Method and mechanism for adjusting a clip voltage during substrate manufacturing

Abstract

Disclosed is an electronic device manufacturing system, the electronic device manufacturing system including: a substrate holder configured to fasten a substrate during processing; and a controller, the controller being operably coupled to the substrate holder. The controller is configured to apply a first voltage to an electrode of the substrate holder. The controller is further configured to determine a first impedance value between the substrate holder and the substrate. The controller is further configured to determine an increment value between the first impedance value and a predetermined second impedance value, and determine whether the increment value satisfies a threshold criterion. In response to the delta value failing to meet a threshold criterion, the controller is further configured to apply a second voltage to the substrate, where the second voltage is greater than the first voltage.

Description

Technical Field

[0001] The present disclosure relates to electrostatic chucks, and more particularly, to methods and mechanisms for adjusting clamping voltage during substrate manufacturing. Background Art

[0002] In a semiconductor processing chamber using a high-power plasma process, there is a risk of damaging the hardware if certain chamber hardware contacts the plasma in an unexpected manner. The substrate holder (also referred to as a "chuck") that holds the substrate may have a heater to raise the temperature of the substrate as specified in a specific process recipe. Such a heater or substrate holder also provides an electrical ground for the plasma used in a deposition or etching reactor. In order to achieve the desired process control and prevent damage to the hardware and / or substrate, the substrate should be placed in the center of the xy plane (i.e., the center of the wafer is properly aligned with the chuck) and / or when proper contact between the chuck and the substrate is established in the z direction. In the case of an electrostatic chuck (ESC), an electrostatic holding force can be applied to the substrate to hold the substrate in place. However, the substrate may have a certain "bend" that prevents proper contact with the chuck and heater. This may not only expose the heater to high-power plasma, resulting in damage to the heater / panel, but may also result in an undesirable coating on the back of the substrate, which may cause the substrate to be completely discarded. Summary of the invention

[0003] The following is a brief summary of the present invention in order to provide a basic understanding of some aspects of the present invention. This summary is not an extensive review of the present disclosure. It is neither intended to identify the key or important elements of the present disclosure, nor to describe any scope of the specific embodiments of the present disclosure or any scope of the claims. Its only purpose is to present some concepts of the present disclosure in a simplified form as a preface to a more detailed description presented later.

[0004] In aspects of the present disclosure, an electronic device manufacturing system includes a substrate holder configured to secure a substrate during processing; and a controller operably coupled to the substrate holder. The controller is configured to apply a first voltage to an electrode of the substrate holder. The controller is further configured to determine a first impedance value between the substrate holder and the substrate. The controller is further configured to determine an incremental value between the first impedance value and a predetermined second impedance value, and to determine whether the incremental value meets a threshold criterion. In response to the incremental value failing to meet the threshold criterion, the controller is further configured to apply a second voltage to the substrate, wherein the second voltage is greater than the first voltage.

[0005] Another aspect of the disclosure includes a method according to any aspect or embodiment described herein.

[0006] Another aspect of the present disclosure includes a non-transitory computer-readable storage medium comprising instructions that, when executed by a processing device operably coupled to a memory, perform operations according to any aspect or implementation described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings.

[0008] Figure 1 is a schematic top view of an exemplary manufacturing system according to certain embodiments.

[0009] Figure 2 is a cross-sectional schematic side view of an exemplary processing chamber of an exemplary manufacturing system according to certain embodiments.

[0010] Figure 3 is a flow chart of a method for performing a clamping sequence on a substrate according to certain embodiments.

[0011] Figure 4 is a flow chart of a method for performing a dechucking sequence on a substrate according to certain embodiments.

[0012] Figure 5 is a flow chart of a method for determining a de-chucking profile during a manufacturing process on a substrate according to certain embodiments.

[0013] Figure 6 is a block diagram illustrating a computer system according to certain embodiments. DETAILED DESCRIPTION

[0014] The present invention relates to a method and mechanism for adjusting a clamping voltage during substrate manufacturing. An electronic device manufacturing system may be configured to perform one or more manufacturing processes (e.g., a deposition process, an etching process, a polishing process, etc.) on a substrate in one or more processing chambers. For example, during a deposition process (e.g., a deposition (CVD) process, an atomic layer deposition (ALD) process, etc.), a film may be deposited on the surface of a substrate. The manufacturing system may use one or more robots to position the substrate on a substrate holder (e.g., a "chuck") inside a processing chamber. The substrate holder may have a heater to increase the temperature of the substrate as specified by a specific process recipe, which defines a set of specific operations to be performed on the substrate during the process, and may include one or more settings associated with each operation. For example, a deposition process recipe may include a temperature setting for the processing chamber, a pressure setting for the processing chamber, a flow rate setting for a precursor of a material contained in a film deposited on a substrate surface, etc. Some substrate holders, such as an electrostatic chuck (ESC), may include a workbench with an electrode biased with a DC voltage to establish an electrostatic holding force, thereby holding the substrate in a proper position relative to the substrate holder.

[0015] In some cases, a layer formed by a deposition process or a previous deposition process may cause the substrate to experience "bow" (deviation of the center point of the mid-surface of the substrate from a reference plane) that prevents proper contact with the substrate holder and heater. For example, a layer formed by a deposition process may exert a force on the edge of the substrate greater than the electrostatic force used to hold the substrate in place, causing the edge of the substrate to lift or warp. This not only exposes the surface of the chuck to high power plasma, causing damage to the chuck, but may also cause undesirable coatings on the back side of the substrate.

[0016] In other cases, once the clamping voltage is stopped, the residual electrostatic force may take a certain amount of time to dissipate. This dissipation time may vary based on different factors, such as the strength of the clamping voltage, the number and / or thickness of deposited layers, etc. Removing the substrate via the robot before the electrostatic force dissipates may result in excessive force being applied to the substrate, resulting in damage to the substrate, damage to the chuck, etc.

[0017] Various aspects and embodiments of the present disclosure address these and other shortcomings of the prior art by adjusting the clamping voltage before, during, and / or after substrate manufacturing. Such substrate manufacturing may include a deposition process, an etching process, and the like. In one embodiment, once the substrate is positioned on a substrate holder, the substrate holder may apply an initial clamping voltage (e.g., 400 volts (V)) to the substrate. The initial clamping voltage may be set during calibration of the manufacturing system and based on a minimum or average clamping voltage sufficient to clamp a substrate (e.g., a flat substrate or a substrate with an average or minimum amount of curvature). The manufacturing system may then measure an impedance value between the substrate holder and the substrate. For example, the manufacturing system may use a set of electrical sensors coupled to the substrate holder to obtain a set of impedance readings and determine an average impedance value. The manufacturing system may compare this current impedance value with an expected impedance value to determine an incremental value (i.e., the difference between the current impedance value and the expected impedance value, expressed as |current impedance value-expected impedance value|, as the case may be). The expected impedance value may be an impedance value indicating that the clamped substrate does not experience curvature (or an acceptable minimum curvature). The manufacturing system may determine whether the incremental value meets a clamping threshold criterion (e.g., whether the incremental value is below an allowable limit). In response to the incremental value being greater than the allowed limit, the manufacturing system may increase the clamping voltage by the incremental value (e.g., 10 V). The manufacturing system may then determine a new impedance value, determine the incremental value, and determine whether the incremental value meets the clamping threshold criteria. The manufacturing system may perform this loop until the incremental value meets the clamping threshold criteria.

[0018] In one embodiment, once the delta value is less than an allowable threshold (indicating that the substrate is clamped without bow), the processing chamber initiates a fabrication process. During the fabrication process, the fabrication system may take periodic impedance readings, and in response to determining that bowing has occurred (e.g., the delta value has become greater than an allowable threshold), the fabrication system may increase the clamping voltage to remove the bow.

[0019] Once the manufacturing process is complete, the manufacturing system can perform a de-chucking operation to de-chuck the substrate. Specifically, the manufacturing system can gradually reduce the clamping voltage while measuring the impedance between the substrate and the substrate holder to determine an incremental value. Once the incremental value is greater than a de-chucking threshold (indicating that the electrostatic force has dissipated or is insufficient to cause damage to the substrate during its removal), the manufacturing system can remove the substrate from the substrate holder via a transfer chamber robot.

[0020] Aspects of the present disclosure result in a technical advantage of significantly reducing the time spent clamping and de-clamping a substrate. Aspects of the present disclosure further result in a technical advantage of preventing substrate bending during the manufacturing process, thereby preventing damage to the heater and / or the panel of the substrate holder, and preventing undesirable coatings on the back side of the substrate. Aspects of the present disclosure further result in a technical advantage of preventing damage to the substrate or heater due to removal of a substrate clamped due to residual electrostatic forces. Therefore, in an embodiment, the present disclosure can prevent damaged or abnormal products, as well as unplanned user time or downtime for maintenance.

[0021] Figure 1 1 is a schematic top view of an exemplary manufacturing system 100 according to various aspects of the present disclosure. The manufacturing system 100 can perform one or more processes to produce a product, such as an electronic device, following a recipe or performing a run within a certain time period. Examples of substrate processes include a deposition process for depositing one or more layers of film on the surface of a substrate, an etching process for forming a pattern on the surface of a substrate, and the like. The substrate 102 can be any suitable rigid, fixed-size planar article suitable for manufacturing electronic devices or circuit components thereon, such as, for example, a silicon-containing disk or wafer, a patterned wafer, a glass plate, and the like. The manufacturing device 100 can perform each process according to a process recipe. The process recipe defines a set of specific operations to be performed on the substrate 102 during the process, and can include one or more settings associated with each operation. For example, a deposition process recipe can include a temperature setting for a processing chamber, a pressure setting for a processing chamber, a flow rate setting for a precursor of a material contained in a film deposited on the surface of the substrate, and the like.

[0022] The manufacturing system 100 may include a processing tool 104 and a factory interface 106 coupled to the processing tool 104. The processing tool 104 may include a housing 108 having a transfer chamber 110 therein. The transfer chamber 110 may include one or more processing chambers (also referred to as processing chambers) 114, 116, 118 disposed around and coupled thereto. The processing chambers 114, 116, 118 may be coupled to the transfer chamber 110 via corresponding ports (such as slit valves, etc.). The transfer chamber 110 may also include a transfer chamber robot 112 configured to transfer the substrate 102 between the processing chambers 114, 116, 118, a load lock mechanism 120, etc. The transfer chamber robot 112 may include one or more arms, wherein each arm includes one or more end effectors at the end of each arm. The end effector may be configured to handle a specific object, such as a wafer, a sensor disk, a sensor tool, etc.

[0023] The processing chambers 114, 116, 118 may be adapted to perform any number of processes on the substrate 102. The same or different substrate processes may be performed in each of the processing chambers 114, 116, 118. The substrate processes may include atomic layer deposition (ALD), physical vapor deposition (PVD), chemical vapor deposition (CVD), etching, annealing, curing, pre-cleaning, metal or metal oxide removal, etc. Other processes may be performed on the substrates therein. The processing chambers 114, 116, 118 may each include one or more sensors configured to capture data of the substrate 102 before, after, or during the substrate process. For example, the one or more sensors may be configured to capture spectral data and / or non-spectral data of a portion of the substrate 102 during the substrate process. In other or similar embodiments, the one or more sensors may be configured to capture data associated with the environment within the processing chambers 114, 116, 118 before, after, or during the substrate process. For example, the one or more sensors may be configured to capture data associated with the temperature, pressure, gas concentration, etc. of the environment within the processing chambers 114, 116, 118 during substrate processing.

[0024] A load lock mechanism 120 may also be coupled to the housing 108 and the transfer chamber 110. The load lock mechanism 120 may be configured to interface and couple to the transfer chamber 110 and the factory interface 106 on one side. In some embodiments, the load lock mechanism 120 may have an environmentally controlled atmosphere that can be changed from a vacuum environment (wherein substrates can be transferred to and from the transfer chamber 110) to an inert gas environment at or near atmospheric pressure (wherein substrates can be transferred to and from the factory interface 106). The factory interface 106 may be any suitable housing, such as, for example, an Equipment Front End Module (EFEM). The factory interface 106 may be configured to receive the substrate 102 from a substrate carrier 122 (e.g., a Front Opening Unified Pod (FOUP)) docked at each load port 124 of the factory interface 106. A factory interface robot 126 (shown in phantom) may be configured to transfer substrates 102 between a carrier (also referred to as a container) 122 and the load lock mechanism 120. The carrier 122 may be a substrate storage carrier or a replacement part storage carrier.

[0025] The manufacturing system 100 may also be connected to a client device (not shown) that is configured to provide information about the manufacturing system 100 to a user (e.g., an operator). The client device may include a computing device such as a personal computer (PC), a laptop, a mobile phone, a smart phone, a tablet computer, a netbook computer, an Internet-connected television ("smart TV"), an Internet-connected media player (e.g., a Blu-ray player), a set-top box, an over-the-top (OTT) streaming device, an operator box, etc. In some embodiments, the client device may provide information to a user of the manufacturing system 100 via one or more graphical user interfaces (GUIs). For example, according to embodiments described herein, the client device may provide information about a clamping or unclamping state via a GUI.

[0026] The manufacturing system 100 may also include a system controller 128. The system controller 128 may be and / or include a computing device, such as a personal computer, a server computer, a programmable logic controller (PLC), a microcontroller, etc. The system controller 128 may include one or more processing devices, which may be general-purpose processing devices, such as a microprocessor, a central processing unit, etc. More specifically, the processing device may be a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, or a processor that implements other instruction sets, or a processor that implements a combination of instruction sets. The processing device may also be one or more special-purpose processing devices, such as an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, etc. The system controller 128 may include a data storage device (e.g., one or more disk drives and / or solid-state drives), a main memory, a static memory, a network interface, and / or other components. The system controller 128 may execute instructions to perform any one or more of the methods and / or embodiments described herein. In some embodiments, the system controller 128 may execute instructions to perform one or more operations at the manufacturing system 100 according to a process recipe. The instructions may be stored on a computer-readable storage medium, which may include a main memory, a static memory, a secondary storage device, and / or a processing device (during execution of the instructions).

[0027] The system controller 128 may receive data from sensors included on or within various portions of the manufacturing system 100 (e.g., the processing chambers 114, 116, 118, the transfer chamber 110, the load lock mechanism 120, etc.). In some embodiments, the data received by the system controller 128 may include spectral data and / or non-spectral data of a portion of the substrate 102. In other or similar embodiments, the data received by the system controller 128 may include data associated with processing the substrate 102 at the processing chambers 114, 116, 118 as previously described. For purposes of this description, the system controller 128 is described as receiving data from sensors included within the processing chambers 114, 116, 118. However, according to embodiments described herein, the system controller 128 may receive data from any portion of the manufacturing system 100 and may use the data received from that portion. In the illustrative example, the system controller 128 may receive data from one or more sensors of the processing chambers 114, 116, 118 before, after, or during substrate processing at the processing chambers 114, 116, 118. The data received from the sensors of various parts of the manufacturing system 100 may be stored in a data store 150. The data store 150 may be included as a component within the system controller 128, or may be a separate component from the system controller 128.

[0028] The data storage device 150 may be a memory (e.g., random access memory), a drive (e.g., a hard drive, a flash drive), a database system, or another type of component or device capable of storing data. The data storage device 150 may include multiple storage components (e.g., multiple drives or multiple databases) that may span multiple computing devices (e.g., multiple server computers). The data storage device 150 may store data associated with processing a substrate at the manufacturing equipment 100. For example, the data storage device 150 may store data (referred to as process data) collected by sensors at the manufacturing equipment before, during, or after a substrate process. The process data may refer to historical process data (e.g., process data generated for a previous substrate processed at the manufacturing system) and / or current process data (e.g., process data generated for a current substrate processed at the manufacturing system). The data storage device 150 may also store spectral data or non-spectral data associated with a portion of a substrate processed at the manufacturing equipment 100. The spectral data may include historical spectral data and / or current spectral data.

[0029] The data storage device 150 may also store contextual data associated with one or more substrates processed at the manufacturing system. The contextual data may include a recipe name, a recipe step number, a preventive maintenance indicator, an operator, etc. The contextual data may refer to historical contextual data (e.g., contextual data associated with a previous process performed on a previous substrate) and / or current processing data (e.g., contextual data associated with a current process or a future process to be performed on a previous substrate). The contextual data may further include identification sensors associated with a particular subsystem of the processing chamber.

[0030] The data storage device 150 may also store task data. The task data may include one or more groups of operations to be performed on the substrate during the deposition process, and may include one or more settings associated with each operation. For example, the task data for the deposition process may include a temperature setting for the processing chamber, a pressure setting for the processing chamber, a flow rate setting for a precursor of the material of the film deposited on the substrate, and the like. In another example, the task data may include controlling the pressure at a defined pressure point for a flow value. The task data may refer to historical task data (e.g., task data associated with a previous process performed on a previous substrate) and / or current task data (e.g., task data associated with a current process or a future process to be performed on the substrate).

[0031] In some embodiments, the data storage device 150 can store clamping profiles. The clamping profiles can include clamping voltages for different steps of a process recipe. For example, for a particular deposition recipe, the clamping profile can include a first clamping voltage (450V) for the first twenty deposited layers or a first layer thickness range, a second clamping voltage (470V) for the next twenty deposited layers or a second layer thickness range, a third clamping voltage (e.g., 500V) for the next thirty layers or a third layer thickness range, and so on. Each clamping profile can be generated using user input or during the manufacturing process. For example, during a deposition process using a particular recipe, the manufacturing system can execute a clamping sequence (e.g., Figure 3 ) and determine which steps of the process recipe will experience increases in clamping voltage. A clamping profile can be generated based on these increases, and during subsequent deposition processes using a particular deposition recipe, the manufacturing system can increase the clamping voltage during specific process steps as indicated by the clamping profile.

[0032] In some embodiments, the data storage device 150 can store a de-clamping profile. The de-clamping profile can include a clamping voltage for safely removing a substrate from a substrate holder. For example, for a particular deposition recipe, the de-clamping profile can include a clamping voltage that reflects an electrostatic force that is not strong enough to cause damage to the substrate during substrate removal (hereinafter "removal clamping voltage"). Each de-clamping profile can be generated using user input or during a manufacturing process. For example, during a deposition process using a particular recipe, a manufacturing system can execute a de-clamping sequence (such as Figure 4 The manufacturing system may reduce the clamping voltage to the removal clamping voltage as indicated by the de-clamping profile during a subsequent deposition process using a particular deposition recipe.

[0033] In some embodiments, the data storage device 150 may be configured to store data that is not accessible to users of the manufacturing system. For example, a user of the manufacturing system (e.g., an operator) cannot access process data, spectral data, contextual data, etc. obtained for a substrate processed at the manufacturing system. In some embodiments, all data stored at the data storage device 150 may be inaccessible to users of the manufacturing system. In other or similar embodiments, a portion of the data stored at the data storage device 150 may be inaccessible to the user, while another portion of the data stored at the data storage device 150 may be accessible to the user. In some embodiments, one or more portions of the data stored at the data storage device 150 may be encrypted using an encryption mechanism unknown to the user (e.g., the data is encrypted using a private encryption key). In other or similar embodiments, the data storage device 150 may include multiple data storage devices, wherein the data that is not accessible to the user is stored in one or more first data storage devices, and the data that is accessible to the user is stored in one or more second data storage devices.

[0034] Figure 2 is a cross-sectional schematic side view of a processing chamber 200 according to an embodiment of the present disclosure. In some embodiments, the processing chamber 200 may correspond to reference Figure 1The processing chambers 114, 116, 118 described above. The processing chamber 200 can be used for processes in which a corrosive plasma environment is provided. For example, the processing chamber 200 can be a chamber for a plasma etcher or a plasma etching reactor, etc. In another example, the processing chamber can be a chamber for a deposition process as previously described. In one embodiment, the processing chamber 200 includes a chamber body 201 and a showerhead 230 surrounding an internal space 206. The showerhead 230 can include a showerhead base and a showerhead gas distribution plate. Alternatively, the showerhead 230 can be replaced by a cover and a nozzle in some embodiments, or by a plurality of pie-shaped showerhead compartments and a plasma generation unit in other embodiments. The chamber body 201 can be made of aluminum, stainless steel, or other suitable materials such as titanium (Ti). The chamber body 201 typically includes a sidewall 208 and a bottom 210. An exhaust port 226 can be defined in the chamber body 201, and the internal space 206 can be coupled to a pump system 228. The pump system 228 may include one or more pumps and throttle valves for evacuating and regulating the pressure of the interior space 206 of the process chamber 200 .

[0035] The showerhead 230 can be supported on the sidewall 208 of the chamber body 201. The showerhead 220 (or lid) can be opened to allow access to the interior space 206 of the processing chamber 200, and can provide a seal for the processing chamber 200 when closed. The gas panel 258 can be coupled to the processing chamber 200 to provide process gases and / or cleaning gases to the interior space 206 via the showerhead 230 or the lid and nozzle (e.g., via the apertures of the showerhead or the lid and nozzle). For example, the gas panel 258 can provide a precursor for the material of the film 251 deposited on the surface of the substrate 202. In some embodiments, the precursor may include a silicon-based precursor or a boron-based precursor. The showerhead 230 may include a gas distribution plate (GDP) and may have a plurality of gas delivery holes 232 (also referred to as channels) throughout the GDP.

[0036] The substrate support assembly 248 is disposed in the interior space 206 of the processing chamber 200 below the showerhead 230. The substrate support assembly 248 holds the substrate 202 using, for example, a substrate holder 250 during processing (eg, during a deposition process).

[0037] The substrate holder 250 may include an electrostatic chuck (ESC), but the scope of the present disclosure is not limited to an ESC. The ESC may be or include a stage having an electrode 255 that may be biased with a voltage (e.g., a direct current (“DC”) voltage) to establish an electrostatic holding force to hold the substrate 202 in position relative to the substrate holder 250.

[0038] A power source 272 (e.g., a DC power source) may be coupled to the electrode 255 of the substrate holder 150 to generate an electrostatic force that holds the substrate 202 downward. In embodiments, the power source 272 may be a monopolar source or a bipolar source. A controller 275 may be coupled to the electrode 255 (or coupled to the power source 272 coupled to the electrode 255). In embodiments, the controller 275 corresponds to Figure 1 The controller 275 may regulate the power supplied by the power source 272 that powers the electrode 255 to adjust the electrostatic clamping force.

[0039] In an embodiment, the substrate holder 250 includes one or more heating elements 260 that can heat the substrate holder 250 and one or more regions of the substrate 202. A power source 273 can be connected to the heating element 273 and can provide power to the heating element 260 to heat the substrate 202 to a target temperature before, during, and / or after processing. A controller 275 can be connected to the power source 273 to control the power source 273. Different layers on the substrate 202 can have different coefficients of thermal expansion. These different coefficients of thermal expansion can cause the substrate 202 to bend when the substrate 202 is heated.

[0040] Ideally, there should not be any gap between the substrate 202 and the surface of the substrate holder 250. However, due to improper clamping and / or excessive substrate bending, an undesirable limited gap may exist between the substrate 202 and the surface of the substrate holder 250. Due to this gap, arc discharge may occur between the substrate 202 and the substrate holder 250 when the high power RF plasma is turned on, and the arc discharge may damage the exposed portion of the substrate holder 250 (including the heater and the faceplate) as well as the substrate 202 itself. Moreover, when the plasma reaches the gap, an undesirable coating may adhere to the back side of the substrate 202.

[0041] The substrate holder 250 may include one or more electrical sensors 270 to measure one or more electrical properties between the substrate 202 and the substrate holder 250 (e.g., impedance, magnetic fluctuations in the feed conductor, current, voltage, resistance, etc.). The electrical sensor 270 may also measure the value of one or more of current, alternating current (AC) amplitude, phase, waveform (e.g., alternating current (AC) waveform, pulse waveform), direct current (DC), non-sinusoidal AC waveform, voltage, etc. In some embodiments, the electrical sensor 270 may be embedded in the substrate holder (e.g., a non-contact sensor). In some embodiments, the electrical sensor 270 may be positioned on the surface of the substrate holder and exposed to the surface. In some embodiments, the electrical sensor 270 may be one or more of a piezoelectric sensor, a charge output sensor, a charge coupled device (CCD), a capacitive sensor, and a resistive sensor, or any other type of electrical sensor capable of measuring one or more electrical properties.

[0042] The controller 275 may be connected to the electrical sensor 270 and may receive measurements from the electrical sensor 270. The controller 275 may be coupled to a data storage device 280, which may correspond to the data storage device 150 in embodiments. The controller 275 may determine a target or threshold measurement value from the data storage device 150 and may compare the measured electrical value received from the electrical sensor 270 with a stored value. The stored value may indicate a value obtained when the supported substrate is in full contact with the surface of the substrate holder 250. If the deviation of the measured value from the stored value is greater than a deviation threshold, this may indicate that the substrate is bent (and therefore a portion of the substrate is not in full contact with the surface of the substrate holder 250). Therefore, the controller 275 may adjust the power delivered to the electrode 255 in response to determining that the measured value deviates from the target value by more than a threshold difference. The increased power or voltage may cause the electrode to flatten the substrate, thereby ensuring full contact between the substrate and the surface of the substrate holder. Such full contact promotes proper heat transfer between the substrate holder 250 and the substrate 202 and eliminates any gaps between the substrate holder 250 and the substrate 202 that could cause arcing, could cause the exposed backside of the substrate to be coated, and the like.

[0043] Figure 3 is a flow chart of a method 300 for performing a clamping sequence on a substrate according to aspects of the present disclosure. The method 300 is performed by processing logic, which may include hardware (circuitry, dedicated logic, etc.), software (e.g., running on a general purpose computer system or a dedicated machine), firmware, or some combination thereof. In one embodiment, the method 300 may be performed by Figure 1 The manufacturing system 100 and / or Figure 2 The method 300 may be performed by one or more components of the processing chamber 200 (such as the system controller 128 and / or the controller 275). In other or similar embodiments, one or more operations of the method 300 may be performed by one or more other machines (such as, for example, a client device) not depicted in the figure.

[0044] At operation 310, processing logic positions a substrate on a substrate holder. For example, processing logic may be configured to command a transfer chamber robot (e.g., transfer chamber robot 112) to transfer a substrate (e.g., substrate 102) to a processing chamber (e.g., processing chambers 114, 116, 118) and position the substrate on a substrate holder.

[0045] At operation 320, processing logic applies an initial clamping voltage to the substrate located on the substrate holder. In some embodiments, the initial clamping voltage may be set during calibration of the manufacturing system or processing chamber. For example, the initial clamping voltage may be determined based on a minimum or average clamping voltage sufficient to clamp the substrate without bending and / or warping. In some embodiments, the initial clamping voltage may be set by user input via a client device. In some embodiments, the initial clamping voltage may be determined using a clamping profile. In some embodiments, before positioning the substrate on the substrate holder, the curvature of the incoming substrate may be measured, and the power of the DC source may be adjusted accordingly to adjust an electrostatic clamping force sufficient to maintain contact with the substrate holder with a determined amount of curvature. The curvature may be measured using one or more sensors of the manufacturing system 100 (e.g., using a distance measurement sensor to determine the distance from the center of the substrate to one or more ends of the substrate) or via manual calculation by a user. Based on the determined curvature, the processing logic may determine a corresponding initial clamping voltage by reference to a data structure stored on a data storage device (having a set of data values, relationships between data values, and / or a format of functions or operations that may be applied to the data values). For example, different amounts of bend can be associated with different initial clamping voltages. The higher the amount of bend, the higher the initial clamping voltage used to overcome the bend and flatten the substrate against the substrate holder. In some embodiments, once the substrate is received, the processing logic can wait for a predetermined period of time before performing operation 320.

[0046] At operation 330, processing logic determines a current impedance value (or other measurement value) between the substrate holder and the substrate. In some embodiments, processing logic may determine the current impedance value (or other measurement value) by obtaining one or more measurements using one or more electrical sensors coupled to the substrate holder. For example, processing logic may obtain multiple impedance readings from different electrical sensors coupled to or embedded in the substrate holder and determine an average impedance value from the multiple impedance readings.

[0047] At operation 340, processing logic determines a delta value between a current value (e.g., an impedance value) and an expected or target value (e.g., an impedance value). In one embodiment, the delta is determined by subtracting the expected value from the current value and / or determining the absolute value of the difference between the two values. The expected value (e.g., an impedance value) may be a value indicating that the clamped substrate experiences no bending (or an acceptable minimum bending). In some embodiments, the expected value may be obtained from a data structure stored on a data storage device. The expected value may be determined based on, for example, experimental results performed by one or more users.

[0048] At operation 350, processing logic determines whether the incremental value satisfies a clamping threshold criterion. In some embodiments, the clamping threshold criterion is a predetermined threshold. For example, processing logic may determine whether the incremental value is below a predetermined threshold. In response to the incremental value satisfying the clamping threshold (e.g., below the predetermined threshold, thus indicating that the substrate is clamped), processing logic proceeds to operation 370, where processing logic may perform one or more operations of the process recipe. In response to the incremental value not satisfying the predetermined threshold (e.g., greater than the predetermined threshold), processing logic proceeds to operation 360.

[0049] At operation 360, processing logic may increase the clamping voltage applied to the substrate. In some embodiments, processing logic may increase the clamping voltage by a predetermined increment. For example, processing logic may increase the clamping voltage by 10V. In some embodiments, in response to increasing the clamping voltage, processing logic may wait a predetermined amount of time before proceeding to the next operation. Such a delay may allow electrostatic forces to affect the substrate. Processing logic then proceeds to operation 330 and determines a new value (e.g., a new impedance value) between the substrate holder and the substrate. This new value may then be compared to an expected value to again determine if the substrate is properly clamped. If not, the method may again return to block 330 after increasing the clamping voltage again. This process may continue until the substrate is fully clamped.

[0050] Once the substrate is properly clamped (ie, the bow of the substrate has been effectively eliminated and / or the threshold criteria have been met), the method proceeds to operation 370 and the manufacturing process is performed.

[0051] In some embodiments, during the manufacturing process, the manufacturing system may take periodic readings (e.g., periodic impedance readings). After each such reading, the measured value (e.g., impedance value) may be compared to an expected value, and the absolute value of the difference between the two values ​​may be compared to a threshold criterion. The manufacturing process may have caused the substrate to bend (or bend further than the substrate was initially bent), which may cause the substrate to no longer be properly clamped. Therefore, in response to determining that bending has occurred (e.g., the incremental value is greater than the clamping threshold), the manufacturing system may increase the clamping voltage until the new incremental value has met the threshold criterion. Therefore, in addition to or in lieu of before the manufacturing process begins, the operations of blocks 330 to 370 may be performed periodically or continuously during the manufacturing process.

[0052] In some embodiments, processing logic may generate and / or update a clamping profile. For example, a clamping profile may be associated with a particular process recipe used with a clamped substrate. Processing logic may update the clamping profile to include a clamping voltage used to clamp the substrate prior to executing the process recipe, and associate each clamping voltage increase (or a set of clamping voltage increases) with each corresponding process recipe step. Thus, during a subsequent manufacturing process using a particular process recipe, processing logic may use the clamping profile to set an initial clamping voltage and perform clamping voltage increases during specified steps of the process recipe.

[0053] Figure 4 is a flow chart of a method 400 for performing a de-chucking sequence on a substrate in accordance with aspects of the present disclosure. The method 400 is performed by processing logic, which may include hardware (circuitry, dedicated logic, etc.), software (e.g., running on a general purpose computer system or a dedicated machine), firmware, or some combination thereof. In one embodiment, the method 400 may be performed by Figure 1 The manufacturing system 100 and / or Figure 2 The method 400 may be performed by one or more components of the processing chamber 200 (such as the system controller 128 and / or the controller 275). In other or similar embodiments, one or more operations of the method 400 may be performed by one or more other machines (such as, for example, a client device) not depicted in the figure.

[0054] At operation 410, processing logic applies a clamping voltage to a substrate clamped to a substrate holder. In some embodiments, the clamping voltage may be the same as the clamping voltage last applied during the manufacturing process. In some embodiments, the clamping voltage may be a maximum clamping voltage that the substrate holder is capable of applying. In some embodiments, the clamping voltage may be a user-defined voltage, a predetermined voltage, or a voltage obtained from a de-clamping profile. In some embodiments, before performing operation 410, processing logic may wait for a predetermined period of time after the manufacturing process is completed on the substrate. In some embodiments, processing logic may perform one or more de-clamping procedures, such as flushing the processing chamber with an inert gas, before performing operation 410.

[0055] At operation 420, processing logic determines a current impedance value (or other measurement value) between the substrate holder and the substrate. In some embodiments, processing logic may determine the current impedance value (or other measurement value) by obtaining one or more measurements using one or more electrical sensors coupled to the substrate holder. For example, processing logic may obtain multiple impedance readings from different electrical sensors coupled to or embedded in the substrate holder and determine an average impedance value from the multiple impedance readings.

[0056] At operation 430, processing logic determines a delta value between a current value (e.g., an impedance value) and an expected or target value (e.g., an impedance value). In one embodiment, the delta is determined by subtracting the expected value from the current value and / or determining the absolute value of the difference between the two values. The expected value (e.g., an impedance value) can be a value indicating that the electrostatic force is dissipated or not strong enough to cause damage to the substrate during substrate removal. In some embodiments, the expected value can be obtained from a data structure stored on a data storage device. The expected value can be determined based on, for example, experimental results performed by one or more users.

[0057] At operation 440, processing logic determines whether the incremental value satisfies a de-clamping threshold criterion. In some embodiments, the de-clamping threshold criterion is a threshold value. For example, processing logic may determine whether the incremental value is greater than a predetermined threshold value. In response to the incremental value satisfying the de-clamping threshold value (e.g., being greater than the predetermined threshold value, thereby indicating that the substrate is de-clamped), processing logic proceeds to operation 460, where processing logic may indicate to the manufacturing system that the substrate is de-clamped. In response to the incremental value not satisfying the predetermined threshold value (e.g., being less than the predetermined threshold value), processing logic proceeds to operation 450. In some embodiments, the de-clamping threshold criterion is similar to or the same as the clamping threshold criterion. In other embodiments, the de-clamping threshold criterion is a value that is independent of the clamping threshold criterion.

[0058] At operation 450, processing logic reduces the clamping voltage applied to the substrate. In some embodiments, processing logic may reduce the clamping voltage by a predetermined increment. For example, processing logic may reduce the clamping voltage by 10V. In some embodiments, in response to reducing the clamping voltage, processing logic may wait a predetermined amount of time before proceeding to the next operation. This delay may allow electrostatic forces to dissipate from the substrate and / or substrate holder. Processing logic then proceeds to operation 420 and determines a new value (e.g., a new impedance value) between the substrate holder and the substrate. This new value may then be compared to an expected value to again determine whether the substrate is unclamped. If not, the method may again return to block 420 after reducing the clamping voltage again. This process may continue until the substrate is unclamped.

[0059] Once the substrate is properly unclamped, the method proceeds to operation 460 and a transfer chamber robot (eg, the transfer chamber robot 112 ) may remove the substrate from the substrate holder.

[0060] In some embodiments, processing logic may generate and / or update a de-chucking profile. For example, processing logic may update the de-chucking profile to include a de-chucking voltage at which the substrate becomes de-chucking. Thus, during a subsequent manufacturing process, processing logic may use the clamping profile to set an initial clamping voltage during a de-chucking operation.

[0061] Figure 5 is a flow chart of a method 500 for determining a de-chucking profile during a manufacturing process on a substrate in accordance with aspects of the present disclosure. The method 500 is performed by processing logic that may include hardware (circuitry, dedicated logic, etc.), software (e.g., running on a general purpose computer system or a dedicated machine), firmware, or some combination thereof. In one embodiment, the method 500 may be performed by Figure 1 The manufacturing system 100 and / or Figure 2 The method 500 may be performed by one or more components of the processing chamber 200 (such as the system controller 128 and / or the controller 275). In other or similar embodiments, one or more operations of the method 500 may be performed by one or more other machines (such as, for example, a client device) not depicted in the figure. The method 500 may be initiated in response to user input or automatically (e.g., according to a step of a recipe, in response to completion of a manufacturing process, etc.).

[0062] The method 500 may be performed while a manufacturing process is being performed on a substrate.

[0063] At operation 510, processing logic determines whether the manufacturing system includes a de-clamping profile for the executed process recipe. For example, processing logic may query a data storage device for any corresponding de-clamping profile. In response to determining that the manufacturing system includes a corresponding de-clamping profile, processing logic proceeds to operation 570. In response to determining that the manufacturing system does not include a corresponding de-clamping profile, processing logic proceeds to operation 515.

[0064] At operation 515, processing logic applies a maximum clamping voltage to the substrate clamped to the substrate holder. The maximum clamping voltage may be a maximum voltage value that the substrate holder may apply to the coupled electrode.

[0065] At operation 520, processing logic determines a current impedance value (or other measurement value) between the substrate holder and the substrate. In some embodiments, processing logic may determine the current impedance value (or other measurement value) by obtaining one or more measurements using one or more electrical sensors coupled to the substrate holder. For example, processing logic may obtain multiple impedance readings from different electrical sensors coupled to or embedded in the substrate holder and determine an average impedance value from the multiple impedance readings. In some embodiments, processing logic may determine the current impedance value by obtaining one or more measurements over a predetermined period of time (e.g., a monitoring time).

[0066] At operation 525, processing logic decreases the clamping voltage applied to the substrate. In some embodiments, processing logic may decrease the clamping voltage by a predetermined increment (e.g., 10 V). In some embodiments, in response to increasing the clamping voltage, processing logic may wait a predetermined amount of time before proceeding to the next operation to allow electrostatic forces to dissipate from the substrate and / or substrate holder.

[0067] At operation 530, processing logic determines whether the clamping voltage reaches a minimum clamping voltage. The minimum clamping voltage may be a minimum voltage required to clamp the substrate to the substrate holder. In response to determining that the clamping voltage reaches the minimum clamping voltage, processing logic proceeds to operation 545. In response to determining that the clamping voltage does not reach the minimum clamping voltage, processing logic proceeds to operation 540.

[0068] At operation 540, processing logic determines whether the impedance change is greater than a threshold value. In particular, processing logic may first determine a delta value between the current impedance value and an expected or target impedance value. In one embodiment, the delta is determined by subtracting an expected value from a current value and / or determining an absolute value of the difference between the two values. The expected value may be a value indicating that the clamped substrate does not experience bending (or an acceptable minimum bending). In some embodiments, the expected value may be obtained from a data structure stored on a data storage device. The expected value may be determined based on, for example, experimental results performed by one or more users. Processing logic may then determine whether the delta value meets a clamping threshold criterion. In some embodiments, the clamping threshold criterion is a predetermined threshold. For example, processing logic may determine whether the delta value is below a predetermined threshold. In response to the delta value meeting the clamping threshold (e.g., below a predetermined threshold, thereby indicating that the substrate is clamped), processing logic proceeds to operation 525 to reduce the clamping voltage applied to the substrate. In response to the delta value not meeting the predetermined threshold (e.g., greater than a predetermined threshold, thereby indicating that the substrate is being unclamped), processing logic proceeds to operation 545.

[0069] At operation 545, processing logic increases the clamping voltage to clamp the substrate. In some implementations, processing logic may increase the clamping voltage by the predetermined increment used in operation 525 (eg, 10V), or by any other predetermined increment.

[0070] At operation 550, the processing logic may store the voltage value reflecting the delta value that does not meet the predetermined threshold in the metadata table. In particular, the processing logic may store the voltage value when the substrate is not clamped (e.g., the voltage value before operation 545). In some embodiments, the processing logic may generate a de-chucking profile for the current process recipe based on this voltage value.

[0071] At operation 555 , processing logic initiates an automatic compensator clamping sequence to automatically hold the substrate clamped on the substrate holder. For example, processing logic may initiate method 300 .

[0072] Returning to operation 510, in response to determining that the manufacturing system includes a corresponding de-chucking profile, processing logic proceeds to operation 570. At operation 570, processing logic applies a de-chucking voltage obtained from the de-chucking profile.

[0073] At operation 575, processing logic determines whether the automatic compensator clamping sequence is enabled. In response to determining that the automatic compensator clamping sequence is enabled, processing logic proceeds to operation 580 and initiates the automatic compensator clamping sequence to automatically hold the substrate clamped on the substrate holder. In response to determining that the automatic compensator clamping sequence is not enabled, processing logic proceeds to operation 585 and maintains the current clamping voltage.

[0074] Figure 6 It is a block diagram of a computer system 600 according to certain embodiments. In some embodiments, the computer system 600 can be connected (for example, via a network, such as a local area network (LAN), an intranet, an extranet or the Internet) to other computer systems. The computer system 600 can operate as a server or client computer in a client-server environment, or as a peer computer in a peer-to-peer or distributed network environment. The computer system 600 can be provided by any device of a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a cellular phone, a network device, a server, a network router, a switch or a bridge, or a set of instructions (sequential or otherwise) that can be executed to specify the action to be taken by the device. In addition, the term "computer" should include any computer collection that executes a set (or multiple sets) of instructions individually or jointly to execute any one or more methods of the methods described herein.

[0075] In another aspect, the computer system 600 may include a processing device 602, a volatile memory 604 (e.g., a random access memory (RAM)), a non-volatile memory 606 (e.g., a read-only memory (ROM) or an electrically erasable programmable ROM (EEPROM)), and a data storage device 616, which may communicate with each other via a bus 608.

[0076] The processing device 602 may be provided by one or more processors, such as a general-purpose processor (e.g., a complex instruction set computing (CISC) microprocessor, a reduced instruction set computing (RISC) microprocessor, a very long instruction word (VLIW) microprocessor, a microprocessor that implements other types of instruction sets, or a microprocessor that implements a combination of multiple instruction sets) or a special-purpose processor (e.g., an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), or a network processor).

[0077] The computer system 600 may also include a network interface device 622 (e.g., coupled to the network 674). The computer system 600 may also include a video display unit 610 (e.g., LCD), an alphanumeric input device 612 (e.g., keyboard), a cursor control device 614 (e.g., mouse), and a signal generating device 620.

[0078] In some embodiments, the data storage device 616 may include a non-transitory computer-readable storage medium 624 on which may be stored instructions 626 encoding any one or more of the methods or functions described herein, including instructions for performing the following operations: Figure 1 In some embodiments, the clamping module may perform the operations of method 300. In some embodiments, the de-clamping module may perform the operations of method 400.

[0079] The instructions 626 may also reside, completely or partially, within the volatile memory 604 and / or within the processing device 602 during execution by the computer system 600, and thus, the volatile memory 604 and the processing device 602 may also constitute machine-readable storage media.

[0080] Although computer-readable storage medium 624 is illustrated as a single medium in the illustrative example, the term "computer-readable storage medium" shall include a single medium or multiple media (e.g., a centralized or distributed database, and / or associated caches and servers) that store one or more sets of executable instructions. The term "computer-readable storage medium" shall also include any tangible medium that can store or encode a set of instructions executed by a computer, which cause the computer to perform any one or more of the methods described herein. The term "computer-readable storage medium" shall include, but is not limited to, solid-state memories, optical media, and magnetic media.

[0081] The methods, components, and features described herein may be implemented by discrete hardware components, or integrated into the functionality of other hardware components (such as ASICS, FPGAs, DSPs, or similar devices). In addition, the methods, components, and features may be implemented by firmware modules or functional circuit systems within hardware devices. Further, the methods, components, and features may be implemented in any combination of hardware devices and computer program components or in a computer program.

[0082] Unless otherwise specifically stated, terms such as "receive", "execute", "provide", "obtain", "cause", "access", "determine", "add", "use", "train", etc., refer to actions and processes performed or implemented by a computer system, which manipulate and transform data represented as physical (electronic) quantities within computer system registers and memories into other data similarly represented as physical quantities within computer system memories or registers or other such information storage devices, transmission or display devices. In addition, the terms "first", "second", "third", "fourth", etc., as used herein, are meant as labels to distinguish different elements and cannot have an order meaning according to their numerical names.

[0083] The examples described herein also relate to an apparatus for performing the methods described herein. Such an apparatus may be specially constructed for performing the methods described herein, or it may comprise a general purpose computer system selectively programmed by a computer program stored in the computer system. Such a computer program may be stored in a computer readable tangible storage medium.

[0084] The methods and illustrative examples described herein are not inherently related to any particular computer or other device. Various general purpose systems may be used in accordance with the teachings described herein, or it may prove convenient to construct more specialized devices to perform the methods described herein and / or each of their individual functions, routines, subroutines, or operations. Examples of the structures of various such systems are set forth in the above description.

[0085] The above description is intended to be illustrative, not limiting. Although the present disclosure has been described with reference to specific illustrative examples and embodiments, it will be appreciated that the present disclosure is not limited to the described examples and embodiments. The scope of the present disclosure should be determined with reference to the following claims and the full scope of equivalents of the claims.

Claims

1. A method comprising the following steps: applying a first voltage to an electrode of the substrate holder; determining a first impedance value between the substrate holder and the substrate; determining an incremental value between the first impedance value and a predetermined second impedance value; determining whether the incremental value satisfies a threshold criterion; and In response to the incremental value not satisfying the threshold criterion, a second voltage is applied to the substrate, wherein the second voltage is greater than the first voltage.

2. The method of claim 1, wherein the first voltage reflects an electrostatic clamping force sufficient to maintain the substrate in contact with the substrate holder.

3. The method of claim 1, wherein the first impedance value comprises an average impedance determined from a plurality of measurements using one or more electrical sensors coupled to the substrate holder. 4 . The method of claim 1 , wherein the second impedance value comprises an impedance value indicating that the clamped substrate is not experiencing bending. The method of claim 1 , wherein the second voltage comprises a sum of the first voltage and a delta voltage value.

6. The method of claim 1, further comprising the steps of: In response to the delta value satisfying the threshold criterion, one or more operations of the process recipe are performed.

7. The method of claim 1, further comprising the steps of: determining a third impedance value between the substrate holder and the substrate; determining a new incremental value between the third impedance value and a predetermined fourth impedance value; determining whether the incremental value satisfies a de-clamping threshold criterion; and In response to the new increment value not satisfying the de-chucking threshold criterion, a fourth voltage is applied to the substrate, wherein the fourth voltage is lower than the third voltage.

8. An electronic device manufacturing system, comprising: a substrate holder configured to secure the substrate during processing; and a controller operably coupled to the substrate holder, the controller configured to: applying a first voltage to an electrode of the substrate holder; determining a first impedance value between the substrate holder and the substrate; determining an incremental value between the first impedance value and a predetermined second impedance value; determining whether the incremental value satisfies a threshold criterion; and In response to the incremental value not satisfying the threshold criterion, a second voltage is applied to the substrate, wherein the second voltage is greater than the first voltage.

9. The electronic device manufacturing system of claim 8, wherein the first voltage reflects an electrostatic clamping force sufficient to maintain the substrate in contact with the substrate holder.

10. The electronic device manufacturing system of claim 8, wherein the first impedance value comprises an average impedance determined from a plurality of measurements using one or more electrical sensors coupled to the substrate holder.

11. The electronic device manufacturing system of claim 8, wherein the second impedance value comprises an impedance value indicating that the clamped substrate does not experience bending. 12 . The electronic device manufacturing system of claim 8 , wherein the second voltage comprises a sum of the first voltage and an incremental voltage value.

13. The electronic device manufacturing system of claim 8, wherein in response to the delta value satisfying the threshold criterion, one or more operations of a process recipe are performed.

14. The electronic device manufacturing system of claim 8, wherein the processing device further performs operations including: determining a third impedance value between the substrate holder and the substrate; determining a new incremental value between the third impedance value and a predetermined fourth impedance value; determining whether the incremental value satisfies a de-clamping threshold criterion; and In response to the new increment value not satisfying the de-chucking threshold criterion, a fourth voltage is applied to the substrate, wherein the fourth voltage is lower than the third voltage.

15. A non-transitory computer-readable storage medium comprising instructions that, when executed by a processing device operably coupled to a memory, perform operations comprising: applying a first voltage to an electrode of the substrate holder; determining a first impedance value between the substrate holder and the substrate; determining an incremental value between the first impedance value and a predetermined second impedance value; determining whether the incremental value satisfies a threshold criterion; and In response to the incremental value not satisfying the threshold criterion, a second voltage is applied to the substrate, wherein the second voltage is greater than the first voltage.

16. The non-transitory computer readable storage medium of claim 15, wherein the first voltage reflects an electrostatic clamping force sufficient to maintain the substrate in contact with the substrate holder. 17 . The non-transitory computer readable storage medium of claim 15 , wherein the first impedance value comprises an average impedance determined from a plurality of measurements using one or more electrical sensors coupled to the substrate holder. 18 . The non-transitory computer-readable storage medium of claim 15 , wherein the second impedance value comprises an impedance value indicating that the clamped substrate is not experiencing bending.

19. The non-transitory computer readable storage medium of claim 15, responsive to the delta value satisfying the threshold criterion, performing one or more operations of a process recipe.

20. The non-transitory computer-readable storage medium of claim 15, wherein the processing device further performs operations comprising: determining a third impedance value between the substrate holder and the substrate; determining a new incremental value between the third impedance value and a predetermined fourth impedance value; determining whether the incremental value satisfies a de-clamping threshold criterion; and In response to the new increment value not satisfying the de-chucking threshold criterion, a fourth voltage is applied to the substrate, wherein the fourth voltage is lower than the third voltage.

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