positioned on the first wafer support and the calibration wafer, cause each of the first image sensors to acquire a corresponding second image of the reference portion of the first wafer support and the reference portion of the calibration wafer; h) based on the gap size between the reference portions of the first wafer support and the calibration wafer in the second image, further configured to determine the wafer / wafer support horizontal offset between the center point of the calibration wafer and the center point of the first wafer support.

[0026] In some embodiments of the system, the second controller and the first controller as a whole: i) compare the wafer / wafer support horizontal offset with a threshold wafer / wafer support horizontal offset; j) in response to a determination that the wafer / wafer support horizontal offset exceeds the threshold wafer / wafer support horizontal offset, cause the wafer handling robot to reposition the calibration wafer relative to the first wafer support to reduce the wafer / wafer support horizontal offset.

[0027] In some embodiments of the system, the second controller and the first controller as a whole are further configured to perform the earlier of: repeating (f) through (j) N times, or repeating until the wafer / wafer support horizontal offset is less than or equal to the threshold wafer / wafer support horizontal offset.

[0028] In some embodiments of the system, the second controller and the first controller as a whole may be further configured to: d) cause the wafer handling robot to remove the first edge ring; e) cause the wafer handling robot to transfer the first edge ring to the first wafer support such that, when viewed along the vertical axis, the center point of the first edge ring is nominally centered on the center point of the first wafer support.

[0029] In some embodiments of the system, the second controller and the first controller as a whole may be further configured to: f) cause the wafer handling robot to position the auto-calibration wafer over the first wafer support and the first edge ring; g) cause each of the first image sensors to acquire a corresponding second image of a reference portion of the first wafer support and a reference portion of the first edge ring while the auto-calibration wafer is positioned over the first wafer support and the first edge ring; h) determine an edge ring / wafer support horizontal offset between the center point of the first edge ring and the center point of the first wafer support based on a gap size between the reference portions of the first wafer support and the first edge ring in the second image.

[0030] In some embodiments of the system, the second controller and the first controller as a whole may be further configured to: i) compare the edge ring / wafer support horizontal offset with a threshold edge ring / wafer support horizontal offset; j) in response to a determination that the edge ring / wafer support horizontal offset exceeds the threshold edge ring / wafer support horizontal offset, cause the wafer handling robot to reposition the first edge ring wafer relative to the first wafer support to reduce the edge ring / wafer support horizontal offset.

[0031] In some embodiments of the system, the second controller and the first controller, as a whole, may be further configured to perform the first of the following that occurs: repeat (f) through (j) N times, or repeat until the edge ring / wafer support horizontal offset is less than or equal to the threshold edge ring / wafer support horizontal offset.

[0032] In some embodiments of the system, the second controller and the first controller, as a whole, may be further configured to: (f) cause the wafer handling robot to remove the calibration wafer; (g) cause the wafer handling robot to transfer the calibration wafer to the first wafer support such that, when viewed along the vertical axis, the center point of the calibration wafer is nominally centered on the center point of the first edge ring.

[0033] In some embodiments of the system, the second controller and the first controller, as a whole, may be further configured to: (h) cause the wafer handling robot to position the auto-calibration wafer over the first wafer support, the first edge ring, and the calibration wafer; (i) while the auto-calibration wafer is positioned over the first wafer support, the calibration wafer, and the first edge ring, cause each of the first image sensors to acquire a corresponding second image of a reference portion of the calibration wafer and a reference portion of the first edge ring; (j) determine an edge ring / wafer horizontal offset between the center point of the first edge ring and the center point of the calibration wafer based on the gap size between the reference portions of the calibration wafer and the first edge ring in the second image.

[0034] In some implementations of the system, the second controller and the first controller, as a whole, may be further configured to: k) compare the edge ring / wafer horizontal offset with a threshold edge ring / wafer horizontal offset; and l) in response to a determination that the edge ring / wafer horizontal offset exceeds the threshold edge ring / wafer horizontal offset, cause the wafer handling robot to reposition the calibration wafer relative to the first edge ring to reduce the edge ring / wafer horizontal offset.

[0035] In some implementations of the system, the second controller and the first controller, as a whole, may be further configured to perform (h) through (l) M times, or until the edge ring / wafer horizontal offset is less than or equal to the threshold edge ring / wafer horizontal offset, whichever occurs first.

[0036] In some implementations of the system, the second controller and the first controller, as a whole, may be further configured to cause the wafer handling robot to reposition the auto-calibration wafer onto the first wafer support, the first edge ring, and the calibration wafer, and while the auto-calibration wafer is positioned over the first wafer support, the calibration wafer, and the first edge ring, cause each of the first image sensors to acquire a corresponding third image of a reference portion of the calibration wafer and a reference portion of the first wafer support, and based on a gap size between the reference portions of the calibration wafer and the first wafer support in the third image, determine a wafer support / wafer horizontal offset between a center point of the first wafer support and a center point of the calibration wafer.

[0037] In some embodiments of the system, the second controller and the first controller as a whole may be further configured to compare the wafer support / wafer horizontal offset with a threshold wafer support / wafer horizontal offset, and in response to a determination that the wafer support / wafer horizontal offset exceeds the threshold wafer support / wafer horizontal offset, cause at least one article selected from the group consisting of a calibration wafer and an edge ring to be repositioned relative to the first wafer support to the wafer handling robot.

[0038] In some embodiments of the system, the semiconductor processing tool may include a semiconductor processing chamber, the first wafer station may be within the semiconductor processing chamber, and the first wafer support may include a pedestal within the semiconductor processing chamber.

[0039] In some embodiments of the system, the semiconductor processing tool may include a load lock for transferring wafers between different pressure environments, the first wafer station may be within the load lock, and the first wafer support may be a structure within the load lock.

[0040] In some embodiments of the system, the semiconductor processing tool may include a buffer for storing one or more wafers before, after, or during a processing operation, the first wafer station may be within the buffer, and the first wafer support may be one of a plurality of wafer support ledges within the buffer.

[0041] In some embodiments of the system, the semiconductor processing tool may include a load lock for transferring wafers between different pressure environments, the first wafer station may be within the load lock, and the first wafer support may be a structure within the load lock.

[0042] In some implementations of the system, the system may further include a semiconductor processing tool, which may include a wafer handling robot, one or more wafer stations, and a second controller. In such a system, each wafer station may include one or more corresponding wafer supports, the wafer handling robot and the second controller may be communicatively connected, and the second controller and the first controller as a whole may be configured to: a) select a first wafer support among one or more wafer supports of a first wafer station among one or more wafer stations; b) cause the wafer handling robot to transfer a calibration wafer onto the first wafer station; and c) cause one or more orientation sensors to obtain an inclination measurement of the substrate.

[0043] In some implementations of the system, the second controller may be configured to remove an edge ring from the first wafer support before performing (b).

[0044] In some embodiments of the system, the system may further include a semiconductor processing tool, which may include a wafer handling robot, one or more wafer stations, and a second controller. In such embodiments, each wafer station may include one or more corresponding wafer supports, the wafer handling robot and the second controller are communicatively connected, and the second controller and the first controller as a whole: a) select a first wafer support among the one or more wafer supports of a first wafer station among the one or more wafer stations; b) cause relative translational movement between a plurality of lift pins of the first wafer support and the first wafer support to project the lift pins from the first wafer support; c) transfer an auto-calibration wafer to the lift pins by the wafer handling robot; d) cause further relative translational movement between the lift pins and the first wafer support while the auto-calibration wafer is supported by the lift pins; e) obtain vibration data from one or more vibration sensors during (d); f) evaluate the vibration data to determine whether the vibration data indicates vibrations exceeding a predetermined threshold; g) may be configured to provide a notification when the vibration data exceeds the predetermined threshold.

[0045] In some embodiments of the system, the second controller may be configured to cause further relative translational movement between the lift pins and the first wafer support as part of (d) such that the auto-calibration wafer is placed on the upper surface of the first wafer support without the lift pins protruding from the first wafer support any further.

[0046] In some implementations of the system, the system may include a semiconductor processing tool, which may include a wafer handling robot, one or more wafer stations, and a second controller. In such a system, the wafer handling robot and the second controller may be communicatively connected, and the second controller and the first controller together are, based at least in part on an indication that an edge ring is supported by a first wafer support, a) selecting a first wafer support of one or more wafer supports of a first wafer station of the one or more wafer stations, b) placing a self-calibrating wafer on the edge ring, c) causing each of the proximity sensors to measure a distance between the first wafer support and the self-calibrating wafer, d) determining one or more height measurements associated with the edge ring based on the one or more distances, e) evaluating the one or more height measurements to determine whether a height associated with the edge ring exceeds a predetermined threshold, and f) providing a notification when the height associated with the edge ring exceeds the predetermined threshold.

[0047] The various implementations disclosed herein are depicted in the figures of the accompanying drawings by way of illustration and not limitation, and like reference numerals refer to like elements in the figures.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0065] The figures in this specification are not generally drawn to a consistent scale, although various aspects of the figures can be drawn to a consistent scale, for example, as discussed below.

[0066] In a typical semiconductor processing system, accurately positioning a wafer for various semiconductor processing operations and / or preparation of wafer handling operations is achieved by a manual or semi - automatic teaching process, which (1) "teaches" a wafer handling robot the desired locations of a wafer support such as a semiconductor wafer, an edge ring, and / or an electrostatic chuck (ESC) relative to each other or relative to the end effector of the wafer handling robot, (2) "teaches" an active wafer centering (AWC) system, and (3) typically requires skilled personnel or other humans to manage in order to perform wafer placement reproducibility verification. Once the wafer handling robot has been taught such locations, any deviation from such locations, which can occur in the wafer placement of any given wafer, for example, due to a slight misalignment between the wafer and the end effector that occurs while transferring the wafer to the end effector, can be corrected using the AWC. Such a manual or semi - automatic teaching process is time - consuming and cumbersome to implement.

[0067] Such an educational process typically begins by training a wafer handling robot at various locations where wafers are removed or placed during the operation of a semiconductor processing tool. Generally speaking, a wafer handling robot may initially be configured to generally understand where each of such locations is within the tool, but the wafer handling robot will need some degree of customization to adapt its operation to the unique characteristics of the particular semiconductor processing tool in which they are installed, for example, to accommodate various assembly tolerances or component tolerances. To achieve this, the wafer handling robot may be set to an "educational" mode, in which the wafer handling robot is guided to a position or configuration corresponding to the position where the wafer handling robot would be present under specific "ideal" conditions for each location to be "educated", for example, the position or configuration is within a known distance (generally, a distance that desirably may be minimized or reduced to zero) from a reference point on the end effector of the wafer handling robot and, for example, within a known distance (generally, a distance that desirably may be minimized or reduced to zero) from the center of the wafer support at that location when the center of the semiconductor wafer is positioned.

[0068] In the training of a typical wafer handling robot, the "ideal" positioning of the wafer handling robot for each location can be achieved, for example, by using one or more fixtures or other structures that can interface with a feature on the end effector of the wafer handling robot that functions as a reference point, and another feature fixed relative to the target location. For example, in some wafer handling robot training scenarios, a disk-shaped fixture having a diameter similar to that of the semiconductor wafer may be fastened to a predetermined position on the end effector of the wafer handling robot using a shaft or pin, the shaft or pin passing, for example, through the center of the disk and through a reference feature, such as a hole, in the centered end effector at a location intended to be the location where the semiconductor wafer will be centered when carried by the wafer handling robot using the end effector. There may be a similar pin that may be placed in a feature of the wafer support, and when the end effector / disk is pressed against such a pin, the pin contacts the edge of the disk, thereby guiding the disk and the end effector to a particular position, such as a centered position. During movement of such a wafer handling robot, the wafer handling robot may be placed in a powered-off state so that an operator can manually move the joints / arm segments of the wafer handling robot with ease. Once the wafer handling robot is properly positioned, the wafer handling robot controller may obtain measurements of the various linkage positions of the wafer handling robot, for example, by obtaining measurements of the relative or absolute angular displacements of the various rotational joints of the wafer handling robot, in order to determine what the kinematic state associated with the wafer handling robot is when the wafer handling robot is in the desired position.Once a wafer handling robot acquires such position information and associates it with that location, that location may be considered to be taught to the wafer handling robot.

[0069] Once various locations where wafers are to be delivered (or where wafers are to be retrieved) are taught to the wafer handling robot, the wafer handling robot may be controlled to enter the kinematic state taught for that location when performing future wafer transfer operations related to that location. When a semiconductor wafer placed on the end effector of the wafer handling robot is arranged to be precisely centered on the reference point of the end effector, when the same semiconductor wafer is placed at the target location by the end effector of the wafer handling robot, after the wafer handling robot is returned to the kinematic state taught for that location, similarly, it will be properly centered at that location. However, due to various reasons, the semiconductor wafer placed on the end effector of the wafer handling robot may not be precisely centered on the reference point of the end effector. Such misalignment may appear relatively small, for example, on the scale of dozens of micrometers, but even such a slight misalignment may have an adverse effect on wafer processing operations. The use of an Active Wafer Centering (AWC) system that enables correction of such end effector / wafer misalignment has become common in the industry.

[0070] In a typical AWC configuration, an optical AWC sensor and an optical beam emitter are positioned at fixed locations outside of a semiconductor wafer processing chamber such that as a semiconductor wafer passes into the processing chamber by a wafer handling robot, the semiconductor wafer moves through two or more of the optical beams emitted by the optical beam emitter. The AWC sensor may detect when each optical beam encounters the edge of the semiconductor wafer (as indicated by the interruption or re - establishment of an optical beam directed at one of the optical sensors). The AWC system may obtain, from the sensors of the wafer handling robot, the location of defined coordinates relative to a reference point, e.g., a point nominally centered on the semiconductor wafer on the end - effector of the wafer handling robot (which may be only an estimated or desired center location as the exact placement of the semiconductor wafer on the end - effector may not be known), each time the edge of the semiconductor wafer triggers one of the AWC optical sensors. For a circular semiconductor wafer, when using at least two AWC optical beam sensors, four or more resulting coordinates are sufficient to determine the location of the center point of the semiconductor wafer relative to the semiconductor processing chamber (the number of coordinates used can be reduced to three) (both the AWC sensors and the wafer handling robot base are fixedly attached relative to the semiconductor processing chamber). Once such wafer center information is obtained, it may be used as a reference location for future wafer placement or may serve as a measurement of the current wafer position that requires correction.

[0071] For example, to train an AWC system, a certain reference wafer may be manually centered on a desired destination, such as a pedestal within a semiconductor processing chamber. Such manual centering may be performed, for example, using a fixture or jig that guides the reference wafer to be properly centered with respect to the pedestal. Once the reference wafer is deemed to be sufficiently centered on the pedestal, the wafer handling robot may be controlled to remove the reference wafer and remove it from the semiconductor processing chamber. When the reference wafer is removed from the semiconductor processing chamber, the AWC system may be used to measure and determine the center of the reference wafer. By combining this information with information from the wafer handling robot that describes the displacement the reference wafer undergoes when moving from the centering location on the pedestal to the center location determined by the AWC system, future wafer placement can be adjusted to achieve similar centering of the wafer pedestal. For example, when a new wafer is placed on the wafer handling robot and passes through the AWC sensor, similar to the reference wafer, it may be found that the center of the new wafer is offset, for example, 0.5 mm in the X direction and 0.25 mm in the Y direction, from the previously determined center location of the reference wafer. To correct for such variations, when placing the new wafer on the pedestal, the wafer handling robot may be controlled to account for such variations by applying a correction displacement, for example, moving the new wafer -0.5 mm in the X direction and -0.25 mm in the Y direction, opposite to the displacement used to move the reference wafer from the pedestal to the AWC sensor, either before, after, or during the displacement of the new wafer.

[0072] To adjust the placement of the edge ring on the wafer support, a similar approach using an AWC system can also be used. For example, using the AWC, when the edge ring passes through the optical beam of the AWC system, the center point of the edge ring can be determined, and any offset between such a center point of the edge ring and, for example, a reference location used by the AWC system as an "ideal" center placement for the wafer or edge ring can be determined. In embodiments where the AWC system is used in conjunction with edge ring placement, due to the edge ring having both an inner edge and an outer edge, there may be more edge / optical beam intersections in the semiconductor wafer than in the case of a semiconductor wafer (thus, the number of edge / optical beam intersections detected by each optical sensor when the edge ring passes through the AWC optical sensor can be four, which is different from only two when the semiconductor wafer passes through the optical beam sensor). In such embodiments, data resulting from some of the edge / optical beam intersections, such as the intersection of the optical beam with the outer edge of the edge ring, may be ignored, and the center of the edge ring may be determined based on the remaining edge / optical beam intersections, such as the intersection of the optical beam with the inner edge of the edge ring. The reference point used by the AWC system to evaluate the degree to which the edge ring deviates from the desired placement on the end effector of the wafer handling robot may, in some embodiments, be the same reference point that can be used for AWC correction of the semiconductor wafer, i.e., a reference point determined based on measurements obtained from the semiconductor wafer using the AWC system. In other embodiments, the reference point used for edge ring AWC correction may be obtained based on measurements obtained from the edge ring using the AWC system. For example, the AWC system may be trained on the edge ring to obtain a reference point for future edge ring placement. It will be understood that the placement techniques discussed herein, as well as the AWC training and correction techniques discussed herein, are generally applicable in the context of both semiconductor wafer placement operations and edge ring placement operations.

[0073] AWC systems are widely used in the semiconductor processing industry and have typically provided good wafer centering performance. However, the training process is labor-intensive and can take an extremely long time, and is prone to user errors. Such training may be performed as part of the initial setup of semiconductor processing tools, but such training may be required to be repeated periodically throughout the life of the tool if, for example, any changes occur in the relative locations of the semiconductor processing chamber, AWC sensors, and wafer handling robots, or if the wafer processing operations begin to exhibit non-uniformity and indicate that the placement of the semiconductor wafer on the pedestal is off-center, or generally if any maintenance, including wet cleaning, is performed on the chamber. It will be understood that references in various implementations to the placement of wafers or edge rings on a wafer support, pedestal, or other equipment by a wafer handling robot may implicitly also include the indirect placement of wafers or edge rings on the wafer support. For example, in many semiconductor processing machines, lift pins that move vertically and are positioned on the wafer support may be used to lift a wafer from the end effector of the wafer handling robot, at which time it is possible to move the end effector from under the wafer without moving the wafer. Then, the lift pins can be controlled to lower the wafer onto the wafer support. The same process can be repeated in reverse to remove the wafer or other structure from the wafer support. As used herein, the term "wafer support" can refer to any of a variety of structures (other than the end effector of the wafer handling robot) configured to support a semiconductor wafer within a semiconductor processing tool.A wafer support may be, for example, a pedestal, an ESC, or other generally circular platform-like structure located within a semiconductor processing chamber (or other chamber) that generally contacts the semiconductor wafer dispersively through face-to-face contact between, for example, the back surface of the semiconductor wafer and the top surface of the wafer support, and an arcuate support ledge that can contact the semiconductor wafer only at points along the outer periphery of the semiconductor wafer, i.e., more limited contact. The wafer support may include a structure that can support the semiconductor wafer through such. The wafer support may include not only components that directly contact the semiconductor wafer, but also components or portions that extend beyond the outer periphery of the semiconductor wafer, such as an annular portion of a pedestal or ESC that extends beyond the outer periphery of the semiconductor wafer. The wafer support may optionally be equipped to provide movement of the semiconductor wafer supported by the wafer support, such as vertical movement and / or rotational movement. The wafer support may also optionally include lift pins as discussed above, or other mechanisms that extend upward relative to the remainder of such a wafer support and thereby lift the semiconductor wafer from the remainder of the wafer support. Optionally, the wafer support may include various removable components such as an edge ring. For example, some wafer supports may be configured to be used with one or more non-removable edge rings, such as an edge ring not designed to be removable by a wafer handling robot of a semiconductor processing tool, that interface with a non-removable edge ring, such as an edge ring designed to be removable by a wafer handling robot of a semiconductor processing tool. Such non-removable edge rings are considered part of the wafer support in the present disclosure and may of course still be removed by a technician.

[0074] The present disclosure is directed, inter alia, to an automatic calibration system, such as an adaptive positioning system, that can be used in connection with an AWC system (or similar device) and / or a wafer handling robot to provide automatic teaching of the AWC system and / or the wafer handling robot for semiconductor processing tools. Such a system may be used for the automatic teaching of a wafer handling robot either under vacuum or at atmospheric pressure, since the chamber in which the teaching is performed may be sealed as in normal semiconductor processing operations. Such an automatic calibration system may also be able to evaluate and / or correct various aspects of component or wafer placement, as necessary, to comply with process requirements. The automatic calibration system may be used to guide the placement of an edge ring, which is typically a nominally annular structure having an inner diameter sized slightly larger (or in some cases smaller) than the outer diameter of a semiconductor processing wafer, thereby effectively “expanding” the diameter of the semiconductor wafer being processed. The edge ring has the effect of causing any “edge effects” that may degrade the uniformity of process results on the wafer to occur at the outer edge of the edge ring, rather than on the semiconductor wafer itself, which has little impact on the uniformity of the wafer.

[0075] Central to the automatic calibration system is the automatic calibration wafer, also referred to as an adaptive positioning system (APS) wafer, which may collect a large amount of information from various on-board sensors, thereby enabling the automatic calibration wafer to be used as part of a fully automated teaching process. Such an automatic calibration wafer may be used, for example, to perform a diagnostic evaluation of components within a semiconductor processing tool and to obtain information that enables adjustment of the operation of the semiconductor processing tool to improve wafer processing performance.

[0076] Generally speaking, an automatic calibration wafer for a particular semiconductor processing tool may have the same size and shape as the wafers and / or edge rings configured to be processed by the semiconductor processing tool, such that during processing, the automatic calibration wafer can be transported by the wafer handling robot of the semiconductor processing tool in generally the same manner as the semiconductor wafer is transported. Thus, the automatic calibration wafer may be dimensioned to have a maximum height and diameter that are less than the minimum clearances in the vertical and horizontal directions of the path of the semiconductor processing tool through which the wafer can be transported by the wafer handling robot.

[0077] As described above, the automatic calibration wafer may include various sensors, but the number and type of sensors may vary depending on the particular functions provided by the automatic calibration wafer. It will be understood that the automatic calibration wafers according to the present disclosure may be configured to provide any one, several, or all of the sensors / functions discussed herein.

[0078] In addition to the various sensors that the automatic calibration wafer may include, the automatic calibration wafer may also include various components for communicating with other components (e.g., the controller of the semiconductor processing tool) for controlling and acquiring data from those sensors, and / or for storing and / or manipulating the data collected from the sensors. Thus, such an automatic calibration wafer is linked to the controller of the semiconductor processing tool and introduced into the semiconductor processing tool, and then, during various phases of the calibration routine or placement routine implemented by the semiconductor processing tool, various sensing and data collection operations may be performed by the actions of one or both of the controller(s) of the automatic calibration wafer and the controller(s) of the semiconductor processing tool. As will be apparent from the examples discussed in more detail below, such calibration routines or placement routines can be implemented by the semiconductor processing tool with little or no human supervision.

[0079] Generally speaking, the automatic calibration wafer may have a substrate that is similar to the overall shape of the semiconductor wafer, for example, substantially circular, but in some cases, the automatic calibration wafer may have a different shape. For example, a portion of the substrate that is not used to support sensors or other components, or that does not contact the lift pins of the contact pads or pedestals on the end effector, may be omitted, thereby resulting in an opening or notch in the automatic calibration wafer. Moreover, in some embodiments, the automatic calibration wafer may have a peninsula-shaped protrusion or other protrusion along an outer edge that is nominally circular otherwise, and may support sensors, for example, at locations that exceed the nominal outer diameter of the corresponding semiconductor wafer. The automatic calibration wafer may also include one or more indexing features, such as a flat edge, notch, etc., along the outer boundary to provide a mechanism for identifying the orientation of the automatic calibration wafer. In this specification, reference can be made to the "center" of the automatic calibration wafer, which is intended to be positioned at the same location as the center of the semiconductor wafer or edge ring when the automatic calibration wafer is transported or positioned within the semiconductor processing tool in the same manner as the semiconductor wafer or edge ring is typically transported or positioned within the semiconductor processing tool. It will be understood that the center of the automatic calibration wafer refers to the point on the automatic calibration wafer that is so positioned. The center of the automatic calibration wafer may coincide with the geometric center of the substrate and / or the center of mass of the automatic calibration wafer, but it will be understood that such alignment is not a requirement.

[0080] In most implementations, the auto-calibration wafer may have a plurality of downward-facing image sensors, such as charge-coupled device (CCD) sensors or complementary metal-oxide semiconductor (CMOS) sensors, which are located at various positions radially offset from the center of the auto-calibration wafer. Such offsets may be selected such that when the auto-calibration wafer is positioned above a semiconductor wafer disposed on a wafer support of a semiconductor processing tool, for example, each image sensor has a field of view wide enough to capture a portion of the edge of the semiconductor wafer as well as a portion of the wafer support. When a semiconductor processing tool typically uses an edge ring during wafer processing operations, the image sensors may be radially offset from the center of the auto-calibration wafer so that (when disposed on the wafer support) the field of view of the image sensors is wide enough to also capture a portion of the edge ring. In some implementations of the auto-calibration wafer, the downward-facing image sensors may be arranged along a circle having a diameter nominally the same size as the semiconductor wafer configured to be processed by the semiconductor processing tool, for example within ±10% or ±20% of the diameter. In still other implementations, the downward-facing image sensors may be arranged along a circle having a diameter between the diameter of the semiconductor wafer configured to be processed by the semiconductor processing tool and the diameter of the edge ring configured to be used by the semiconductor processing tool. In some such implementations, the downward-facing image sensors may be positioned along a diameter that is the average, or within the average, for example within ±10% of the average, of the nominal outer diameter of the edge ring and the nominal inner diameter of the edge ring or the nominal outer diameter of the semiconductor wafer. Such positioning allows, for example, when the auto-calibration wafer is positioned generally centered above the wafer support (and when the semiconductor wafer and / or edge ring are centered on the wafer support), the downward-facing image sensors to simultaneously capture the outer edge of the wafer support (or the edge of a feature on the wafer support, such as an ESC), the outer edge and / or inner edge of the edge ring, and the outer edge of the semiconductor wafer within their fields of view.

[0081] Such an arrangement of image sensors enables the automatic calibration wafer to simultaneously acquire images of various reference portions associated with the wafer support and the semiconductor wafer, and / or an edge ring disposed on the wafer support. As used herein, a reference portion refers to a feature that is assumed to be generally fixed with respect to a particular structure. For example, a circular edge of a component can function as a reference portion for the center point of the structure (it will be understood that such reference portions may change in size and / or shape over time due to erosion or deposition resulting from wafer processing operations. Such gradual changes in shape and / or size should not be considered to change the "fixed" nature of such reference portions in the context of the present disclosure. In the examples discussed herein, the reference portions used are the outer edge of the semiconductor wafer, the outer and / or inner edges of the edge ring, the outer edge of the wafer support or the edge of a feature of the wafer support, a surface discontinuity in the wafer support (for example, the upper surface of the wafer support may have a circular boss surrounded by an annular surface that is recessed downward from the circular boss; the transition between the circular boss and the annular surface may be such a surface discontinuity), or any other feature suitable for the techniques discussed herein, etc.

[0082] Next, an image obtained for a given set of reference portions of a semiconductor wafer, an edge ring, or other structure may be analyzed to determine an offset(s) between reference points on two structures associated with those reference portions. For example, if the reference portions used are the circular outer edge of a semiconductor wafer and the circular inner edge of an edge ring surrounding the semiconductor wafer, in each image, determine the relative size of the radial gap between the outer edge of the semiconductor wafer and the inner edge of the edge ring, and use it to generate an estimate of how much the center of the semiconductor wafer is offset from the center of the edge ring. Generally speaking, to make such a determination, it is necessary to use images from at least three image sensors (although a similar approach can be executed using only images from two image sensors, but it is usually not as accurate because the relative sizes of the reference portions need to be assumed). In some cases, some reference portions may not always be visible. In that case, an intermediate reference portion may be needed. For example, if a semiconductor wafer is centered on an ESC having an outer diameter smaller than the diameter of the wafer and the outer edge of the ESC is to function as a reference portion for such a wafer placement, it is impossible to obtain an image from an automatic calibration wafer where the outer edge of the ESC and the outer edge of the semiconductor wafer are both visible. Thus, any radial gap existing between such edges cannot be identified, and the centricity of the semiconductor wafer on the ESC cannot be directly determined. In such a case, an estimate of the centricity of the semiconductor wafer on the ESC can still be determined using an intermediate reference portion, such as the inner edge of an edge ring. For example, if an edge ring is placed on a wafer support so as to surround the ESC, an automatic calibration wafer may be used to determine the radial gap between the inner edge of the edge ring and the outer edge of the ESC. Then, based on the radial gap, determine the offset between the centers of the inner edge of the edge ring and the outer edge of the ESC, and if necessary, reposition the edge ring until it is centered on the ESC to an acceptable degree.After the edge ring is centered, the inner edge of the edge ring may function as a "proxy" for the outer edge of the ESC. Then, when the semiconductor wafer is placed on the wafer support and within the edge ring, an image sensor of an auto-calibration wafer may be used to obtain an image of the radial gap between the outer edge of the semiconductor wafer and the inner edge of the edge ring. Since the inner edge of the edge ring is centered on the outer edge of the ESC, the center-to-center offset between the outer edge of the semiconductor wafer and the inner edge of the edge ring can function as a proxy for the center-to-center offset between the outer edge of the semiconductor wafer and the outer edge of the ESC. In such a case, based on the actually measured center-to-center offsets between the outer edge of the semiconductor wafer and the inner edge of the edge ring, and between the inner edge of the edge ring and the outer edge of the ESC, the center-to-center offset between the outer edge of the semiconductor wafer and the inner edge of the edge ring can be further improved. For example, the edge ring may be finally positioned such that the center of the inner edge of the edge ring has XY offsets within an acceptable range of centricity (15μm, 10μm) from the center of the outer edge of the ESC, and then, if the semiconductor wafer is placed such that the center of the outer edge of the semiconductor wafer has XY offsets (-5μm, 12μm) (in the same coordinate system) from the center of the inner edge of the edge ring, the XY offset between the center of the semiconductor wafer and the center of the outer edge of the ESC may be determined by summing these two offset pairs, e.g., (15μm - 5μm, 10μm + 12μm) = (10μm, 22μm), and for example, the total offset is about 24μm.

[0083] Once the reference portions of the two structures are imaged by the auto-calibration wafer and the offset between the two structures is determined, this offset can be compared to a threshold offset that may represent the maximum offset between the structures considered acceptable for proper operation of the semiconductor processing tool. If the offset exceeds the threshold offset, the semiconductor processing tool may be made to take corrective action.

[0084] Various techniques can be used to determine the center - to - center offset between two structures, and such techniques are considered to be within the scope of the present disclosure. An exemplary technique for determining such an offset is provided in connection with FIG. 1. FIG. 1 shows an example of a calibration wafer disposed relative to an edge ring. In FIG. 1, edge ring 162 is shown together with calibration wafer 160 disposed within the inner diameter of edge ring 162. For clarity, in this specification, the term calibration wafer or reference wafer is used to refer to a wafer having the same or similar size as a typical semiconductor wafer processed by a semiconductor processing tool, and the calibration wafer is intended to function as a substitute for such a normal wafer, e.g., such that it can be processed by a semiconductor processing tool. A calibration or reference wafer may optionally include calibration markers or other features, which may be recognized by machine vision algorithms to assist in centering and calibration operations. As used herein, an auto - calibration wafer refers to a “smart” wafer or a wafer equipped with sensors and other electronics that enable such an auto - calibration wafer to acquire data and measure various parameters related to the performance of a semiconductor processing tool.

[0085] In FIG. 1, calibration wafer 160 and edge ring 162 are not shown to scale, for example, to better visualize the misalignment between the center (indicated by the cross - hairs) of edge ring 162 and calibration wafer 160, and the gap 164 between the outer edge of calibration wafer 160 and the inner edge of edge ring 162. Calibration wafer 160 may include a set of calibration markers 170, which may be positioned along the outer perimeter of the calibration wafer and spaced apart by a known amount, e.g., 120° apart in this example. A first image sensor of the auto - calibration wafer facing downward may be positioned such that calibration markers 170 and gap 164 between edge ring 162 and calibration wafer 160 are within the field of view 128 of the first image sensor.

[0086] In such an approach, certain assumptions may be made regarding various factors. For example, it may be assumed that the diameter of the calibration wafer is a known quantity, such as 300 mm. Thus, the radius r from the center point of the calibration wafer 160 to the edge of the calibration wafer 160 w may be assumed to be constant (e.g., if there is an index flat or notch along the edge, there may be some portions along the edge of the calibration wafer where the radius may be shorter, but the calibration wafer may have a constant radius within the field of view of the first image sensor). As described above, the calibration wafer may also have, for example, calibration markers 170, and their locations may be known with high certainty. In this example, it can be seen that the calibration markers 170 are arranged 120° apart around the circumference of the calibration wafer. The calibration markers may include, for example, a radial line (which is identified in the image data and used to establish a direction vector in each image, along which the gap 164 is evaluated), and a known size, such as 2 mm, and may include features such as a square or a circle (as shown) that can be used to determine the scale of the imaged features. For example, if a gap 164 is identified in the image and it has a size that is 0.23 times the size of the edge of a 2 mm calibration marker square in the same image, the size of the gap can be determined to be 0.23 × 2 mm = 0.46 mm. In some implementations, such calculations can take into account image distortion due to lens effects (e.g., using a checkerboard pattern), for example, using calibration data associated with an auto-calibration wafer, and correct such distortion.

[0087] It will be understood that the calibration markers discussed above may be omitted in some implementations, and reference portions such as the circular edges of various components may be used instead to determine the center locations of such components.

[0088] Assuming that the center of the calibration wafer 160 also functions as the origin of the coordinate system when determining the center-to-center offset between the edge ring 162 and the calibration wafer 160, the center location of the edge ring can be obtained by determining the locations of three points along the inner (or outer) edge of the edge ring 162 and then determining the center location of the circle defined by those three points. Once the center location of the edge ring 162 in the coordinate system of the calibration wafer is known, extracting the center-to-center offset between these two components is a straightforward process.

[0089] The gap 164 can be used in conjunction with the radius r of the calibration wafer 160 w and the angle along which each gap 164 is measured to determine the locations of three points along the inner edge of the edge ring 162. For example, in the case of gap 164 δ1, the gap δ1 can be added to the radius r w to obtain the radial distance from the origin / center of the calibration wafer to the inner edge of the edge ring 162. The XY coordinate pair of the point where the gap ends at the inner edge of the edge ring can be determined using trigonometric relationships based on the angular position of the radius extending from the center of the calibration wafer to the point where the gap ends at the inner edge of the edge ring 162. In this example, the angular position of this radius is 0 degrees. Thus, the XY coordinates of such a point can be determined as follows. X = (r w + δ x ) sin(θ) Y = (r w + δ x ) cos(θ) where δ x is the associated gap distance, r w is the radius of the calibration wafer, and θ is the angle between the radius extending from the origin of the calibration wafer to the gap and the polar axis extending from the origin.

[0090] Thus, for example, when r w = 150 mm, δ1 = 17.338 mm, δ2 = 22.823 mm, and δ3 = 37.69 mm,

Table 1

[0091] The above dimensions are to scale based on the ratio of FIG. 1, and it will be understood that such values of δ are unrealistically large for typical semiconductor processing tools and wafer handling robots. In reality, the possible values of δ obtained are often, for example, less than approximately 1 mm, such as 800 μm.

[0092] Once the three pairs of XY coordinates are known for locations along the inner edge of the edge ring, the location of the center of the edge ring 162 relative to the origin of the coordinate system (center of the calibration wafer) may be determined using the following equations.

Equation

Equation

[0093] FIG. 2 shows a schematic diagram of an exemplary auto - calibration wafer, with the dashed - line / shaded regions showing the wafer support, the edge ring, and the calibration wafer positioned thereunder. In FIG. 2, an auto - calibration wafer 200 including a substrate 202 is shown, and a plurality of different sensors and other electrical components are attached to the substrate. Also shown in FIG. 2, although not part of the auto - calibration wafer 200, are a calibration wafer 260, an annular edge ring 262, and a wafer support 252. These additional components are shown configured concentrically with the auto - calibration wafer 200, which is the same as in some stages of normal use when the calibration wafer 260, the edge ring 262, the wafer support 252, and the auto - calibration wafer 200 are all centered with respect to each other. In the illustrated example, the auto - calibration wafer 200 is shown as having a diameter larger than that of the wafer support 252, the edge ring 262, and the calibration wafer 260, but in practice, the auto - calibration wafer 200 may be similar in size to the calibration wafer 260. As described above, the wafer support 252 may include a plurality of components, for example, an ESC that is slightly smaller in diameter than the calibration wafer 260, and a support structure that extends beyond the ESC and supports the edge ring 262. For simplicity, such individual structures are not shown in FIG. 2.

[0094] The sensors shown as part of the exemplary auto - calibration wafer of FIG. 2 may include, for example, a plurality of first image sensors 222, which may be, for example, CCD or CMOS devices. The first image sensors 222 may be configured with optical components or other focusing systems and may be configured to provide a downward field of view. As shown in FIG. 2, the field of view 228 of the first image sensors 222 is shown as an elongated rectangular region, which extends across the outer edge of the calibration wafer 260, the inner and outer edges of the edge ring 262, and the outer edge of the wafer support 252 when the auto - calibration wafer 200 is positioned at a predetermined height or height range above the calibration wafer 260, the edge ring 262, and the wafer support 252 (e.g., at a height where the end - effector of the wafer - handling robot would typically be when delivering the wafer to the wafer support 252). Each field of view 228 of the first image sensors 222 may be of various shapes, for example, either circular or elliptical, and may extend radially outward by an amount smaller than that shown. For example, in some implementations, the field of view 228 of the first image sensors 222 may extend only far enough to capture the inner edge of the edge ring 262 but not the outer edge of the edge ring 262. By positioning the first image sensors 222 such that they are generally directly above the outer edge of the calibration wafer 260 and, if used, the inner edge of the edge ring 262, the first image sensors 222 may be positioned to acquire image data that more accurately reflects the size of any gaps that may exist between various reference portions in the image, such as the edges of such components. Specifically, such an arrangement of the image sensors may reduce the effect that height mismatches can have on the determination of the gap size, thereby leading to a more accurate estimation of the gap size.For example, when an image sensor acquires image data of a gap along a line of sight at a very shallow angle with respect to an auto-calibration wafer, such as in the case where the image sensor is attached near the center of the auto-calibration wafer, a slight variation in the height of either the edge ring or the calibration wafer is magnified, and the gap size may vary in an unpredictable manner. Placing the image sensor near the periphery of the auto-calibration wafer may function to significantly reduce the impact that such an influence can have.

[0095] In addition to the first image sensor 222, the auto-calibration wafer 200 may optionally include additional image sensors, such as a centrally located downward-facing second image sensor 224, which may be configured to acquire an image directly beneath the center of the auto-calibration wafer. Such an image sensor may be used in a calibration routine where the fiducial portion to be imaged is located near where the center of the semiconductor wafer is typically placed, for example, to assist in finding the location of the center of the wafer support relative to the auto-calibration wafer. For example, the wafer support that houses the wafer may have a fiducial mark in the form of a crosshair located at the center of the wafer support, which may be imaged by the second image sensor. For example, when the auto-calibration wafer 200 is positioned on the wafer support by the end effector of a wafer handling robot, the wafer support may have a fiducial portion at its center that can be imaged by the second image sensor 224 to facilitate teaching the location of the wafer support to the wafer handling robot. Such sensors can also be used to center the auto-calibration wafer on the end effector of a wafer handling robot. For example, the end effector of the wafer handling robot may include a fiducial portion that is generally positioned at a location observable by the second image sensor 224 when the auto-calibration wafer 200 is generally centered on the end effector. When the wafer handling robot is actuated to remove the auto-calibration wafer, the end effector may be moved beneath the auto-calibration wafer such that the fiducial portion enters the field of view of the second image sensor 224. The second image sensor 224 may then be caused to acquire an image of the fiducial portion, and the image may be analyzed to determine how much the fiducial portion is offset from the center with respect to the center of the auto-calibration wafer 200. The end effector of the wafer handling robot can then be repositioned such that the offset in the centrality of the fiducial portion with respect to the auto-calibration wafer 200 is reduced to an acceptable limit. It will be understood that in other embodiments of the auto-calibration wafer 200 discussed herein, sensors other than image sensors may be used to acquire radial gap data and / or centrality data.For example, an ultrasonic sensor may be used to obtain a contour map that can indicate a three-dimensional reference portion, and the distances and gaps described above may be determined from such contour maps in a manner similar to the method by which such distances and gaps can be determined from image data. Accordingly, it will be understood that any sensor that can be used to evaluate the gap between the reference portions described above and / or the centricity of the automatic calibration wafer 200 with respect to the wafer support may be used in place of the image sensors described above.

[0096] Some embodiments of the automatic calibration wafer 200 may also include various non-image sensors, such as one or more vibration sensors 230, orientation / tilt sensor(s) 232, and / or one or more proximity sensors 234.

[0097] The vibration sensor 230 may be used to monitor vibrations experienced by the auto-calibration wafer during various operations, such as during the operation of a wafer handling robot or during the retraction or extension of lift pins. For example, in some wafer stations, the wafer support may be a pedestal or similar structure and may include a plurality of, e.g., three, lift pins, which may be thin pins that translate vertically relative to an electrostatic chuck (ESC) or other wafer support structure. Such lift pins are typically configured in an equilateral triangle within a circular boundary defined by a semiconductor wafer centered on the wafer support. Thus, when the lift pins are in the extended position relative to the surface of the wafer support, the lift pins support any wafer present at that wafer station. When the lift pins are retracted into the wafer support, the wafer supported by the lift pins contacts the upper surface of the wafer support. During such retraction of the lift pins, the wafer may experience small vibrations, e.g., due to wear of the equipment. The vibration sensor(s) may be used to evaluate the nature of such vibrations and provide an indication of the health of the lift pin mechanism. The vibration sensor may include, for example, an accelerometer, a piezoelectric vibration sensor, an optical distance measurement sensor, or an optical microphone (such sensors may detect vibrations, e.g., by measuring displacement of the substrate of the auto-calibration wafer relative to the wafer support, thereby providing insight into the vibration level experienced by the wafer), and other types of sensors.

[0098] One or more orientation / tilt sensors 232 may be used to evaluate whether the wafer support or other components are supporting the auto-calibration wafer (and thus other wafers) in a horizontal state. For example, if one of the lift pins of the wafer support is shorter or longer than the other lift pins, the wafer supported by the wafer support will exhibit a slight tilt. Such a tilt may cause one side of the wafer to contact the wafer support before the other side of the wafer, thereby causing a slight variation in the state in which the wafer is placed on the wafer support, and in some situations, sliding movement may occur between some of the lift pins and the wafer while the wafer is being placed on the wafer support (this may cause the wafer to be damaged and / or cause particle contamination). In addition, after the auto-calibration wafer is placed on the wafer support, such sensors may be used to evaluate the levelness of the wafer support itself. Thus, an auto-calibration wafer having an orientation sensor may be used to evaluate the levelness of both the wafer support and other equipment. The orientation sensor may include, for example, an accelerometer, and an inclination sensor or an inclinometer.

[0099] FIG. 3 shows a view of a wafer support 352 having an extended lift pin 372 shown as supporting an auto-calibration wafer 300. The lift pin 372 can be retracted downward (and / or the wafer support 352 can be translated upward) to place the auto-calibration wafer 300 on the wafer support 352.

[0100] One or more proximity sensors 234 can be used to evaluate the height of various structures in the wafer station. For example, it may be desirable to evaluate the height of an edge ring or a portion of an edge ring on a wafer support, e.g., on the ESC of the wafer support, around its circumference (a non-uniform height in the circumferential direction of the edge ring may cause or increase process non-uniformities). When the proximity sensor is provided on the auto-calibration wafer and positioned at a location that enables direct or indirect distance measurement between the auto-calibration wafer and the edge ring (or other structure), the data obtained can be used to determine how uniform the height of the edge ring or a portion thereof is around its circumference.

[0101] In other embodiments of the automatic calibration wafer, the automatic calibration wafer may be placed on the edge ring so as to be supported by the edge ring. In some such embodiments, the automatic calibration wafer may have a portion that extends beyond the inner diameter of the edge ring and rests on the uppermost surface of the edge ring (whereas a semiconductor wafer intended to be used with the edge ring is typically completely contained within the inner diameter of the edge ring). However, in other such embodiments, the automatic calibration wafer may be dimensioned to have a diameter similar to the diameter of the semiconductor wafer configured to be used with the edge ring. In some such embodiments, the edge ring may have a stepped inner diameter, for example, the upper surface of the edge ring may have a diameter slightly larger than the diameter of the semiconductor wafer used with the edge ring, and the bottom surface of the edge ring may have a diameter slightly smaller than the diameter of those semiconductor wafers. The resulting shape is an annular recessed surface in the edge ring, which can be used to support the semiconductor wafer during processing. Thus, the automatic calibration wafer supported by such an edge ring may have a small gap between the wafer support that supports the automatic calibration wafer. A proximity sensor can be used to determine the size of this gap at various locations around the circumference of the automatic calibration wafer / edge ring. The resulting measurements can be analyzed to determine variations in flatness or thickness at the portion of the edge ring between the wafer support and the automatic calibration wafer.

[0102] FIG. 4 shows a side view of an auto-calibration wafer having a set of proximity sensors that may be used to determine the height of an edge ring. In FIG. 4, an edge ring 462 is positioned on a wafer support 452. The auto-calibration wafer 400 is positioned to rest on the circumferential ledge of the edge ring 462 and is thus held slightly above the wafer support 452. As can be seen from the figure, the edge ring has a non-uniform height in the ledge region. The right side of the ledge is higher than the left side, such that the auto-calibration wafer 400 has a slight angle with respect to the wafer support 452 and the edge ring 462. Proximity sensors 434 within the auto-calibration wafer 400 may be configured to measure the distance between each proximity sensor 434 and the nearest opposing surface, e.g., the upper surface of the wafer support 452. In this case, the left proximity sensor 434 measures a distance Δ1 and the right proximity sensor 434 measures a distance Δ2. These distances can be evaluated against one or more conditions to determine whether the height of the edge ring exceeds an acceptable value. For example, in some implementations, if |Δ1 - Δ2| > x, or max(Δ1, Δ2) > y, then the edge ring can be considered to have an edge ring height that exceeds a limit and corrective action may be taken, e.g., installation of a new edge ring may be required.

[0103] In some such embodiments, two sets of proximity sensors may be provided on the auto-calibration wafer. One set is positioned to acquire distance measurements between the auto-calibration wafer and the edge ring, and the other set is positioned to acquire distance measurements between the auto-calibration wafer and a structure other than the edge ring, such as a calibration wafer disposed at the center of the edge ring or the surface of a wafer support. In such embodiments, the auto-calibration wafer may be supported, for example, by lift pins or a wafer handling robot and positioned in a location just above the edge ring, and the proximity sensors may be used to acquire distance measurements between the auto-calibration wafer and the edge ring and between the auto-calibration wafer and the other structure. In such embodiments, the auto-calibration wafer is dimensioned larger (or has a portion protruding beyond its diameter) than a typical semiconductor wafer used in semiconductor processing tools, such that the auto-calibration wafer radially overlaps the edge ring with a sufficient margin, enabling the proximity sensors attached to the auto-calibration wafer to radially overlap the edge ring and thus determine the distance between the upward-facing surface of the edge ring and those proximity sensors. Other proximity sensors can be positioned on the auto-calibration wafer to radially overlap the central opening of the edge ring, thereby enabling these proximity sensors to acquire distance measurements between the auto-calibration wafer and, for example, a calibration wafer disposed at the center of the edge ring or, if no such wafer exists, the exposed surface of the wafer support.

[0104] Simultaneous measurements may be acquired from both sets of proximity sensors, and an estimated value of the edge ring height at the location of each proximity sensor may be determined, for example, by subtracting the distance between the auto-calibration wafer / edge ring from the corresponding distance between the auto-calibration wafer / wafer support or auto-calibration wafer / calibration wafer.

[0105] FIG. 5 shows a side view of another auto - calibration wafer having two sets of proximity sensors, each set being located along circular paths of different diameters. In FIG. 5, the auto - calibration wafer 500 is supported above the wafer support 552 and the edge ring 562 by the end - effector 558 of a wafer - handling robot. When the auto - calibration wafer 500 is nominally centered above the edge ring 562, the outermost proximity sensor 534 is located at a radial position that radially overlaps the edge ring 562, and the innermost proximity sensor 534 is located at a radial position that radially overlaps inside the edge ring 562. The proximity sensors 534 are controlled to simultaneously determine the distances, for example, distances Δ 1a , Δ 2a , Δ 1b , and Δ 2b , between the proximity sensors 534 and the surface directly below the proximity sensors, and this can be evaluated to determine whether the height of the edge ring has changed beyond an acceptable range. For example, if |Δ 2a - Δ 2b |>x or max(Δ 2a , Δ 2b )>y, or if |(Δ 1a - Δ 1b )-(Δ 2a - Δ 2b )|>x or max((Δ 1a - Δ 1b ), Δ 2a - Δ 2bIf it is >y, the height of the edge ring can be considered to exceed the acceptable threshold. In some such embodiments, this measurement can be used to activate the edge ring lift pins to adjust the height of the edge ring above the wafer support, e.g., above the ESC, to create a closed-loop system that can maintain the height of the edge ring above the wafer support, e.g., the ESC. A similar approach can be used for the initial calibration of the edge ring lift pins to determine, e.g., what the individual heights of each edge ring lift pin should be in order to flatten the edge ring with respect to the wafer support. For clarity, the wafer support may have multiple sets of lift pins. For example, one set may include lift pins located at locations within the area of the wafer support where the semiconductor wafer will be placed, and another set may include lift pins located outside that area but within the zone of the wafer support occupied by the edge ring. Each set of lift pins may be actuated separately to lift or lower the semiconductor wafer or to lift or lower the edge ring.

[0106] For example, various types of proximity sensors may be used, including capacitive distance sensors, inductive distance sensors, optically based distance sensors, etc. In some cases, the auto-calibrating wafer may also include one or more other types of sensors, such as temperature sensors, pressure sensors, humidity sensors, light sensors, etc.

[0107] The various sensors included in the auto-calibration wafer may be communicatively coupled to a first controller 208 that may include one or more first processors 210 and one or more first memories 212. The first controller 208 may also be electrically connected to a power source 214, such as a battery, a capattery, or other power source. In some embodiments, for example, when the auto-calibration wafer 200 is placed within a docking station, the power source 214 may be operably connected to a charging feature by electrical contact pins positioned at a location aligned with the charging feature of the docking station used, for example, to store the auto-calibration wafer 200. In the embodiment shown in FIG. 2, a wireless charging function 216 is shown, which may be an inductive charging coil, such as a Qi-compatible inductive charging coil, or other suitable wireless charging interface. In such a case, the docking station used to store the auto-calibration wafer 200 may have a similar wireless charging interface configured to charge the auto-calibration wafer 200 when the auto-calibration wafer 200 is placed therein.

[0108] The first controller 208 may also be communicatively coupled to a first wireless communication interface, such as a WiFi, Bluetooth, or other wireless communication interface, whereby commands and / or data may be sent from and / or to the first controller 208, and thus the auto-calibration wafer 200. For example, a semiconductor processing tool that interfaces with the auto-calibration wafer 200 may include a second controller having one or more second processors and one or more second memories. The second controller may be communicatively coupled to a second wireless communication interface, which may then be configured to interface with the first wireless communication interface of the auto-calibration wafer. Thus, the auto-calibration wafer 200 can communicate wirelessly with the semiconductor processing tool, thereby enabling information, commands, and other data to be transmitted between the auto-calibration wafer 200 and the semiconductor processing tool.

[0109] FIG. 6 is a photograph of an exemplary auto - calibration wafer. The auto - calibration wafer 600 includes a substrate 602 having printed circuit traces that provide electrical connections between various components, including a power source 614 which is a rechargeable battery in this example, a processor 610, a memory device 612, and a wireless charging function 616 that can be used to inductively transfer power to the rechargeable battery during wireless charging. Also visible in FIG. 6 are three first image sensors 622 mounted at equally - spaced intervals around the perimeter of the substrate 602, and a second image sensor 224 mounted at the center. In the general vicinity of each of the first image sensors 622, a corresponding proximity sensor 634 is located, which is a capacitive proximity sensor in this example.

[0110] FIG. 7 shows a plan view drawn along the lines of another exemplary auto - calibration wafer 700. In this example, the auto - calibration wafer 700 has a generally circular substrate 702 that has three lobes spaced around its outer perimeter, with each lobe housing a corresponding first image sensor 722. In this example, the substrate 702 generally has the same diameter as a typical semiconductor wafer. The lobes extend beyond this diameter and position the first image sensors 722 such that the photosensitive regions of the first image sensors 722 are centered above the outer edges of a semiconductor wafer placed below, and centered below the auto - calibration wafer 700. The auto - calibration wafer 700 in this example also includes two power sources 714, such as rechargeable batteries, which may be charged using a wireless charging function 716, such as an inductive charging coil. The batteries may supply power to various electrical components of the auto - calibration wafer 700, such as a processor 710, a memory 712, a wireless communication interface 718, the first image sensors 722, the second image sensors 724, the proximity sensors 734, and an accelerometer 736 that can be used as an orientation or tilt sensor.

[0111] Figures 8a-8i illustrate schematic diagrams of a semiconductor processing tool at various stages of using an auto-calibration wafer. Figure 8a shows a portion of the semiconductor processing tool. The illustrated portion of the semiconductor processing tool includes two wafer stations 844a and 844b, although the tool may further include additional wafer stations. Each wafer station corresponds to a location where one or more wafers can be placed during various operations performed by the semiconductor processing tool. The wafer stations can be, for example, but not limited to, within one or more process chambers of the tool, within a buffer used to store wafers before or after processing, within an airlock or load lock that enables transferring wafers between environments with different pressures, a load port, a front-opening unified pod (FOUP) that can dock to the load port, etc. In Figure 8a, wafer station 844a is provided by semiconductor processing chamber 850. In contrast, wafer station 844b is provided by docking station 868 dedicated to storing auto-calibration wafer 800 (however, in some implementations, such a dedicated docking station may not be included). Docking station 868 may have features (not shown) for charging auto-calibration wafer 800, or alternatively, may be configured to interface with various aspects of auto-calibration wafer 800. In some implementations, the docking station may be located within (or attached to) a vacuum transfer module (VTM) and may be accessible by a wafer handling robot within the vacuum transfer module, and then the wafer handling robot may be trained using the auto-calibration wafer. In other implementations, the docking station may be located in an equipment front-end module (EFEM) or other location at or near atmospheric pressure, in which case, the auto-calibration wafer may be first retrieved using a wafer handling robot located within the EFEM and then transferred to another wafer handling robot located within the VTM.

[0112] Each wafer station 844 may have an associated wafer support 852, such as the wafer support 852a / pedestal 854 of wafer station 844a (although no wafer support is shown within wafer station 844b, the wafer station may also have a wafer support, and when an auto-calibration wafer 800 is placed within the wafer station, the wafer support may accommodate the auto-calibration wafer). Optionally, the wafer station may be associated with an Active Wafer Centering (AWC) system 866, which may enable acquisition of measurements of the wafer center location when a wafer is introduced to or removed from the associated wafer station 844. In this example, the AWC system 866 is associated with wafer station 844a and includes two vertically oriented optical beam sensors (represented by dots within the AWC system 866) that may detect when the edge of the wafer crosses either optical beam. As discussed above, the AWC system 866 can be used to determine the center location of a wafer supported by the end effector 858 of the tool's wafer handling robot 856 relative to a particular known reference frame, thereby enabling determination of any positioning corrections that may need to be performed before placing the wafer in the desired location.

[0113] As shown in FIG. 8a, the wafer handling robot 856 supports the edge ring 862 on the end effector 858 in preparation for placing the edge ring 862 on the wafer support 852a / pedestal 854. The auto-calibration wafer 800 is temporarily stored within the wafer station 844b / docking station 868.

[0114] In FIG. 8b, the wafer handling robot 856 is actuated to place the edge ring 862 at a nominally centered location on the wafer support 852a / pedestal 854 and is further actuated to retrieve the auto-calibration wafer 800 from the wafer station 844b / docking station 868.

[0115] In FIG. 8c, the wafer handling robot 856 has finished taking out the auto-calibration wafer 800 from the wafer station 844b / docking station 868, and is preparing to position the auto-calibration wafer on the wafer support 852a / pedestal 854 and the edge ring 862.

[0116] In FIG. 8d, the wafer handling robot 856 extends the end effector 858 to position the auto-calibration wafer 800 on the wafer support 852a / pedestal 854 and the edge ring 862. Thus, the auto-calibration wafer 800 is positioned such that the field of view of the first downward image sensor of the auto-calibration wafer 800, indicated by three dotted rectangles spaced along the outer edge of the auto-calibration wafer 800, includes the edge ring 862 and one or more features of the wafer support 852a / pedestal 854. Next, the second controller 842 causes the first controller of the auto-calibration wafer 800 to acquire, from the first image sensor, image data of a gap, for example, between the inner edge of the edge ring 862 and a reference portion of the wafer support 852a / pedestal 854, such as the outer edge of the ESC of the wafer support 852a. As discussed above, these gaps may be used to determine the amount by which the center of the edge ring 862 is offset with respect to the center of the wafer support 852a / pedestal 854. If this offset exceeds an acceptable threshold, the edge ring may be repositioned to reduce the offset. In this example, the edge ring 862 is positioned acceptably, and the wafer handling robot 856 may remove the auto-calibration wafer 800 from the wafer station 844a and return it to the wafer station 844b, as shown in FIG. 8e.

[0117] In FIG. 8f, the wafer handling robot is actuated to retrieve the calibration wafer 860, which may also be stored within the docking station 868, for example, below or above the automatic calibration wafer 800, or may be obtained from a completely different location, such as a load lock or an airlock. The calibration wafer 860 may then be placed within the wafer station 844a / semiconductor processing station 850 and transferred to the wafer support 852a / pedestal 854 so as to be nominally centered with respect to the center of the edge ring 862, as shown in FIG. 8g.

[0118] In FIG. 8h, the wafer handling robot is actuated again to remove the automatic calibration wafer 800 from the wafer station 844b / docking station 868. In FIG. 8i, the wafer handling robot is further actuated to position the automatic calibration wafer 800 over the wafer support 852a / pedestal 854, the calibration wafer 860, and the edge ring 862. Similar to FIG. 8d, the automatic calibration wafer 800 may then be controlled to acquire image data of the gap, such as gap 864, between the edge ring 862 and the calibration wafer 860, thereby making it possible to determine any offset between the center of the calibration wafer 860 and the center of the edge ring 862.

[0119] Various techniques that can be implemented using an automatic calibration wafer, as discussed above, will be examined in more detail below with reference to FIGS. 9 - 14.

[0120] FIG. 9 shows a flowchart of a method for determining the location of a reference point of a structure in a wafer station using an auto-calibration wafer. Such a method may be used, for example, when teaching a wafer handling robot the various locations where a wafer can be placed (or retrieved). In block 902, an auto-calibration wafer may be retrieved using the end effector of the wafer handling robot. In block 904, the auto-calibration wafer may be centered on the end effector of the wafer handling robot (in some implementations, blocks 902 and 904 may be performed simultaneously). For example, the auto-calibration wafer may be placed on the end effector such that the center of the auto-calibration wafer (or another known reference point on the auto-calibration wafer) is centered on a known reference point of the end effector, thereby establishing the spatial relationship between the two reference points and enabling the measurements obtained using the auto-calibration wafer to be mapped or transformed into the coordinate system used by the wafer handling robot.

[0121] Such an arrangement of the auto-calibration wafer on the end effector can be achieved by any suitable mechanism, including the use of physical index features or other contact-based techniques that ensure the auto-calibration wafer is properly positioned on the end effector. However, in some cases, instead, the imaging function of the auto-calibration wafer itself may be used to reliably center the auto-calibration wafer on the end effector. For example, immediately prior to loading the auto-calibration wafer onto the end effector, the auto-calibration wafer may be positioned on the end effector, and one or more image sensors of the auto-calibration wafer may be activated to acquire an image of the end effector or the end effector area. The imaged portion of the end effector may include a reference portion that defines, for example, a reference point on the end effector, such as a location on the end effector that coincides with the XY center point of a theoretically perfect semiconductor wafer perfectly placed on the end effector. This image data may then be analyzed to determine the extent to which a reference point of the auto-calibration wafer, such as the center of the auto-calibration wafer, is offset from the reference point / reference portion of the end effector. The wafer handling robot may then be actuated to move the end effector to reduce or cancel this offset before the auto-calibration wafer is placed on the end effector, thereby centering the auto-calibration wafer on the end effector.

[0122] In block 906, for calibration, a wafer station may be selected for determining a reference point, for example, on a structure of the wafer station, such as a wafer support, at which the center of a wafer delivered to the wafer station is intended to be located. In block 908, a wafer handling robot may be actuated so that an end effector and an auto-calibration wafer are positioned over the selected wafer station such that, for example, the auto-calibration wafer is generally centered over a reference point of the wafer support of the selected wafer station. Such initial positioning can be based on, for example, an estimation of the location of the reference point of the wafer support determined based on the designed locations of various components in the system, which can generally enable, in most cases, an alignment accuracy within 1 millimeter or within a few millimeters.

[0123] In block 908, image data of the reference portion(s) on a target structure located at the selected wafer station may be acquired by the auto-calibration wafer. The reference portion(s) may be associated with, for example, a reference point of the wafer station at which the center of a wafer delivered to the wafer station is intended to be located. For example, an outer edge of an ESC of a wafer support at the selected wafer station may function as a reference portion. Such a reference portion may not directly indicate the reference point of the wafer station, but can still be clearly defined. For example, a circular or arcuate edge of the ESC may define a center point that functions as a reference point. In another example, the wafer support may include a certain reference portion that directly marks the reference point, such as an etched “+” or other marking, for example, the center of the wafer support can be used as the reference point, and the intersection of the two lines in the “+” can indicate the reference point.

[0124] In block 912, the location of the reference point of the selected wafer station structure, such as the wafer support, for the auto-calibration wafer may be determined based on the image data of the reference portion. For example, the image data may indicate that the reference point of the structure has an XY offset of (0.3 mm, 0.5 mm) in the coordinate system of the auto-calibration wafer, for example, from the reference point of the auto-calibration wafer, for example, from the center of the auto-calibration wafer.

[0125] Next, in block 914, the location of the reference point of the structure may be determined relative to the coordinate system of the wafer handling robot. For example, the XY offset determined relative to the coordinate system of the auto-calibration wafer in block 912 may undergo a coordinate system transformation to be converted to equivalent coordinates in the coordinate system of the wafer handling robot, for example, to account for the expected angular misalignment between the coordinate system of the auto-calibration wafer and the coordinate system of the wafer handling robot.

[0126] When the calibration method of FIG. 9 is used, in some cases, it may be desirable to calibrate the auto-calibration wafer before implementing this method. For example, it may be desirable to establish the position of the image sensor(s) used to acquire image data relative to the reference point, such as the center point, of the auto-calibration wafer, so that the location information determined from such sensor(s) is properly processed. Each image sensor may be considered to provide XY location data (based on the rectangular or linear array of pixels that each such sensor may have) in a coordinate system that is specific to each image sensor and that is offset by a specific XY distance and / or rotation angle from the reference point of the auto-calibration wafer. By calibrating the auto-calibration wafer, it becomes possible to determine such XY and angular offsets for each image sensor with respect to the coordinate system. Then, any location subsequently determined from the image sensor data may then be appropriately transformed to accurately position relative to the coordinate system of the reference point of the auto-calibration wafer.

[0127] In such an example of calibration, the auto-calibration wafer may be placed within a fixture having index pins or other alignment features. The index pins or other alignment features contact the outer edge of the auto-calibration wafer and physically constrain the auto-calibration wafer to be centered over the reference portion. The reference portion is part of the fixture and is known to be centered relative to the constrained outer edge of the auto-calibration wafer. Once the auto-calibration wafer is mounted within the fixture and centered over the reference portion, an image sensor mounted at the center may acquire an image of the reference portion. Then, for example, it may be determined which pixel(s) coincide with the center point indicated by the reference portion, thereby providing information that can be later used to transform any location data obtained from the image of the image sensor mounted at the center into a coordinate system associated with the reference point. A similar reference portion may be provided within the fixture at a location that coincides with the field of view of other image sensors, enabling calibration of all image sensors prior to use.

[0128] FIG. 10 shows a flowchart of a method for determining the relative positioning of two structures in a wafer station using an auto-calibration wafer. The method of FIG. 10 begins at block 1002, where an auto-calibration wafer is retrieved from, for example, a docking station or other holding area used to store the auto-calibration wafer, using a wafer handling robot of a semiconductor processing tool. At block 1004, a wafer station of the semiconductor processing tool may be selected for calibration. The structures for which relative positioning is to be determined are assumed to already be located at the selected wafer station. For example, the selected wafer station may have an edge ring (the first structure) disposed on, for example, a wafer support (the second structure).

[0129] In block 1006, the wafer handling robot may be actuated to position the auto-calibration wafer on the wafer support of the selected wafer station. The wafer handling robot may be positioned, for example, such that the auto-calibration wafer is nominally centered above the wafer support / edge ring of the selected wafer station, such that a first image sensor is positioned along the outer periphery of the auto-calibration wafer in a manner that enables the acquisition of images of reference portions of two structures, such as the inner edge of the edge ring and the edge of a feature of the wafer support, such as the outer edge of the ESC of the wafer support, above the edge ring and the wafer support. In block 1008, the auto-calibration wafer may be caused to acquire such images. In block 1010, the images may be analyzed to determine, for example, the gap size between the reference portions in each image. For example, an edge detection algorithm may be used to identify the inner edge of the edge ring and the edge of the wafer support in each image, and the relative distance of the gap between each pair of edges may be determined. The determined gap between each pair of edges can be estimated based on the assumed vertical distance between the first image sensor and the imaged structure. Such estimates may be somewhat inaccurate, but are typically scaled similarly in each image. When the reference portions for each structure are located along a common reference circle, for example, the arcuate outer edge or inner edge (or its single circular edge) of the edge ring, all of which are in the same radial direction relative to each other, can function as a reference portion for the edge ring, and the arcuate edge (or its single circular edge) of the wafer support, all of which are in the same radial direction relative to each other, can function as a reference portion for the wafer support. It will be understood that other reference portions can be used for a similar effect and that the techniques discussed herein are generally applicable to any suitable reference portions and applicable algorithms and can determine the relative offset between such structures based on the selected reference portions.

[0130] In block 1010, a determination may be made regarding the offset between both reference points, e.g., structures, based on the relative gap size between the imaged reference portions of the two structures. Such an offset can be compared to a threshold offset to examine whether the deviation in centrality of the two structures is within an acceptable range. Such a threshold offset can be established based on the non-uniformity requirements of a particular semiconductor processing technique. If the measurement value of non-centrality is not within the acceptable range, appropriate actions may be taken. For example, one of the structures may be repositioned based on the measured central offset, and this procedure may be repeated until the measurement value of non-centrality is within the acceptable range.

[0131] FIG. 11 shows a flowchart of a method for determining the location of the center point of a wafer support using an auto-calibration wafer. In block 1102, the auto-calibration wafer may be retrieved using the end effector of a wafer handling robot. In block 1104, the position of the auto-calibration wafer relative to the wafer handling robot end effector may be determined. Blocks 1102 and 1104 may, in some cases, be executed in tandem. For example, the wafer handling robot may be controlled (as previously described herein) to pick up the auto-calibration wafer with the end effector such that the auto-calibration wafer is centered on the reference point of the end effector, and thus the position of the auto-calibration wafer relative to the end effector is established.

[0132] In block 1106, a wafer station may be selected to determine the center point of its wafer support. In block 1108, the wafer handling robot is actuated to position the auto-calibration wafer on the wafer support of the selected wafer station, e.g., at a default center location associated with that wafer station.

[0133] In block 1110, image data of the reference part(s) of the wafer support may be acquired using, for example, one or more image sensors of an auto-calibration wafer. Such a reference part may be, for example, an etched pattern located at the center of the wafer support. Alternatively, the reference part may be a circular edge that defines the center point of the wafer support of a part of the wafer support, for example, a part of an ESC that is part of the wafer support. In the former case, the reference part may be imaged using an image sensor located near or at the center of the auto-calibration wafer. In the latter case, the reference part may be imaged using an image sensor located near the outer edge of the auto-calibration wafer.

[0134] In block 1112, the image data may be analyzed to determine an offset between a reference point of the auto-calibration wafer, such as the center point, and a reference point of a selected wafer station defined by the reference part. In block 1114, the offset determined in block 1112 may be converted into the coordinate system of the wafer handling robot. Optionally, to account for the offset determined in block 1114, the “default” location corresponding to the center of the selected wafer support may be updated (alternatively, the default location may be left as is and adjusted based on the offset for each subsequent wafer placement at that wafer station). In some implementations, the wafer handling robot may then be actuated to shift the auto-calibration wafer so that the auto-calibration wafer center is positioned at the updated center location with respect to the wafer support (similar to block 1108). In such implementations, blocks 1110 - 1114 may be repeated as necessary to confirm that the updated centered position is properly centered. If the updated default location (or correction of the default location) is found to produce an inter-center offset that is still not within acceptable limits, this process may be repeated one or more times.

[0135] The above discussion has focused on using an auto-calibration wafer to determine the absolute location of the center of a wafer support or other structure in the coordinate system used by a wafer handling robot. However, as further explained below, an auto-calibration wafer may be used to determine the relative positioning between two components.

[0136] FIG. 12 shows a flowchart of a method for calibrating the placement of an edge ring on a wafer support. In block 1202, the wafer handling robot of a semiconductor processing tool may be actuated to cause the wafer handling robot to remove the edge ring from a wafer station. In block 1204, the wafer handling robot may be further actuated to place the edge ring on a wafer support, such as a pedestal, of a selected wafer station of the semiconductor processing tool. Blocks 1202 and 1204 may be optional. This is because the edge ring may have been manually placed or installed on the wafer support, or may have been previously placed or installed on the wafer support, for example, during another operation phase.

[0137] In block 1206, the wafer handling robot may be controlled to cause the wafer handling robot to retrieve an auto-calibration wafer from a docking station or other location. In block 1208, the wafer handling robot may be further actuated to position the auto-calibration wafer at a location on the wafer support (and the edge ring positioned thereon) of the selected wafer station.

[0138] Once positioned on the wafer support of the selected wafer station, in block 1210, the auto-calibration wafer may be caused to acquire image data of the gap between the inner edge of the edge ring and the outer edge of a feature of the wafer support (or other reference portion), such as the outer edge of an ESC that is part of the wafer support, using an edge camera of the auto-calibration wafer, such as a first image sensor.

[0139] In block 1212, an estimated offset between the center of the edge ring and the center of the wafer support may be determined based on the relative size of gaps between reference portions within the image. In block 1214, a determination may be made as to whether the estimated edge ring / wafer support offset exceeds a predetermined threshold offset. If the estimated edge ring / wafer support offset exceeds the predetermined threshold offset, the method may proceed to block 1216, where the wafer handling robot is actuated to remove the auto-calibration wafer from a position above the wafer support and return it, for example, to a docking station (or some other temporary holding location). Next, in block 1218, the wafer handling robot is actuated to remove the edge ring from the wafer support of the selected wafer station. For example, lift pins may be used to lift the edge ring from the wafer support such that the end effector of the wafer handling robot can be inserted beneath the edge ring, and then the lift pins may be retracted into the wafer support to lower the edge ring onto the end effector.

[0140] In block 1218, after removing the edge ring from the wafer support using a wafer handling robot, the wafer handling robot may be further controlled to relocate the edge ring on the wafer support to a new location taking into account the offset of the edge ring, such that the edge ring and the wafer support are more accurately centered with respect to each other. After block 1218, the method may return to block 1206 and a further evaluation of the edge ring / wafer support center offset may be made. Optionally, this part of the method may be repeated for a threshold number of times, or until the estimated center offset between the edge ring and the wafer support falls within a predetermined threshold offset. In block 1214, if it is found that the estimated edge ring / wafer support offset is within a predetermined threshold offset, the method may proceed to block 1222 where it may be considered that the calibration of the edge ring placement is complete.

[0141] It will be appreciated that the evaluation of the relative offset between two structures using an auto-calibration wafer can be achieved without precise positioning of the auto-calibration wafer with respect to the end effector of the wafer handling robot, or even without knowledge of such precise positioning. In particular, the method discussed herein may be used when the auto-calibration wafer is sufficiently centered on the end effector such that the field of view of the first image sensor of the auto-calibration wafer can image various gaps between reference portions of the two structures. It will also be understood that a similar method may be used to center other components with respect to the wafer support, for example, to center the calibration wafer with respect to the wafer support.

[0142] Once an edge ring is properly positioned on a wafer support, the edge ring can typically maintain its position over multiple wafer processing operations. However, with respect to centering a calibration wafer, the calibration wafer only functions as a substitute or proxy for the wafers that will be positioned in future operations. Thus, using the automated calibration wafer techniques discussed herein, once a calibration wafer is centered on a desired structure, such as a wafer support or an edge ring, the calibration wafer can be removed from the centered location using a wafer handling robot and used to teach an Active Wafer Centering (AWC) system, which can then "learn" the desired center point of the calibration wafer with respect to the end effector for the motion path of a given wafer handling robot. Then, to determine the offset between the center point of such a wafer and the learned center point, the AWC system can be used to evaluate the future placement of the wafer onto the end effector of the wafer handling robot. The wafer handling robot can then be actuated so that the wafer is positioned on the wafer support in a manner corresponding to this determined offset. While an edge ring may generally maintain a predetermined position over multiple processing operations, an edge ring may sometimes be replaced, and it will be understood that a similar AWC technique as discussed above may be implemented to compensate for any misalignment between such an edge ring and the end effector during the placement of such a subsequent edge ring.

[0143] Using the techniques discussed herein, the relative offset between two movable components, such as an edge ring and a wafer, may be determined. As an example, FIG. 13 shows a flowchart of a technique for calibrating the placement of a wafer relative to an edge ring on a wafer support.

[0144] In block 1302, a wafer station of a semiconductor processing tool may be selected in block 1302. Similar to the method of FIG. 12, in block 1304, an edge ring is placed on the wafer support of the selected wafer station, and then in block 1306, the edge ring may be centered on the wafer support, for example, using the centering method discussed above with respect to FIG. 12. Blocks 1304 and 1306 may be optional. The edge ring may also be placed on the wafer support of the selected wafer station by other means, such as manual placement, or may already be placed on the wafer support before selecting the selected wafer station.

[0145] In block 1308, the wafer handling robot may be caused to retrieve a calibration wafer, for example, an unprocessed or dummy wafer having the same size and thickness as the wafer for processing, from a storage location. In block 1310, the wafer handling robot may transfer the calibration wafer to the wafer support of the selected wafer station such that the center of the calibration wafer is nominally centered on the center of the edge ring.

[0146] In block 1312, the wafer handling robot may be controlled to retrieve an auto-calibration wafer from a storage location such as a docking station or another location accessible to the wafer handling robot. In block 1314, the wafer handling robot may be controlled to position the auto-calibration wafer on the wafer support of the selected wafer station such that the auto-calibration wafer is generally centered on the center point of the calibration wafer and / or the edge ring. In block 1316, the auto-calibration wafer may be controlled to cause an edge camera of the auto-calibration wafer, for example, a first image sensor, to acquire image data of the gap between the edge ring and the calibration wafer.

[0147] In block 1318, the image data may be analyzed to determine a wafer / edge ring offset between the inner diameter of the edge ring and the outer diameter of the calibration wafer based on the relative gap size within the image. In block 1320, a determination may be made as to whether the wafer / edge ring offset exceeds a predetermined threshold offset. If so, the method may proceed to block 1322, where the wafer handling robot is actuated and the auto-calibration wafer may be returned to the docking station (or other temporary holding location), and then proceed to block 1324, where the wafer handling robot is further actuated and the calibration wafer may be removed from the wafer support of the selected wafer station. For example, the lift pins for the wafer support may be controlled to lift the calibration wafer from the edge ring so that the end effector of the wafer handling robot can be positioned below the calibration wafer. Once so positioned, the lift pins may be further controlled to lower the calibration wafer onto the end effector.

[0148] In block 1326, the wafer handling robot is actuated so that the calibration wafer center is repositioned on the wafer support of the selected wafer station to a new location considering the wafer / edge ring offset determined at block 1318. The method may then return to block 1312 and initiate an imaging operation of a further auto-calibration wafer for the gap size between the calibration wafer and the edge ring. This repositioning and reanalysis of the calibration wafer and edge ring centrality may be performed multiple times, for example, until the determined wafer / edge ring offset is below a predetermined threshold or until such a repetition occurs a predetermined number of times. In block 1320, if it is determined that the wafer and the edge ring are sufficiently centered with respect to each other, i.e., the determined wafer / edge ring offset is within a predetermined threshold, the method may proceed to block 1328, where it may be considered that the calibration of the wafer / edge ring placement is complete. At this point, the calibration wafer is removed from the wafer station using the wafer handling robot and may be used, for example, for training an active wafer centering system. This is, for example, the same method as when a calibration wafer manually centered with respect to the wafer support using a fixture or other mechanical centering system is used. Training of an active wafer centering system based on a centered wafer or based on a wafer placed in another way on the end effector of the wafer handling robot in a calibrated wafer is well known in the industry and is not described in detail in the present disclosure for the sake of brevity.

[0149] It will be understood that the above-described methodology can be implemented in a variety of different ways to achieve similar results. For example, in a tool having a plurality of wafer handling robots, or a wafer handling robot having a dual arm / end effector, one arm / end effector of a wafer handling robot can be used to place or relocate an object, such as a calibration wafer and / or an edge ring, onto a wafer support, while the other arm / end effector of the wafer handling robot can be used to hold the automatic calibration wafer. Thus, for example, a first arm can be used to place an edge ring onto a wafer support and then retract, and then a second arm can move an automatic calibration wafer over the placed edge ring to obtain a measurement of the center-to-center offset between the edge ring and the wafer support. The second arm can then be retracted, and if necessary, the edge ring can be lifted from the wafer support, for example using lift pins, and the first arm can be used to relocate the edge ring to correct the center-to-center offset between the edge ring and the wafer support. The first arm can then be withdrawn, and the second arm can move the automatic calibration wafer over the edge ring and the wafer support again to obtain a second measurement of the center-to-center offset. This process can be repeated as necessary until the desired amount of center-to-center offset between the edge ring and the wafer support is achieved.

[0150] The placement of a wafer and / or an edge ring onto a wafer support guided by an auto-calibration wafer is an iterative process in which an estimate of the relative offset between two structures, e.g., a wafer and a wafer support, an edge ring and a wafer support, or an edge ring and a wafer, is obtained using the auto-calibration wafer, and then that estimate is used to guide the repositioning of one of the two structures relative to the other structure which may remain stationary. It will be further understood that such placement and evaluation assisted by an auto-calibration wafer may generally be repeated until the measured offset falls within a predetermined maximum allowable offset for a given set of components of a given semiconductor processing tool. When both the edge ring and the calibration wafer are subject to a centering operation using the auto-calibration wafer, further evaluation may be made of the relative center offset between any pair of the three components (edge ring, wafer support, and calibration wafer) that are not directly centered with respect to each other. For example, if the edge ring is centered with respect to the wafer support and then the calibration wafer is centered with respect to the edge ring, the calibration wafer will not be directly centered with respect to the wafer support (it will only be indirectly centered via the centering of the edge ring). In such an embodiment, the auto-calibration wafer may additionally be used to evaluate the centricity of the calibration wafer with respect to the wafer support. In some such embodiments, the predetermined threshold offset for each pair of structures may be selected such that two of the three center-to-center offsets can be within the corresponding predetermined threshold offset while the third center-to-center offset may actually exceed the corresponding predetermined offset. (Of course, it is also possible to select a predetermined threshold offset such that this scenario does not occur, but this may, in some cases, allow an unacceptable process uniformity or may require some of the predetermined thresholds to be made smaller than generally necessary, thereby increasing the number of centering iterations that may have to be performed.)Generally speaking, in such embodiments, the threshold offset may typically be selected such that the scenario of 2 successes out of 3 / 1 failure out of 3 is avoided in most cases with respect to compliance of the threshold offset. However, for example, if the edge ring is positioned relative to the wafer support at the limit of the offset of a particular edge ring / wafer support in a particular direction, and the calibration wafer is positioned relative to the edge ring at the limit of the offset of a particular wafer / edge ring in the same direction, the calibration wafer will have a maximum center-to-center offset from the wafer support that can exceed the maximum center-to-center offset specific to the calibration wafer / wafer support.

[0151] In such embodiments, if the scenario of 2 successes out of 3 / 1 failure out of 3 occurs, the semiconductor processing tool may take various corrective measures. For example, in some embodiments, the controller of the semiconductor processing tool may cause the wafer handling robot to remove one or both of the calibration wafer and the edge ring, and then reposition them using a more precise corresponding predetermined threshold offset, for example, for placement, using a method similar to that described above.

[0152] It will also be understood that some semiconductor processing tools may perform both the placement / centering operations of the calibration wafer and the edge ring by using an auto-calibration wafer to center both components relative to the wafer support (instead of centering the edge ring relative to the wafer support and the calibration wafer relative to the edge ring, or vice versa).

[0153] Once the calibration wafer is centered on the wafer support or on an edge ring centered on the wafer support and then used to train the active wafer centering system, the trained active wafer centering system is optionally tested using the self - calibration wafer to ensure that the trained active wafer centering system will provide a reliably centered wafer placement. FIG. 14 shows a flowchart of such a method for verifying the reproducibility of wafer placement (the method of FIG. 14 is intended to be practiced after the active wafer centering system has already been trained). This method assumes that the active wafer centering system has been trained with a wafer centered on the wafer support, but with appropriate modifications, it may also be used with an active wafer centering system trained using, for example, a wafer centered on an edge ring.

[0154] In block 1402, a wafer station of the semiconductor processing tool may be selected. The selected wafer station will have, for example, a calibration wafer previously centered on the wafer support using the method discussed above, and the active wafer centering system associated with that wafer station will be trained based on the centered location of that calibration wafer. In block 1404, the controller of the semiconductor processing tool may cause the wafer handling robot of the semiconductor processing tool to retrieve the calibration wafer from the holding station of the semiconductor processing tool, for example, from a buffer, FOUP, or other location. In block 1406, the wafer handling robot may be controlled so that the calibration wafer is placed on the wafer support of the selected wafer station.

[0155] After placing the calibration wafer on the wafer support, at block 1408, the wafer handling robot may retrieve the automatic calibration wafer from, for example, a docking station or other storage location. At block 1410, the wafer handling robot may be actuated so that each of the first image sensors of the automatic calibration wafer has the edge of the calibration wafer and the edge of the wafer support within its field of view, and the automatic calibration wafer may be positioned on the calibration wafer and the wafer support of the selected wafer station.

[0156] At block 1412, the automatic calibration wafer may be caused to acquire image data of the gap between the edge of the calibration wafer and the edge of the wafer support, and at block 1414, a determination may be made regarding the offset between the center of the wafer support and the center of the calibration wafer. This offset may be saved for later reference. At block 1416, counter X may be incremented to X+1, and at block 1418, it may be determined whether X exceeds a given threshold value Y. X may represent the number of test arrangements implemented as part of the method, and Y may represent the total number of test arrangements to be implemented as part of the method.

[0157] In block 1418, if it is determined that X is not greater than Y, the method may proceed to block 1420 before returning to block 1404. In block 1420, the calibration wafer may be returned to its original location or another location within the holding station with a randomized offset, and then, in block 1422, the wafer handling robot is returned to the default or "home" position. The randomized offset may be selected to be within the typical expected offset of the wafer under normal operating use, for example, an offset of less than 0.8 mm. Thus, in block 1404, when the calibration wafer is retrieved again by the wafer handling robot (the wafer handling robot is typically returned to the same position each time to retrieve the calibration wafer), the calibration wafer will have a correspondingly randomized offset position with respect to the end effector of the wafer handling robot. It will also be understood that the randomization of the wafer placement may alternatively occur at other times, for example, immediately before retrieving the calibration wafer from the holding station or another location, and a randomized displacement may be imparted to the wafer handling robot such that the position of the calibration wafer with respect to the end effector is similarly randomized. Such randomization may serve to represent a slight misalignment of the wafer placed within the holding station during normal operation.

[0158] In block 1418, if it is determined that sufficient test wafer placement has been performed, the method may proceed to block 1424, where the center offset may be evaluated or analyzed for Y wafer placements. Such an analysis may include any of a variety of different analysis techniques or tests. For example, the statistical parameters of the captured population of test wafer center offsets may be determined and compared to corresponding threshold values. For example, the mean, median, and standard deviation of the offsets may be determined and evaluated against the threshold values corresponding to such values to determine whether acceptable consistency of the test method and wafer placement has been obtained. In block 1426, it may be determined whether the test has been successful, where the offsets are compared against their threshold values (or more precisely, the statistical parameters derived from the offsets may be compared to their corresponding threshold values). If the comparison in block 1426 indicates that one or more acceptable parameters have been exceeded, the method may proceed to block 1428, where an error state may be generated. If the comparison in block 1426 indicates that all of the one or more parameters are within the acceptable range, the method may proceed to block 1430, where the method may complete normally.

[0159] To evaluate the reproducibility of the edge ring placement, it will be understood that a similar approach may also be performed using the edge ring, for example, by repeating the edge ring placement and randomizing the end effector / edge ring offset between each placement.

[0160] FIG. 15 shows a flowchart of a method for evaluating the height of an edge ring. In block 1502, a wafer station of a semiconductor processing tool may be selected. The selected wafer station should already have an edge ring at a predetermined position on the wafer support. For example, the method of FIG. 15 may be performed at regular intervals during a processing operation using the edge ring that remains at a predetermined position on the wafer support during such an operation, and as a result of repeated exposure to the semiconductor wafer processing cycle, it may be determined whether the edge ring has deteriorated non-uniformly (or to an unacceptable extent regardless of uniformity).

[0161] In block 1504, an auto-calibration wafer may be removed by a wafer handling robot and then delivered to the wafer support of the selected wafer station. Such delivery of the auto-calibration wafer to the wafer support may include, for example, lifting the calibration wafer from the wafer handling robot using lift pins and then lowering the auto-calibration wafer onto the edge ring by retracting the lift pins, thereby placing the auto-calibration wafer directly on the edge ring.

[0162] In block 1508, a proximity sensor of the auto-calibration wafer may be used to obtain a distance measurement value between the auto-calibration wafer and the wafer support for the auto-calibration wafer. In some implementations, such distance measurement values may typically be obtained using proximity sensors located at at least three locations around the circumference of the auto-calibration wafer, thereby enabling determination of the orientation of the plane defined by the auto-calibration wafer with respect to the plane defined by the upper surface of the wafer support. If the distance between the two planes exceeds a specific threshold at any point centered on a circle of a diameter that is at or near the inner diameter of the edge ring and centered on the edge ring, this may indicate that the thickness of the edge ring is out of the allowable range and that the edge ring needs to be replaced.

[0163] In block 1510, an auto-calibration wafer may be removed from the wafer support using a wafer handling robot. In block 1512, the obtained distance measurements may be evaluated, and it may be determined whether the measured distance indicates that the edge ring is within an acceptable height limit or not. For example, if any of the proximity distances falls below (or above) a predetermined threshold, this may indicate that the height of the edge ring is too small (or too large). Another metric that may be used to evaluate the height of the edge ring is the variation between different distance measurements. For example, for a given measurement cycle using an auto-calibration wafer, the difference between the maximum distance measurement to an edge ring and the shortest distance measurement to that edge ring may be compared to another predetermined threshold to determine whether the change in the height of the edge ring around the circumference of the edge ring is an unacceptable amount. In block 1512, if the distance measurements are determined to be within an acceptable range, the method may proceed to block 1516, where a success condition may be determined. In block 1512, if the distance measurements are determined not to be within an acceptable range, the method may proceed to block 1514, where a defect or fault condition may be generated. Such a condition may cause the semiconductor processing tool to stop further processing operations at that wafer station until a new edge ring is attached, centered, and height measurements are performed.

[0164] As described above, in some implementations, an auto-calibration wafer may also be used to determine dynamic characteristics of a semiconductor processing tool, such as the vibration and tilt of lift pins. FIG. 16 shows a flowchart of a method for evaluating the vibration of lift pins.

[0165] The method of FIG. 16 may start at block 1602, where a wafer station for vibration evaluation of lift pins may be selected. At block 1604, the wafer handling robot may be actuated to remove an auto-calibration wafer from a storage location such as a docking station. At block 1606, the auto-calibration wafer may be positioned on the wafer support of the selected wafer station, and then the auto-calibration wafer may be lifted from the end effector of the wafer handling robot by the lift pins of the wafer support. At block 1608, acquisition of vibration data from the vibration sensor of the auto-calibration wafer may be started by the auto-calibration wafer. It will be understood that such data may also be acquired earlier than this, or continuously, in some implementations. At block 1610, the lift pins may be actuated to move the auto-calibration wafer, for example, in a direction perpendicular to the wafer support. In some implementations, such movement may include lowering the auto-calibration wafer onto the wafer support and then lifting it again, as a semiconductor wafer would typically experience during normal wafer placement operations. In other implementations, the lift pins may be actuated in a manner that does not correspond to normal wafer placement movements, but may be designed to be more likely to induce a specific vibration response. In any case, the auto-calibration wafer is subjected to movement by the actuation of the lift pins, and the vibration data may be collected by the vibration sensor(s) during such movement.

[0166] In block 1612, the wafer handling robot may be controlled to remove the auto - calibration wafer from the lift pins. In block 1614, vibration data may be analyzed to determine whether it is within an acceptable range. For example, if the magnitude of the vibration exceeds a predetermined threshold, or if the magnitude of a specific frequency component of the vibration exceeds a predetermined threshold, it may be determined that the vibration measurement value exceeds the tolerance limit, and the present method may proceed to block 1618, where a fault condition may be generated. The duration of the lift pin movement at each stage of the lift pin movement is also measured and compared with the acceptable range to determine whether there is a fault condition in the lift pin mechanism. In such a case, for example, until the lift pin mechanism is serviced and the problem is solved, the semiconductor processing tool may temporarily stop the wafer processing operation using that wafer processing station. When the lift pin mechanism is controlled via an actuator, a closed - loop system can be implemented to automatically calibrate the lift pin mechanism using the vibration data. In some embodiments, the semiconductor processing tool may generate a warning that the lift pin mechanism requires maintenance or repair, but the semiconductor processing operation at that wafer station may continue (and the lift pin mechanism may be used) until subsequent vibration evaluation of the lift pin indicates that the vibration occurring during the operation of the lift pin exceeds a second set of acceptable limits. In some such embodiments, the semiconductor processing tool may operate the lift pin mechanism at a reduced performance level, for example, at a slower speed compared to the normal speed of the lift pin mechanism, after encountering a fault condition, in order to potentially reduce the magnitude of the vibrations it will experience. Such a throughput - reduced operation may continue until the lift pin mechanism is serviced and the problem is solved, or until the vibration generated by the operation of the lift pin mechanism deteriorates to an unacceptable level, in which case the use of that wafer station and the lift pin mechanism may be interrupted until maintenance is performed.The vibration data of the lift pin mechanism may be transmitted to a data center outside the tool having big data and machine learning capabilities, and this data center may receive vibration data from a number of similar semiconductor processing tools to establish normal or abnormal lift pin signatures regarding the vibration of the lift pin. In such a case, raw vibration data or vibration signatures (after machine learning feature extraction) may be transmitted to the data center. The data center may use the vibration data received across the population of semiconductor processing tools to train a machine learning model, such as a neural network, tensorflow, etc., to classify the lift pin mechanism as normal or abnormal.

[0167] Another test method that can be implemented with an auto-calibration wafer is to assess the levelness of the wafer support (or other equipment, such as the end effector of a wafer handling robot, lift pin mechanism, load port module (LPM), wafer support, ESC, etc.). FIG. 17 shows a flowchart of a method for evaluating the levelness of a wafer support, and this method can be practiced for various different wafer handling components.

[0168] In block 1702, a wafer station of a semiconductor processing tool may be selected for measurement of the levelness of its wafer support.

[0169] In block 1704, the semiconductor processing wafer handling robot may be made to retrieve the auto-calibration wafer from a docking station or other storage location, and in block 1706, the wafer handling robot may be controlled such that the auto-calibration wafer is placed directly on the wafer support. If an edge ring is present on the wafer support and prevents the direct placement of the auto-calibration wafer on the wafer support, the edge ring may be removed, for example, using the semiconductor processing tool's wafer handling robot, before placing the auto-calibration wafer on the wafer support.

[0170] Once the auto-calibration wafer is placed on the wafer support, in block 1708, the auto-calibration wafer may be caused to obtain a level measurement value using an orientation sensor such as a speedometer or an inclination sensor. In some embodiments, multiple level sensors may be utilized to obtain such measurement values.

[0171] In block 1710, the auto-calibration wafer may be removed from the wafer support using a wafer handling robot, and in block 1712, a determination may be made as to whether the measured value of the level of the wafer support is within an acceptable range. If not, the method may proceed to block 1714, where an error state may be generated. If so, the method may proceed to block 1716, where a success state may be generated.

[0172] It will be appreciated that the various techniques described herein can be combined in various forms to provide a fully automated system for constructing a semiconductor processing tool. For example, the semiconductor processing tool may be configured to have an "initial setup" mode into which the semiconductor processing tool can enter, in which mode the tool removes an edge ring, centers the edge ring on each wafer support within the semiconductor processing chamber using an auto-calibration wafer, and then, for each wafer support, centers the calibration wafer and the associated edge ring using the auto-calibration wafer, trains the active wafer centering system and the wafer handling robot using the centered calibration wafer, and then checks that the trained active wafer centering system provides a reliable wafer placement. The semiconductor processing tool may periodically perform various health checks, such as checking whether the center-to-center offset with respect to the edge ring and the calibration wafer has drifted to an unacceptable distance, checking whether the height of the edge ring is still within range after a predetermined period or a predetermined number of wafer processing operations have been performed, and / or checking whether the wafer support is horizontal and / or whether the vibration of the lift pins is within an acceptable range.

[0173] As described above, the controller may be part of a system, and the system may include semiconductor processing equipment including processing tool(s), chamber(s), processing platform(s), and / or specific processing components (such as wafer pedestals, gas flow systems). These systems may be incorporated into electronics for controlling operations before, during, and after the processing of semiconductor wafers or substrates. The electronics may be referred to as a "controller" that may control various components or sub-components of the system(s). The controller may be programmed to control any of the processes disclosed herein, as well as various parameters affecting semiconductor processing, such as delivery of processing gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and operation settings, tools and other transfer tools connected to or interfacing with a particular system and / or wafer transfer in and out of a load lock, depending on the processing requirements and / or the type of system.

[0174] Broadly speaking, a controller may be defined as an electronic device having various integrated circuits, logic, memory, and / or software, which receives instructions, issues instructions, controls operations, enables cleaning operations, and enables endpoint measurements. The integrated circuits may include a chip in the form of firmware that stores program instructions, a digital signal processor (DSP), a chip defined as an application-specific integrated circuit (ASIC), and / or one or more microprocessors, or a microcontroller that executes program instructions (e.g., software). The program instructions are instructions communicated to the controller in the form of various individual settings (or program files) that may define operating parameters for performing a particular process on or with respect to a semiconductor wafer or a system. In some embodiments, the operating parameters may be part of a recipe defined by a process engineer to implement one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or wafer dies.

[0175] In some embodiments, the controller may be integrated with or connected to the system, or otherwise be part of a computer networked to the system, or connected to such a computer, or a combination thereof. For example, the controller may be within the "cloud" or be all or part of a fab host computer system, thereby enabling remote access to wafer processing. The computer may enable remote access to the system, monitor the current progress of manufacturing operations, investigate the history of past manufacturing operations, investigate trends or performance metrics from multiple manufacturing operations to change the parameters of the current process, set the processing steps following the current process, or initiate a new process. In some examples, a remote computer (e.g., a server) may provide a process recipe to the system via a network that may include a local network or the Internet. The remote computer may include a user interface that enables input or programming of parameters and / or settings, and the parameters and / or settings are then communicated from the remote computer to the system. In some examples, the controller receives instructions in a data format that specifies parameters for each processing step to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process being performed and the type of tool that the controller is configured to interface with or control. Thus, as described above, the controller may be distributed, for example, by comprising one or more individual controllers networked together and aimed at a common purpose such as the processes and controls described herein. An example of a distributed controller for such a purpose may be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (e.g., at the platform level or as part of a remote computer), and these are combined to control the process in the chamber.

[0176] Without being limiting, exemplary systems may include a plasma etching chamber or module, a deposition chamber or module, a spin rinse chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel edge etching chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etching (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing system that may be associated with or used in the fabrication and / or manufacture of semiconductor wafers.

[0177] As described above, depending on the process steps performed by the tool, the controller may communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout the factory, the main computer, another controller, or a tool used for material transport to and from a tool location and / or load port within a semiconductor manufacturing facility.

[0178] The above discussion has focused on automatic calibration wafer systems that typically feature multiple image sensors and, in various further embodiments, one or more additional sensors. However, some embodiments may have the feature that there is only a single centrally mounted image sensor and no image sensors located at the edges, or only image sensors located at the edges and no image sensors mounted centrally. Such embodiments may, in some cases, be less functional than embodiments that feature both a centrally mounted image sensor and edge-mounted image sensors, but this is not necessarily the case. The present disclosure should be understood to encompass such alternative embodiments as well.

[0179] As used herein, the term "wafer" may refer to a semiconductor wafer or substrate, or other similar types of wafers or substrates. As used herein, the term "wafer station" may refer to any location within a semiconductor processing tool where a wafer may be placed during any of a variety of wafer processing operations or wafer transfer operations. As used herein, a wafer support refers to any structure within a wafer station that is configured to receive and support a semiconductor wafer, such as a pedestal, an electrostatic chuck, a wafer support shelf, and the like.

[0180] As used herein, the term "nominal centered" refers to a relative arrangement in two or more objects such that a particular location, such as a center point or a similar location, is generally aligned with each other within the XY plane. Such alignment may not be perfect for various reasons, such as slippage of one of the objects, drift of the sensor, etc., but in most cases, the nominally centered objects are within 1 to 2 millimeters of the perfectly centered objects.

[0181] Also, in this specification, the use of ordinal indicators, such as (a), (b), (c),..., is for structural purposes only, and it should be understood that it is not intended to convey any particular order or importance to the items associated with each ordinal indicator. For example, "(a) obtaining information regarding speed, (b) obtaining information regarding position" includes obtaining information regarding position before obtaining information regarding speed, obtaining information regarding speed before obtaining information regarding position, and obtaining information regarding position simultaneously with obtaining information regarding speed. Nevertheless, some items associated with ordinal indicators may essentially require a specific sequence, such as "(a) obtaining information regarding speed, (b) determining a first acceleration based on the information regarding speed, (c) obtaining information regarding position". In this example, since (b) depends on the information obtained in (a), (a) must be performed before (b), but (c) can be performed either before or after either (a) or (b).

[0182] For example, it should be understood that the use of the word "each" in phrases such as "for each <item> among one or more items" or "of each <item>", as used in this specification, is to be understood as including both single-item groups and multi-item groups. That is, the phrase "for each" is used in the sense in which it is used in a programming language to refer to each of every group of items being referred to. For example, if the group of items being referred to is a single item, "each" will refer to only the single item (despite the fact that the dictionary definition of "each" often defines this term as referring to "each one of two or more things"), and it does not mean that there must be at least two of those items. Similarly, when a selected item may have one or more sub-items and a selection of one of those sub-items is made, it will be understood that when the selected item has only one sub-item, the selection of that one sub-item is specific to the selection of the item itself.

[0183] References to a plurality of controllers configured to perform various functions as a whole include both the situation where only one of the controllers is configured to perform all of the disclosed or discussed functions, and the situation where each of the various controllers performs a sub - portion of the discussed functions. For example, an auto - calibration wafer may include a controller that is configured to control the operation of various sensors on the auto - calibration wafer and communicate data from those sensors to another controller associated with a semiconductor processing tool. The controller of the semiconductor processing tool may then analyze such data to determine various operating parameters used in the semiconductor processing tool.

[0184] Various changes to the embodiments described in this disclosure may become readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Accordingly, the claims are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the disclosure, the principles, and the novel features disclosed herein.

[0185] The specific features described herein in the context of separate embodiments may also be combined to be implemented in a single embodiment. Conversely, the various features described in the context of a single embodiment may be implemented separately in a plurality of embodiments or in any suitable sub - combination. Moreover, features may be described above as functioning in a particular combination and initially claimed as such, but one or more features in the claimed combination may in some cases be separable from the combination and the claimed combination may be directed to a sub - combination or variation of a sub - combination.

[0186] Similarly, while the operations are shown in the drawings in a particular order, this should not be understood as requiring that the operations be performed in the particular order or sequence shown, or that all of the illustrated operations be performed, in order to achieve the desired result. Further, the drawings may schematically depict another exemplary process in the form of a flowchart. However, other operations not shown can be incorporated into the exemplary process that is schematically shown. For example, one or more additional operations can be performed before, after, simultaneously with, or between any of the illustrated operations. In certain situations, multitasking and parallel processing may be advantageous. Moreover, in the above-described embodiments, various system components are separated, but this should not be understood as being necessary in all embodiments, and it should be understood that the described program components and systems may generally be integrated together into a single software product or packaged into multiple software products. Additionally, other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve the desired result.

Claims

1. A system for assisting in the calibration of a wafer handling robot for a semiconductor processing tool, the system comprising: an auto-calibration wafer, the auto-calibration wafer comprising: a substrate dimensioned to be carried by the wafer handling robot, the substrate having a first surface configured to contact an end effector of the wafer handling robot when the substrate is carried by the wafer handling robot; a plurality of first image sensors supported by the substrate and positioned at locations offset from a common point of the substrate, each of the first image sensors having a downward field of view when the substrate is oriented with the first surface facing downward; a first controller communicatively connected to each of the first image sensors.

2. The system of claim 1, wherein the first image sensors are configured in a circular array around the common point.

3. The system of claim 1, wherein the substrate is nominally circular and has the same diameter as a semiconductor wafer configured to be processed by the semiconductor processing tool.

4. The system of claim 1, wherein the substrate is nominally circular and has the same diameter as an edge ring configured to be used by the semiconductor processing tool.

5. The system of claim 1, wherein the substrate is nominally circular and has a diameter between an outer diameter and an inner diameter of an edge ring configured to be used by the semiconductor processing tool.

6. The system of claim 1, wherein the substrate is nominally circular and has a diameter within ±10% of an average of an outer diameter and an inner diameter of an edge ring configured to be used by the semiconductor processing tool.

7. The system of claim 1, wherein the substrate is a nominally circular disk having a diameter selected from the group consisting of 200 mm, 300 mm, and 450 mm.

8. The system of claim 1, wherein the auto-calibration wafer further comprises a power source configured to supply power to at least the first controller and the first image sensors.

9. The system of claim 8, wherein The power supply is a rechargeable battery, The system further includes a wireless charging function configured to charge the rechargeable battery when interfacing with an electromagnetic field, wherein the automatic calibration wafer is configured to charge the rechargeable battery when interfacing with an electromagnetic field.

10. The system according to claim 1, The automatic calibration wafer further includes a first wireless communication interface, The system, wherein the first wireless communication interface is communicably connected to the first controller.

11. The system according to claim 10, wherein the first wireless communication interface includes one or more wireless communication interfaces selected from the group consisting of a Bluetooth transceiver and a WiFi transceiver.

12. The system according to claim 1, The automatic calibration wafer further includes one or more orientation sensors, The system, wherein the one or more orientation sensors are communicably connected to the first controller.

13. The system according to claim 12, wherein each of the orientation sensors is selected from the group consisting of an inclinometer and an accelerometer.

14. The system according to claim 1, The automatic calibration wafer further includes one or more vibration sensors, The system, wherein the one or more vibration sensors are communicably connected to the first controller.

15. The system according to claim 14, wherein each of the vibration sensors is selected from the group consisting of an accelerometer, a laser microphone, and an optical distance measurement sensor.

16. The system according to claim 1, The automatic calibration wafer further includes one or more proximity sensors, each of which is configured to measure the distance between the first surface and an object located below the proximity sensor when the first surface is facing downward, The system, wherein the one or more proximity sensors are communicably connected to the first controller.

17. The system according to claim 16, wherein each of the proximity sensors is selected from the group consisting of an optical proximity sensor, an inductive proximity sensor, and a capacitive proximity sensor.

18. The system according to claim 1, The first image sensor is configured in a circular array around the common point, The substrate is nominally circular and has the same diameter as a semiconductor wafer configured to be processed by the semiconductor processing tool, The substrate is a nominally circular disk having a diameter selected from the group consisting of 200 mm, 300 mm, and 450 mm, The automatic calibration wafer, A rechargeable battery configured to supply power to at least the first controller and the first image sensor, A wireless charging function configured to charge the rechargeable battery when interfacing with an electromagnetic field, A first wireless communication interface communicatively connected to the first controller and including one or more wireless communication interfaces selected from the group consisting of a Bluetooth transceiver and a WiFi transceiver, One or more vibration sensors communicatively connected to the first controller, One or more proximity sensors, each of the proximity sensors being communicatively connected to the first controller and configured to measure the distance between the first surface and an object located below the proximity sensor when the first surface is oriented downward, a system further comprising.

19. The system according to any one of claims 1 to 18, wherein the system further comprises the semiconductor processing tool, and the semiconductor processing tool, A wafer handling robot, One or more wafer stations, A second controller, including, Each of the wafer stations includes one or more corresponding wafer supports, The wafer handling robot and the second controller are communicatively connected, The second controller and the first controller as a whole, a) Select a first wafer support of one or more wafer supports of a first wafer station among one or more of the wafer stations, b) Position the automatic calibration wafer on the first wafer station by the wafer handling robot, c) While the automatic calibration wafer is positioned on the first wafer support, cause each of the first image sensors to acquire a corresponding first image of a reference portion of the first wafer support, A system configured as such.

20. The system according to claim 19, wherein the second controller and the first controller are further configured as a whole to determine location information of the center point of the first wafer support based on the first image.

21. The system according to claim 19, wherein the second controller and the first controller as a whole d) causing the wafer handling robot to take out a calibration wafer, e) causing the wafer handling robot to transfer the calibration wafer to the first wafer support such that the center point of the calibration wafer is centered nominally on the center point of the first wafer support when viewed along the vertical axis. The system is further configured as follows.

22. The system according to claim 21, wherein the second controller and the first controller as a whole f) causing the wafer handling robot to position the auto-calibration wafer over the first wafer support and the calibration wafer, g) while the auto-calibration wafer is positioned over the first wafer support and the calibration wafer, causing each of the first image sensors to acquire a corresponding second image of a reference portion of the first wafer support and a reference portion of the calibration wafer, h) determining a wafer / wafer support horizontal offset between the center point of the calibration wafer and the center point of the first wafer support based on a gap size between the reference portions of the first wafer support and the calibration wafer in the second image. The system is further configured as follows.

23. The system according to claim 22, wherein the second controller and the first controller as a whole i) comparing the wafer / wafer support horizontal offset with a threshold wafer / wafer support horizontal offset, j) in response to a determination that the wafer / wafer support horizontal offset exceeds the threshold wafer / wafer support horizontal offset, causing the wafer handling robot to reposition the calibration wafer relative to the first wafer support to reduce the wafer / wafer support horizontal offset. The system is further configured as follows.

24. The system according to claim 23, wherein the second controller and the first controller as a whole repeat (f) to (j) N times, or repeat until the wafer / wafer support horizontal offset becomes less than or equal to the threshold wafer / wafer support horizontal offset, whichever occurs first.

25. The system according to claim 19, wherein the second controller and the first controller as a whole d) cause the wafer handling robot to take out a first edge ring, e) cause the wafer handling robot to transfer the first edge ring to the first wafer support such that, when viewed along the vertical axis, the center point of the first edge ring is nominally centered on the center point of the first wafer support. The system is further configured as described above.

26. The system according to claim 25, wherein the second controller and the first controller as a whole f) cause the wafer handling robot to position the auto-calibration wafer over the first wafer support and the first edge ring, g) while the auto-calibration wafer is positioned over the first wafer support and the first edge ring, cause each of the first image sensors to acquire a corresponding second image of a reference portion of the first wafer support and a reference portion of the first edge ring, h) determine an edge ring / wafer support horizontal offset between the center point of the first edge ring and the center point of the first wafer support based on a gap size between the reference portions of the first wafer support and the first edge ring in the second image. The system is further configured as described above.

27. The system according to claim 26, wherein the second controller and the first controller as a whole i) compare the edge ring / wafer support horizontal offset with a threshold edge ring / wafer support horizontal offset, j) In response to a determination that the edge ring / wafersupport horizontal offset exceeds the threshold edge ring / wafersupport horizontal offset, cause the wafer handling robot to relocate the first edge ring relative to the first wafer support to reduce the edge ring / wafersupport horizontal offset. A system, further configured as such. **Claim 28** The system according to claim 27, wherein the second controller and the first controller are configured as a whole to perform, whichever occurs first, (f) to (j) N times, or to repeat until the edge ring / wafersupport horizontal offset is less than or equal to the threshold edge ring / wafersupport horizontal offset. A system, further configured as such. **Claim 29** The system according to claim 25, wherein the second controller and the first controller are configured as a whole. f) Cause the wafer handling robot to remove the calibration wafer. g) Cause the wafer handling robot to transfer the calibration wafer to the first wafer support such that, when viewed along the vertical axis, the center point of the calibration wafer is nominally centered on the center point of the first edge ring. A system, further configured as such. **Claim 30** The system according to claim 29, wherein the second controller and the first controller are configured as a whole. h) Cause the wafer handling robot to position the auto-calibration wafer over the first wafer support, the first edge ring, and the calibration wafer. i) While the auto-calibration wafer is positioned over the first wafer support, the calibration wafer, and the first edge ring, cause each of the first image sensors to acquire a corresponding second image of a reference portion of the calibration wafer and a reference portion of the first edge ring. j) Determine an edge ring / wafersupport horizontal offset between the center point of the first edge ring and the center point of the calibration wafer based on a gap size between the reference portions of the calibration wafer and the first edge ring in the second image. A system, further configured as such. **Claim 31** The system according to claim 30, wherein the second controller and the first controller as a whole, k) comparing the edge ring / wafer horizontal offset with a threshold edge ring / wafer horizontal offset, l) in response to a determination that the edge ring / wafer horizontal offset exceeds the threshold edge ring / wafer horizontal offset, causing the wafer handling robot to reposition the calibration wafer relative to the first edge ring to reduce the edge ring / wafer horizontal offset, A system further configured as described above.

32. The system according to claim 31, wherein the second controller and the first controller as a whole perform (h) to (l) M times, or repeat until the edge ring / wafer horizontal offset is less than or equal to the threshold edge ring / wafer horizontal offset, whichever occurs first. A system further configured to perform the foregoing.

33. The system according to claim 32, wherein the second controller and the first controller as a whole, reposition the automatic calibration wafer on the first wafer support, the first edge ring, and the calibration wafer on the wafer handling robot, while the automatic calibration wafer is positioned on the first wafer support, the calibration wafer, and the first edge ring, causing each of the first image sensors to acquire a corresponding third image of the reference portion of the calibration wafer and the reference portion of the first wafer support, Based on the gap size between the reference portions of the calibration wafer and the first wafer support in the third image, determining a wafer support / wafer horizontal offset between the center point of the first wafer support and the center point of the calibration wafer. A system further configured as described above.

34. The system according to claim 32, wherein the second controller and the first controller as a whole, compare the wafer support / wafer horizontal offset with a threshold wafer support / wafer horizontal offset, In response to a determination that the wafer support / water horizontal offset exceeds the threshold wafer support / water horizontal offset, the wafer handling robot is further configured to relocate at least one article selected from the group consisting of the calibration wafer and the edge ring with respect to the first wafer support. A system.

35. The system according to claim 34, The semiconductor processing tool includes a semiconductor processing chamber, The first wafer station is within the semiconductor processing chamber, The first wafer support includes a pedestal within the semiconductor processing chamber. A system.

36. The system according to claim 34, The semiconductor processing tool includes a load lock for transferring wafers between different pressure environments, The first wafer station is within the load lock, The first wafer support is a structure within the load lock. A system.

37. The system according to claim 34, The semiconductor processing tool includes a buffer for storing one or more wafers before, after, or during a processing operation, The first wafer station is within the buffer, The first wafer support is one of a plurality of wafer support ledges within the buffer. A system.

38. The system according to claim 34, The semiconductor processing tool includes a load lock for transferring wafers between different pressure environments, The first wafer station is within the load lock, The first wafer support is a structure within the load lock. A system.

39. The system according to claim 12 or 13, wherein the system further comprises the semiconductor processing tool, the semiconductor processing tool comprising: A wafer handling robot; One or more wafer stations; A second controller, Each of the wafer stations includes one or more corresponding wafer supports, The wafer handling robot and the second controller are communicatively connected, The second controller and the first controller as a whole, a) Select the first wafer support among the one or more wafer supports of the first wafer station among the one or more wafer stations, b) causing the wafer handling robot to transfer the automatic calibration wafer onto the first wafer station; c) causing the one or more orientation sensors to obtain an inclination measurement value of the substrate; A system configured as described above. **Claim 40** The system according to claim 39, wherein the second controller is configured to remove an edge ring from the first wafer support before executing (b). **Claim 41** The system according to claim 14 or 15, further comprising the semiconductor processing tool, the semiconductor processing tool comprising: a wafer handling robot; one or more wafer stations; a second controller, each of the wafer stations including one or more corresponding wafer supports; the wafer handling robot and the second controller being communicably connected; the second controller and the first controller together: a) selecting a first wafer support of the one or more wafer supports of a first wafer station among the one or more wafer stations, the first wafer support including a plurality of lift pins; b) causing a relative translational movement between the lift pins and the first wafer support such that the lift pins protrude from the first wafer support; c) causing the wafer handling robot to transfer the automatic calibration wafer to the lift pins; d) causing a further relative translational movement between the lift pins and the first wafer support while the automatic calibration wafer is supported by the lift pins; e) obtaining vibration data from the one or more vibration sensors during (d); f) evaluating the vibration data to determine whether the vibration data indicates vibrations exceeding a predetermined threshold; g) providing a notification when the vibration data exceeds the predetermined threshold. **Claim 42** The system according to claim 41, wherein the second controller is configured, as part of (d), to cause a further relative translational movement between the lift pins and the first wafer support such that the automatic calibration wafer is placed on the upper surface of the first wafer support without the lift pins protruding from the first wafer support any further. **Claim 43** The system according to claim 16 or 17, wherein the system further comprises the semiconductor processing tool, and the semiconductor processing tool comprises a wafer handling robot, one or more wafer stations, and a second controller, wherein the wafer handling robot and the second controller are communicably connected, and the second controller and the first controller as a whole a) select a first wafer support of the one or more wafer supports of a first wafer station among the one or more wafer stations, at least partially based on an indication that an edge ring is supported by the first wafer support; b) place the auto-calibration wafer on the edge ring; c) measure, for each of the proximity sensors, a distance between the first wafer support and the auto-calibration wafer; d) determine one or more height measurements associated with the edge ring based on the one or more distances; e) evaluate the one or more height measurements to determine whether a height associated with the edge ring exceeds a predetermined threshold; f) provide a notification when the height associated with the edge ring exceeds the predetermined threshold. A system configured as such.

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