Integrated adaptive positioning system and routines for training and health checking of automated wafer handling robots

Abstract

Systems and techniques are disclosed for determining and using multiple types of offsets for presenting a wafer to a wafer support in a wafer station of a semiconductor processing tool, where such techniques and systems may use an autocalibration wafer, which may include multiple sensors, including multiple image sensors located at its edges, which may be used to image fiducial portions associated with two different structures located within a selected wafer station.

Description

[Background technology]

[0001] [Related Application Data] A PCT application is being filed contemporaneously herewith as a part of this application. Each of the applications to which this application claims benefit or priority, as identified in the contemporaneously filed PCT application, is hereby incorporated by reference in its entirety for all purposes.

[0002] Semiconductor processing tools utilize 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 because the semiconductor wafer is not rigidly secured to the end effector of the wafer handling robot, there is often some variation in relative positioning between the end effector and the semiconductor wafer placed thereon. Due to the sensitivity of semiconductor processing operations, when a wafer handling robot is used to position a semiconductor wafer, it is typical to compensate for such variations so that the semiconductor wafer is positioned within a corresponding processing station at a desired location within an acceptable tolerance, e.g., typically centered within the processing station. Modern semiconductor processing tools utilize active wafer centering (AWC) systems to assist with such wafer positioning. Summary of the Invention

[0003] The 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 become apparent from the description, drawings, and claims of this specification. The following non-limiting implementations are considered part of this disclosure. Other implementations will become apparent from the entirety of this disclosure and the accompanying drawings.

[0004] In some implementations, a system may be provided to assist in the calibration of a wafer handling robot for a semiconductor processing tool, the system may include, for example, an auto-calibration wafer, the auto-calibration wafer including a substrate sized 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 carried by the wafer handling robot, a plurality of first image sensors supported by the substrate and positioned at offset locations from a common point on 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 coupled to each of the first image sensors.

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

[0006] In some implementations of the system, the substrate may be nominally circular and may have the same diameter as the semiconductor wafers that the semiconductor processing tool is configured to process.

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

[0008] In some implementations of the system, the substrate may be nominally circular and may have a diameter between the outer and inner diameters of an edge ring that the semiconductor processing tool is configured to use.

[0009] In some implementations of the system, the substrate may be nominally circular and may have a diameter within ±10% of the average between the outer and inner diameters of the edge ring that the semiconductor processing tool is configured to use.

[0010] In some implementations 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 implementations of the system, the auto-calibration wafer may further include a power supply configured to provide power to at least the first controller and the first image sensor.

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

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

[0014] In some implementations of the system, the first wireless communication interface may include one or more wireless communication interfaces, such as a Bluetooth transceiver or a WiFi transceiver.

[0015] In some implementations 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 implementations of the system, each orientation sensor may be an inclinometer or an accelerometer.

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

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

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

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

[0021] In some implementations of the system, the first image sensors may be arranged in a circular array around a common point, the substrate may be nominally circular and may have the same diameter as a semiconductor wafer that the semiconductor processing tool is configured to process, 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 provide power to at least the first controller and the first image sensor, a wireless charging capability configured to charge the rechargeable battery when interfaced with an electromagnetic field, a first wireless communication interface 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 may be communicatively connected to the first controller, and one or more proximity sensors, each of the proximity sensors communicatively connected to the first controller and configured to measure a distance between the first surface and an object located below the proximity sensor when the first surface is facing downward.

[0022] 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 implementations, each wafer station may include one or more corresponding wafer supports, the wafer handling robot and the second controller may be communicatively coupled, and the second controller and the first controller may collectively be configured to: a) select a first wafer support of the one or more wafer supports for a first wafer station of the one or more wafer stations, b) cause the wafer handling robot to position the auto-calibration wafer over the first wafer station, and c) cause each of the first image sensors to acquire a corresponding first image of a reference portion of the first wafer support while the auto-calibration wafer is positioned on the first wafer support.

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

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

[0025] In some implementations of the system, the second controller and the first controller may collectively be further configured to: f) cause the wafer handling robot to position the automatic calibration wafer over the first wafer support and the calibration wafer; g) cause each of the first image sensors to acquire corresponding second images of a reference portion of the first wafer support and a reference portion of the calibration wafer while the automatic calibration wafer is positioned over the first wafer support and the calibration wafer; and h) determine a wafer / wafer support horizontal offset between a center point of the calibration wafer and a 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 images.

[0026] In some implementations of the system, the second controller and the first controller collectively may be further configured to: i) compare the wafer / wafer support horizontal offset to a threshold wafer / wafer support horizontal offset; and j) in response to determining 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 implementations of the system, the second controller and the first controller collectively may be further configured to perform (f) through (j), whichever occurs first, repeating N times or until the wafer / wafer support horizontal offset is less than or equal to a threshold wafer / wafer support horizontal offset.

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

[0029] In some implementations of the system, the second controller and the first controller may be further configured, collectively, 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 corresponding second images 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; and h) determine an edge ring / wafer support horizontal offset between a center point of the first edge ring and a 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 images.

[0030] In some implementations of the system, the second controller and the first controller collectively are further configured to: i) compare the edge ring / wafer support horizontal offset to a threshold edge ring / wafer support horizontal offset; and j) in response to determining 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 implementations of the system, the second controller and the first controller collectively may be further configured to perform (f) through (j), whichever occurs first, repeating N times or until the edge ring / wafer support horizontal offset is less than or equal to a threshold edge ring / wafer support horizontal offset.

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

[0033] In some implementations of the system, the second controller and the first controller may be further configured, collectively, to: h) cause the wafer handling robot to position the automatic calibration wafer over the first wafer support, the first edge ring, and the calibration wafer; i) cause each of the first image sensors to acquire corresponding second images of a reference portion of the calibration wafer and a reference portion of the first edge ring while the automatic calibration wafer is positioned over the first wafer support, the calibration wafer, and the first edge ring; and j) determine an edge ring / wafer horizontal offset between a center point of the first edge ring and a 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 images.

[0034] In some implementations of the system, the second controller and the first controller collectively may be further configured to k) compare the edge ring / wafer horizontal offset to a threshold edge ring / wafer horizontal offset, and l) in response to determining 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 collectively 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 a threshold edge ring / wafer horizontal offset, whichever occurs first.

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

[0037] In some implementations of the system, the second controller and the first controller collectively may be further configured to compare the wafer support / wafer horizontal offset to a threshold wafer support / wafer horizontal offset, and in response to determining that the wafer support / wafer horizontal offset exceeds the threshold wafer support / wafer horizontal offset, cause the wafer handling robot to reposition at least one item selected from the group consisting of a calibration wafer and an edge ring relative to the first wafer support.

[0038] In some implementations 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 implementations 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 implementations of the system, the semiconductor processing tool may include a buffer for storing one or more wafers before, after, or during processing operations, the first wafer station may be within the buffer, and the first wafer support may be one of multiple wafer support ledges within the buffer.

[0041] In some implementations 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 coupled, and the second controller and the first controller may collectively be configured to: a) select a first wafer support of the one or more wafer supports for a first wafer station of the one or more wafer stations, b) cause the wafer handling robot to transfer an auto-calibration wafer onto the first wafer station, and c) cause the one or more orientation sensors to obtain tilt measurements of the substrate.

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

[0044] 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 an implementation, each wafer station may include one or more corresponding wafer supports, and the wafer-handling robot and the second controller may be communicatively coupled, and the second controller and the first controller may be collectively configured to: a) select a first wafer support of the one or more wafer supports of a first wafer station of 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 cause the lift pins to protrude from the first wafer support; c) cause the wafer-handling robot to transfer the auto-calibration wafer to the lift pins; 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) acquire vibration data from the one or more vibration sensors during (d); f) evaluate the vibration data to determine whether the vibration data indicates a vibration that exceeds a predetermined threshold; and g) provide a notification when the vibration data exceeds the predetermined threshold.

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

[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 coupled, and the second controller and the first controller may be collectively configured to: a) select a first wafer support of the one or more wafer supports of a first wafer station of the one or more wafer stations based at least in part on an indication that the edge ring is supported by the first wafer support, b) cause the auto-calibration wafer to be positioned on the edge ring, c) cause each of the proximity sensors to measure 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, and f) provide a notification when the height associated with the edge ring exceeds a predetermined threshold.

[0047] Various implementations disclosed herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numbers refer to similar elements. [Brief description of the drawings]

[0048] [Figure 1] FIG. 1 shows an example of a calibration wafer positioned relative to an edge ring.

[0049] [Diagram 2] FIG. 2 shows a schematic diagram of an exemplary autocalibration wafer.

[0050] [Diagram 3] FIG. 3 shows a diagram of a wafer support with lift pins.

[0051] [Figure 4]FIG. 4 shows a side view of an autocalibrated wafer having a set of proximity sensors that may be used to determine the edge ring height.

[0052] [Diagram 5] FIG. 5 shows a side view of another autocalibration wafer having two sets of proximity sensors, each set located along a circular path of a different diameter.

[0053] [Figure 6] FIG. 6 is a photograph of an exemplary autocalibration wafer.

[0054] [Figure 7] FIG. 7 illustrates a top view of another exemplary autocalibration wafer.

[0055] [Figure 8a] FIG. 8a shows a schematic diagram of a semiconductor processing tool in various phases of operation. [Figure 8b] FIG. 8b shows a schematic diagram of a semiconductor processing tool in various phases of operation. [Figure 8c] FIG. 8c shows a schematic diagram of a semiconductor processing tool in various phases of operation. [Figure 8d] FIG. 8d shows a schematic diagram of a semiconductor processing tool in various phases of operation. [Figure 8e] FIG. 8e shows a schematic diagram of a semiconductor processing tool in various phases of operation. [Figure 8f] FIG. 8f shows a schematic diagram of a semiconductor processing tool in various phases of operation. [Figure 8g] FIG. 8g shows a schematic diagram of a semiconductor processing tool in various phases of operation. [Figure 8h] FIG. 8h shows a schematic diagram of a semiconductor processing tool in various phases of operation. [Figure 8i] FIG. 8i shows a schematic diagram of a semiconductor processing tool in various phases of operation.

[0056] [Figure 9] FIG. 9 shows a flow chart of a method for determining the location of a fiducial of a structure in a wafer station using an autocalibration wafer.

[0057] [Figure 10] FIG. 10 shows a flow chart of a method for determining the relative positioning of two structures in a wafer station using an autocalibration wafer.

[0058] [Figure 11] FIG. 11 shows a flow chart of a method for determining the location of the center point of the wafer support using an autocalibration wafer.

[0059] [Figure 12] FIG. 12 shows a flow chart of a method for calibrating the placement of the edge ring on the wafer support.

[0060] [Figure 13] FIG. 13 shows a flow chart of a method for calibrating the placement of a wafer relative to an edge ring on a wafer support.

[0061] [Figure 14] FIG. 14 shows a flow chart of a method for verifying the repeatability of wafer placement.

[0062] [Figure 15] FIG. 15 shows a flow chart of a method for evaluating the height of the edge ring.

[0063] [Figure 16] FIG. 16 shows a flow chart of a method for evaluating lift pin vibration.

[0064] [Figure 17] FIG. 17 shows a flow chart of a method for evaluating the levelness of the pedestal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] The figures herein are generally not drawn to scale, although various aspects of the figures may be drawn to scale, for example, as discussed below.

[0066] In a typical semiconductor processing system, accurate positioning of a wafer in preparation for various semiconductor processing and / or wafer handling operations is accomplished by a manual or semi-automated teaching process that typically requires supervision by a technician or other human to (1) "teach" the wafer handling robot the desired locations of the semiconductor wafer, edge ring, and / or wafer support, such as an electrostatic chuck (ESC), relative to one another or relative to the end effector of the wafer handling robot, (2) "teach" an active wafer centering (AWC) system, and (3) perform wafer placement repeatability verification; once the wafer handling robot has been taught such locations, any deviations from such locations that may occur in the wafer placement of any given wafer, for example due to slight misalignment between the wafer and the end effector during transfer of the wafer to the end effector, can be corrected using the AWC. Such manual or semi-automated teaching processes are time consuming and cumbersome to implement.

[0067] Such an education process typically begins with training the wafer-handling robot as to the various locations from which to pick or place wafers during operation of the semiconductor processing tool. Generally speaking, the wafer-handling robot may initially be configured such that it generally knows where each such location is within the tool, but the wafer-handling robots will require some degree of customization to adapt their operations to the unique characteristics of the particular semiconductor processing tool in which they are installed, for example to accommodate various assembly or part tolerances. To achieve this, the wafer handling robot may be placed in a "teaching" mode, in which for each location to be "taught," the wafer handling robot may be directed to a position that corresponds to the position or configuration in which the wafer handling robot would be under particular "ideal" conditions for that location, e.g., the position or configuration in which the wafer handling robot would be when the center of a semiconductor wafer is positioned within a known distance (generally, a distance that can be desirably minimized or reduced to zero) of a reference point on an end effector of the wafer handling robot, and, e.g., within a known distance (generally, a distance that can be desirably minimized or reduced to zero) of the center of a wafer support at that location.

[0068] In a typical wafer handling robot training, the "ideal" positioning of the wafer handling robot with respect to each location may be achieved by the use of one or more fixtures or other structures that can interface with a feature on the end effector of the wafer handling robot that serves as, for example, a reference point and another feature fixed with respect to the target location. For example, in some wafer handling robot training scenarios, a disk-shaped fixture having a diameter similar to that of a semiconductor wafer may be fastened to a predetermined position on the end effector of the wafer handling robot using a shaft or pin that, for example, passes through the center of the disk and through a reference feature, e.g., a hole, in the end effector that is centered at the location intended to be the location on the end effector where the semiconductor wafer will be centered when carried by the wafer handling robot using the end effector. There may be similar pins that may be installed on features of the wafer support, and when the end effector / disk is pressed against such a pin, the pin may contact the edge of the disk, thereby directing the disk and end effector to a specific location, e.g., a centered location. During such wafer handling robot movements, the wafer handling robot may be placed in a powered-off state to allow easy manual movement of the wafer handling robot joints / arm segments by an operator. Once the wafer handling robot is properly positioned, the wafer handling robot controller may obtain measurements of various linkage positions of the wafer handling robot, for example, by obtaining measurements of relative or absolute angular displacements of various rotational joints of the wafer handling robot, to determine what the kinematic conditions associated with the wafer handling robot are when the wafer handling robot is in a desired position.Once the wafer handling robot has acquired such position information and associated it with its location, the location may be considered to be taught to the wafer handling robot.

[0069] Once the wafer-handling robot is taught the various locations to which a wafer is to be delivered (or from which a wafer is to be removed), the wafer-handling robot may be controlled to enter the kinematic state taught for a location when performing future wafer transfer operations related to that location. If a semiconductor wafer placed on the end effector of the wafer-handling robot is positioned so as to be precisely centered on the reference point of the end effector, when that same semiconductor wafer is placed by the end effector of the wafer-handling robot at a target location, it will also be properly centered at that location after the wafer-handling robot is returned to the kinematic state taught for that location. However, due to various reasons, a 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. Although such misalignment may appear relatively small, for example on the scale of tens of micrometers, even such slight misalignment may adversely affect wafer processing operations. The use of active wafer centering (AWC) systems that allow for correction of such end effector / wafer misalignment has become commonplace in the industry.

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

[0071] For example, to train the AWC system, some reference wafer may be manually centered at a desired destination, e.g., on a pedestal in a semiconductor processing chamber. Such manual centering may be performed, for example, using a fixture or jig that guides the reference wafer so that it is properly centered relative to the pedestal. Once the reference wafer is deemed to be sufficiently centered on the pedestal, a wafer handling robot may be controlled to retrieve the reference wafer and remove it from the semiconductor processing chamber. As 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. This information, combined with information from the wafer handling robot describing the displacement the reference wafer undergoes as it moves from its centered location on the pedestal to a center location determined by the AWC system, allows future wafer placements to be adjusted to achieve similar centering of the wafer pedestal. For example, when a new wafer, like the reference wafer, is placed on the wafer handling robot and passed by the AWC sensor, it may be found that the center of the new wafer is offset somewhat, e.g., 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, the wafer handling robot can be controlled to take such variations into account by applying a compensating displacement when placing the new wafer on the pedestal, e.g., by moving the new wafer −0.5 mm in the X direction and −0.25 mm in the Y direction, opposite the displacements used to move the reference wafer from the pedestal to the AWC sensor, before, after, or during the displacement of the new wafer.

[0072] A similar approach using an AWC system can also be used to adjust the placement of the edge ring on the wafer support, e.g., the AWC can be used to determine the center point of the edge ring as it passes through the optical beam of the AWC system, and any offset between such center point of the edge ring and a reference location used by the AWC system as an "ideal" center placement for the wafer or edge ring, for example. In implementations where an AWC system is used in conjunction with an edge ring placement, there may be more edge / optical beam intersections than in a semiconductor wafer due to the edge ring having both an inner edge and an outer edge (thus, there may be four edge / optical beam intersections detected by each optical sensor as the edge ring passes through the AWC optical sensors, as opposed to only two when a semiconductor wafer passes through the optical beam sensors). In such implementations, data resulting from some of the edge / optical beam intersections, e.g., intersections 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, e.g., intersections of the optical beam with the inner edge of the edge ring. The reference points used by the AWC system to assess the extent to which the edge ring deviates from a desired placement on the end effector of the wafer handling robot may, in some implementations, be the same reference points that may be used for AWC correction of the semiconductor wafer, i.e., reference points determined based on measurements obtained from the semiconductor wafer using the AWC system. In other implementations, the reference points used for edge ring AWC correction may be obtained based on measurements obtained from the edge ring using the AWC system, e.g., the AWC system may be trained on the edge ring to obtain reference points for future edge ring placements. It will be appreciated 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 have been widely used in the semiconductor processing industry and have typically provided good wafer centering performance. However, the training process is labor intensive, can be quite time consuming, and is prone to user error. Although such training may be performed as part of the initial setup of a semiconductor processing tool, such training may need to be repeated periodically throughout the life of the tool, for example, if any changes occur in the relative locations of the semiconductor processing chamber, the AWC sensor, and the wafer handling robot, or if the wafer processing operation begins to exhibit non-uniformity indicating off-center placement of the semiconductor wafer on the pedestal, or generally, if any maintenance, including wet clean, is performed on the chamber. It will be understood that references to placement of the wafer or edge ring on the wafer support, pedestal, or other equipment by the wafer handling robot may also implicitly include indirect placement of the wafer or edge ring on the wafer support in various implementations. For example, in many semiconductor processing machines, vertically moving lift pins positioned on a wafer support may be used to lift a wafer from an end effector of a wafer handling robot, allowing the end effector to be moved from under the wafer without moving the wafer. The lift pins can then 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 an end effector of a wafer handling robot) configured to support a semiconductor wafer within a semiconductor processing tool.The wafer supports may include, for example, pedestals, ESCs, or other generally circular platform-like structures that are located within a semiconductor processing chamber (or other chamber) and generally contact the semiconductor wafer in a distributed manner, e.g., through face-to-face contact between the backside of the semiconductor wafer and the top surface of the wafer support, as well as structures that may support the semiconductor wafer through more limited contact, e.g., an arcuate support ledge that may contact the semiconductor wafer only at points along the periphery of the semiconductor wafer. The wafer supports may include components that directly contact the semiconductor wafer, as well as components or portions that extend beyond the periphery of the semiconductor wafer, e.g., an annular portion of a pedestal or ESC that extends beyond the periphery of the semiconductor wafer. The wafer supports may optionally be equipped to provide motion, e.g., vertical and / or rotational motion, of the semiconductor wafer supported by the wafer supports. The wafer supports may also optionally include lift pins as discussed above, or other mechanisms that extend upward relative to the remainder of such wafer support, thereby lifting the semiconductor wafer from the remainder of the wafer support. In some cases, the wafer supports may include various removable components, such as edge rings, etc. For example, some wafer supports may be configured for use with one or more non-removable edge rings, e.g., edge rings designed to be removable by a wafer handling robot of a semiconductor processing tool, that may interface with non-removable edge rings, e.g., edge rings not designed to be removable by a wafer handling robot of a semiconductor processing tool, and such non-removable edge rings are considered part of the wafer support in this disclosure and, of course, may still be removed by a technician.

[0074] The present disclosure contemplates, inter alia, an automatic calibration system, e.g., an adaptive positioning system, that can be used in conjunction with an AWC system (or similar device) and / or a wafer handling robot to provide automatic teaching of the AWC system and / or wafer handling robot for a semiconductor processing tool. Such a system may be used for automatic teaching of a wafer handling robot either under vacuum or atmospheric pressure, since the chamber in which teaching occurs may be sealed, as in normal semiconductor processing operations. Such an automatic calibration system may also allow various aspects of the components or wafer placement to be evaluated and / or corrected 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 with an inner diameter sized slightly larger (or sometimes smaller) than the outer diameter of a semiconductor processing wafer, thereby effectively "expanding" the diameter of the semiconductor wafer during processing. Edge rings have the effect of causing any "edge effects" that may reduce the uniformity of process results across a wafer to occur at the outer edge of the edge ring (which has little effect on wafer uniformity) rather than at the semiconductor wafer itself.

[0075] At the heart of an auto-calibration system is an auto-calibration wafer, also known as an adaptive positioning system (APS) wafer, which may collect a large amount of information from a variety of on-board sensors, allowing the auto-calibration wafer to be used as part of a fully automated education process. Such auto-calibration wafers may be used, for example, to perform diagnostic evaluations of components within a semiconductor processing tool, as well as to obtain information that allows adjustments to be made to the operation of the semiconductor processing tool to improve wafer processing performance.

[0076] Generally speaking, an autocalibration wafer for a particular semiconductor processing tool may have a similar size and shape as the wafers and / or edge rings that the semiconductor processing tool is configured to process, thereby allowing the autocalibration wafer to be transported by the wafer handling robot of the semiconductor processing tool in generally the same manner that the wafer handling robot transports semiconductor wafers during processing. Thus, the autocalibration wafer may be dimensioned to have a maximum height and diameter that is less than the minimum vertical and horizontal clearances of the path of the semiconductor processing tool along which the wafer may be transported by the wafer handling robot.

[0077] As mentioned above, an autocalibration wafer may include a variety of sensors, and the number and type of sensors may vary depending on the particular functionality provided by the autocalibration wafer. It will be understood that an autocalibration wafer according to the present disclosure may be configured to provide any one, some, or all of the sensors / functionality discussed herein.

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

[0079] Generally speaking, an autocalibration wafer may have a substrate similar to the overall shape of a semiconductor wafer, e.g., generally circular, although in some cases, the autocalibration wafer may be a different shape, e.g., portions of the substrate that are not used to support sensors or other components, or that do not contact, e.g., contact pads on an end effector or lift pins of a pedestal, may be omitted, which may result in an opening or notch in the autocalibration wafer. Moreover, in some implementations, an autocalibration wafer may have a peninsula or other protrusion along an otherwise nominally circular outer edge, e.g., to support a sensor at a location that exceeds the nominal outer diameter of the corresponding semiconductor wafer. An autocalibration wafer may also include one or more indexing features, e.g., flat edges, notches, etc., along an outer boundary to provide a mechanism for identifying the orientation of the autocalibration wafer. Reference may be made herein to the "center" of an autocalibration wafer, which will be understood to refer to a point on the autocalibration wafer that is intended to be positioned in the same location that the center of a semiconductor wafer or edge ring would be located if the autocalibration wafer were transported or positioned in a semiconductor processing tool in a manner similar to how a semiconductor wafer or edge ring is typically transported or positioned in a semiconductor processing tool. It will be understood that the center of the autocalibration wafer may coincide with the geometric center of the substrate and / or the center of mass of the autocalibration wafer, although such alignment is not a requirement.

[0080] In most implementations, the autocalibration wafer may have multiple downward-facing image sensors, e.g., charge-coupled device (CCD) sensors or complementary metal-oxide semiconductor (CMOS) sensors, located at various locations radially offset from the center of the autocalibration wafer. Such offsets may be selected such that when the autocalibration wafer is positioned above a semiconductor wafer disposed, for example, on a wafer support of a semiconductor processing tool, 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. If the semiconductor processing tool typically uses an edge ring during wafer processing operations, the image sensor may be radially offset from the center of the autocalibration wafer such that the field of view of the image sensor (when disposed on the wafer support) is wide enough to capture a portion of the edge ring as well. In some implementations of the autocalibration wafer, the downward-facing image sensors may be positioned along a circle having a diameter nominally the same size as the semiconductor wafers that the semiconductor processing tool is configured to process, e.g., within ±10% or ±20%. In yet other implementations, the downward-facing image sensors may be positioned along a circle having a diameter between the diameter of the semiconductor wafer that the semiconductor processing tool is configured to process and the diameter of the edge ring that the semiconductor processing tool is configured to use. In some such implementations, the downward-facing image sensors may be positioned along a diameter that is the average, or within the average, e.g., 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, for example, allows the downward-facing image sensors to simultaneously capture within their field of view the outer edge of the wafer support (or the edges of features on the wafer support, e.g., the ESC), the outer edge and / or inner edge of the edge ring, and the outer edge of the semiconductor wafer when the autocalibration wafer is positioned in a location generally centered above the wafer support (and the semiconductor wafer and / or edge ring are centered on the wafer support).

[0081] Such an image sensor arrangement enables the autocalibration wafer to simultaneously acquire images of various fiducial features associated with the wafer support and the semiconductor wafer and / or edge ring disposed on the wafer support. A fiducial, as the term is used herein, 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 may serve as a fiducial for the center point of that structure (it will be understood that such a fiducial may change in size and / or shape over time, for example, 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 a fiducial in the context of this disclosure). In the examples discussed herein, the fiducial used is a feature such as an outer edge of a semiconductor wafer, an outer edge and / or an inner edge of an edge ring, an outer edge of a wafer support or an edge of a feature of a wafer support, a surface discontinuity in a wafer support (e.g., a top surface of a wafer support may have a circular boss surrounded by an annular surface recessed downwardly 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 approaches discussed herein.

[0082] Images acquired for a given set of fiducial features on a semiconductor wafer, edge ring, or other structure may then be analyzed to determine the offset(s) between the fiducial points on the two structures associated with those fiducial features. For example, if the fiducial features used are a circular outer edge of the semiconductor wafer and a circular inner edge of an edge ring surrounding the semiconductor wafer, the relative size of the radial gap between the outer edge of the semiconductor wafer and the inner edge of the edge ring in each image can be determined and used to generate an estimate of the degree to which the center of the semiconductor wafer is offset from the center of the edge ring. Generally speaking, images from at least three image sensors must be used to make such a determination (similar techniques can be performed using images from only two image sensors, but are usually less accurate since the relative sizes of the fiducial features must be assumed). In some cases, some fiducial features may not always be visible, in which case intermediate fiducial features may be required. 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 serve as a reference part for such wafer placement, it is not possible to acquire an image from the image sensor of an auto-calibration wafer in which the outer edge of the ESC and the outer edge of the semiconductor wafer are simultaneously visible. Therefore, any radial gaps present between such edges cannot be identified, and the centrality of the semiconductor wafer on the ESC cannot be directly determined. In such a case, an estimate of the centrality of the semiconductor wafer on the ESC can still be determined using an intermediate reference part, for example, the inner edge of the edge ring. For example, if an edge ring is placed on the wafer support to surround the ESC, the auto-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, a center-to-center offset of the inner edge of the edge ring and the outer edge of the ESC is determined, and the edge ring is repositioned, if necessary, until the edge ring is acceptably centered on the ESC.After the edge ring is centered, the inner edge of the edge ring may serve as a "proxy" for the outer edge of the ESC. Then, when the semiconductor wafer is placed on the wafer support and in the edge ring, an image sensor of the auto-calibration wafer may be used to acquire an image of the radial gap between the outer edge of the semiconductor wafer and the inner edge of the edge ring. Because 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 may serve as a surrogate 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, the center-to-center offset between the outer edge of the semiconductor wafer and the inner edge of the edge ring may be further refined based on the actual measured center-to-center offset 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. For example, if the edge ring is finally positioned such that the center of the inner edge of the edge ring has an XY offset from the center of the outer edge of the ESC of (15 μm, 10 μm), which may be considered to be within an acceptable range of centrality, and then the semiconductor wafer is positioned such that the center of the outer edge of the semiconductor wafer has an XY offset (in the same coordinate system) from the center of the inner edge of the edge ring of (-5 μm, 12 μm), 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., (15 μm-5 μm, 10 μm+12 μm)=(10 μm, 22 μm), e.g., a total offset of approximately 24 μm.

[0083] Once the reference portions of the two structures are imaged with the autocalibration wafer and the offset between the two structures is determined, this offset can be compared against a threshold offset, which may represent the maximum offset between the structures that is deemed acceptable for proper operation of the semiconductor processing tool, and if the offset exceeds the threshold offset, it may cause the semiconductor processing tool to take corrective action.

[0084] While various techniques can be used to determine the center-to-center offset between two structures and are considered within the scope of this disclosure, an exemplary technique for determining such offset is provided in connection with FIG. 1. FIG. 1 illustrates an example of a calibration wafer positioned relative to an edge ring. In FIG. 1, an edge ring 162 is shown with a calibration wafer 160 positioned within the inner diameter of the edge ring 162. For clarity, the terms calibration wafer or reference wafer are used herein to refer to wafers having the same or similar size as typical semiconductor wafers processed by a semiconductor processing tool, and the calibration wafer is intended to serve as a surrogate for such a regular wafer, e.g., as may be processed by a semiconductor processing tool. Calibration or reference wafers may, in some cases, include calibration markers or other features that may be recognized by machine vision algorithms to aid 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] 1, the calibration wafer 160 and edge ring 162 are not shown to scale, for example, to better view the misalignment between the center of the edge ring 162 and the calibration wafer 160 (indicated by crosshairs), and the gap between the outer edge of the calibration wafer 160 and the inner edge of the edge ring 162. The calibration wafer 160 may include a set of calibration markers 170, which may be positioned along the periphery of the calibration wafer and spaced apart a known amount, for example, 120° apart in this example. A first image sensor of the downward-facing autocalibration wafer may be positioned such that the calibration markers 170 and the gap 164 between the edge ring 162 and the 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, the diameter of the calibration wafer may be assumed to be a known amount, for example 300 mm. Thus, the radius r from the center point of the calibration wafer 160 to the edge of the calibration wafer 160 may be w may be assumed to be constant (e.g., the calibration wafer may have a constant radius within the field of view of the first image sensor, although there may be some portions along the edge of the calibration wafer that may have a shorter radius if there is an index flat or notch along the edge). As discussed above, the calibration wafer may also have, for example, calibration markers 170, whose locations may be known with a high degree of certainty. In this example, it is seen that the calibration markers 170 are spaced 120° apart around the circumference of the calibration wafer. The calibration markers may include features such as, for example, radial lines (which are identified in the image data and used to establish a direction vector in each image along which the gap 164 is evaluated), and a square or circle (as shown) that has a known size, e.g., 2 mm, and can be used to determine the scale of the imaged features. For example, if a gap 164 is identified in an image and 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 may be determined to be 0.23 x 2 mm = 0.46 mm. In some implementations, such calculations may take into account image distortions due to lens effects (e.g., using a checkerboard pattern), for example, using machine vision or optical image correction techniques, and may correct for such distortions using calibration data associated with, for example, an auto-calibrated wafer.

[0087] It will be appreciated that the calibration markers discussed above may be omitted in some implementations, and reference portions such as 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 serves as the origin of the coordinate system in determining the center-to-center offset between the edge ring 162 and the calibration wafer 160, the location of the center of the edge ring can be found by determining the locations of three points along the inner (or outer) edge of the edge ring 162 and then determining the location of the center of the circle defined by those three points. Once the location of the center of the edge ring 162 in the calibration wafer's coordinate system is known, it is a straightforward process to extract the center-to-center offset between these two components.

[0089] The gap 164 is defined as the radius r of the calibration wafer 160. w and the angle along which each gap 164 is measured may be used to determine the locations of three points along the inner edge of the edge ring 162. For example, for gap 164 δ1, the gap δ1 is located at a 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 may be determined using a trigonometric relationship based on the angular position of a radius that extends 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. Therefore, 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) In the formula, δ x is the relevant 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] So, for example, r w = 150 mm, δ1 = 17.338 mm, δ2 = 22.823 mm, and δ3 = 37.69 mm. [Table 1]

[0091] It will be appreciated that the above dimensions are to scale based on the proportions of Figure 1, and that such values ​​of δ are impractically large for typical semiconductor processing tools and wafer handling robots. In practice, δ values ​​that may be obtained may often be less than about 1 mm, e.g., 800 μm.

[0092] Once the three XY coordinate pairs are known for the 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 (the center of the calibration wafer) may be determined using the following equation:

number

number

[0093] FIG. 2 shows a schematic diagram of an exemplary autocalibration wafer, with dashed / shaded areas showing the wafer support, edge ring, and calibration wafer positioned thereunder. In FIG. 2, autocalibration wafer 200 is shown including a substrate 202 having a number of different sensors and other electrical components attached thereto. Also shown in FIG. 2, although not part of autocalibration wafer 200, are calibration wafer 260, annular edge ring 262, and wafer support 252. These additional components are shown configured concentrically with autocalibration wafer 200, as would be the case during some stages of normal use when calibration wafer 260, edge ring 262, wafer support 252, and autocalibration wafer 200 are all centered relative to one another. In the illustrated example, autocalibration wafer 200 is shown as being larger in diameter than wafer support 252, edge ring 262, and calibration wafer 260, although in practice autocalibration wafer 200 may be similar in size to calibration wafer 260. As previously mentioned, wafer support 252 may include multiple components, such as an ESC that is slightly smaller in diameter than calibration wafer 260, as well as a support structure that extends beyond the ESC and supports edge ring 262. For simplicity, such separate structures are not shown in FIG. 2.

[0094] The sensors shown as part of the exemplary auto-calibration wafer in 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 optics or other focusing systems 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 area that 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 range of heights above the calibration wafer 260, the edge ring 262, and the wafer support 252 (e.g., at a height where an end effector of a wafer handling robot would typically be when delivering the wafer to the wafer support 252). The field of view 228 of each of the first image sensors 222 may be of various shapes, e.g., either circular or elliptical, and may extend radially outwardly a smaller amount than shown. For example, in some implementations, the field of view 228 of the first image sensor 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 sensor 222 such that it is located 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 sensor 222 may be positioned to acquire image data that may more accurately reflect the size of any gaps that may exist between various fiducial portions in the image, e.g., edges of such components. In particular, such an image sensor placement may reduce the effect that height mismatches may have on the determination of the gap size, leading to a more accurate estimation of the gap size.For example, if the image sensor acquires image data of the gap along a line of sight that is at a very shallow angle relative to the autocalibration wafer, such as would be the case for an image sensor mounted near the center of the autocalibration wafer, small variations in the height of either the edge ring or the calibration wafer may be magnified and cause the gap size to vary in an unpredictable manner. Locating the image sensor near the periphery of the autocalibration wafer may serve to significantly reduce the impact that such effects may have.

[0095] In addition to the first image sensor 222, the autocalibration wafer 200 may optionally include an additional image sensor, such as a centrally located, downward facing second image sensor 224, which may be configured to capture an image directly below the center of the autocalibration wafer. Such an image sensor may be used in a calibration routine such that the imaged fiducial is located near where the center of a semiconductor wafer is typically located; for example, to aid in locating the center of the wafer support relative to the autocalibration wafer, the wafer support housing the wafer may have a crosshair fiducial located at the center of the wafer support, which may be imaged by the second image sensor. For example, when the autocalibration wafer 200 is positioned on the wafer support by an end effector of a wafer handling robot, the wafer support may have a fiducial in its center that may be imaged by the second image sensor 224 to facilitate teaching the wafer handling robot the location of the wafer support. Such a sensor may also be used to center the autocalibration wafer on the end effector of the 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 that is observable by the second image sensor 224 when the autocalibration wafer 200 is generally centered on the end effector. When the wafer handling robot is actuated to remove the autocalibration wafer, the end effector may be moved under the autocalibration wafer such that the fiducial portion is within the field of view of the second image sensor 224. The second image sensor 224 may then acquire an image of the fiducial portion, which may be analyzed to determine how off-center the fiducial portion is relative to the center of the autocalibration wafer 200. The wafer handling robot may then reposition the end effector such that the off-centering of the fiducial portion relative to the autocalibration wafer 200 is reduced to an acceptable limit. It will be appreciated that in other implementations of the autocalibration wafer 200 discussed herein, sensors other than image sensors may be used to acquire the radial gap data and / or the centrality data.For example, ultrasonic sensors may be used to obtain contour maps that may be indicative of the three-dimensional fiducials, and the distances and gaps described above may be determined from those contour maps in a manner similar to how such distances and gaps may be determined from image data. Thus, it will be appreciated that any sensor that can be used to assess the gaps between the fiducials described above and / or the centrality of the auto-calibration wafer 200 relative to the wafer support may be used in place of the image sensors described above.

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

[0097] Vibration sensor 230 may be used to monitor vibrations experienced by the auto-calibrated wafer during various operations, e.g., during operation of a wafer handling robot or during 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 multiple, e.g., three, lift pins, which are thin pins that may be translated vertically relative to an electrostatic chuck (ESC) or other wafer support structure. Such lift pins are typically configured in an equilateral triangular shape within a circular boundary defined by a semiconductor wafer centered on the wafer support. Thus, when the lift pins are in an extended position relative to the surface of the wafer support, they support whatever wafer is present at that wafer station. When the lift pins are retracted into the wafer support, the wafer supported by the lift pins contacts the top surface of the wafer support. During such retraction of the lift pins, the wafer may experience small vibrations, e.g., caused by equipment wear. A vibration sensor(s) may be used to assess the nature of such vibrations and provide an indication of the health of the lift pin mechanism. The vibration sensors may include, for example, accelerometers, piezoelectric vibration sensors, optical distance measurement sensors, or optical microphones (such sensors may detect vibrations, for example, by measuring the displacement of a substrate of an auto-calibrated wafer relative to a wafer support, thereby providing insight into the vibration levels experienced by the wafer), and other types of sensors.

[0098] The orientation / tilt sensor(s) 232 may be used to assess whether the wafer support or other components are supporting the autocalibration wafer (and therefore other wafers) in a level state. For example, if one of the lift pins of the wafer support becomes shorter or longer than the other lift pins, the wafer supported by the wafer support will exhibit a slight tilt. Such tilt may cause one side of the wafer to contact the wafer support before the other side of the wafer, which may cause slight variations in how the wafer is placed on the wafer support and, in some circumstances, may cause sliding movement between some of the lift pins and the wafer while it is being placed on the wafer support (which may damage the wafer and / or cause particle contamination). In addition, such sensors may be used to assess the levelness of the wafer support itself after the autocalibration wafer is placed on the wafer support. Thus, an autocalibration wafer with an orientation sensor may be used to assess the levelness of both the wafer support and other equipment. Orientation sensors may include, for example, an accelerometer and a tilt sensor or inclinometer.

[0099] 3 shows a view of the wafer support 352 with extended lift pins 372 shown supporting the autocalibration wafer 300. The lift pins 372 can be retracted downward (and / or the wafer support 352 translated upward) to place the autocalibration wafer 300 on the wafer support 352.

[0100] The proximity sensor(s) 234 can be used to assess the height of various structures at the wafer station. For example, it may be desirable to assess the height of an edge ring or a portion of an edge ring around its circumference on the wafer support, e.g., on the ESC of the wafer support (where a non-uniform height of the edge ring around its circumference may create or increase process non-uniformity). When a proximity sensor is provided on the autocalibration wafer and positioned in a location that allows direct or indirect distance measurement between the autocalibration wafer and the edge ring (or other structure), the resulting data can be used to determine how uniform the height of the edge ring or a portion thereof is around its circumference.

[0101] In other implementations of the autocalibration wafer, the autocalibration wafer may be placed on an edge ring so that it can be supported by the edge ring. In some such implementations, the autocalibration wafer may have a portion that extends beyond the inner diameter of the edge ring and may rest on the top surface of the edge ring (whereas the semiconductor wafer intended for use with the edge ring is typically contained entirely within the inner diameter of the edge ring). However, in other such implementations, the autocalibration wafer may be sized to have a diameter similar to the diameter of the semiconductor wafer that is configured to be used with the edge ring. In some such implementations, the edge ring may have a stepped inner diameter, e.g., the top surface of the edge ring may have a diameter slightly larger than the diameter of the semiconductor wafers that are 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 concave surface in the edge ring that can be used to support the semiconductor wafer during processing. Thus, an autocalibration wafer supported by such an edge ring may have a small gap between the wafer support that supports the autocalibration wafer. Proximity sensors can be used to determine the size of this gap at various locations around the circumference of the autocalibration wafer / edge ring, and the resulting measurements can be analyzed to determine the variation in levelness or thickness at the portion of the edge ring between the wafer support and the autocalibration wafer.

[0102] FIG. 4 shows a side view of an autocalibration wafer with a set of proximity sensors that may be used to determine the height of the edge ring. In FIG. 4, an edge ring 462 is positioned on a wafer support 452. The autocalibration wafer 400 is positioned to rest on the circumferential ledge of the edge ring 462 and is therefore held slightly above the wafer support 452. As can be seen, the edge ring is non-uniform in height in the ledge area. The right side of the ledge is higher than the left side, resulting in the autocalibration wafer 400 being at a slight angle relative to the wafer support 452 and edge ring 462. The proximity sensors 434 in the autocalibration wafer 400 may be configured to measure the distance between each proximity sensor 434 and the closest opposing surface, such as the top surface of the wafer support 452. In this case, the left proximity sensor 434 measured a distance Δ1 and the right proximity sensor 434 measured a distance Δ2. These distances may be evaluated against one or more conditions to determine whether the edge ring height exceeds a tolerance. For example, in some implementations, if |Δ1-Δ2|>x, or max(Δ1, Δ2)>y, then the edge ring may be considered to have an edge ring height that exceeds a limit, and corrective action may be taken, such as requesting the installation of a new edge ring.

[0103] In some such implementations, two sets of proximity sensors may be provided on the autocalibration wafer. One set is positioned to obtain distance measurements between the autocalibration wafer and the edge ring, and the other set is positioned to obtain distance measurements between the autocalibration wafer and structures other than the edge ring, such as a calibration wafer or a surface of a wafer support located in the center of the edge ring. In such implementations, the autocalibration wafer may be positioned at a location just above the edge ring, for example supported by lift pins or a wafer handling robot, and the proximity sensors may be used to obtain distance measurements between the autocalibration wafer and the edge ring, and between the autocalibration wafer and other structures. In such implementations, the autocalibration wafer is sized larger (or has portions that protrude beyond its diameter) than a typical semiconductor wafer used in a semiconductor processing tool, such that the autocalibration wafer radially overlaps the edge ring by a sufficient margin to allow the proximity sensors attached to the autocalibration wafer to radially overlap the edge ring and thus determine the distance between the upwardly facing surface of the edge ring and the proximity sensors. Other proximity sensors can be positioned on the autocalibration wafer so as to radially overlap the central opening of the edge ring, thereby enabling these proximity sensors to obtain distance measurements between the autocalibration wafer and, for example, a calibration wafer located in the center of the edge ring, or, if no such wafer is present, the exposed surface of the wafer support.

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

[0105] 5 shows a side view of another autocalibration wafer having two sets of proximity sensors, each set located along a circular path of a different diameter. In FIG. 5, an autocalibration wafer 500 is supported by an end effector 558 of a wafer handling robot over a wafer support 552 and an edge ring 562. When the autocalibration wafer 500 is nominally centered over the edge ring 562, an outermost proximity sensor 534 is located at a radial position that radially overlaps the edge ring 562, and an innermost proximity sensor 534 is located at a radial position that radially overlaps the interior of the edge ring 562. The proximity sensors 534 are controlled to measure the distance between the proximity sensor 534 and the surface directly below the proximity sensor, e.g., distance Δ 1a , Δ 2a , Δ 1b , and Δ 2b , may be determined simultaneously and evaluated to determine whether the edge ring height has changed beyond an acceptable range. For example, |Δ 2a -Δ 2b |>x or max(Δ 2a ,Δ 2b )>y, or |(Δ 1a -Δ 1b )-(Δ 2a -Δ 2b )|>x or max((Δ 1a -Δ 1b ),Δ 2a -Δ 2b))>y, the edge ring height may be considered to be above an acceptable threshold. In some such implementations, this measurement may be used to actuate the edge ring lift pins to adjust the edge ring height above the wafer support, e.g., above the ESC, to create a closed loop system that can maintain the edge ring height above the wafer support, e.g., the ESC. A similar approach may be used for initial calibration of the edge ring lift pins to determine, for example, how high each edge ring lift pin must be individually to flatten the edge ring against the wafer support. For clarity, note that the wafer support may have multiple sets of lift pins, e.g., 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 that the edge ring occupies. 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] Various types of proximity sensors may be used, including, for example, capacitive distance sensors, inductive distance sensors, optically based distance sensors, etc. In some cases, the auto-calibration wafer may also include one or more other types of sensors, such as, for example, temperature sensors, pressure sensors, humidity sensors, light sensors, etc.

[0107] The various sensors included in the autocalibration wafer may be communicatively connected to a first controller 208, which 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, e.g., a battery, a capacitive load, or other power source. In some implementations, the power source 214 may be operatively connected to a charging feature, e.g., by an electrical contact pin located at a location aligned with the charging feature located on a docking station used to store the autocalibration wafer 200, e.g., when the autocalibration wafer 200 is placed in the docking station. In the implementation shown in FIG. 2, a wireless charging capability 216 is shown, which may be, e.g., 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 autocalibration wafer 200 may have a similar wireless charging interface configured to charge the autocalibration wafer 200 when the autocalibration wafer 200 is placed therein.

[0108] The first controller 208 may also be communicatively connected to a first wireless communication interface, e.g., WiFi, Bluetooth, or other wireless communication interface, by which commands and / or data may be transmitted to and / or from the first controller 208 and thus the auto-calibrated wafer 200. For example, a semiconductor processing tool that interfaces with the auto-calibrated 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 connected to a second wireless communication interface, which may in turn be configured to interface with the first wireless communication interface of the auto-calibrated wafer. Thus, the auto-calibrated wafer 200 may wirelessly communicate with the semiconductor processing tool, thereby allowing information, commands, and other data to be transmitted between the auto-calibrated 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 in this example is a rechargeable battery, a processor 610, a memory device 612, and a wireless charging feature 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 locations around the periphery of the substrate 602, as well as a centrally mounted second image sensor 224. Located generally adjacent to each of the first image sensors 622 is a corresponding proximity sensor 634, which in this example is a capacitive proximity sensor.

[0110] FIG. 7 shows a line plan view of another exemplary autocalibration wafer 700. In this example, the autocalibration wafer 700 has a generally circular substrate 702 having three lobes spaced around its periphery, each lobe housing a corresponding first image sensor 722. In this example, the substrate 702 has generally the same diameter as a typical semiconductor wafer. The lobes extend beyond this diameter, allowing the first image sensor 722 to be positioned such that the photosensitive area of ​​the first image sensor 722 is, for example, centered above the outer edge of the underlying semiconductor wafer and centered below the autocalibration wafer 700. The autocalibration wafer 700 in this example also includes two power sources 714, e.g., rechargeable batteries, which may be charged using wireless charging capabilities 716, e.g., inductive charging coils. The battery may power various electrical components of the auto-calibration wafer 700, such as the processor 710, the memory 712, the wireless communication interface 718, the first image sensor 722, the second image sensor 724, the proximity sensor 734, and the accelerometer 736, which may be used as an orientation or tilt sensor.

[0111] 8a-8i show schematic diagrams of a semiconductor processing tool at various stages of using an auto-calibration wafer. In FIG. 8a, a portion of the semiconductor processing tool is shown. The depicted portion of the semiconductor processing tool includes two wafer stations 844a and 844b, although the tool may 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. Wafer stations may be present, for example, but not limited to, within the process chamber(s) of the tool, within a buffer used to store wafers before or after processing, within an airlock or loadlock that allows for the transfer of wafers between different pressure environments, a load port, a front opening integrated pod (FOUP) that can dock to a load port, etc. In FIG. 8a, wafer station 844a is provided by a semiconductor processing chamber 850. In contrast, wafer station 844b is provided by a docking station 868 dedicated to storing the auto-calibration wafer 800 (although in some implementations such a dedicated docking station may not be included). Docking station 868 may have features (not shown) for charging the auto-calibration wafer 800 or may otherwise be configured to interface with various aspects of the auto-calibration wafer 800. In some implementations, the docking station may be located in (or attached to) a vacuum transfer module (VTM) and accessible by a wafer handling robot in the vacuum transfer module, which may then 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 atmospheric or near atmospheric pressure location, in which case a wafer handling robot located in the EFEM may be used to first retrieve the auto-calibration wafer and then transfer it to another wafer handling robot located in the VTM.

[0112] Each wafer station 844 may have an associated wafer support 852, such as wafer support 852a / pedestal 854 of wafer station 844a (although no wafer support is shown in wafer station 844b, the wafer station may also have a wafer support that may accommodate the auto-calibration wafer 800 when placed in the wafer station). In some cases, a wafer station may be associated with an active wafer centering (AWC) system 866, which may enable measurements of the wafer center location to be taken as the 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 may include two perpendicularly oriented optical beam sensors (represented by dots in the AWC system 866) to detect when the edge of the wafer crosses either optical beam. As discussed above, the AWC system 866 can be used to determine the location of the center of a wafer being supported by the end effector 858 of the tool's wafer handling robot 856 relative to a particular known reference frame, thereby making it possible to determine as to any positioning corrections that may need to be made before placing the wafer at the desired location.

[0113] 8a, a wafer handling robot 856 supports an edge ring 862 on an end effector 858 in preparation for placing the edge ring 862 on the wafer support 852a / pedestal 854. The autocalibration wafer 800 is temporarily stored in wafer station 844b / docking station 868 for an interim period.

[0114] In FIG. 8b, the wafer handling robot 856 is actuated to position the edge ring 862 in 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. 8 c , wafer handling robot 856 has finished retrieving autocalibration wafer 800 from wafer station 844 b / docking station 868 and is ready to position the autocalibration wafer onto wafer support 852 a / pedestal 854 and edge ring 862 .

[0116] In FIG. 8d, the wafer handling robot 856 extends the end effector 858 to position the autocalibration wafer 800 over the wafer support 852a / pedestal 854 and edge ring 862. The autocalibration wafer 800 is thus positioned such that the field of view of the downward facing first image sensor of the autocalibration wafer 800, indicated by three dashed rectangles spaced along the outer edge of the autocalibration wafer 800, includes the edge ring 862 and one or more features of the wafer support 852a / pedestal 854. The second controller 842 then causes the first controller of the autocalibration wafer 800 to acquire image data from the first image sensor, for example, of a gap between the inner edge of the edge ring 862 and a reference portion of the wafer support 852a / pedestal 854, for example, the outer edge of the ESC of the wafer support 852a. As discussed above, these gaps may be used to determine the amount that the center of the edge ring 862 is offset relative 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 acceptably positioned, and the wafer handling robot 856 may remove the autocalibration wafer 800 from wafer station 844a and return it to wafer station 844b, as shown in FIG. 8e.

[0117] In Figure 8f, the wafer handling robot has been actuated to retrieve a calibration wafer 860, which may also be stored in a docking station 868, for example below or above the autocalibration wafer 800, or may be retrieved from an entirely different location, for example from a load lock or air lock. The calibration wafer 860 may then be placed in the wafer station 844a / semiconductor processing station 850 and transferred to the wafer support 852a / pedestal 854 so that it is nominally centered relative to the center of the edge ring 862, as shown in Figure 8g.

[0118] In Figure 8h, the wafer handling robot is again actuated to remove the auto-calibration wafer 800 from wafer station 844b / docking station 868. In Figure 8i, the wafer handling robot is further actuated to position the auto-calibration wafer 800 over wafer support 852a / pedestal 854, calibration wafer 860, and edge ring 862. Similar to Figure 8d, the auto-calibration wafer 800 may then be controlled to acquire image data of the gap between edge ring 862 and calibration wafer 860, e.g., gap 864, which allows any offset between the center of calibration wafer 860 and the center of edge ring 862 to be determined.

[0119] Various techniques that can be implemented using autocalibration wafers, such as those discussed above, are examined in more detail below with reference to FIGS.

[0120] FIG. 9 shows a flow chart of a technique for determining the location of a reference point of a structure at a wafer station using an auto-calibration wafer. Such a technique may be used, for example, in teaching a wafer handling robot various locations where a wafer may be placed (or removed). In block 902, an auto-calibration wafer may be removed using an 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 auto-calibration wafer center (or other known reference point on the auto-calibration wafer) is centered on a known reference point of the end effector, thereby establishing a spatial relationship between the two reference points and allowing measurements taken using the auto-calibration wafer to be mapped or transformed into a coordinate system used by the wafer handling robot.

[0121] Such placement of the autocalibration wafer on the end effector can be accomplished by any suitable mechanism, including the use of physical index features or other contact-based techniques that ensure the autocalibration wafer is properly positioned on the end effector. In some cases, however, imaging capabilities of the autocalibration wafer itself may instead be used to ensure that the autocalibration wafer is centered on the end effector. For example, immediately prior to loading the autocalibration wafer onto the end effector, the autocalibration wafer may be positioned over the end effector and one or more image sensors of the autocalibration wafer may be activated to capture an image of the end effector or an area of ​​the end effector. The imaged portion of the end effector may include, for example, a fiducial portion that defines a reference point on the end effector, e.g., a location on the end effector that coincides with the XY center point of a theoretical semiconductor wafer perfectly positioned on the end effector. This image data may then be analyzed to determine the degree to which the reference point of the autocalibration wafer, e.g., the center of the autocalibration wafer, is offset from the reference point / reference portion of the end effector. The wafer handling robot can 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, so that the auto-calibration wafer is centered on the end effector.

[0122] At block 906, a wafer station may be selected for calibration, e.g., for determination of a reference point on a structure of the wafer station, e.g., a wafer support, where a center of a wafer delivered to the wafer station is intended to be located. At block 908, a wafer handling robot may be actuated to, e.g., position an end effector and an auto-calibration wafer over the selected wafer station such that the auto-calibration wafer is approximately centered over a reference point on the wafer support of the selected wafer station. Such initial positioning may be based, for example, on an estimate of the location of the reference point of the wafer support determined based on the as-designed locations of various components in the system, which may generally allow placement accuracy to within a millimeter or within a few millimeters in most cases.

[0123] In block 908, the auto-calibration wafer may acquire image data of a fiducial portion(s) on the target structure located at the selected wafer station. The fiducial portion(s) may be associated with a reference point of the wafer station, for example, where the center of a wafer delivered to the wafer station is intended to be located. For example, the outer edge of the ESC of the wafer support at the selected wafer station may function as a fiducial portion. Such a fiducial portion may not directly indicate the reference point of the wafer station, but may still clearly define it. For example, a circular or arc-shaped edge of the ESC may define a center point that serves as the reference point. In another example, the wafer support may include some kind of fiducial portion, such as an etched "+" or other marking, that directly marks the reference point; for example, the center of the wafer support may be the reference point, and the intersection of the two lines in the "+" may indicate the reference point.

[0124] In block 912, a location of a reference point of a selected wafer station structure, e.g., a wafer support, relative to the autocalibration wafer may be determined based on image data of the reference portion. For example, the image data may indicate that the reference point of the structure has an XY offset in the coordinate system of the autocalibration wafer from a reference point of the autocalibration wafer, e.g., from the center of the autocalibration wafer, of (0.3 mm, 0.5 mm).

[0125] The location of the reference point of the structure may then be determined relative to the coordinate system of the wafer-handling robot in block 914. For example, the XY offsets determined relative to the coordinate system of the auto-calibrated wafer in block 912 may undergo a coordinate system transformation to convert them to equivalent coordinates in the coordinate system of the wafer-handling robot, e.g., to accommodate an expected angular shift between the coordinate system of the auto-calibrated wafer and the coordinate system of the wafer-handling robot.

[0126] When the calibration technique of FIG. 9 is used, it may be desirable in some cases to calibrate the auto-calibration wafer prior to implementing the technique. For example, it may be desirable to establish the position of the image sensor(s) used to acquire image data relative to a reference point, e.g., a center point, of the auto-calibration wafer so that location information determined from such sensors can be appropriately processed. Each image sensor can be considered, for example, as providing XY location data (based on a rectangular or linear array of pixels that each such sensor may have) in a coordinate system that is unique to each image sensor and offset a particular XY distance and / or rotation angle from the reference point of the auto-calibration wafer. Calibrating the auto-calibration wafer allows such XY and angular offsets to be determined for the coordinate system, each image sensor. Any locations subsequently determined from the image sensor data may then be appropriately transformed to be accurately located relative to the coordinate system of the reference point of the auto-calibration wafer.

[0127] In an example of such a calibration, the autocalibration wafer may be placed in a fixture that has index pins or other alignment features that contact the outer edge of the autocalibration wafer to physically constrain the autocalibration wafer to be centered over a fiducial portion. The fiducial portion is part of the fixture and is known to be centered relative to the constrained outer edge of the autocalibration wafer. Once the autocalibration wafer is mounted in the fixture and centered over the fiducial portion, a centrally mounted image sensor may be caused to acquire an image of the fiducial portion, which may then determine, for example, which pixel(s) coincide with the center point indicated by the fiducial portion, thereby providing information that may be used later to transform any location data obtained from the image of the centrally mounted image sensor into a coordinate system associated with the fiducial point. Similar fiducial portions may be provided in the fixture at locations that coincide with the fields of view of other image sensors to allow calibration of all image sensors prior to use.

[0128] FIG. 10 shows a flow chart of a methodology for determining the relative positioning of two structures at a wafer station using an auto-calibration wafer. The methodology of FIG. 10 begins at block 1002, where a wafer handling robot of a semiconductor processing tool is used to retrieve the auto-calibration wafer, for example, from a docking station or other holding area used to store the auto-calibration wafer. At block 1004, a wafer station of the semiconductor processing tool may be selected for calibration. It is assumed that the structure for which the relative positioning is to be determined is already located at the selected wafer station. For example, the selected wafer station may have an edge ring (first structure) disposed on, for example, a wafer support (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, for example, position the auto-calibration wafer so that it is nominally centered above the wafer support / edge ring of the selected wafer station, and position a first image sensor positioned along the periphery of the auto-calibration wafer above the edge ring and wafer support in a manner that allows the first image sensor to acquire images of fiducial portions of two structures, e.g., the inner edge of the edge ring, and the edge of a feature of the wafer support, e.g., the outer edge of the ESC of 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, for example, determine the gap size between the fiducial 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 expected vertical distance between the first image sensor and the imaged structures. Such estimates may be somewhat inaccurate, but are typically scaled similarly in each image. If the reference portion for each structure is located along a common reference circle, for example, the arcuate outer or inner edge of the edge ring (or a single circular edge thereof), all in the same radial direction as each other, can serve as the reference portion for the edge ring, and the arcuate edge of the wafer support (or a single circular edge thereof), all in the same radial direction as each other, can serve as the reference portion for the wafer support. It will be understood that other reference portions can be used to similar effect, and that the techniques discussed herein are generally applicable to any suitable reference portion and applicable algorithms to determine the relative offset between such structures based on the selected reference portion.

[0130] In block 1010, a decision may be made regarding an offset between both fiducials, e.g., structures, based on the relative gap size between the imaged fiducial portions of the two structures. Such offset may be compared to a threshold offset to see if the misalignment of the centrality of the two structures is within an acceptable range. Such a threshold offset may be established based on the non-uniformity requirements of a particular semiconductor processing recipe. If the non-centrality measurement is not within an acceptable range, appropriate action may be taken. For example, one of the structures may be repositioned based on the measured central offset, and the procedure may be repeated until the non-centrality measurement is within an acceptable range.

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

[0132] At block 1106, a wafer station may be selected to determine the center point of its wafer support. At 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 a reference portion(s) of the wafer support may be acquired, for example, using one or more image sensors of the autocalibration wafer. Such a reference portion may be, for example, an etched pattern located at the center of the wafer support. Alternatively, the reference portion may be a circular edge of a portion of the wafer support, for example, of a portion of the ESC that is part of the wafer support, that defines a center point of the wafer support. In the former case, the reference portion may be imaged using an image sensor located near or in the center of the autocalibration wafer. In the latter case, the reference portion may be imaged using an image sensor located near an outer edge of the autocalibration wafer.

[0134] In block 1112, the image data may be analyzed to determine an offset between a reference point, e.g., a center point, of the auto-calibrated wafer and a reference point of the selected wafer station defined by the fiducial portion. In block 1114, the offset determined in block 1112 may be transformed to the coordinate system of the wafer handling robot. If necessary, a "default" location corresponding to the center of the selected wafer support may be updated to account for the offset determined in block 1114 (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 cause the wafer handling robot to shift the auto-calibrated wafer (similar to block 1108) such that the auto-calibrated wafer center is positioned at the updated center location relative to the wafer support. In such implementations, blocks 1110-1114 may be repeated as necessary to ensure that the updated centered location is properly centered. If it is found that the updated default location (or a correction to the default location) still produces a center-to-center offset that is not within acceptable limits, this process may be repeated one or more times.

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

[0136] 12 shows a flow chart of a method for calibrating the placement of an edge ring on a wafer support. In block 1202, a wafer handling robot of a semiconductor processing tool may be actuated to cause the wafer handling robot to retrieve 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 because the edge ring may have been manually placed or placed on the wafer support or may have been previously placed or placed on the wafer support, such as during another phase of operation.

[0137] In block 1206, the wafer handling robot may be controlled to cause the wafer handling robot to retrieve the auto-calibration wafer from the docking station or other location. In block 1208, the wafer handling robot may be further operated to position the auto-calibration wafer at a location on the wafer support (and 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 use an edge camera, e.g., a first image sensor, of the auto-calibration wafer to acquire image data of the gap between the inner edge of the edge ring and the outer edge (or other reference portion) of a feature on the wafer support, e.g., the outer edge of an ESC that is part of the wafer support.

[0139] At 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 the gap between the fiducials in the image. At 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 methodology may proceed to block 1216, where the wafer handling robot may be actuated to remove the auto-calibrated wafer from its position above the wafer support and return it, for example, to a docking station (or some other temporary holding location). Then, at block 1218, the wafer handling robot may be actuated to retrieve the edge ring from the wafer support of the selected wafer station. For example, the edge ring may be lifted off the wafer support using lift pins so that an end effector of the wafer handling robot can be inserted under the edge ring, and the edge ring may then be lowered onto the end effector by retracting the lift pins into the wafer support.

[0140] In block 1218, the wafer handling robot may be used to remove the edge ring from the wafer support, and the wafer handling robot may then be further controlled to reposition the edge ring on the wafer support such that the edge ring center is relocated to a new location that takes into account the edge ring offset, so that the edge ring and the wafer support are more accurately centered with respect to each other. After block 1218, the methodology may return to block 1206, where further evaluation of the edge ring / wafer support center offset may be made. If necessary, this portion of the methodology may be repeated a threshold number of times, or until the estimated center offset between the edge ring and the wafer support is within a predetermined threshold offset. If in block 1214, the estimated edge ring / wafer support offset is found to be within the predetermined threshold offset, the methodology may proceed to block 1222, where the calibration of the edge ring placement may be considered complete.

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

[0142] For an edge ring, once the edge ring is properly positioned on the wafer support, the edge ring can typically maintain its position over multiple wafer processing operations. However, for centering a calibration wafer, the calibration wafer only serves as a surrogate or proxy for the wafer to be placed in future operations. Thus, once a calibration wafer is centered on a desired structure, such as a wafer support or edge ring, using the auto-calibration wafer approach discussed herein, the calibration wafer may be removed from the centered location using a wafer handling robot and used to train an active wafer centering (AWC) system, which can then "learn" the desired center point of the calibration wafer relative to the end effector for a given wafer handling robot motion path, and future placements of wafers on the end effector of the wafer handling robot can then be evaluated using the active wafer centering system to determine an offset between such wafer center point and the learned center point. The wafer handling robot may then be actuated to place the wafer on the wafer support in a manner corresponding to the determined offset. It will be appreciated that while an edge ring may generally maintain a predetermined position over multiple processing operations, the edge ring may be replaced from time to time and similar AWC techniques as discussed above may be implemented during such subsequent edge ring placement to compensate for any misalignment between such edge ring and the end effector.

[0143] Using the techniques discussed herein, the relative offset between two moving components, such as an edge ring and a wafer, may be determined. As an example, Figure 13 shows a flow chart 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 technique of Figure 12, an edge ring may be placed on the wafer support of the selected wafer station in block 1304, and then the edge ring may be centered on the wafer support in block 1306, for example, using the centering technique discussed above with respect to Figure 12. Blocks 1304 and 1306 may be optional. The edge ring may also have been placed on the wafer support of the selected wafer station by other means, for example, manual placement, or may already have been placed on the wafer support prior to selecting the selected wafer station.

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

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

[0147] At 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 sizes in the images. At block 1320, a determination may be made as to whether the wafer / edge ring offset exceeds a predetermined threshold offset. If so, the methodology may proceed to block 1322, where the wafer handling robot may be activated to return the auto-calibration wafer to a docking station (or other temporary holding location), and then proceed to block 1324, where the wafer handling robot may be further activated to remove the calibration wafer from the wafer support of the selected wafer station. For example, lift pins for the wafer support may be caused to lift the calibration wafer off the edge ring so that an 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 may be actuated to reposition the calibration wafer on the wafer support of the selected wafer station such that the calibration wafer center is located at a new location that takes into account the wafer / edge ring offset determined in block 1318. The methodology may then return to block 1312 to initiate further automated calibration wafer imaging operations of the gap size between the calibration wafer and the edge ring. This repositioning and centrality reanalysis of the calibration wafer and edge ring may be performed multiple times, for example, until the determined wafer / edge ring offset falls below a predetermined threshold or until a predetermined number of such iterations have occurred. If, in block 1320, it is determined that the wafer and edge ring are sufficiently centered relative to one another, i.e., the determined wafer / edge ring offset is within a predetermined threshold, the methodology may proceed to block 1328, where the calibration of the wafer / edge ring placement may be considered complete. At this point, the calibration wafer may be removed from the wafer station using a wafer handling robot and used, for example, to train an active wafer centering system, in the same manner as if a calibration wafer that was manually centered relative to the wafer support using, for example, a fixture or other mechanical centering system were used. Training of active wafer centering systems based on a centered wafer, or based on a wafer otherwise placed on the end effector of a wafer handling robot in a calibrated wafer, is well known in the industry and will not be described in detail in this disclosure for the sake of brevity.

[0149] It will be appreciated that the techniques described above may be implemented in a variety of different ways to achieve similar results. For example, in a tool with multiple wafer handling robots, or a wafer handling robot with dual arms / end effectors, one wafer handling robot arm / end effector may be used to place or reposition an object, such as a calibration wafer and / or edge ring, on the wafer support, while the other wafer handling robot arm / end effector may be used to hold the auto-calibration wafer. Thus, for example, a first arm may be used to place an edge ring on the wafer support and then retracted, and then a second arm may move the auto-calibration wafer over the positioned edge ring to obtain a measurement of the center-to-center offset between the edge ring and the wafer support. The second arm may then be retracted and, if necessary, the edge ring may be lifted off the wafer support, e.g., using lift pins, and the first arm may be used to reposition the edge ring to correct for the center-to-center offset between the edge ring and the wafer support. The first arm may then be withdrawn and the second arm may again move the auto-calibrated wafer over the edge ring and wafer support to obtain a second measurement of the center-to-center offset. This process may be repeated as necessary until the desired amount of center-to-center offset between the edge ring and the wafer support is achieved.

[0150] It will be further appreciated that the positioning of the wafer and / or edge ring on the wafer support guided by the auto-calibration wafer is an iterative process in which an estimate of the relative offset between two structures, e.g., the wafer and wafer support, the edge ring and wafer support, or the edge ring and wafer, is obtained using the auto-calibration wafer, and then the estimate is used to guide the repositioning of one of the two structures relative to the other structure, which may remain stationary. Such auto-calibration wafer assisted positioning and evaluation 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. If both the edge ring and the calibration wafer are subjected to a centering operation using the auto-calibration wafer, a 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 relative to each other. For example, if an edge ring is centered relative to the wafer support and then a calibration wafer is centered relative to the edge ring, the calibration wafer would not be directly centered relative to the wafer support (it would only be indirectly centered via the centering of the edge ring). In such implementations, an autocalibration wafer may be used to additionally evaluate the centrality of the calibration wafer relative to the wafer support. In some such implementations, the predetermined threshold offsets for each pair of structures may be selected such that two of the three center-to-center offsets are allowed to be within the corresponding predetermined threshold offsets, while the third center-to-center offset actually exceeds the corresponding predetermined offset. (Of course, it is possible to select the predetermined threshold offsets such that this scenario does not occur, but this may in some cases result in accepting unacceptable process uniformity or may require some predetermined thresholds to be smaller than typically required, which may increase the number of centering iterations that may have to be performed.)Generally speaking, in such implementations, the threshold offset may typically be selected such that a 2 out of 3 success / 1 out of 3 failure scenario with respect to threshold offset compliance is avoided in most cases; however, for example, if an edge ring is positioned relative to the wafer support in a particular orientation at the limit of a given edge ring / wafer support offset and a calibration wafer is positioned relative to the edge ring in the same orientation at the limit of the given wafer / edge ring offset, the calibration wafer will have a maximum center-to-center offset from the wafer support that may exceed the maximum center-to-center offset characteristic of the calibration wafer / wafer support.

[0151] In such implementations, when a 2 out of 3 success / 1 out of 3 failure scenario occurs, the semiconductor processing tool may take various corrective actions. For example, in some implementations, a controller of the semiconductor processing tool may cause a wafer handling robot to remove and then replace the calibration wafer and / or edge ring using a similar approach as described above, e.g., using a corresponding tighter predetermined threshold offset for placement.

[0152] It will also be appreciated that some semiconductor processing tools may use an automated calibration wafer to perform both the calibration wafer and edge ring positioning / centering operations by centering 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 a calibration wafer has been centered on the wafer support or 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 an auto-calibration wafer to ensure that the trained active wafer centering system produces reliably centered wafer placement. FIG. 14 shows a flow chart of such a technique for verifying wafer placement repeatability (the technique of FIG. 14 is intended to be practiced after the active wafer centering system has already been trained). This technique assumes that the active wafer centering system has been trained with a wafer centered relative to the wafer support, but with appropriate modifications may be used with an active wafer centering system that has been trained using, for example, a wafer centered relative to an edge ring.

[0154] At block 1402, a wafer station of a semiconductor processing tool may be selected. The selected wafer station will have a calibration wafer previously centered on its wafer support, e.g., using the techniques discussed above, and an active wafer centering system associated with the wafer station will have been trained based on the centered location of the calibration wafer. At block 1404, a controller of the semiconductor processing tool may cause a wafer handling robot of the semiconductor processing tool to retrieve the calibration wafer from a holding station of the semiconductor processing tool, e.g., from a buffer, FOUP, or other location. At block 1406, the wafer handling robot may be controlled to place the calibration wafer on the wafer support of the selected wafer station.

[0155] After the calibration wafer is placed on the wafer support, the wafer handling robot may be caused to retrieve the auto-calibration wafer, for example from a docking station or other storage location, in block 1408. In block 1410, the wafer handling robot may be actuated to position the auto-calibration wafer over the calibration wafer and wafer support of the selected wafer station such that each of the first image sensors of the auto-calibration wafer has an edge of the calibration wafer and an edge of the wafer support within its field of view.

[0156] At block 1412, the auto-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 an offset between the center of the wafer support and the center of the calibration wafer. This offset may be stored for future reference. At block 1416, a counter X may be incremented to X+1, and at block 1418, it may be determined whether X exceeds a given threshold Y. X may represent the number of test placements that have been performed as part of the recipe, and Y may represent the total number of test placements that will be performed as part of the recipe.

[0157] If, in block 1418, it is determined that X is not greater than Y, the methodology may proceed to block 1420 before returning to block 1404. In block 1420, the calibration wafer may be returned to its original location or other location in the holding station with the randomized offset, after which the wafer handling robot is returned to a default or "home" position in block 1422. The randomized offset may be selected to be within a typical expected offset of the wafer under normal operational use, e.g., an offset of less than 0.8 mm. Thus, when the calibration wafer is retrieved again by the wafer handling robot in block 1404 (the wafer handling robot is typically returned to the same location each time to retrieve the calibration wafer), the calibration wafer will have a correspondingly randomized offset position relative to the end effector of the wafer handling robot. It will also be appreciated that randomization of wafer placement may alternatively occur at other times, such as immediately prior to retrieving the calibration wafer from the holding station or other location, and the wafer handling robot may be given randomized displacements such that the position of the calibration wafer relative to the end effector is similarly randomized. Such randomization may be useful to account for slight misalignments of wafers placed in the holding station during normal operation.

[0158] If it is determined at block 1418 that sufficient test wafer placements have been performed, the methodology may proceed to block 1424, where the center offsets for the Y wafer placements may be evaluated or analyzed. Such analysis may include any of a variety of different analysis methods or tests, such as, for example, statistical parameters of a captured population of test wafer center offsets may be determined and compared to corresponding thresholds. For example, the mean, median, and standard deviation of the offsets may be determined and evaluated against corresponding thresholds to determine whether the test methodology resulted in acceptable consistency of wafer placement. At block 1426, the offsets may be compared against those thresholds (or, more precisely, statistical parameters derived from the offsets may be compared to their corresponding thresholds) to determine whether the test was successful. If the comparison at block 1426 indicates that one or more acceptable parameters have been exceeded, the methodology may proceed to block 1428, where an error condition may be generated. If the comparison at block 1426 indicates that one or more parameters are all within acceptable ranges, the methodology may proceed to block 1430, where the methodology may complete successfully.

[0159] It will be appreciated that a similar technique may also be performed using an edge ring to assess the repeatability of edge ring placement, e.g., performing edge ring placements repeatedly and randomizing the end effector / edge ring offset between each placement.

[0160] FIG. 15 illustrates a flow chart of a technique 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 in place on its wafer support. For example, the technique of FIG. 15 may be performed at intervals during a processing operation, using the edge ring that remains in place on the wafer support during such operation, to determine whether the edge ring has degraded non-uniformly (or unacceptably, regardless of uniformity) as a result of repeated exposure to semiconductor wafer processing cycles.

[0161] In block 1504, the auto-calibration wafer may be picked up by the wafer handling robot and then delivered to a wafer support of the selected wafer station. Such delivery of the auto-calibration wafer to the wafer support may include placing the auto-calibration wafer directly onto the edge ring, for example, by 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.

[0162] In block 1508, the autocalibration wafer may be caused to obtain distance measurements between the autocalibration wafer and the wafer support using proximity sensors on the autocalibration wafer. In some implementations, such distance measurements may be obtained using proximity sensors typically located at at least three locations around the circumference of the autocalibration wafer, allowing a determination to be made regarding the orientation of a plane defined by the autocalibration wafer relative to a plane defined by a top surface of the wafer support. If the distance between the two planes exceeds a certain threshold at any point centered on the inner diameter of the edge ring or a diametric circle near the inner diameter and centered on the edge ring, this may indicate that the edge ring thickness is out of tolerance and that the edge ring needs to be replaced.

[0163] In block 1510, the auto-calibrated wafer may be removed from the wafer support using a wafer handling robot, and in block 1512, the obtained distance measurements may be evaluated to determine whether the measured distances indicate that the edge ring is within acceptable height limits or not. For example, if any of the proximity distances are below (or above) a predefined threshold, this may indicate that the edge ring height is too small (or too large). Another metric that may be used to evaluate the edge ring height is the variation between different distance measurements. For example, for a given measurement cycle using the auto-calibrated wafer, the difference between the maximum distance measurement for an edge ring and the minimum distance measurement for that edge ring may be compared to another predefined threshold to determine whether the edge ring height changes an unacceptable amount around the edge ring circumference. If in block 1512, the distance measurements are determined to be within acceptable limits, the methodology may proceed to block 1516, where a success condition may be determined. If, at block 1512, it is determined that the distance measurement is not within the acceptable range, the methodology may proceed to block 1514, where a fault or failure 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 installed, centered, and a height measurement is performed.

[0164] As mentioned above, in some implementations, the autocalibration wafer can also be used to determine dynamic characteristics of a semiconductor processing tool, such as lift pin vibration and tilt. Figure 16 shows a flowchart of a method for evaluating lift pin vibration.

[0165] The methodology of FIG. 16 may begin at block 1602, where a wafer station may be selected for lift pin vibration evaluation. At block 1604, a wafer handling robot may be actuated to retrieve an auto-calibration wafer from a storage location, such as, for example, a docking station. At block 1606, the auto-calibration wafer may be positioned on a wafer support of the selected wafer station, after which the lift pins of the wafer support may lift the auto-calibration wafer from an end effector of the wafer handling robot. At block 1608, the auto-calibration wafer may begin acquiring vibration data from a vibration sensor of the auto-calibration wafer. It will be appreciated that such data may also be acquired prior to or continuously in some implementations. At block 1610, the lift pins may be actuated to move the auto-calibration wafer, for example, vertically relative to the wafer support. In some implementations, such motion may include lowering the autocalibration wafer onto a wafer support and then lifting it back up, as would normally be experienced by a semiconductor wafer 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 motions, but may be designed to be more likely to induce a particular vibration response. In either case, the autocalibration wafer may be subjected to motion by actuation of the lift pins, and vibration data may be collected by the vibration sensor(s) during such motion.

[0166] At block 1612, a wafer handling robot may be controlled to remove the auto-calibrated wafer from the lift pins, and at block 1614, the 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 particular frequency component of the vibration exceeds a predetermined threshold, a determination may be made that the vibration measurement is outside of an acceptable limit, and the methodology 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 may also be measured and compared to an acceptable range to determine whether a fault condition exists in the lift pin mechanism. In such a case, the semiconductor processing tool may suspend wafer processing operations using that wafer processing station, for example, until the lift pin mechanism is serviced and the problem is resolved. If the lift pin mechanism is controlled via an actuator, a closed loop system may be implemented to automatically calibrate the lift pin mechanism using the vibration data. In some implementations, the semiconductor processing tool may generate a warning that the lift pin mechanism requires maintenance or repair, but may continue to perform semiconductor processing operations at that wafer station (and use the lift pin mechanism) until a subsequent vibration evaluation of the lift pins indicates that the vibrations generated during operation of the lift pins exceed a second set of acceptable limits. In some such implementations, the semiconductor processing tool may operate the lift pin mechanism at a reduced performance level, e.g., at a slower speed compared to the normal lift pin mechanism speed, after encountering a fault condition to potentially reduce the magnitude of vibrations that will be experienced. Such reduced throughput operation may continue until the lift pin mechanism is serviced and the problem is resolved, or until the vibrations generated by operation of the lift pin mechanism further deteriorate to unacceptable levels, in which case use of the wafer station and lift pin mechanism may be suspended until maintenance is performed.The vibration data of the lift pin mechanism may be transmitted to an off-tool data center with big data and machine learning capabilities that receives vibration data from a large number of similar semiconductor processing tools to establish normal or abnormal lift pin signatures for the vibrations of the lift pins. In such a case, the raw vibration data or the vibration signatures (after machine learning feature extraction) may be transmitted to the data center. The data center may use the received vibration data across a population of semiconductor processing tools to train a machine learning model, e.g., neural network, tensorflow, etc., to classify the lift pin mechanism as normal or abnormal.

[0167] Another test technique that can be performed with the auto-calibrated wafer is to assess the levelness of the wafer support (or other equipment, e.g., end effectors of a wafer handling robot, lift pin mechanisms, load port modules (LPMs), wafer supports, ESCs, etc.). FIG. 17 shows a flow chart of a technique for assessing the levelness of the wafer support, although this technique can be implemented for a variety of 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] A wafer handling robot of the semiconductor processing tool may be caused to retrieve the auto-calibration wafer from a docking station or other storage location in block 1704, and the wafer handling robot may be controlled to place the auto-calibration wafer directly on the wafer support in block 1706. If an edge ring is present on the wafer support that prevents the auto-calibration wafer from being placed directly on the wafer support, the edge ring may be removed, for example, using the wafer handling robot of the semiconductor processing tool, before placing the auto-calibration wafer on the wafer support.

[0170] Once the auto-calibration wafer is placed on the wafer support, the auto-calibration wafer may have level measurements taken using an orientation sensor, such as a speedometer or tilt sensor, at block 1708. In some implementations, multiple level sensors may be utilized to take such measurements.

[0171] At block 1710, the auto-calibration wafer may be removed from the wafer support using a wafer handling robot, and at block 1712, a determination may be made as to whether the measured levelness of the wafer support is within tolerance. If not, the methodology may proceed to block 1714, where a failure condition may be generated. If so, the methodology may proceed to block 1716, where a success condition may be generated.

[0172] It will be appreciated that the various approaches described herein can be combined in various ways to provide a fully automated system for configuring a semiconductor processing tool. For example, a semiconductor processing tool may be configured to have an "initial setup" mode that the semiconductor processing tool can enter, in which the tool retrieves an edge ring and uses an auto-calibration wafer to center the edge ring on each wafer support in the semiconductor processing chamber, then for each wafer support, the auto-calibration wafer is used to center the calibration wafer and the associated edge ring, the centered calibration wafer is used to train an active wafer centering system and wafer handling robot, and then verify that the trained active wafer centering system provides reliable wafer placement. Semiconductor processing tools may periodically perform various health checks, such as checking whether the center-to-center offset for the edge ring and calibration wafer has drifted to an unacceptable distance, checking whether the edge ring height is still within range after a predetermined period or number of wafer processing operations have been performed, and / or checking whether the wafer support is level and / or whether the lift pin vibrations are within acceptable ranges.

[0173] As mentioned above, the controller may be part of a system that may include semiconductor processing equipment, including processing tool(s), chamber(s), processing platform(s), and / or specific processing components (wafer pedestal, gas flow systems, etc.). These systems may be integrated with electronics for controlling pre-, during, and post-processing operations of the semiconductor wafer or substrate. The electronics may be referred to as a "controller" that may control various components or subparts of the system(s). Depending on the processing requirements and / or type of system, the controller may be programmed to control any of the processes disclosed herein, as well as various parameters that affect semiconductor processing, such as delivery of process 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 settings, fluid delivery settings, position and operation settings, transfer of wafers to and from tools and other transport tools and / or load locks connected or interfaced with the particular system.

[0174] Broadly speaking, a controller may be defined as an electronic device having various integrated circuits, logic, memory, and / or software to receive instructions, issue instructions, control operations, enable cleaning operations, and enable endpoint measurements. Integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files) that define operational parameters for performing a particular process on or for a semiconductor wafer or for a system. In some embodiments, the operational parameters may be part of a recipe defined by a process engineer to accomplish 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 implementations, the controller may be part of or connected to a computer integrated or connected to the system or otherwise networked to the system, or a combination thereof. For example, the controller may be in the "cloud" or all or part of a fab host computer system, which may enable remote access of wafer processing. The computer may enable remote access to the system to monitor the current progress of a manufacturing operation, examine the history of past manufacturing operations, examine trends or performance metrics from multiple manufacturing operations, modify parameters of a current process, set up processing steps following a current process, or start a new process. In some examples, a remote computer (e.g., a server) may provide a process recipe to the system over a network, which may include a local network or the Internet. The remote computer may include a user interface that allows for entry or programming of parameters and / or settings, which are then communicated from the remote computer to the system. In some examples, the controller receives instructions in the form of data specifying 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 having one or more individual controllers that are networked together and directed to a common purpose, such as the process or control described herein. An example of a distributed controller for such purposes may be one or more integrated circuits on the chamber in communication with one or more remotely located (e.g., at the platform level or as part of a remote computer) integrated circuits that combine to control the process at the chamber.

[0176] Without being limited thereto, exemplary systems may include a plasma etch 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 etch 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 etch (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 manufacturing of semiconductor wafers.

[0177] As described above, depending on the process steps being 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, a main computer, another controller, or tools used to transport materials to and from tool locations and / or load ports in a semiconductor manufacturing factory to transport wafer containers in and out of the tool locations.

[0178] While the above discussion has typically focused on auto-calibrating wafer systems featuring multiple image sensors, and in various further implementations, one or more additional sensors, some implementations may feature only a single centrally mounted image sensor and no edge-located image sensors, or only edge-located image sensors and no centrally mounted image sensors. Such implementations may, in some cases, but not necessarily, be correspondingly less functional than implementations featuring both centrally mounted and edge-mounted image sensors. The present disclosure should be understood to encompass such alternative implementations.

[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 the various wafer processing or wafer transfer operations. Wafer support is used herein to refer to any structure within a wafer station, e.g., a pedestal, electrostatic chuck, wafer support shelf, etc., that is configured to receive and support a semiconductor wafer.

[0180] As used herein, the term "nominal centered" refers to a relative arrangement in which two or more objects have specific locations, e.g., midpoints or similar locations, that are generally aligned with one another in the XY plane. Such alignment may not be perfect for a variety of reasons, e.g., slippage of one of the objects, sensor drift, etc., but in most cases, a nominally centered object will be within 1-2 millimeters of a perfectly centered object.

[0181] It should also be understood that the use of ordinal indicators, e.g., (a), (b), (c), ..., herein is for organizational purposes only and is not intended to convey any particular order or importance to the items associated with each ordinal indicator. For example, "(a) obtain information regarding velocity, and (b) obtain information regarding position" includes obtaining information regarding position before obtaining information regarding velocity, obtaining information regarding velocity before obtaining information regarding position, and obtaining information regarding position simultaneously with obtaining information regarding velocity. Nonetheless, some items associated with ordinal indicators may inherently require a particular sequence, e.g., "(a) obtain information regarding velocity, (b) determine a first acceleration based on information regarding velocity, and (c) obtain information regarding position." In this example, (a) needs to be performed before (b) because (b) depends on information obtained in (a), but (c) can be performed before or after either (a) or (b).

[0182] For example, it should be understood that the use of the word "each" in the phrases "for each <item> of one or more items" or "of each <item>" as used herein should be understood to include both single-item groups and multiple-item groups. That is, the phrase "for each" is used in the sense that it is used in programming languages ​​to refer to each of the items of any collection of referenced items. For example, if the collection of referenced items is a single item, then "each" will refer only to the single item (despite the fact that dictionary definitions of "each" often define the term as referring to "every one of two or more items") and does not mean that there must be at least two of the items. Similarly, if a selected item may have one or more subitems and a selection of one of the subitems is made, it will be understood that if the selected item has only one subitem, then the selection of that one subitem is specific to the selection of the item itself.

[0183] Reference to multiple controllers configured to perform various functions as a whole is intended to encompass situations where only one of the controllers is configured to perform all of the disclosed or discussed functions, as well as situations where the various controllers each perform a subportion of the discussed functions. For example, an autocalibration wafer may include a controller configured to control operation of various sensors on the autocalibration wafer and communicate data from the 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 modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the spirit or scope of the disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with the disclosure, the principles, and novel features disclosed herein.

[0185] Certain features described herein in the context of separate implementations may also be combined and implemented in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as functioning in a particular combination and initially claimed as such, one or more features in the claimed combination may in some cases be separated from the combination and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0186] Similarly, although the figures show operations in a particular order, this should not be understood as requiring that such operations be performed in the particular order or sequence shown, or that all of the operations shown be performed, to achieve desirable results. Additionally, the figures may generally show another exemplary process in the form of a flow diagram. However, other operations not shown may be incorporated into the exemplary process shown generally. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the operations shown. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, while the implementations described above separate various system components, it should be understood that such separation is not required in all implementations, and that the program components and systems described may generally be integrated together into a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve desirable results. The present disclosure can also be realized as the following application examples. [Application example 1] 1. A system for assisting in calibration of a wafer handling robot for a semiconductor processing tool, the system comprising: an autocalibration wafer, the autocalibration wafer comprising: a substrate sized 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 offset locations from a common point on 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. [Application example 2] A system as described in Application Example 1, wherein the first image sensor is arranged in a circular array around the common point. [Application example 3] 2. The system of claim 1, wherein the substrate is nominally circular and has the same diameter as the semiconductor wafers that the semiconductor processing tool is configured to process. [Application example 4] A system as described in Application Example 1, wherein the substrate is nominally circular and has the same diameter as an edge ring that the semiconductor processing tool is configured to use. [Application example 5] A system as described in Application Example 1, wherein the substrate is nominally circular and has a diameter between an outer diameter and an inner diameter of an edge ring that the semiconductor processing tool is configured to use. [Application Example 6] A system as described in Application Example 1, wherein the substrate is nominally circular and has a diameter within ±10% of the average between the outer and inner diameters of an edge ring that the semiconductor processing tool is configured to use. [Application Example 7] A system according to application example 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. [Application Example 8] A system as described in Application Example 1, wherein the auto-calibration wafer further includes a power supply configured to supply power to at least the first controller and the first image sensor. [Application Example 9] The system according to Application Example 8, the power source is a rechargeable battery; The system, wherein the auto-calibration wafer further includes a wireless charging capability configured to charge the rechargeable battery when interfaced with an electromagnetic field. [Example 10] The system according to Application Example 1, the auto-calibration wafer further includes a first wireless communication interface; The first wireless communication interface is communicatively coupled to the first controller. [Application Example 11] The system described in Application Example 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. [Example 12] The system according to Application Example 1, the autocalibration wafer further comprises one or more orientation sensors; The one or more orientation sensors are communicatively connected to the first controller. [Application Example 13] The system of application example 12, wherein each of the orientation sensors is selected from the group consisting of an inclinometer and an accelerometer. [Example 14] The system according to Application Example 1, the autocalibration wafer further comprises one or more vibration sensors; The one or more vibration sensors are communicatively connected to the first controller. [Example 15] The system of application example 14, wherein each of the vibration sensors is selected from the group consisting of an accelerometer, a laser microphone, and an optical distance measuring sensor. [Example 16] The system according to Application Example 1, The auto-calibration wafer further includes one or more proximity sensors, each of the proximity sensors configured to measure a distance between the first surface and an object located below the proximity sensor when the first surface is oriented downward; The one or more proximity sensors are communicatively connected to the first controller. [Application Example 17] The system of application example 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. [Example 18] The system according to Application Example 1, the first image sensor is arranged in a circular array around the common point; the substrate is nominally circular and has the same diameter as the semiconductor wafers that the semiconductor processing tool is configured to process; the substrate is a nominally circular disk having a diameter selected from the group consisting of 200 mm, 300 mm, and 450 mm; The autocalibration wafer comprises: a rechargeable battery configured to power at least the first controller and the first image sensor; a wireless charging function configured to charge the rechargeable battery when interfaced with an electromagnetic field; a first wireless communication interface communicatively coupled to the first controller, the first wireless communication interface comprising 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; and one or more proximity sensors, each of the proximity sensors communicatively connected to the first controller and configured to measure a distance between the first surface and an object located below the proximity sensor when the first surface is pointed downward. [Example 19] The system according to any one of Application Examples 1 to 18, further comprising the semiconductor processing tool, 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 collectively: a) selecting a first wafer support of the one or more wafer supports of a first wafer station of the one or more wafer stations; b) having the wafer handling robot position the auto-calibration wafer over the first wafer station; c) causing each of the first image sensors to acquire a corresponding first image of a reference portion of the first wafer support while the auto-calibration wafer is positioned on the first wafer support; The system is configured as follows: [Example 20] A system as described in Application Example 19, wherein the second controller and the first controller as a whole are further configured to determine location information of the center point of the first wafer support based on the first image. [Example 21] In the system according to example 19, the second controller and the first controller collectively: d) having said wafer handling robot retrieve a calibration wafer; e) causing the wafer handling robot to transfer the calibration wafer to the first wafer support such that a midpoint of the calibration wafer is nominally centered on a midpoint of the first wafer support when viewed along a vertical axis; The system further comprises: [Example 22] 22. The system according to claim 21, wherein the second controller and the first controller collectively: f) having the wafer handling robot position the auto-calibration wafer over the first wafer support and the calibration wafer; g) causing each of the first image sensors to acquire corresponding second images of a reference portion of the first wafer support and a reference portion of the calibration wafer while the auto-calibration wafer is positioned over the first wafer support and 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 further comprises: [Example 23] 23. The system according to claim 22, wherein the second controller and the first controller collectively: i) comparing said wafer / wafer support horizontal offset to a threshold wafer / wafer support horizontal offset; j) in response to determining 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 further comprises: [Example 24] The system of Example 23, wherein the second controller and the first controller together are further configured to perform (f) through (j), whichever occurs first, repeating N times or until the wafer / wafer support horizontal offset is less than or equal to the threshold wafer / wafer support horizontal offset. [Example 25] In the system according to example 19, the second controller and the first controller collectively: d) having the wafer handling robot retrieve a first edge ring; e) having the wafer handling robot transfer the first edge ring to the first wafer support such that a midpoint of the first edge ring is nominally centered on a midpoint of the first wafer support when viewed along a vertical axis; The system further comprises: [Example 26] 26. The system according to claim 25, wherein the second controller and the first controller collectively: f) having the wafer handling robot position the auto-calibration wafer over the first wafer support and the first edge ring; g) 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 first edge ring while the auto-calibration wafer is positioned on the first wafer support and the first edge ring; h) determining 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 further comprises: [Example 27] 27. The system according to claim 26, wherein the second controller and the first controller collectively: i) comparing said edge ring / wafer support horizontal offset to a threshold edge ring / wafer support horizontal offset; j) in response to determining that the edge ring / wafer support horizontal offset exceeds the threshold edge ring / wafer support horizontal offset, causing the wafer handling robot to reposition the first edge ring relative to the first wafer support to reduce the edge ring / wafer support horizontal offset. The system further comprises: [Example 28] The system of Example 27, wherein the second controller and the first controller together are further configured to perform (f) through (j), whichever occurs first, repeating N times or until the edge ring / wafer support horizontal offset is less than or equal to the threshold edge ring / wafer support horizontal offset. [Example 29] 26. The system according to claim 25, wherein the second controller and the first controller collectively: f) causing said wafer handling robot to retrieve a calibration wafer; g) causing the wafer handling robot to transfer the calibration wafer to the first wafer support such that a midpoint of the calibration wafer is nominally centered on the midpoint of the first edge ring when viewed along a vertical axis; The system further comprises: [Example 30] 30. The system of claim 29, wherein the second controller and the first controller collectively: h) having the wafer handling robot position the auto-calibration wafer over the first wafer support, the first edge ring, and the calibration wafer; i) causing 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 while the auto-calibration wafer is positioned over the first wafer support, the calibration wafer, and the first edge ring; j) determining 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 a gap size between the reference portions of the calibration wafer and the first edge ring in the second image; The system further comprises: [Example 31] 31. The system of claim 30, wherein the second controller and the first controller collectively: k) comparing said edge ring / wafer horizontal offset to a threshold edge ring / wafer horizontal offset; l) in response to determining 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. The system further comprises: [Example 32] The system of Example 31, wherein the second controller and the first controller together are further configured to perform (h) to (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. [Example 33] 33. The system of claim 32, wherein the second controller and the first controller collectively: having the wafer handling robot reposition the auto-calibration wafer onto the first wafer support, the first edge ring, and the calibration wafer; causing each of the first image sensors to acquire a corresponding third image of the reference portion of the calibration wafer and a reference portion of the first wafer support while the auto-calibration wafer is positioned over the first wafer support, the calibration wafer, and the first edge ring; The system is further configured to determine a wafer support / wafer horizontal offset between the center point of the first wafer support and the center point of the calibration wafer based on a gap size between the reference portions of the calibration wafer and the first wafer support in the third image. [Example 34] 33. The system of claim 32, wherein the second controller and the first controller collectively: comparing the wafer support / wafer horizontal offset to a threshold wafer support / wafer horizontal offset; The system is further configured to, in response to determining that the wafer support / wafer horizontal offset exceeds the threshold wafer support / wafer horizontal offset, cause the wafer handling robot to reposition at least one item selected from the group consisting of the calibration wafer and the edge ring relative to the first wafer support. [Example 35] The system according to application example 34, the semiconductor processing tool includes a semiconductor processing chamber; the first wafer station is within the semiconductor processing chamber; The system, wherein the first wafer support comprises a pedestal within the semiconductor processing chamber. [Example 36] The system according to application example 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 system, wherein the first wafer support is a structure within the load lock. [Example 37] The system according to application example 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 system, wherein the first wafer support is one of a plurality of wafer support ledges in the buffer. [Example 38] The system according to application example 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 system, wherein the first wafer support is a structure within the load lock. [Example 39] 14. The system of claim 12 or 13, further comprising the semiconductor processing tool, 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 collectively: a) selecting a first wafer support of the one or more wafer supports for a first wafer station of the one or more wafer stations; b) having the wafer handling robot transfer the auto-calibration wafer onto the first wafer station; c) causing the one or more orientation sensors to obtain tilt measurements of the substrate; The system is configured as follows: [Example 40] The system of Example 39, wherein the second controller is configured to remove an edge ring from the first wafer support before performing (b). [Example 41] 16. The system of claim 14 or 15, further comprising the semiconductor processing tool, 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 collectively: a) selecting a first wafer support of the one or more wafer supports of a first wafer station of the one or more wafer stations, the first wafer support including a plurality of lift pins; b) generating relative translational movement between the lift pins and the first wafer support such that the lift pins protrude from the first wafer support; c) having the wafer handling robot transfer the auto-calibration wafer to the lift pins; d) inducing further relative translation between the lift pins and the first wafer support while the autocalibration wafer is supported by the lift pins; e) acquiring vibration data from the one or more vibration sensors during (d); f) evaluating the vibration data to determine whether the vibration data exhibits vibrations exceeding a predetermined threshold; g) providing a notification when the vibration data exceeds the predetermined threshold. [Example 42] The system of Example 41, wherein the second controller is configured, as part of (d), to cause further relative translational movement between the lift pins and the first wafer support such that the auto-calibration wafer is placed on an upper surface of the first wafer support without the lift pins protruding from the first wafer support. [Example 43] 18. The system of claim 16 or 17, further comprising the semiconductor processing tool, A wafer handling robot; one or more wafer stations; a second controller; the wafer handling robot and the second controller are communicatively connected; The second controller and the first controller collectively: a) selecting a first wafer support of the one or more wafer supports for a first wafer station of the one or more wafer stations based at least in part on an indication that an edge ring is supported by the first wafer support; b) placing the autocalibration wafer on the edge ring; c) causing each of the proximity sensors to measure a distance between the first wafer support and the autocalibration 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; f) providing a notification when the height associated with the edge ring exceeds the predetermined threshold. The system is configured as follows:

Claims

1. 1. A system for semiconductor processing, comprising:

1. A semiconductor processing tool comprising: A wafer handling robot; one or more wafer stations; A first controller, each of the wafer stations having one or more corresponding wafer supports; a semiconductor processing tool, the wafer handling robot communicatively coupled to the first controller; 1. An auto-calibration wafer, comprising: a substrate sized 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; an auto-calibration wafer comprising: a plurality of first image sensors supported by the substrate and positioned at offset locations from a common point on 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 second controller; Equipped with the second controller is communicatively connected to each of the first image sensors; The second controller and the first controller collectively: a) selecting a first wafer support of the one or more wafer supports of a first wafer station of the one or more wafer stations; b) having the wafer handling robot position the auto-calibration wafer above the first wafer station; c) causing each of the first image sensors to acquire a corresponding first image of a reference portion of the first wafer support while the auto-calibration wafer is positioned on the first wafer support; d) determining location information of a center point of the first wafer support based on the first image; e) having said wafer handling robot retrieve a calibration wafer; f) causing the wafer handling robot to transfer the calibration wafer to the first wafer support such that a midpoint of the calibration wafer is nominally centered on a midpoint of the first wafer support when viewed along a vertical axis; g) having the wafer handling robot position the auto-calibration wafer over the first wafer support and the calibration wafer; h) causing each of the first image sensors to acquire corresponding second images of a reference portion of the first wafer support and a reference portion of the calibration wafer while the auto-calibration wafer is positioned over the first wafer support and the calibration wafer; i) 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; It is configured as follows: system.

2. 10. The system of claim 1, wherein the auto-calibration wafer further comprises a rechargeable battery configured to power at least the second controller and the first image sensor; The system further comprises a wireless charging capability configured to charge the rechargeable battery when interfaced with an electromagnetic field.

3. 2. The system of claim 1, the auto-calibration wafer further comprises a first wireless communication interface; the first wireless communication interface comprises one or more wireless communication interfaces selected from the group consisting of a Bluetooth transceiver and a WiFi transceiver; The first wireless communication interface is communicatively coupled to the second controller.

4. 2. The system of claim 1, the autocalibration wafer further comprising one or more orientation sensors; each of the orientation sensors is selected from the group consisting of an inclinometer and an accelerometer; The one or more orientation sensors are communicatively connected to the second controller.

5. 2. The system of claim 1, the autocalibration wafer further comprising one or more vibration sensors; each of the vibration sensors is selected from the group consisting of an accelerometer, a laser microphone, and an optical distance measurement sensor; The one or more vibration sensors are communicatively connected to the second controller.

6. 2. The system of claim 1, the auto-calibration wafer further comprising one or more proximity sensors, each of the proximity sensors configured to measure a distance between the first surface and an object located below the proximity sensor when the first surface is oriented downward; 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; The one or more proximity sensors are communicatively connected to the second controller.

7. 2. The system of claim 1, the first image sensor is arranged in a circular array around the common point; the substrate is nominally circular and has the same diameter as the semiconductor wafers that the semiconductor processing tool is configured to process; the substrate is a nominally circular disk having a diameter selected from the group consisting of 200 mm, 300 mm, and 450 mm; The autocalibration wafer comprises: a rechargeable battery configured to power at least the second controller and the first image sensor; a wireless charging function configured to charge the rechargeable battery when interfaced with an electromagnetic field; a first wireless communication interface communicatively coupled to the second controller, the first wireless communication interface comprising 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 second controller; and one or more proximity sensors, each of the proximity sensors communicatively connected to the second controller and configured to measure a distance between the first surface and an object located below the proximity sensor when the first surface is pointed downward.

8. 2. The system of claim 1, wherein the first controller and the second controller collectively comprise: j) comparing said wafer / wafer support horizontal offset to a threshold wafer / wafer support horizontal offset; k) in response to determining 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 further comprises:

9. A system according to any one of claims 1 to 7, The first controller and the second controller collectively: j) having the wafer handling robot retrieve a first edge ring; k) having the wafer handling robot transfer the first edge ring to the first wafer support such that a midpoint of the first edge ring is nominally centered on a midpoint of the first wafer support when viewed along a vertical axis; l) having the wafer handling robot position the auto-calibration wafer over the first wafer support and the first edge ring; m) causing each of the first image sensors to acquire corresponding second images 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 on the first wafer support and the first edge ring; n) determining 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 configured as follows:

10. 10. The system of claim 9, wherein the first controller and the second controller collectively comprise: o) comparing said edge ring / wafer support horizontal offset to a threshold edge ring / wafer support horizontal offset; p) in response to determining that the edge ring / wafer support horizontal offset exceeds the threshold edge ring / wafer support horizontal offset, causing the wafer handling robot to reposition the first edge ring relative to the first wafer support to reduce the edge ring / wafer support horizontal offset. The system further comprises:

11. 10. The system of claim 9, wherein the second controller and the first controller collectively comprise: o) causing said wafer handling robot to retrieve a calibration wafer; p) having the wafer handling robot transfer the calibration wafer to the first wafer support such that a midpoint of the calibration wafer is nominally centered on the midpoint of the first edge ring when viewed along a vertical axis; q) having the wafer handling robot position the auto-calibration wafer over the first wafer support, the first edge ring, and the calibration wafer; r) causing each of the first image sensors to acquire a corresponding second image of a reference portion of the calibration wafer and the reference portion of the first edge ring while the auto-calibration wafer is positioned over the first wafer support, the calibration wafer, and the first edge ring; s) comparing said edge ring / wafer horizontal offset to a threshold edge ring / wafer horizontal offset; t) in response to determining 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; The system further comprises:

12. 5. The system of claim 4, The first controller and the second controller collectively: j) causing the wafer handling robot to transfer the auto-calibration wafer to the first wafer station; k) causing the one or more orientation sensors to obtain tilt measurements of the substrate; The system is configured as follows:

13. 6. The system of claim 5, the first wafer support comprises a plurality of lift pins; The first controller and the second controller collectively: j) causing relative translation between the lift pins and the first wafer support such that the lift pins protrude from the first wafer support; k) causing the wafer handling robot to transfer the auto-calibration wafer to the lift pins; l) inducing further relative translation between the lift pins and the first wafer support while the auto-calibration wafer is supported by the lift pins; m) acquiring vibration data from the one or more vibration sensors during (l); n) evaluating the vibration data to determine whether the vibration data exhibits vibrations exceeding a predetermined threshold; o) providing a notification when said vibration data exceeds said predetermined threshold.

14. 7. The system of claim 6, The second controller and the first controller collectively: j) determining that one of the one or more wafer supports of the one or more wafer stations supports an edge ring; k) placing the autocalibration wafer on the edge ring; l) causing each of the proximity sensors to measure a distance between the wafer support supporting the edge ring and the autocalibration wafer; m) determining one or more height measurements associated with the edge ring based on the one or more distances; n) evaluating the one or more height measurements to determine whether a height associated with the edge ring exceeds a predetermined threshold; o) providing a notification when the height associated with the edge ring exceeds the predetermined threshold. The system further comprises:

15. A system for semiconductor processing, comprising:

1. A semiconductor processing tool comprising: A wafer handling robot; one or more wafer stations; A first controller, each of the wafer stations includes one or more corresponding wafer supports; a semiconductor processing tool, the wafer handling robot communicatively coupled to the first controller; 1. An auto-calibration wafer, comprising: a substrate sized 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; an auto-calibration wafer comprising: a plurality of first image sensors supported by the substrate and positioned at offset locations from a common point on 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 second controller; Equipped with the second controller is communicatively connected to each of the first image sensors; The second controller and the first controller collectively: a) selecting a first wafer support of the one or more wafer supports of a first wafer station of the one or more wafer stations; b) having the wafer handling robot position the auto-calibration wafer above the first wafer station; c) causing each of the first image sensors to acquire a corresponding first image of a reference portion of the first wafer support while the auto-calibration wafer is positioned on the first wafer support; d) having the wafer handling robot retrieve a first edge ring; e) having the wafer handling robot transfer the first edge ring to the first wafer support such that a midpoint of the first edge ring is nominally centered on a midpoint of the first wafer support when viewed along a vertical axis; f) having the wafer handling robot position the auto-calibration wafer over the first wafer support and the first edge ring; g) 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 first edge ring while the auto-calibration wafer is positioned on the first wafer support and the first edge ring; h) determining 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 further comprises:

16. The system of claim 15, wherein the auto-calibration wafer further comprises a rechargeable battery configured to power at least the second controller and the first image sensor; The system further comprises a wireless charging capability configured to charge the rechargeable battery when interfaced with an electromagnetic field.

17. The system of claim 15, the auto-calibration wafer further comprises a first wireless communication interface; the first wireless communication interface comprises one or more wireless communication interfaces selected from the group consisting of a Bluetooth transceiver and a WiFi transceiver; The first wireless communication interface is communicatively coupled to the second controller.

18. The system of claim 15, the autocalibration wafer further comprising one or more orientation sensors; each of the orientation sensors is selected from the group consisting of an inclinometer and an accelerometer; The one or more orientation sensors are communicatively connected to the second controller.

19. The system of claim 15, the autocalibration wafer further comprising one or more vibration sensors; each of the vibration sensors is selected from the group consisting of an accelerometer, a laser microphone, and an optical distance measurement sensor; The one or more vibration sensors are communicatively connected to the second controller.

20. The system of claim 15, the auto-calibration wafer further comprising one or more proximity sensors, each of the proximity sensors configured to measure a distance between the first surface and an object located below the proximity sensor when the first surface is oriented downward; 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; The one or more proximity sensors are communicatively connected to the second controller.

21. The system of claim 15, the first image sensor is arranged in a circular array around the common point; the substrate is nominally circular and has the same diameter as the semiconductor wafers that the semiconductor processing tool is configured to process; the substrate is a nominally circular disk having a diameter selected from the group consisting of 200 mm, 300 mm, and 450 mm; The autocalibration wafer comprises: a rechargeable battery configured to power at least the second controller and the first image sensor; a wireless charging function configured to charge the rechargeable battery when interfaced with an electromagnetic field; a first wireless communication interface communicatively coupled to the second controller, the first wireless communication interface comprising 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 second controller; and one or more proximity sensors, each of the proximity sensors communicatively connected to the second controller and configured to measure a distance between the first surface and an object located below the proximity sensor when the first surface is pointed downward.

22. The system of claim 15, further comprising: The first controller and the second controller collectively: i) determining location information of a center point of the first wafer support based on the first image; j) causing said wafer handling robot to retrieve a calibration wafer; k) causing the wafer handling robot to transfer the calibration wafer to the first wafer support such that a midpoint of the calibration wafer is nominally centered on a midpoint of the first wafer support when viewed along a vertical axis; l) having the wafer handling robot position the auto-calibration wafer over the first wafer support and the calibration wafer; m) causing each of the first image sensors to acquire corresponding second images of a reference portion of the first wafer support and a reference portion of the calibration wafer while the auto-calibration wafer is positioned over the first wafer support and the calibration wafer; n) 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; o) comparing said wafer / wafer support horizontal offset to a threshold wafer / wafer support horizontal offset; p) in response to determining 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 further comprises:

23. The system of claim 15, wherein the first controller and the second controller collectively comprise: i) comparing said edge ring / wafer support horizontal offset to a threshold edge ring / wafer support horizontal offset; j) in response to determining that the edge ring / wafer support horizontal offset exceeds the threshold edge ring / wafer support horizontal offset, causing the wafer handling robot to reposition the first edge ring relative to the first wafer support to reduce the edge ring / wafer support horizontal offset. The system further comprises:

24. The system of claim 15, wherein the first controller and the second controller collectively comprise: i) having said wafer handling robot retrieve a calibration wafer; j) having the wafer handling robot transfer the calibration wafer to the first wafer support such that a midpoint of the calibration wafer is nominally centered on the midpoint of the first edge ring when viewed along a vertical axis; k) having the wafer handling robot position the auto-calibration wafer over the first wafer support, the first edge ring, and the calibration wafer; l) causing each of the first image sensors to acquire corresponding second images of a reference portion of the calibration wafer and the reference portion of the first edge ring while the auto-calibration wafer is positioned over the first wafer support, the calibration wafer, and the first edge ring; m) comparing said edge ring / wafer horizontal offset to a threshold edge ring / wafer horizontal offset; n) in response to determining 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; The system further comprises:

25. The system of claim 18, The first controller and the second controller collectively: i) causing the wafer handling robot to transfer the auto-calibration wafer to the first wafer station; j) causing the one or more orientation sensors to obtain tilt measurements of the substrate; The system is configured as follows:

26. The system of claim 19, the first wafer support comprises a plurality of lift pins; The first controller and the second controller collectively: i) generating relative translational movement between the lift pins and the first wafer support such that the lift pins protrude from the first wafer support; j) causing the wafer handling robot to transfer the auto-calibration wafer to the lift pins; k) inducing further relative translation between the lift pins and the first wafer support while the autocalibration wafer is supported by the lift pins; l) acquiring vibration data from the one or more vibration sensors during (k); m) evaluating the vibration data to determine whether the vibration data exhibits vibrations exceeding a predetermined threshold; n) providing a notification when said vibration data exceeds said predetermined threshold.

27. The system of claim 20, The first controller and the second controller collectively: i) determining that one of the one or more wafer supports of the one or more wafer stations supports an edge ring; j) placing the autocalibration wafer on the edge ring; k) causing each of the proximity sensors to measure a distance between the wafer support supporting the edge ring and the autocalibration wafer; l) determining one or more height measurements associated with the edge ring based on the one or more distances; m) evaluating the one or more height measurements to determine whether a height associated with the edge ring exceeds a predetermined threshold; n) providing a notification when the height associated with the edge ring exceeds the predetermined threshold. The system is configured as follows:

28. A system for semiconductor processing, comprising:

1. A semiconductor processing tool comprising: A wafer handling robot; one or more wafer stations; A first controller, each of the wafer stations having one or more corresponding wafer supports; a semiconductor processing tool, the wafer handling robot communicatively coupled to the first controller; 1. An auto-calibration wafer, comprising: a substrate sized 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; an auto-calibration wafer comprising: a plurality of first image sensors supported by the substrate and positioned at offset locations from a common point on 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; one or more vibration sensors, each of the vibration sensors being an accelerometer, a laser microphone, or an optical distance measuring sensor; A second controller; Equipped with The second controller is communicatively connected to each of the plurality of first image sensors and each of the one or more vibration sensors. The first controller and the second controller collectively: a) selecting a first wafer support of the one or more wafer supports of a first wafer station of the one or more wafer stations, the first wafer support comprising a plurality of lift pins; b) generating 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 auto-calibration wafer to the lift pins; d) inducing further relative translation between the lift pins and the first wafer support while the auto-calibration wafer is supported by the lift pins; e) acquiring vibration data from the one or more vibration sensors during (d); f) evaluating the vibration data to determine whether the vibration data exhibits vibrations exceeding a predetermined threshold; g) providing a notification when the vibration data exceeds the predetermined threshold. It is configured as follows: system.

29. The system of claim 28, wherein the auto-calibration wafer further comprises a rechargeable battery configured to power at least the second controller and the first image sensor; The system, wherein the auto-calibration wafer further includes a wireless charging capability configured to charge the rechargeable battery when interfaced with an electromagnetic field.

30. The system of claim 28, the auto-calibration wafer further comprises a first wireless communication interface; the first wireless communication interface comprises one or more wireless communication interfaces selected from the group consisting of a Bluetooth transceiver and a WiFi transceiver; The first wireless communication interface is communicatively coupled to the second controller.

31. The system of claim 28, the autocalibration wafer further comprising one or more orientation sensors; each of the orientation sensors is selected from the group consisting of an inclinometer and an accelerometer; The one or more orientation sensors are communicatively connected to the second controller.

32. The system of claim 28, the auto-calibration wafer further comprising one or more proximity sensors, each of the proximity sensors configured to measure a distance between the first surface and an object located below the proximity sensor when the first surface is oriented downward; 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; The one or more proximity sensors are communicatively connected to the second controller.

33. The system of claim 28, the first image sensor is arranged in a circular array around the common point; the substrate is nominally circular and has the same diameter as the semiconductor wafers that the semiconductor processing tool is configured to process; the substrate is a nominally circular disk having a diameter selected from the group consisting of 200 mm, 300 mm, and 450 mm; The autocalibration wafer comprises: a rechargeable battery configured to power at least the second controller and the first image sensor; a wireless charging function configured to charge the rechargeable battery when interfaced with an electromagnetic field; a first wireless communication interface communicatively coupled to the second controller, the first wireless communication interface comprising one or more wireless communication interfaces selected from the group consisting of a Bluetooth transceiver and a WiFi transceiver; and one or more proximity sensors, each of the proximity sensors communicatively connected to the second controller and configured to measure a distance between the first surface and an object located below the proximity sensor when the first surface is pointed downward.

34. The system of any one of claims 28 to 33, comprising: The first controller and the second controller collectively: h) having the wafer handling robot position the auto-calibration wafer above the first wafer station; i) causing each of the first image sensors to acquire a corresponding first image of a reference portion of the first wafer support while the auto-calibration wafer is positioned on the first wafer support; j) determining location information of a center point of the first wafer support based on the first image; k) causing said wafer handling robot to retrieve a calibration wafer; l) causing the wafer handling robot to transfer the calibration wafer to the first wafer support such that a midpoint of the calibration wafer is nominally centered on a midpoint of the first wafer support when viewed along a vertical axis; m) having the wafer handling robot position the auto-calibration wafer over the first wafer support and the calibration wafer; n) causing each of the first image sensors to acquire corresponding second images of a reference portion of the first wafer support and a reference portion of the calibration wafer while the auto-calibration wafer is positioned over the first wafer support and the calibration wafer; o) 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; p) comparing said wafer / wafer support horizontal offset to a threshold wafer / wafer support horizontal offset; q) in response to determining 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 further comprises:

35. The system of any one of claims 28 to 33, wherein the first controller and the second controller collectively comprise: h) having the wafer handling robot position the auto-calibration wafer on the first wafer station; i) causing each of the first image sensors to acquire a corresponding first image of a reference portion of the first wafer support while the auto-calibration wafer is positioned on the first wafer support; j) having the wafer handling robot retrieve a first edge ring; k) having the wafer handling robot transfer the first edge ring to the first wafer support such that a midpoint of the first edge ring is nominally centered on a midpoint of the first wafer support when viewed along a vertical axis; l) having the wafer handling robot position the auto-calibration wafer over the first wafer support and the first edge ring; m) causing each of the first image sensors to acquire corresponding second images 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 on the first wafer support and the first edge ring; n) determining 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 configured as follows:

36. The system of claim 35, wherein the first controller and the second controller collectively comprise: o) comparing said edge ring / wafer support horizontal offset to a threshold edge ring / wafer support horizontal offset; p) in response to determining that the edge ring / wafer support horizontal offset exceeds the threshold edge ring / wafer support horizontal offset, causing the wafer handling robot to reposition the first edge ring relative to the first wafer support to reduce the edge ring / wafer support horizontal offset. The system further comprises:

37. The system of claim 35, The first controller and the second controller collectively: q) causing said wafer handling robot to retrieve a calibration wafer; r) having the wafer handling robot transfer the calibration wafer to the first wafer support such that a midpoint of the calibration wafer is nominally centered on a midpoint of the first edge ring when viewed along a vertical axis; s) having the wafer handling robot position the auto-calibration wafer over the first wafer support, the first edge ring, and the calibration wafer; t) causing 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 while the auto-calibration wafer is positioned on the first wafer support, the first edge ring, and the first edge ring; u) comparing said edge ring / wafer horizontal offset to a threshold edge ring / wafer horizontal offset; v) in response to determining 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. The system further comprises:

38. The system of claim 31, The first controller and the second controller collectively: h) causing the wafer handling robot to transfer the auto-calibration wafer onto the first wafer station; i) causing the one or more orientation sensors to obtain tilt measurements of the substrate; The system is configured as follows:

39. The system of claim 32, The first controller and the second controller collectively: h) determining that one of the one or more wafer supports of the one or more wafer stations supports an edge ring; i) placing the autocalibration wafer on the edge ring; j) causing each of the proximity sensors to measure a distance between the wafer support supporting the edge ring and the autocalibration wafer; k) determining one or more height measurements associated with the edge ring based on the one or more distances; l) evaluating the one or more height measurements to determine whether a height associated with the edge ring exceeds a predetermined threshold; m) providing a notification when the height associated with the edge ring exceeds the predetermined threshold. The system is configured as follows:

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