TWI879762B - High precision edge ring centering for substrate processing systems - Google Patents

Abstract

An edge ring centering system for a plasma processing system includes a processing chamber including a substrate support and R edge ring lift pins, where R is an integer greater than or equal to 3. An edge ring includes P grooves located on a bottom surface thereof, where P is an integer greater than or equal to R. A robot arm includes an end effector. A controller is configured to cause the optical sensor to sense a first position of the edge ring on the end effector; cause the robot arm to deliver the edge ring to a first center location on the edge ring lift pins; retrieve the edge ring from the edge ring lift pins; and cause the optical sensor to sense a second position of the edge ring on the end effector.

Description

High-precision edge ring centering for substrate processing systems

The present disclosure relates to edge ring centering for substrate processing systems, and more particularly, to high precision centering of movable edge rings for plasma processing systems.

The background description provided here is for the purpose of generally presenting the context of the present disclosure. Within the scope described in this prior art section, the works of the inventors designated by the present invention and the description contents in this description that may not qualify as prior art at the time of application are neither explicitly nor implicitly admitted to be prior art against the present disclosure.

A substrate processing system may be used to process substrates, such as semiconductor wafers. Exemplary processes that may be applied to a substrate include, but are not limited to, chemical vapor deposition (CVD), atomic layer deposition (ALD), conductor etching, and/or other etching, deposition, or cleaning processes. Within a processing chamber of the substrate processing system, a substrate may be disposed on a substrate support, such as a pedestal, an electrostatic chuck (ESC), etc. During etching, a gas mixture containing one or more precursors may be introduced into the processing chamber and plasma may be used to induce a chemical reaction.

The substrate support may include a ceramic layer configured to support a substrate. For example, the substrate may be electrostatically clamped to the ceramic layer during processing. The substrate support may include an edge ring configured around an outer portion (e.g., outside and/or adjacent to an edge) of the substrate support. The edge ring may be provided to confine and/or shape plasma above the substrate and improve etch uniformity.

An edge ring centering system for a plasma processing system includes a processing chamber, the processing chamber including a substrate support and R edge ring rise pins, where R is an integer greater than or equal to 3. An edge ring includes P grooves located on a bottom surface thereof, where P is an integer greater than or equal to R. A robot arm includes an end effector. A controller is configured to cause an optical sensor to sense a first position of the edge ring on the end effector; cause the robot arm to transport the edge ring to a first center position on the edge ring rise pins; retract the edge ring from the edge ring rise pins; and cause the optical sensor to sense a second position of the edge ring on the end effector.

In other features, the controller is further configured to generate a first offset based on a difference between the second position and the first position. The controller is further configured to generate a first adjusted center position of the edge ring based on the first center position and the first offset.

In other features, the controller is further configured to cause the robotic arm to transport the edge ring to the edge ring lifting pin based on the first adjusted center position; to retract the edge ring from the edge ring lifting pin; and to cause the optical sensor to sense a third position of the edge ring on the robotic arm.

In other features, the controller is further configured to generate a second offset based on a difference between the third position and the second position. The controller is further configured to generate a second adjustment center position based on the first adjustment center position and the second offset.

In other features, the controller is further configured to cause the robot arm to transport the edge ring onto the edge ring lifting pin based on the second adjusted center position; to retract the edge ring from the edge ring lifting pin; and to cause the optical sensor to sense a fourth position of the edge ring on the robot arm. The controller is further configured to generate a third offset based on a difference between the fourth position and the third position. The controller is further configured to compare the third offset to a predetermined offset.

In other features, the controller is further configured to determine whether the edge ring is centered based on the comparison. The P grooves are "V" shaped. The P grooves are spaced 360°/P around the bottom surface of the edge ring. The P grooves are "V" shaped. A bottommost portion of the P grooves extends radially.

More applicable areas of this disclosure will become clearer through implementation content, patent application scope and diagrams. The detailed description and specific examples are for illustrative purposes only and are not intended to limit the scope of this disclosure.

100: Substrate processing system

102: Processing room

104: Upper electrode

106: Baseboard support

108: Substrate

109: Shower head

110: Base

112: Ceramic layer

114: Adhesive layer

116: Coolant pipe

120:RF generation system

122:RF voltage generator

124: Matching and allocating networks

130: Gas delivery system

132: Gas source

134: Valve

136:Mass flow controller

140: Manifold

142: Temperature controller

144: Heating element

146: Coolant assembly

150: Valve

152: Pump

160: System controller

170:Robot

172: Load lock

176: Protective seal

180:Edge ring

182:Optical sensor

210: Shell

214: Room entrance

218: Open mouth

220: Edge Ring

232-1,232-2: End effector

234: Robotic Arm

240:Optical sensor

320: Baseboard support

330: First level

332: Adhesive layer

334: Base

336: Edge Ring

340: Edge ring rising pin

350: Groove

410: Ring

500:Methods

The present disclosure will be more fully understood through the implementation section and the accompanying figures, wherein: FIG. 1 is a functional block diagram of an example of a plasma processing system according to the present disclosure; FIG. 2 is a three-dimensional diagram of an example of a processing chamber, a machine arm including an end effector, and an edge ring according to the present disclosure; FIG. 3 is a cross-sectional diagram of an example of a substrate support and an edge ring supported by a riser pin according to the present disclosure; FIG. 4 is a top view of an example of an edge ring including a groove according to the present disclosure; and FIG. 5 is a flow chart of an example of a method for centering an edge ring according to the present disclosure.

In the drawings, reference numbers may be repeated to identify similar and/or equivalent components.

In some substrate systems, an edge ring may be used to shape the plasma and increase etch uniformity. When the edge ring corrodes, the edge ring may be adjusted in height by edge ring riser pins so that etch uniformity is maintained despite corrosion. After processing multiple substrates, the edge ring is sufficiently worn by the plasma and needs to be replaced.

Some substrate processing systems may replace the edge ring without breaking vacuum using a robotic arm that is typically used to transport and remove substrates from a processing chamber. Systems and methods according to the present disclosure may be used to precisely center the edge ring relative to the substrate support.

Referring now to FIG. 1 , an illustrative substrate processing system 100 is shown. By way of example only, the substrate processing system 100 may be used to perform etching and/or other types of substrate processing using RF plasma. The substrate processing system 100 includes a processing chamber 102 that encloses the substrate 100 and other components and contains the RF plasma. The processing chamber 102 includes an upper electrode 104 and a substrate support 106 (e.g., an electrostatic chuck (ESC)). During operation, a substrate 108 is disposed on the substrate support 106. Although a particular substrate processing system 100 and processing chamber 102 are shown as an example, the principles of the present disclosure may be applied to other types of substrate processing systems and chambers using the edge ring, such as a substrate processing system using remote plasma generation and delivery (e.g., using a plasma tube, a microwave tube), etc.

By way of example only, the upper electrode 104 may include a gas distribution device, such as a showerhead 109, which introduces and distributes the process gas. The showerhead 109 may include a rod having one end connected to a ceiling of the processing chamber. A base portion is generally cylindrical and extends radially outward from an opposite end of the rod at a position spaced from the ceiling of the processing chamber. A surface or panel of the showerhead base portion facing the substrate includes a plurality of holes through which the process gas or purge gas flows. Alternatively, the upper electrode 104 may include a conductive plate and the process gas may be introduced in another manner.

The substrate support 106 includes a base 110 that is conductive and acts as a lower electrode. The base 110 supports a ceramic layer 112. In some examples, the ceramic layer 112 may include a resistive heater, an RF electrode, and/or an electrostatic electrode (all not shown). An adhesive layer 114 may be disposed between the ceramic layer 112 and the base 110 and may act as a thermal resistance layer. The base 110 may include one or more coolant pipes 116 to allow coolant to flow through the base 110.

An RF generation system 120 generates and outputs an RF voltage to one of the upper electrode 104 and the lower electrode (e.g., the base 110 of the substrate support 106). The other of the upper electrode 104 and the base 110 may be DC grounded, AC grounded, or floating. By way of example only, the RF generation system 120 may include an RF voltage generator 122 that generates an RF voltage that is fed to the upper electrode 104 or the base 110 with a matching and distribution network 124. Although the RF generation system 120 corresponds to a capacitively coupled plasma (CCP) system, the principles of the present disclosure may also be implemented in other suitable systems, such as (for example only): transformer coupled plasma (TCP) system, inductively coupled plasma (TCP), CCP cathode system, remote microwave plasma generation and delivery system, etc.

A gas delivery system 130 includes one or more gas sources 132-1, 132-2, and 132-N (collectively referred to as gas sources 132), where N is an integer greater than 0. The gas source 132 supplies one or more process gases, inert gases, purge gases, etching gases, precursors and/or other gas mixtures therein. Vaporized precursors may also be used. The gas source 132 is connected to a manifold 140 via valves 134-1, 134-2, ..., and 134-N (collectively referred to as valves 134) and mass flow controllers 136-1, 136-2, ..., and 136-N (collectively referred to as mass flow controllers 136). An output of the manifold 140 is fed to the processing chamber 102. For example only, the output of the manifold 140 is fed to the showerhead 109.

A temperature controller 142 may be connected to a plurality of heating elements 144, such as thermal control elements (TCEs) disposed in the ceramic layer 112. For example, the heating element 144 may include, but is not limited to, macro heating elements corresponding to respective zones in a multi-zone heating plate, and/or an array of micro heating elements arranged on a plurality of zones of a multi-zone heating plate. The temperature controller 142 may be used to control the plurality of heating elements 144 to control the temperature of the substrate support 106 and the substrate 108.

The temperature controller 142 may be in communication with a coolant assembly 146 to control the flow of coolant through the coolant pipe 116. For example, the coolant assembly 146 may include a coolant pump and a storage tank. The temperature controller 142 operates the coolant assembly 146 to selectively flow the coolant through the coolant pipe 116 to cool the substrate support 106.

A valve 150 and pump 152 may be used to evacuate reactants from the processing chamber 102. A system controller 160 may be used to control components of the substrate processing system 100. A robot 170 may be used to transport substrates to and remove substrates from the substrate support 106. For example, the robot 170 may transfer substrates between the substrate support 106 and a load lock 172. Although shown as separate controllers, the temperature controller 142 may be implemented in the system controller 160. In some examples, a protective seal 176 may be provided around the periphery of the adhesive layer 114 between the ceramic layer 112 and the base 110.

During processing, an edge ring 180 surrounds the substrate support 106. The edge ring 180 is movable relative to the substrate 106 (e.g., can be moved up and down in a vertical direction). For example, the edge ring 180 may be controlled by an actuator and edge ring lift pins (e.g., see FIG. 3) responsive to the controller 160, as described in more detail below. An optical sensor 182 may be used to measure the position of the edge ring 180 relative to an arm/end effector of the robot 170.

Using any suitable method, a corrected center position of the edge ring relative to the substrate support can be initially determined. A suitable example of a correction process is shown and described in commonly assigned U.S. Patent No. 10,541,168, entitled "Edge Ring Centering Method Using Ring Dynamic Alignment Data" and issued on January 21, 2020, the contents of which are incorporated herein by reference.

In the calibration process described in U.S. Patent No. 10541168, the edge ring includes a bevel and a lower edge ring includes a complementary bevel. When the bevels overlap, the edge ring tends to move or slide until it lies flat on the substrate surface. When the edge ring moves due to the bevels, the optical sensor can be used to measure the position change or offset. When the edge ring is not fully aligned, a non-zero offset value greater than a predetermined threshold value occurs.

The calibration process is an iterative process in which the robot moves the edge ring on the substrate support in four orthogonal directions. Before and after each transport and removal of the edge ring, an optical sensor measures the position of the edge ring on the end effector of the robot arm. A controller uses the position change before and after placement to calculate the offset and finally determines a calibration center position after a large number of iterations. It can be understood that the calibration process usually takes more than 12 hours to converge. In addition, the calibration process is repeated every time the edge ring is replaced, which reduces operation time and efficiency.

In some examples, an improved calibration process is used. According to the present disclosure, during the initial calibration process, the edge ring is placed on the edge ring riser pin, and one or more shims are used to initially center the edge ring relative to one or more surrounding elements (such as a middle edge ring or a bottom edge ring). The shims are then removed. The robot's end effector is used to remove the edge ring, and a position of the edge ring is determined using an optical sensor. Thereafter, the edge ring is transported in orthogonal directions around a center position, the position is measured, and the offset is calculated. Finally, a calibrated center position is determined based on the movement and offset. Thereafter, a significantly shorter calibration process (using a limited number of transports and removal iterations) as described below can be used. In some cases, the replacement edge ring can be transported and removed multiple times (e.g., 3 to 5 times) and the edge ring can be centered to within 30 μm of a corrected center position in less than 15 minutes (which is significantly less than 12 hours).

Referring now to FIG. 2 , the processing chamber 102 includes a housing 210 having a top, sides, and a bottom. A chamber opening 214 includes a door or opening 218 through which substrates are transported and removed. More specifically, a robotic arm 234 having an end effector 232 transports substrates to the substrate support through the opening 218 prior to substrate processing and removes the substrate from the substrate support after substrate processing. In some examples, the robotic arm 234 may form part of a substrate transfer module operating in a vacuum.

The robot arm 234 may also be used to transport a new edge ring 220 to the processing chamber after removing a worn edge ring 220 from the processing chamber through the chamber opening 214. The robot arm 234 includes one or more end effectors 232 (end effectors 232-1 and 232-2 are shown). In FIG. 2 , the edge ring 220 is disposed on the end effector 232-1. In some examples, an optical sensor 240 is disposed adjacent to the opening 218 of the chamber opening 214 to sense the position of the edge ring on the end effector, but other locations inside or outside the chamber may be used.

As will be further described below, the robot arm 234 initially places the edge ring 220 on the edge ring lifting pins (see FIG. 4 ) using a corrected center position and/or a previous center position. The edge ring 220 includes grooves aligned with the edge ring lifting pins (see FIGS. 3 and 4 ). In some examples, the number of grooves is greater than or equal to the number of edge ring lifting pins. After the robot arm transports the edge ring 220 onto the edge ring lifting pins, the edge ring 220 may move from the placement position. In other words, when the edge ring 220 is placed on the edge ring lifting pins, the edge ring 220 may move from the placement position.

After the edge ring 220 is placed, the robot arm 234 picks up the edge ring 220 and uses the optical sensor to measure the new position of the edge ring 220 on the robot arm 234. The controller calculates the offset (the difference between the previous position of the edge ring and the new position of the edge ring).

The centering position of the edge ring is adjusted based on the offset and the previous position (to remove the offset). In other words, the center position is adjusted in the opposite direction of the offset to eliminate the offset. Using the new center position (based on the previous center position and the offset), the robot arm 234 places the groove of the edge ring 220 on the edge ring riser pin. In some examples, the process is repeated Q times, where Q is an integer. In some examples, a relatively small number of iterations can be performed. In some examples, Q<10. In some examples, Q=3 or Q=5.

After the Q iterations, a final offset value is determined and compared to an offset threshold. If the final offset value is less than or equal to the offset threshold corresponding to the center position, the edge ring is considered properly centered and the substrate processing chamber can continue with substrate processing.

If the final offset value is greater than the threshold value, the edge ring is not considered to be properly centered. If the offset is greater than the threshold value, the optical sensor may be out of calibration and/or one or more of the grooves on the bottom surface of the edge ring may not be properly contacting one or more of the corresponding edge ring riser pins.

Referring now to FIG. 3 , a substrate support 320 is shown to include a first layer 330, an adhesive layer 332, and a base 334. In some examples, the first layer 330 is made of ceramic and includes electrostatic electrodes, radio frequency electrodes, and/or heating elements. A lower edge ring 336 is radially disposed outside the base 334 and at least partially radially disposed outside the edge ring 220. The edge ring 220 is disposed on edge ring riser pins 340 extending into a groove 350 located on a bottom surface of the edge ring 220. The edge ring riser pins 340 support the edge ring 220 and are received by the groove 350.

Referring now to FIG. 4 , the edge ring 220 includes an annular body 410 and a plurality of grooves 350-1, 350-2, ..., and 350-P (where P is an integer greater than or equal to 3) located on the bottom surface of the edge ring 220. In some examples, the groove 350 defines a cavity having a "V" shape. In some examples, the edge ring 220 includes P grooves 350 spaced apart at 360°/P azimuth angles. In some examples, when the annular body of the edge ring is placed flat against the upper surface of the substrate support, the bottommost portions or grooves of the plurality of grooves 350-1, 350-2, ..., and 350-P extend substantially parallel to the upper surface of the substrate support. The bottom of the plurality of grooves 350-1, 350-2, ..., and 350-P extends radially relative to the center of the edge ring.

Referring now to FIG. 5 , a method 500 of edge ring centering is shown. At 510 , an edge ring center position is calibrated. In some examples, the calibration method described above is used, but other types of calibration may be used. At 512 , Q is set equal to 0. At 514 , the position of the edge ring on the end effector of the robot is measured. At 516 , using the end effector of the robot arm, the edge ring is placed on the edge ring rise pin (with the edge ring rise pin located in the groove). The robot arm releases the edge ring and the edge ring is allowed to self-seat on the edge ring rise pin.

At 518, the edge ring is removed using the robot. At 522, the position of the edge ring is determined using the optical sensor, and the offset is calculated from the corrected edge ring center position or a previous edge ring center position. At 526, the offset is applied to the center position. In other words, the robot arm is moved in a direction opposite to the offset to adjust the center position and eliminate the offset. At 530, Q is set equal to Q+1.

At 534, the method determines whether Q=M, where Q and M are integers. In some examples, M is greater than or equal to 2 (e.g., 3, 5, etc.). If 534 is false, the method returns to 514 and repeats. If 534 is true, the method continues to 538 and determines whether the last offset value (Offset _last ) is less than or equal to an offset threshold (Offset _TH ). If 538 is true, the edge ring is considered centered at 544 because the offset is within the predetermined threshold. If 538 is false, an error occurs at 542 and the edge ring is not considered centered because the offset is greater than the predetermined threshold. In some examples, the substrate processing system may be disabled to allow further diagnosis of the edge ring centering problem.

It will be appreciated that the edge ring centering system described herein is capable of repeatedly placing the edge ring on the edge ring riser pin with high accuracy in a relatively short period of time. In some examples, the edge ring centering system is capable of placing the edge ring within 30 μm (and three standard deviations of 15 μm) per substrate transfer module arm per chamber in 15 minutes.

The foregoing description is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or use. The broad teachings of the present disclosure can be implemented in a variety of different forms. Therefore, while the present disclosure includes specific examples, the true scope of the present disclosure should not be so limited, as other modifications will become apparent upon study of the drawings, specification, and subsequent patent applications. It is to be understood that one or more steps in a method may be performed in a different order (or simultaneously) without changing the principles of the present disclosure. Further, while each of the above embodiments is described as having specific features, any one or more of these features described with respect to any embodiment of the present disclosure may be implemented in features of any other embodiment and/or combined with features of any other embodiment, even if the combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the replacement of one or more embodiments with another embodiment is still within the scope of the present disclosure.

Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using a variety of different terms, including "connected," "joined," "coupled," "adjacent," "adjacent," "near," "on," "above," "below," and "configured." Unless the relationship between a first and a second element is explicitly described as "direct" in the above disclosed description, the relationship may be a direct relationship in which no other intervening elements exist between the first and the second elements, or may be an indirect relationship in which one or more intervening elements exist between the first and the second elements (whether spatially or functionally). As used herein, the phrase "at least one of A, B, and C" should be understood to mean a logical relationship (A or B or C) using a non-mutually exclusive logical operator "OR", and should not be understood to mean "at least one of A, at least one of B, and at least one of C".

In some implementations, a controller is part of a system, which may be part of one of the examples above. Such a system may include semiconductor processing equipment, including one or more processing tools, processing chambers, processing platforms, and/or specific processing components (a substrate pedestal, a gas flow system, etc.). These systems may be integrated with electronic components to control their operation before, during, or after the processing of semiconductor substrates or substrates. The electronic components may be referred to as the "controller", which may control various different components or subcomponents of the one or more systems. Depending on the processing requirements and/or system type, the controller may be programmed to control any of the processes disclosed herein, including the delivery of process gases, temperature settings (e.g., heating and/or cooling), pressure settings, vacuum settings, power settings, RF generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and operation settings, substrate movement in and out of a tool or other transfer tool and/or load locks that connect to or interface with a particular system.

Broadly speaking, the controller may be defined as an electronic component having various integrated circuits, logic gates, memory, and/or software that receives instructions, issues instructions, controls operations, initiates cleaning operations, initiates end-of-line measurement, etc. The integrated circuit may include a chip in the form of firmware that stores program instructions, a digital signal processor (DSP), a chip defined as an application specific integrated circuit (ASIC), and/or one or more microprocessors or microcontrollers that execute program instructions (such as software). Program instructions may be transmitted to the controller in the form of various different independent configurations (or program files) that define operating parameters for a particular process to be performed on or on a semiconductor substrate or on a system. The process parameters may, in some embodiments, be part of a recipe defined by a process engineer to perform one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and/or die of a substrate.

The controller, in some implementations, may be part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the "cloud" or all or a portion of a wafer fab host computer system that allows remote access to the substrate processing. The computer may allow remote access to the system to monitor the progress of current manufacturing operations, view the history of past manufacturing operations, view trends or performance indicators from multiple manufacturing operations, to change parameters of the current process, to set processing steps to follow a current process, or to start a new process. In some examples, a remote computer (e.g., a server) may provide process recipes to a system via a network, which may include a local area network or the Internet. The remote computer may include a user interface that allows the input or programming of parameters and/or settings, which are then transmitted from the remote computer to the system. In some examples, the controller receives instructions in the form of data that specify parameters for processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool the controller is configured to connect to or control. Thus, as described above, the controller may be distributed, such as by including one or more separate controllers that are collectively networked and operate toward a common purpose (such as the process and control described herein). An example of a distributed controller used for such a purpose is one or more integrated circuits on a chamber communicating with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.

Without limitation, exemplary systems may include a plasma etching chamber or module, a deposition chamber or module, a spin cleaning chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel etching chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical deposition chamber (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etching (ALE) chamber or module, an ion implantation chamber or module, a path chamber or module, and any other semiconductor processing system that may be associated with or used in the manufacture and/or production of semiconductor substrates.

As described above, depending on one or more steps of the process to be performed by the tool, the controller may communicate with one or more other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, adjacent tools, tools throughout a factory, a host computer, another controller, or tools used in material transport to carry containers of substrates to and from tool locations and/or loading ports within a semiconductor manufacturing facility.

102: Processing room

210: Shell

214: Room entrance

218: Open mouth

220: Edge Ring

232-1,232-2: End effector

234: Robotic Arm

240:Optical sensor

Claims (14)

An edge ring centering system for a plasma processing system includes: a processing chamber including a substrate support and R edge ring riser pins, where R is an integer greater than or equal to 3; a first edge ring including P grooves located on a bottom surface thereof, where P is an integer greater than or equal to R; a robot arm including an end effector; an optical sensor; and a controller configured to perform an initial calibration to determine a calibration value for the first edge ring. wherein after performing the initial calibration, the controller is configured to perform M iterations of a centering procedure, wherein M is an integer greater than or equal to 2, each of the M iterations comprising: retracting the first edge ring from the R edge ring lifting pins for the first time by the end effector of the robot arm; after retracting the first edge ring, causing the optical sensor to sense a first position of the first edge ring on the end effector; and after sensing the first position Then, the robot arm transports the first edge ring from the end effector to the calibration center position or the last adjustment center position located on the R edge ring lifting pins; the end effector retracts the first edge ring from the R edge ring lifting pins for the second time; after the first edge ring is retracted for the second time, the optical sensor senses a second position of the first edge ring on the end effector, and determines a offset; and based on the correction center position or the previous adjustment center position, applying the offset to the robot arm in the opposite direction of the offset to adjust the current position of the first edge ring to an adjustment center position, and wherein the controller causes the robot arm to transport the first edge ring to the correction center position in the first iteration of the M iterations, and transport the first edge ring to the previous adjustment center position in the subsequent iterations of the M iterations. The edge ring centering system of claim 1, wherein the controller is configured for the first iteration of the M iterations to generate the adjusted center position for the first edge ring based on the corrected center position and the offset. The edge ring centering system of claim 2, wherein the controller is configured to update the offset based on the difference between the first position and the second position during one of the iterations of the centering procedure. The edge ring centering system of claim 3, wherein the controller is configured for a subsequent iteration of the M iterations to generate the adjusted center position based on the previous adjusted center position determined during a previous iteration of the centering process and the updated offset. The edge ring centering system of claim 1, wherein the controller is further configured to compare the offset with a predetermined offset after performing the M iterations of the centering procedure. An edge ring centering system as claimed in claim 5, wherein the controller is further configured to determine whether the first edge ring is centered based on the comparison. As in claim 1, the edge ring centering system, wherein the P grooves are "V" shaped. The edge ring centering system of claim 1, wherein the P grooves are spaced at 360°/P around the bottom surface of the first edge ring. An edge ring centering system as claimed in claim 1, wherein the P grooves are "V" shaped and a bottom portion of the P grooves extends along a radial direction. The edge ring centering system of claim 1, wherein the controller is configured to: determine whether the offset of the Mth iteration of the M iterations is less than a predetermined threshold; in response to the offset of the Mth iteration being less than the predetermined threshold, determine to center the first edge ring; and in response to the offset of the Mth iteration being greater than or equal to the predetermined threshold, determine that an error exists in centering the first edge ring. The edge ring centering system of claim 1, wherein the controller is configured to perform the centering procedure of a replacement edge ring based on the corrected center position of the first edge ring. An edge ring centering system as claimed in claim 1, wherein the controller is configured to: avoid picking up the first edge ring until the first edge ring is placed on the R edge ring lifting pins; and after the first edge ring is placed on the R edge ring lifting pins, cause the robot arm to retract the first edge ring from the R edge ring lifting pins. An edge ring centering system as claimed in claim 1, wherein the calibration center position refers to the center position of the first edge ring relative to the substrate support on the R edge ring riser pins determined during the initial calibration period of using a shim to center the first edge ring. An edge ring centering system as claimed in claim 1, wherein the offset of the first edge ring is due to a change in the position of the first edge ring relative to the R edge ring riser pins caused by removal or replacement of the first edge ring of the end effector.

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