Servo control of a lift device and method of using the same

Abstract

To provide a lift device which does not damage a substrate when the substrate is dechucked from a support.SOLUTION: In the servo control system, the lift pin assembly 300 includes lift pins 321 to move the substrate between the support and the transfer plane, at least one pneumatic actuator 317 including a moving member 318 to provide a load to the lift pins, at least one proportional pneumatic valve 301 to control a flow rate of fluid between the at least one pneumatic actuator and a pressurized fluid supply or between the at least one pneumatic actuator and a vent, a plurality of pressure sensors 313 to individually measure a pressure in respective supply lines to the at least one pneumatic actuator, and at least one position sensor 320 for measuring the position of the moving member 314.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to the field of robotics and to systems and methods for servo control of lifting equipment. [Background technology]

[0002] Semiconductor substrates are typically processed in vacuum processing systems. These systems include one or more chambers, each performing a substrate processing step, such as etching, chemical vapor deposition, or physical vapor deposition, which may involve heating or cooling the substrate to support the process, and plasma. The environment within such processing chambers is typically maintained at a low, subatmospheric pressure. Each chamber includes an inlet and an outlet for exhaust and for the introduction of process gases, and an opening for receiving a substrate, controlled by a slit valve. Such processing chambers may communicate with a substrate transfer chamber, which may have a valve-controlled opening through which a substrate can be received from outside the system.

[0003] Transfer of substrates to and from the chamber and outside the system is typically accomplished mechanically by a robot arm, which has a component (e.g., a blade or end effector) at the end that holds the substrate. To facilitate sliding the end of the robot arm's blade under the substrate, one or more lift pins elevate the substrate approximately 20 mm to 50 mm above the tool (e.g., a chuck assembly). The lift pins may be pneumatically driven. This is achieved using full-stroke actuation by a solenoid valve, which provides two positions for the lift pins: a raised position and a lowered position. The lift pins may have a distance of 30 mm to 40 mm between their raised and lowered positions. To transfer the substrate to the robot arm's end effector, the lift pins are extended to their raised position (e.g., 20 mm to 40 mm), the end effector is positioned under the substrate, and the lift pins are lowered to their lowered position, transferring the substrate to the end effector during the lowering process. The robot arm can then remove the substrate from the processing chamber. However, this transfer process is inefficient because the substrate is extended well above the end effector and then lowered well below the end effector, which takes time to complete.

[0004] Operating the lift pins using full-stroke actuation can also cause damage to the substrate, especially when removing the substrate from a support such as an electrostatic chuck. After a processing step is completed, a pneumatic lift mechanism raises the lift pins to raise the substrate above the support so that it can be removed from the chamber by a robotic arm. When the support is an electrostatic chuck, the substrate must be "dechucked," i.e., the electrostatic forces holding the substrate on the chuck must be released, before the lift pins can lift the substrate. Traditionally, the chucking voltage is turned off, and both the chuck electrode and the substrate are connected to ground, removing the corresponding charge that accumulated on the chuck electrode and substrate during application of the chucking voltage to the chuck electrode. However, this traditional dechucking method may not be successful in releasing all of the electrostatic attractive forces between the substrate and the chuck before the lift pins attempt to lift the substrate from the chuck, potentially causing the substrate to stick to the chuck. After actuation of the lift pins, the substrate may crack, break, and / or fly out of the chuck into a position that makes it difficult for the substrate transfer robot to retrieve and properly align it. In some cases, the misaligned substrate may collide with the robot arm, causing further damage to the robot arm. Substrate sticking can also occur when the support is not an electrostatic chuck, for example, when the support is a pedestal that has a buildup of sputtered material that causes the substrate to stick. All of these problems can lead to process downtime and capital costs to repair the equipment. Summary of the Invention

[0005] According to an embodiment, the present specification describes a lift apparatus for transferring a substrate between a support and a transfer plane, the lift apparatus comprising: a lift pin assembly, the lift pin assembly including lift pins configured to move the substrate between the support and the transfer plane; at least one pneumatic actuator including a moving member configured to apply a load to the lift pins; at least one pneumatic proportional valve configured to control the flow rate of fluid between the at least one pneumatic actuator and a pressurized fluid supply or between the at least one pneumatic actuator and a vent; a plurality of pressure sensors each configured to individually measure the pressure in a respective supply line to the at least one pneumatic actuator; and at least one position sensor configured to measure the position of the member; and a servo control system in communication with the lift pin assembly.

[0006] According to an embodiment, the specification further describes a method, the method including receiving, by a controller, a first pressure measurement from a first pressure sensor measuring a pressure in a first chamber of the pneumatic actuator; receiving, by the controller, a second pressure measurement from a second pressure sensor measuring a pressure in a second chamber of the pneumatic actuator; receiving, by the controller, a position measurement from a position sensor measuring a position of a moving member of the pneumatic actuator; generating a control signal based on the first pressure measurement, the second pressure measurement, and the position measurement; sending a control signal to at least one pneumatic proportional valve of a servo control system to control pressurized fluid to the pneumatic actuator; and operating the servo control system to extend at least one lift pin and lift the substrate from the support via the at least one lift pin.

[0007] According to various embodiments, further described herein is a method, the method including: operating a servo control system to lift a substrate from a substrate support, the servo control system being configured to control a lift pin assembly to lift the substrate; actuating at least one pneumatic proportional valve to allow gas to flow through a first gas line into a first chamber of a pneumatic actuator of the lift pin assembly and through a second gas line into a second chamber of the pneumatic actuator; measuring a pressure in the first gas line with a first pressure sensor and measuring a pressure in the second gas line with a second pressure sensor; measuring a position of a moving member of the pneumatic actuator with a position sensor; controlling the at least one pneumatic proportional valve with the servo control system to apply a contact force of about 2 N to about 10 N to the substrate by the moving member; and lifting the substrate from the support by the lift pins operable to receive a load from the moving member.

[0008] The present disclosure is illustrated by way of example, and not limitation, in the accompanying drawings, in which like elements are designated by like reference numerals. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows a processing chamber including a lift pin assembly. [Figure 2] 1 illustrates a lift pin assembly according to various embodiments. [Figure 3] 1 illustrates a lift pin according to various embodiments. [Figure 4] 1 illustrates a lift pin according to various embodiments. [Figure 5] 1 illustrates a servo control system according to an embodiment. [Figure 6] 1 illustrates a method of transferring a substrate between a support and a transfer chamber, according to various embodiments. [Figure 7] 1 illustrates a method of controlling a lift device using a servo control system, according to various embodiments. [Figure 8] 1 illustrates a method of transferring a substrate from a processing chamber to a transfer chamber using a robotic arm in communication with a servo-controlled lift pin assembly, according to various embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0010] References throughout this specification to "one embodiment," "certain embodiment," "one or more embodiments," or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases "in one or more embodiments," "in a particular embodiment," or "in one embodiment" in various places throughout the specification are not necessarily all referring to the same embodiment of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0011] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a lift pin" includes one lift pin and more than one lift pin.

[0012] As used herein, the term "about" in connection with a measured quantity refers to normal variation in the measured quantity that would be expected by one of ordinary skill in the art making the measurement and exercising a level of care commensurate with the purpose of the measurement and the precision of the measuring device. In certain embodiments, the term "about" includes ±10% of the recited number, e.g., "about 10" includes 9 to 11.

[0013] The term "at least about" in reference to a measured quantity refers to normal variation in the measured quantity that would be expected by one of ordinary skill in the art making the measurement and exercising a level of care commensurate with the purpose of the measurement and the precision of the measuring instrument, and any greater quantity. In certain embodiments, the term "at least about" includes the recited number minus 10% and any greater quantity; for example, "at least about 10" includes 9 and greater than 9. The term can also be expressed as "about 10 or greater." Similarly, the term "less than about" typically includes the recited number plus 10% and any smaller quantity; for example, "less than about 10" includes 11 and less than 11. The term can also be expressed as "about 10 or less."

[0014] Unless otherwise specified, all proportions and percentages are by weight. Weight percentages (wt%) are based on the total composition, excluding volatiles, i.e., on the dry solids content, unless otherwise specified. The servo-controlled lift apparatus is discussed in the context of a lift mechanism for a support (e.g., a chuck, an electrostatic chuck, a pedestal, etc.). However, one skilled in the art will recognize that the servo-controlled lift apparatus can be used in a system with any processing chamber (e.g., a semiconductor processing chamber) that includes a lift mechanism for transferring substrates from the chamber to a robot arm and / or from the robot arm to the chamber.

[0015] Conventional lift mechanisms use an on / off pneumatic valve with a manual throttle to control the speed of a pneumatic cylinder (also referred to herein as a pneumatic actuator). The cylinder's position is monitored solely with a digital end-position sensor, and compressed air delivery to the cylinder is switched on and off by a solenoid-driven spool valve. In the context of an electrostatic chuck assembly, substrate energy release is not always consistent, potentially leading to substrate breakage if the force output of the lift pin pneumatic actuator is greater than the substrate's strength. In some cases, the substrate may be displaced, resulting in a collision between the substrate and the robot arm, potentially causing substrate breakage and / or damage to the robot arm. The lift mechanism does not provide lift pin position tracking or feedback, making it unclear what caused the failure. Conventional lift mechanisms also limit throughput because the pneumatic actuator must move the lift pins slowly enough to be safe for contact with the substrate, which can take 2 to 8 seconds.

[0016] The lift device, according to an embodiment of the present disclosure, includes a position sensor that monitors the position of the pneumatic cylinder throughout the stroke. The lift device further includes a proportional pressure control valve with pressure feedback from both sides of the pneumatic cylinder. This can be achieved using a single 5 / 2 spool-style proportional valve or two separate proportional pressure control valves. Pressure sensors are included on both sides of the pneumatic cylinder. The proportional pressure control valve allows for variable flow and pressure control on both sides of the pneumatic cylinder. The lift device also includes a first position sensor that sends a signal to a controller regarding the position of the cylinder. Once these sensors are available, the controller can control force output by adjusting the delta pressure between the two sides, control position by monitoring position feedback, and control stiffness by adjusting the average pressure between the two sides. The stiffness of the overall system is governed by the mass of gas across both sides of the cylinder.

[0017] This control allows the cylinder to move and stop at intermediate positions within the full stroke length, control the movement time, and sense the substrate sticking to the support (e.g., chuck assembly). Additionally, the lift device, according to embodiments herein, allows for faster lift pin movement, thereby increasing system throughput. The lift device can also control the force output, which can prevent substrate damage if the support (e.g., electrostatic chuck) is not released. The lift device also allows for faster substrate transfer to the robot blade because the lift travel can be shortened (e.g., the total lift stroke is 38 mm, but only 10 mm travel is required to transfer the substrate to the blade). The lift pin position can also be controlled, which allows for a cleaning step on the edge of a new substrate to remove polymer deposits that occurred during the etching step. For example, the substrate can be cleaned after being lifted 1 mm from the support surface.

[0018] 1, during operation of processing chamber 100, a robot arm (not shown) moves a substrate 101 into chamber 100 through slit valve 106. The robot arm places the substrate on the tips of lift pins 142, which have been elevated above the top of support 110 (e.g., an electrostatic chuck) by pneumatic lift mechanism 146. Pneumatic lift mechanism 146, under the control of computer control system 162, then lowers lift pins 142, thereby positioning the substrate on the surface of the support. Pneumatic lift mechanism 146 includes at least one lift pin assembly, which includes at least one pneumatic actuator and a servo control system in fluid communication with the at least one pneumatic actuator, the servo control system including at least one pneumatic proportional valve, a plurality of pressure sensors, and at least one position sensor.

[0019] According to embodiments, a servo-controlled lift apparatus system according to embodiments herein may include a support (e.g., a chuck assembly) and a lift apparatus for transferring a substrate between the support and a transfer chamber. The lift apparatus may include a lift pin assembly including at least one pneumatic actuator, at least one pneumatic proportional valve, a plurality of pressure sensors, at least one position sensor, and a servo control system in communication with the lift pin assembly.

[0020] Once the lift pins lower the substrate 101 onto the support 110, a process may be initiated, which may be an etching process, a deposition process, a cleaning process, or the like. The process may include igniting a plasma. According to certain embodiments, when the support is an electrostatic chuck, the computer control system 162 may apply a DC chucking voltage to the chuck 110 and may apply a heat transfer gas to the substrate-chuck interface. The chucking voltage causes negative and positive charges to accumulate on opposing surfaces of the substrate 101 and the chuck electrode 104, respectively.

[0021] The chuck 110 may include an upper dielectric (e.g., an electrostatic puck) capable of supporting the substrate 101. After the substrate 101 is placed on the upper dielectric of the support 110, the lift pins 142 continue to lower within the pedestal 114. When the support 110 is an electrostatic chuck, opposite charges on the substrate 101 and the chuck electrode 104 generate an attractive electrostatic force that presses the substrate 101 against the upper surface of the chuck 110. A chucking voltage is set to a value that is high enough to generate an electrostatic force between the substrate 101 and the chuck 110 and that is suitable to prevent movement of the substrate during subsequent processing steps in the processing chamber 100. The substrate 101, thus firmly held on the chuck 110, is said to be "chucked."

[0022] After the substrate is placed (e.g., chucked) on the support 110, one or more processing steps, such as deposition on the substrate 101 or etching of a film on the substrate 101, are performed in the chamber 100. For plasma-based processes, an RF power source 130 selectively applies RF power to the antenna 112 and between the cathode pedestal 114 and the grounded anode 104, thereby generating a plasma 103 in a region above the substrate 101. The plasma 103 provides a conductive path between the substrate and ground. However, due to differences in the mobilities of electrons and positive ions, a DC voltage drop appears across the plasma 103, thereby biasing the substrate 101 negatively with respect to ground. If the chucking voltage applied to the chucking electrode (pedestal) 114 by the DC voltage source 120 is a positive voltage, the total DC voltage between the substrate 101 and the chucking electrode 114 is the sum of the substrate bias and the chucking voltage; therefore, the substrate bias increases the electrostatic force holding the substrate 101.

[0023] The lift assembly may include three lift pins 142 mounted on a carriage 140, which are raised and lowered by a pneumatic lift mechanism 146. After a processing step is completed, the pneumatic lift mechanism 146 raises the lift pins 142 to raise the substrate 101 above the supports 110 so that the substrate 101 can be removed from the chamber 100 via a robotic arm (not shown).

[0024] In embodiments in which the support 110 is an electrostatic chuck, the substrate 101 should be electrically dechucked, i.e., the electrostatic forces holding the substrate 101 on the chuck should be eliminated or neutralized, before the lift pins 142 can raise the substrate 101. The chucking voltage source is turned off, and both the chuck electrode 114 and the substrate 101 are connected to ground, thereby removing any corresponding charge that may have accumulated on the chuck electrode 114 and the substrate 101 during the previous application of chucking voltage to the chuck electrode 114. The substrate can be grounded to maintain the plasma 103 by leaving the RF power source 130 on at a reduced power level, which provides a conductive path from the substrate 101 to the grounded walls of the chamber 100. However, as previously described, after dechucking methods are used, residual charge often still remains on the substrate 101 and the chuck 110 due to charge transfer and / or field emission charging. As a result, standard dechucking methods may induce more physical force than necessary to remove the substrate from the chuck. In some cases, using conventional dechucking methods and conventional lift pin assemblies can result in cracked and / or broken substrates, or only partially removed substrates. In the latter situation, when the robot arm moves to remove the partially removed substrate, it can collide with the substrate, causing damage to the robot arm as well as the substrate, resulting in apparatus downtime. Note that in embodiments in which the support 110 is not an electrostatic chuck, sticking issues can still occur. For example, material deposited on the support from a sputtering process can cause the substrate to stick to the support. The lift apparatus and control system described herein are capable of safely removing a substrate from any support without cracking or breaking the substrate.

[0025] The servo-controlled lift apparatus system described herein provides the ability to sense and control the force, position, and stiffness of the pneumatic control valve. The system also allows for faster lift pin movement, thereby increasing system throughput and improving control of force output, which can prevent substrate destruction if the substrate sticks to the support or if, for example, an electrostatic chuck fails to release. The system allows for shorter lift travel, allowing for faster transfer of substrates to the robot blade, and lift pin position control allows for a cleaning step on the edge of a new substrate to remove any liner buildup that occurs during the etching step.

[0026] A lift pin assembly 200 (per lift pin) according to one embodiment of the present disclosure is shown in FIG. 2 . The lift pin assembly 200 includes a low-friction air cylinder 202 with a glass bore and graphite seals. A sleeve 204 is disposed on the shaft of the cylinder 202 and serves as a lower position hard stop for the lift pins 214. A ball joint 206 is also attached to the shaft of the cylinder 202, allowing the lift pin assembly 200 to be aligned with other lift pin assemblies while retaining a substrate. The lift pin assembly 200 can further include a linear slide 208 along which a slide carriage 210 moves vertically. The linear slide 208 is attached to a lift assembly bracket 212. The lift pins 214 extend into the processing chamber through bellows 216, allowing for vertical movement of the lift pins 214 while maintaining a vacuum within the chamber.

[0027] As mentioned above, substrate transfer is accomplished mechanically by a robot arm that terminates in a substrate-holding component, such as an end effector or robot blade. One type of holding component is a flat blade with a vacuum channel formed through the blade and terminating in an outlet. The blade can lift a substrate by contacting the top surface of the blade with the bottom surface of the substrate and optionally applying a vacuum to adhere the substrate to the blade. An advantage of a flat blade is that it is flat and thin, allowing it to be easily maneuvered between the tight spaces of a substrate storage cassette to lift the substrate.

[0028] Another type of substrate holding means includes a shoe attached to the robot arm, which may be a tray-like extension of the end of the arm, with a sloped profile shaped to accommodate the substrate, and which serves to engage the substrate and hold it in place on the arm while the robot arm turns to transfer the substrate to another location.

[0029] FIG. 3 illustrates one embodiment of a lift pin assembly 300 according to an embodiment of the present disclosure. At least one lift pin assembly 300 may be part of a lift apparatus for transferring substrates between a support and a transfer plane (e.g., into a transfer chamber). The lift pin assembly 300 may include a four-way pneumatic proportional valve 301 supplied by a main source 302 of pressurized fluid (e.g., air). The pneumatic proportional valve 301 may include a pair of springs 303A, 303B that enable movement of an actuator between each of four flow passages 305, 306, 307, and 308. Flow passages 305 and 308 allow pressurized gas to enter from the source 302 through lines 309 and 310, respectively. Flow passages 306 and 307 allow gas to be vented through lines 311 and 312, respectively.

[0030] The lift pin assembly 300 further includes pressure sensors 313, 314 that measure the gas pressure in each of the chambers 315, 316 of the pneumatic actuator 317. Each pressure sensor can be a diaphragm-type sensor with a strain gauge, such as a resistance wire strain gauge and / or a piezoresistive strain gauge. According to an embodiment, the proportional pressure control valve can be a single 5 / 2 spool valve-style proportional valve or two separate pressure-controlled proportional valves. In at least one embodiment, the pressure sensor is a proportional pressure regulator using piezoelectric technology. The chambers 315, 316 are defined by the interior of a cylinder housing 319 of the pneumatic actuator 317 on either side of a moving member (e.g., a piston) 318. The pneumatic proportional valve 301 allows pressurized gas to flow into and / or out of the chambers 315, 316. The lift pin assembly 300 may also include a position sensor 320 that determines the position of the moving member 318 within the pneumatic actuator 317. The position sensor may be a linear position sensor and / or an inductive position sensor, such as a magnetic inductive position sensor. The moving member 318 controls the position of the lift pins 321.

[0031] During operation, lift pins 321 have a load 322, which may be a combination of the weight of the substrate (not shown), the spring force from the bellows, and / or the pressure inside the processing chamber. According to an embodiment, lift pin assembly 300 may also include one or more ball joints (not shown) to aid in alignment with other lift pin assemblies in a lift apparatus.

[0032] Another embodiment of a lift pin assembly 400 according to the present disclosure is shown in FIG. 4. At least one lift pin assembly 400 can be part of a lift apparatus for transferring substrates between a support and a transfer plane associated with a transfer chamber. The lift pin assembly 400 can include two two-way pneumatic proportional valves 401A, 401B supplied by one or more main sources 402 (shown) of pressurized fluid (e.g., air). Each pneumatic valve 401 includes springs 401, 403 that enable actuator movement between respective flow paths 405, 406, 407, and 408. Flow paths 405 and 408 allow pressurized gas to enter from source 402 through lines 409 and 410, respectively. Flow paths 406 and 407 allow gas to be vented through lines 411 and 412, respectively.

[0033] The lift pin assembly 400 further includes pressure sensors 413, 414 that measure gas pressure in each of the chambers 415, 416 of the pneumatic actuator 417. The chambers 415, 416 are defined by the interior of a cylinder housing 419 of the pneumatic actuator 417 on either side of a moving member (e.g., piston) 418. Pneumatic proportional valves 401A, 401B allow pressurized gas to flow into and / or vent from the chambers 415, 416. The lift pin assembly 400 may also include a position sensor 420 that determines the position of the moving member 418 within the pneumatic actuator 417. The moving member 418 controls the position of the lift pins 421. During operation, the lift pins 421 have a load 422, which may be a combination of the weight of a substrate (not shown), a spring force from a bellows, and / or pressure inside the processing chamber. According to an embodiment, lift pin assembly 400 may also include one or more ball joints (not shown) to aid in alignment with other lift pin assemblies in a lift apparatus.

[0034] The lift assemblies 300, 400 described above may be part of a servo control system that operates the pneumatic valves 301, 401A, 401B to direct pressurized gas to and / or vent pressurized gas from the chambers 315, 315, 415, 416. The servo control system utilizes measurements from the pressure sensors 313, 314, 413, 414 and the position sensors 320, 420 to determine the output force of the pneumatic actuators 317, 417 and the stiffness of the valves 301, 401A, 401B. In addition to the lift pin assemblies 300, 400, a controller (not shown) completes the servo control system. The servo control system is configured to maintain a closed loop, where at least one of the chamber pressure and the position of the moving member is controlled within the pneumatic actuators. At least one pneumatic proportional valve 301, 401A, 401B is configured to direct pressurized fluid 302, 402 through at least one of a plurality of flow paths 305, 306, 307, 308 in response to a control signal from a servo control system. A controller calculates the appropriate amount of pressure for each pneumatic cylinder chamber to move the lift as fast as possible while avoiding damage to the substrate.

[0035] 5 illustrates a servo control system 500 according to an embodiment of the present disclosure. A path planner 502 determines a trajectory (y cmd The position controller 504 generates a commanded force (f) required to move the lift pin assembly 514 based on the generated trajectory and the feedback (y) received from the position sensor. cmd The function of the force estimator 506 is to determine whether contact between the support and the substrate occurs and whether the support is bonded or released. The estimated force (f e), a force controller 508 instructs the path planner 502 on whether to continue moving or pause until the support (e.g., electrostatic chuck) is fully released, while maintaining a small amount of force to push the substrate without damaging it. The force controller 508 receives two inputs: a commanded force (f) from the position controller 504 and a commanded force (f) from the position controller 504. cmd ) and the estimated force (f e ) and the force controller 508 controls the amount of force (f) to keep the contact force between the lift pins and the substrate below a certain limit (i.e., to prevent damage to the substrate) and to maintain the position of the lift pins close to the substrate. d The pressure controller 510 calculates the required force (f d ), the position controller 504 calculates the commanded pressure for each chamber of the pneumatic actuator 512. The pressure controller 510 actually generates the appropriate amount of force to move the lift pins while preventing damage to the substrate. The pneumatic actuator 512 generates the desired force output (f) to move or maintain contact with the substrate at least one lift pin according to the amount of chamber pressures p1 and p2. It should be noted that each of the position controller 504, force estimator 506, force controller 508, and pressure controller 510 may be a module of a controller in a servo control system, or each may be a separate controller.

[0036] In one embodiment, servo control of the lift device can be achieved via a control algorithm for controlling the lift device. For example, the pneumatic actuators 317, 417 of the lift device can include pneumatic cylinders (see FIGS. 3 and 4). The pressure P in the chambers 315, 316, 415, 416 a , P b The difference between them determines the output force F, and their sum affects the desired stiffness of the cylinder 318, 418. Therefore, to control the force and stiffness of the pneumatic actuators 317, 417, the pressure P in the cylinder chambers 315, 316, 415, 416 is a , V a, A a and P b , V b , A b must be able to be controlled individually.

[0037] The pressure in each chamber P a , V a , A a and P b , V b , A b and air flow rate TIFF2026012668000002.tif7170 and the position of the piston ±X. Each chamber 315, 316, 415, 416 can be modeled as a control volume with the following assumptions: 1) Air is an ideal gas. 2) the pressure and temperature within each chamber are uniformly distributed; and 3) The kinetic and potential energy of the air is negligible. Taking these assumptions into account and applying conservation of mass, the ideal gas model, and conservation of energy to each chamber, we obtain equation (1). TIFF2026012668000003.tif13170 where R is the ideal gas constant, P is pressure, T is absolute temperature, and V is volume. TIFF2026012668000004.tif7170 is the mass flow rate in and out of cylinder chambers 315, 316, 415, 416. The volume of each chamber depends on the piston position as per equation (2). TIFF2026012668000005.tif14170 where V0 is the inactive volume at the end of the stroke, and V is the volume of the tubing connecting the chambers 315, 316, 415, and 416 to the pressure sensor. a , V b where A is the effective piston area, L is the piston stroke, and x p is the position of the piston. The inert volume V in each chamber 315, 316, 415, 416 of the cylinder 318, 418 a , V b The normalized inert length associated with oa=Vo a / A a , and L ob =V ob / A b where a and b refer to the two chambers 315, 316, 415, 416 of the cylinder shown in Figures 3 and 4. The volume of each chamber as a function of the piston position is then given by equation (3), i.e. TIFF2026012668000006.tif14170

[0038] In equations (2) and (3), the plus and minus signs correspond to chambers a and b, respectively. Combining equations (1) and (3), the chamber pressure equations become: TIFF2026012668000007.tif25170

[0039] An isothermal approximation for the chamber charge / discharge process can be used with good results. Nevertheless, to compensate for the assumption of an isothermal process, the controller should be designed to be robust against parameter uncertainties. The force generated by the pneumatic cylinder is shown in equation (5): F = P a A a -P b A b -P atm A r (5) However, A r is the cross-sectional area of ​​the cylinder rod, and P atm is the atmospheric pressure. The stiffness of the cylinder is the rate of change of the cylinder force F with respect to the piston position x, where m is the mass of air inside the chamber. a,b is considered to be constant and is given by the following equation (6). TIFF2026012668000008.tif16170

[0040] Using the force from (5) into (6), we get equation (7). TIFF2026012668000009.tif17170

[0041] Assuming a constant temperature, the pressure in each chamber is a function of the mass of air inside the chamber (m) and the position of the piston (x p ) The time derivative of pressure is expressed by equation (8). TIFF2026012668000010.tif17170

[0042] Comparing (4) and (8), the partial derivative of pressure with respect to position is: TIFF2026012668000011.tif26170

[0043] From (7) and (9), the stiffness of the actuator can be written as (10) below: TIFF2026012668000012.tif16170

[0044] The lift pin assemblies 300, 400 described above can be used in a processing chamber as part of a servo control system to remove (e.g., dechuck) at least one substrate from a support (e.g., an electrostatic chuck assembly).

[0045] The servo-controlled lift device according to embodiments herein can determine the position of at least one lift pin 321, 421 upon receiving a signal from a position sensor 320, 420 indicative of the position (x) of the cylinder 318, 418. The position of the at least one lift pin 321, 421 also indicates the position of the substrate received by the at least one lift pin 321, 421. For example, the position of the at least one lift pin 321, 421 coupled with a substrate of a predetermined thickness allows for accurate determination of the position of the substrate within the processing chamber.

[0046] The servo-controlled lift device according to embodiments herein allows for the determination of the force F generated by the pneumatic cylinder (see equation (5)). According to embodiments, when the servo control system determines that the positive force F (e.g., when the lift pins are rising) reaches a predetermined value, e.g., a relatively high output indicating that the substrate is stuck to the support, the system determines that the pressure P in the chamber 315, 415 is a (e.g., at a linear rate, at an exponential rate) and / or by decreasing the pressure P b By raising the lift pins, the movement of the lift pins can be slowed or reversed, in effect peeling the substrate off of the support. The servo control of the lift device described herein allows the output force to be slowly increased or decreased to prevent substrate damage and / or to slowly peel the substrate off of the support assembly.

[0047] Also disclosed herein is a method for controlling the previously described lift apparatus associated with a processing chamber. FIG. 6 illustrates a process 600 for transferring a substrate between a processing chamber and a transfer plane associated with a transfer chamber. After substrate processing is completed in block 602, the substrate is released from the semiconductor processing chamber (e.g., removed from the support) in block 604. In block 606, the lift pins are activated to remove the substrate from the support. As described above, a servo control system controls the lift apparatus and can determine the position of the substrate and the output force of the pneumatic cylinder. According to an embodiment, the servo control system can control the speed of the lift pins and how high and / or low the lift pins are raised. The servo control system can also control the output force of the cylinder by individually controlling the pressure in each chamber of the pneumatic control valve to avoid excessive force that could damage the substrate. In block 608, a robot arm is activated to grab the substrate from the lift pin assembly. As described above, the robot arm can move a sufficient height to empty the lift pin assembly. In block 610, the robot arm retrieves the substrate from the processing chamber system. Once the substrate is received, the robot arm can transfer the substrate into a transfer chamber. If the system receives a signal to process another substrate through the semiconductor chamber in block 612, the robot arm places the new substrate on the lift pins for processing in block 614. In block 616, the lift pins are lowered with the substrate to place the substrate on the supports.

[0048] Referring to FIG. 7 , according to an embodiment, a method 700 may include, at block 702, receiving, by a controller, a first pressure measurement from a first pressure sensor measuring a pressure in a first chamber of a pneumatic actuator. The controller may be a computing device such as a programmable logic controller or a system on a chip (SoC). The method may further include, at block 704, receiving, by the controller, a second pressure measurement from a second pressure sensor measuring a pressure in a second chamber of the pneumatic actuator. At block 706, the method may include receiving, by the controller, a position measurement from a position sensor measuring a position of a moving member (e.g., a cylinder) of the pneumatic actuator. At block 708, the method may include generating a control signal based on the first pressure measurement, the second pressure measurement, the position measurement, and a maximum allowable contact force between the substrate and the lift mechanism. At block 710, the method may include sending a control signal to at least one pneumatic proportional valve of a servo control system to control pressurized fluid to the pneumatic actuator. At block 712, the method may include operating a servo control system to extend the at least one lift pin and lift the substrate from the support via the at least one lift pin. According to an embodiment, the method may further include transferring the substrate from the at least one lift pin to a transfer plane and into a transfer chamber using a robot arm.

[0049] According to an embodiment, the controller can determine the difference between the first and second pressure measurements to determine the output force of the pneumatic proportional valve. In one embodiment, the controller adds the first pressure measurement to the second pressure measurement to determine the stiffness of the pneumatic proportional valve. To make the control system more robust against friction in the lift mechanism, the stiffness can be set to a high amount. Depending on the output force, the stiffness, and the position of the moving member, the controller can control at least one pneumatic actuator to move the lift mechanism upward while preventing damage to the substrate.

[0050] FIG. 8 illustrates a method 800 for operating a servo control system to lift a substrate from a substrate support. According to embodiments described herein, the servo control system is configured to control a lift pin assembly to lift the substrate. Method 800 may include, at block 802, actuating at least one pneumatic proportional valve to allow gas to flow through a first gas line into (or out of) a first chamber of a pneumatic actuator of the lift pin assembly and through a second gas line into (or out of) a second chamber of the pneumatic actuator. As described herein, in embodiments, the lift pin assembly may include, for example, two pneumatic proportional valves. A first valve may control the pressure in the first gas line, and a second valve may control the pressure in the second gas line, and both valves may be controlled by the servo control system. The at least one pneumatic proportional valve may also include a vent for releasing pressure in the gas supply line as needed to balance the pressure between the first and second chambers and to achieve a desired force output or contact force of the at least one lift pin against the substrate.

[0051] The method 800 may further include measuring the pressure in the first gas line with a first pressure sensor and measuring the pressure in the second gas line with a second pressure sensor at block 804. Each pressure sensor may be located at any point on a line between the at least one pneumatic proportional valve and the pneumatic actuator. In an embodiment, each pressure sensor may be positioned and operable to measure the pressure at the inlet of each chamber of the pneumatic actuator.

[0052] The method 800 may further include measuring the position of a moving member (e.g., a piston connected to a lift pin) of the pneumatic actuator using a position sensor at block 806. As shown in Figures 3 and 4, when the moving member is located approximately at the center of the pneumatic actuator, its position is x = 0. When the moving member moves away from the substrate (e.g., downward), the moving member moves in the negative direction (-x). When the moving member moves toward the substrate (e.g., upward), the moving member moves in the positive direction (+x).

[0053] Method 800 may include block 808, i.e., may further include controlling at least one pneumatic actuator using a servo control system to apply a contact force of about 2 N to about 10 N to the substrate by the moving member. When the moving member, including the lift pins, contacts the substrate to lift it from the support, the force applied by the moving member to the substrate is controlled to about 2 N to about 10 N to avoid breaking or cracking the substrate. The servo control system actuates at least one pneumatic proportional valve to increase, decrease, or maintain the pressure supplied to (or within) each chamber of the pneumatic actuator. According to an embodiment, the pressure supplied to each chamber can be individually controlled by multiple pneumatic proportional valves. For example, the pressure pA in the first chamber can be increased while the pressure pB in the second chamber is reduced (e.g., relieved). If the servo control system determines that moving the moving member causes a contact force on the substrate to exceed about 2N to about 10N, for example, about 2N, about 3N, about 4N, about 5N, about 6N, about 7N, about 8N, about 9N, or about 10N, the servo control system determines that the wafer is stuck and activates at least one pneumatic proportional valve to maintain the pressure in each chamber, thereby applying a constant force to the substrate, for example, to peel the substrate from the support, but without cracking or breaking the substrate.

[0054] The method 800 further includes, at block 810, lifting the substrate from the support with a moving member. As described above, the moving member moves to apply a contact force of about 2 N to about 10 N to the substrate. The moving member can move in a negative direction to stop moving, or move in a positive direction to maintain the contact force on the substrate. Once the moving member moves from its intermediate position (x=0) to a position of about 1 mm to about 7 mm in the positive (+X) direction, the servo control system can accelerate the movement of the moving member together with the wafer thereon. For example, when the moving member position is about 1 mm to about 7 mm, or about 2 mm in the positive direction from the center position of the moving member, the servo control system sends a signal to a pneumatic proportional valve to increase the pressure in at least one of the first chamber or the second chamber to accelerate the moving member in the positive direction. According to embodiments, the method can include accelerating the moving member to a velocity of about 10 mm / s to about 150 mm / s, or about 15 mm / s to about 125 mm / s, or about 20 mm / s to about 100 mm / s, or about 25 mm / s to about 75 mm / s, or about 30 mm / s to about 50 mm / s, or about 30 mm / s to about 35 mm / s, or about 30 mm / s, or about 35 mm / s, or about 100 mm / s. Note that while the drawings in Figures 3 and 4 are shown in a horizontal orientation, the lift pin assembly is typically in a vertical orientation.

[0055] According to various embodiments, during processing of a substrate in the chamber, at least one lift pin is lowered to a hard stop position (y=0). Once processing is complete, the at least one lift pin is moved upward at a rate of about 1 mm / sec to about 3 mm / sec, or about 2 mm / sec, to contact the substrate at a substrate release plane (e.g., y=20 mm). As described above, the contact force of the at least one lift pin on the substrate is controlled to about 2 N to about 10 N. Once the moving member within the pneumatic actuator and the at least one lift pin with the substrate thereon have moved about 2 mm to about 7 mm in the positive direction from the intermediate position within the pneumatic actuator, the servo control system determines that the substrate has been removed from the support.

[0056] The servo control system can then accelerate the moving member to a velocity of about 10 mm / s to about 150 mm / s, or about 15 mm / s to about 125 mm / s, or about 20 mm / s to about 100 mm / s, or about 25 mm / s to about 75 mm / s, or about 30 mm / s to about 50 mm / s, or about 30 mm / s to about 35 mm / s, or about 30 mm / s, or about 35 mm / s, or about 100 mm / s. When the substrate is at or near the substrate exchange plane (e.g., y=25 mm), the servo control system can decelerate the velocity of the at least one lift pin and substrate to about 1 mm / s to about 25 mm / s, or about 5 mm / s to about 20 mm / s, or about 10 mm / s to about 15 mm / s to bring the end effector of the robot arm into soft contact with the substrate positioned in the substrate exchange plane (e.g., y=25 mm). Once the substrate is securely positioned on the end effector, the robot arm with the received substrate can move to the substrate lift plane (e.g., y=30 mm) at a rate of about 35 mm / s to about 50 mm / s to transfer the substrate to the transfer chamber. In embodiments, the upper hard stop is about 15 mm to about 50 mm, or about 35 mm, above the lower hard stop.

[0057] According to embodiments, the above-described method can be performed in reverse. In particular, the robot arm and end effector carrying the received new substrate can be moved from the substrate lift plane to the substrate exchange plane at a speed of about 35 mm / s to about 50 mm / s. In the substrate exchange plane, the substrate is received by at least one lift pin and then lowered at a speed of about 1 mm / s to about 25 mm / s, or about 5 mm / s to about 20 mm / s, or about 10 mm / s to about 15 mm / s. Once the substrate and at least one lift pin have cleared the end effector, the at least one lift pin is lowered at a rate of about 10 mm / s to about 150 mm / s, or about 15 mm / s to about 125 mm / s, or about 20 mm / s to about 100 mm / s, or about 25 mm / s to about 75 mm / s, or about 30 mm / s to about 50 mm / s, or about 30 mm / s to about 35 mm / s, or about 30 mm / s, or about 35 mm / s, or about 100 mm / s. Once the substrate reaches the supports, the rate is reduced to about 1 mm / s to about 3 mm / s, or about 2 mm / s to softly place the substrate on the supports.

[0058] The above-described apparatus, systems, and methods reduce the range of motion of at least one lift pin when lifting and lowering a substrate.

[0059] In the preceding description, numerous specific details are set forth, such as examples of particular systems, components, methods, etc., to provide a thorough understanding of some embodiments of the present disclosure. However, it will be apparent to those skilled in the art that at least some embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known components or methods have not been described in detail or have been presented in simplified block diagram form to avoid unnecessarily obscuring the present disclosure. Thus, the specific details set forth are merely exemplary. A particular implementation may differ from the above example details and still be deemed to be within the scope of the present disclosure.

[0060] Although the method steps herein are shown and described in a particular order, the order of each method step may be changed, such that certain steps may be performed in reverse order, or certain steps may be performed at least partially concurrently with other steps. In other embodiments, instructions or substeps of separate steps may be in a non-sequential and / or interleaved form.

[0061] It is to be understood that the foregoing description is intended to be illustrative, and not limiting. Many other embodiments will be apparent to those skilled in the art upon reading and understanding the foregoing description. The scope of the present disclosure is therefore defined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. 1. A lift device for transferring a substrate between a support and a transfer plane, comprising:

1. A lift pin assembly comprising: lift pins configured to move the substrate between the support and the transfer plane; at least one pneumatic actuator including a moving member configured to apply a load to the lift pin; at least one pneumatic proportional valve configured to control the flow of fluid between the at least one pneumatic actuator and a pressurized fluid supply or between the at least one pneumatic actuator and a vent; a plurality of pressure sensors, each configured to individually measure pressure in a respective supply line to the at least one pneumatic actuator; and a lift pin assembly including at least one position sensor configured to measure a position of the moving member; a servo control system in communication with the lift pin assembly; A lifting device comprising:

2. The lift device of claim 1 , wherein the lift device comprises a plurality of lift pin assemblies.

3. The lift apparatus of claim 2 , wherein the plurality of lift pin assemblies are configured to move the substrate between the support and the transfer plane.

4. The lift apparatus of claim 2 , wherein the servo control system is in communication with the plurality of lift pin assemblies.

5. 5. The lifting device of claim 4, wherein the servo control system is configured to maintain a closed loop, and at least one of chamber pressure or moving member position is controlled within the at least one pneumatic actuator.

6. 5. The lift apparatus of claim 4, wherein the at least one pneumatic proportional valve is configured to direct pressurized fluid to at least one of a plurality of chambers in response to a control signal from the servo control system.

7. 2. The lift device of claim 1, wherein the at least one pneumatic actuator includes a plurality of chambers, each chamber connected to a respective supply line being measured by a respective one of the plurality of pressure sensors.

8. 10. The lift apparatus of claim 1, comprising a plurality of pneumatic proportional valves configured to convey fluid between the at least one pneumatic actuator and the pressurized fluid supply or between the at least one pneumatic actuator and the vent.

9. 2. The lift device of claim 1, wherein the servo control system includes a controller attached to the at least one pneumatic actuator, the plurality of pressure sensors, the at least one position sensor, and the at least one pneumatic proportional valve.

10. 1. A method comprising: receiving, by the controller, a first pressure measurement from a first pressure sensor measuring pressure in a first chamber of the pneumatic actuator; receiving, by the controller, a second pressure measurement from a second pressure sensor measuring pressure in a second chamber of the pneumatic actuator; receiving, by the controller, position measurements from a position sensor that measures a position of a moving member of the pneumatic actuator; generating a control signal based on the first pressure measurement, the second pressure measurement, and the position measurement; sending said control signal to at least one pneumatic proportional valve of a servo control system to control pressurized fluid to said pneumatic actuator; and operating the servo control system to extend at least one lift pin to lift the substrate from the support via the at least one lift pin.

11. The method of claim 10 , further comprising transferring the substrate from the at least one lift pin to a transfer chamber using a robotic arm.

12. 11. The method of claim 10, wherein the controller determines a difference between the first pressure measurement and the second pressure measurement to determine an output force of the pneumatic actuator, and the controller adds the first pressure measurement to the second pressure measurement to determine a stiffness of the pneumatic actuator.

13. 13. The method of claim 12, wherein the controller controls the at least one pneumatic proportional valve by determining a pressure in each of two chambers of the pneumatic actuator in response to the output force, the stiffness, and the position of the moving member.

14. 1. A method comprising: operating a servo control system to lift a substrate from a substrate support, the servo control system being configured to control a lift pin assembly to lift the substrate; actuating at least one pneumatic proportional valve to allow gas to flow through a first gas line into a first chamber of a pneumatic actuator of the lift pin assembly and through a second gas line into a second chamber of the pneumatic actuator; measuring pressure in the first gas line with a first pressure sensor and measuring pressure in the second gas line with a second pressure sensor; measuring the position of a moving member of the pneumatic actuator using a position sensor; controlling the at least one pneumatic proportional valve with the servo control system to apply a contact force of about 2 N to about 10 N to the substrate by the moving member; and lifting the substrate from the support by lift pins operable to receive a load from the moving member.

15. the lift pin assembly the lift pin; the pneumatic actuator including the moving member; the at least one pneumatic proportional valve; the first pressure sensor; the second pressure sensor; the position sensor; The method of claim 14, comprising:

16. The method of claim 14 , wherein a controller of the servo control system is connected to the pneumatic actuator, the at least one pneumatic proportional valve, the plurality of pressure sensors, and the position sensor.

17. 15. The method of claim 14, wherein controlling the at least one pneumatic proportional valve comprises maintaining, reducing, or reversing gas flow to at least one of the first chamber or the second chamber.

18. 15. The method of claim 14, wherein controlling the at least one pneumatic proportional valve comprises maintaining pressure to the first chamber and the second chamber at a constant value so as to apply a constant contact force to the substrate by the moving member.

19. 15. The method of claim 14, wherein when the position of the moving member is between about 1 mm and about 7 mm, or about 2 mm in a positive direction from a center position of the moving member, the servo control system sends a signal to the pneumatic proportional valve to increase pressure in at least one of the first chamber or the second chamber and accelerate the moving member in the positive direction.

20. 20. The method of claim 19, wherein the moving member is accelerated to a velocity of about 50 mm / s to about 150 mm / s, or about 75 mm / s to about 125 mm / s, or about 100 mm / s.

Images