Temperature control of substrate processing chamber plates using PWM to analog converters and proportional valves

Abstract

A temperature control system for a plate of a substrate processing chamber includes: a proportional valve configured to adjust flow of coolant through a cooling channel of the plate; a controller configured to generate a pulse width modulation PWM signal, the PWM signal having a duty cycle; and a PWM to analog converter configured to, based on the duty cycle, convert the PWM signal to a analog signal and supply the analog signal to the proportional valve to adjust an opening percentage of the proportional valve.

Description

TEMPERATURE CONTROL OF SUBSTRATE PROCESSING CHAMBER PLATES USING PWM TO ANALOG CONVERTERS AND PROPORTIONAL VALVESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 641 ,201 , filed on May 1 , 2024. The entire disclosure of the application referenced above is incorporated herein by reference.FIELD

[0002] The present disclosure relates to cooling systems for substrate processing systems, and more particularly to cooling circuits of top and bottom plates of substrate processing chambers.BACKGROUND

[0003] The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0004] A substrate processing chamber of a substrate processing system typically includes a plurality of process stations to perform deposition, etching, and other treatments of substrates such as semiconductor wafers. For example, deposition may be performed to deposit conductive film, dielectric film, or other types of film using chemical vapor deposition (CVD), plasma enhanced CVD (PECVD), atomic layer deposition (ALD), plasma enhance ALD (PEALD), and / or other deposition processes. As an example, etching may be performed to remove material from one or more layers and include atomic layer etching (ALE), high aspect ratio (HAR) etching, plasma etching, and / or other etch processes. During deposition, a substrate is arranged on a substrate support (e.g., a pedestal) and one or more precursor gases may be supplied to a substrate processing chamber using a gas distribution device (e.g., a showerhead) during one or more process steps. In a PECVD or PEALD process, plasma is used to activate chemical reactions within the substrate processing chamber during deposition. Additional examples of processes that may be performed on a substrate include, butare not limited to, dielectric etching, chemical etching, plasma etching, reactive ion etching, and cleaning processes. During the deposition and etching processes, gas mixtures are introduced into the substrate processing chamber via showerheads, and plasma is struck to activate chemical reactions. During the cleaning processes, gases may also be introduced via the showerheads.SUMMARY

[0005] A temperature control system for a first plate of a substrate processing chamber is disclosed. The temperature control system includes: a first proportional valve configured to adjust flow of coolant through a first cooling channel of the first plate; a controller configured to generate a first pulse width modulation (PWM) signal, the first PWM signal having a first duty cycle; and a first PWM to analog converter configured to, based on the first duty cycle, convert the first PWM signal to a first analog signal and supply the first analog signal to the first proportional valve to adjust an opening percentage of the first proportional valve.

[0006] In other features, the first PWM to analog converter supplies a power signal to the first proportional valve to power ON the first proportional valve.

[0007] In other features, the controller is configured to at least one of ramp up or ramp down the first duty cycle to at least one of ramp up or ramp down an opening percentage of the first proportional valve.

[0008] In other features, the first PWM to analog converter includes: a counter configured to generate a count value based on the first PWM signal; a shift register configured to store the count value; and a digital-to-analog converter configured to convert the count value to the first analog signal.

[0009] In other features, the counter is configured to generate the count value based on a clock signal and the first duty cycle of the first PWM signal. In other features, the shift register is configured to store the count value from the counter based on an inverted version of the first PWM signal. In other features, the counter is a 12-bit counter.

[0010] In other features, the temperature control system further includes a second proportional valve configured to adjust flow of coolant through a second cooling channel of a second plate of the substrate processing chamber. The controller is configured to generate a second PWM signal, the second PWM signal has a second duty cycle. Asecond PWM to analog converter is configured to, based on the first duty cycle, convert the second PWM signal to a second analog signal and supply the second analog signal to the second proportional valve to adjust an opening percentage of the second proportional valve.

[0011] In other features, the second PWM to analog converter includes: a counter configured to generate a count value based on the second PWM signal; a shift register configured to store the count value; and a digital-to-analog converter configured to convert the count value to the second analog signal.

[0012] In other features, the temperature control system further includes the first plate and the second plate. The first plate is a top plate of the substrate processing chamber. The second plate is a bottom plate of the substrate processing chamber.

[0013] In other features, the temperature control system further includes a temperature sensor configured to detect a temperature of the first plate. The system controller is configured to at least one of set and adjust the first duty cycle based on the temperature.

[0014] In other features, the system controller is configured to turn ON and OFF one or more heaters in the first plate based on the temperature.

[0015] In other features, the temperature control system further includes a thermocouple configured to detect a temperature of the first plate. The system controller is configured to at least one of set and adjust the first duty cycle based on the temperature.

[0016] In other features, the temperature control system further includes a flow sensor configured to detect a flow rate of the first plate. The system controller is configured to at least one of set and adjust the first duty cycle based on the flow rate.

[0017] In other features, a method of controlling temperature of a first plate of a substrate processing chamber is disclosed. The method includes: generating a first pulse width modulation (PWM) signal having a first duty cycle; and, based on the first duty cycle, converting the first PWM signal to a first analog signal and supplying the first analog signal to a first proportional valve to adjust an opening percentage of the first proportional valve. The first proportional valve configured to adjust flow of coolant through a first cooling channel of the first plate.

[0018] In other features, the method further includes supplying a power signal to the first proportional valve to power ON the first proportional valve.

[0019] In other features, the method further includes at least one of ramping up or ramping down the first duty cycle to at least one of ramping up or ramping down an opening percentage of the first proportional valve.

[0020] In other features, converting the first PWM signal to the first analog signal includes: generating a count value based on the first PWM signal; storing the count value; and converting the count value to the first analog signal.

[0021] In other features, the count value is generated based on a clock signal and the first duty cycle of the first PWM signal. In other features, the count value is stored based on an inverted version of the first PWM signal. In other features, the count value is generated by a 12-bit counter.

[0022] In other features, the method further includes: generating a second PWM signal having a second duty cycle; and, based on the second duty cycle, converting the second PWM signal to a second analog signal and supplying the second analog signal to a second proportional valve to adjust an opening percentage of the second proportional valve. The second proportional valve is configured to adjust flow of coolant through a second cooling channel of a second plate of the substrate processing chamber.

[0023] In other features, converting the second PWM signal to the second analog signal includes: generating a count value based on the second PWM signal; storing the count value; and converting the count value to the second analog signal.

[0024] In other features, the method further includes: detecting the temperature of the first plate; and at least one of setting and adjusting the first duty cycle based on the temperature.

[0025] In other features, the method further includes turning ON and OFF one or more heaters in the first plate based on the temperature.

[0026] In other features, the method further includes: detecting a flow rate of the first plate; and at least one of setting and adjusting the first duty cycle based on the flow rate.

[0027] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description andspecific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0029] FIG. 1 is a functional block diagram of a portion of an example substrate processing system including a temperature control system with proportional valves for cooling plates of a substrate processing chamber in accordance with the present disclosure;

[0030] FIG. 2A is a top cross-sectional view of an example top plate including a cooling channel;

[0031] FIG. 2B is a top view of an example bottom plate including a cooling channel;

[0032] FIG. 3 is a functional block diagram of an example cooling circuit including proportional valves in accordance with the present disclosure;

[0033] FIG. 4 is a functional block diagram of an example control circuit for controlling operation of proportional valves and heaters in accordance with the present disclosure;

[0034] FIG. 5 is a functional block diagram of a PWM to analog converter in accordance with the present disclosure;

[0035] FIG. 6 is a plot of an example PWM input signal and an analog output signal of a PWM to analog converter in accordance with the present disclosure;

[0036] FIG. 7 illustrates an example temperature control method for a cooling plate of a substrate processing chamber in accordance with the present disclosure; and

[0037] FIG. 8 illustrates an example method of operating a PWM to analog converter to control state of a proportional valve in accordance with the present disclosure.

[0038] In the drawings, reference numbers may be reused to identify similar and / or identical elements.DETAILED DESCRIPTION

[0039] A substrate processing chamber can include a top plate and a bottom plate, which can include cooling channels such as copper tubing extending through the top and bottom plates. Coolant is circulated through the coolant channels to cool the topplate and the bottom plate. Flow of the coolant can be controlled via 3-way ON / OFF valves for temperature control. The 3-way ON / OFF valves have two states an ON or fully open state and an OFF or fully closed state. When a 3-way ON / OFF valve is turned ON (or opened), there can be a large temperature gradient over a short period of time (e.g., 5 seconds). As an example, the temperature of the corresponding plate can drop as much as 40°C when the value is turned ON. Similarly, when the valve is turned OFF (or closed), temperature of the plate can quickly increase. The valve can be iteratively cycled between ON and OFF states. Due to the large temperature gradients, fatigue and failures can occur including cracking in the coolant channels such as in the copper tubing. For this reason, the stated cycling is referred to as stress cycling of the valve.

[0040] The examples set forth herein include cooling circuits for cooling top and bottom plates of substrate processing chambers. The cooling circuits include proportional valves that are able to be gradually opened and closed based on received control voltages. The proportional valves are able to be opened any amount based on duty cycles of pulse width modulated (PWM) signals, which are converted to analog signals via PWM to analog converters. This allows for ramping up and ramping down over extended periods of time the cooling of the top and bottom plates, which prevents large temperature gradients over short periods of time and thus preventing and / or minimizing fatigue and degradation to coolant channels.

[0041] FIG. 1 shows a portion 100 of a substrate processing system (or tool) including a temperature control system 102 with proportional valves 104, 105 (examples of which are shown in FIGS. 3-4) for cooling plates 106, 107 (other examples of which are shown in FIGs. 2A-3) of a substrate processing chamber 108. The proportional valves 104, 105 are controlled to gradually increase and decrease the amount of cooling provided to the plates 106, 107. The cooling plates 106, 107 include the top plate 106 and the bottom plate 107. The substrate processing chamber 108 includes multiple processing stations 109. Two processing stations are shown in FIG. 1 , however, the substrate processing chamber 108 may have four processing stations and be a QSM. The processing stations 109 include respective showerheads 110 and substrate supports (e.g., electrostatic chucks) 112. The substrate supports 112 may be referred to as pedestals. The substrate supports 112 may include respective lift pin actuator assemblies 114. The lift pin actuator assemblies 114 include lift pins 116 that areactuated to lift substrates (e.g., substrates 118) on and off of the substrate supports 112 and substrate indexing arms (or transfer paddles) 119.

[0042] Each of the processing stations 109 includes upper and lower electrodes. The showerheads 110 may be implemented as or include the upper electrodes. The substrate supports 112 may be implemented as or include the lower electrodes. The upper and lower electrodes may be implemented as radio frequency (RF) electrodes, bias electrodes, clamping electrodes and / or heating electrodes. For example, the upper electrodes may be implemented as the showerheads 110, which introduce and distribute gases in the processing stations. The showerheads 110 may include stems 120 including ends connected to top surfaces of the substrate processing chamber 108. The showerheads 110 are generally cylindrical and extend radially outward from opposite ends of the stems 120 at a location that is spaced from the top surface of the substrate processing chamber 108. Substrate facing surfaces of faceplates of the heads of the showerheads 110 include holes through which process or purge gas flows.

[0043] A RF generating system 121 generates and outputs RF voltages to the upper electrodes and the lower electrodes. For each of the processing stations 109, one of the upper electrodes and the lower electrodes may be direct current (DC) grounded, alternating current (AC) grounded or at a floating potential. For example, the RF generating system 121 may be controlled by a system controller 122 and include one or more RF generators 123 (e.g., a capacitive coupled plasma RF power generator, a bias power generator, and / or other RF power generator) that generate RF voltages, which are fed by one or more matching and distribution networks 124 to the upper electrodes and / or the lower electrodes. The system controller 122 sets and adjusts frequencies of RF signals output from the RF generators 125, 126. The frequencies may be adjusted to adjust power distribution within and across the substrate supports. The system controller 122 may be connected to and / or include memory, which may store a chamber clean application for implementing cleaning processes disclosed herein.

[0044] As an example, the first RF generator 125, the second RF generator 126, a first RF matching network 127 and a second RF matching network 129 are shown. The first RF generator 125 and the first RF matching network 127 may provide a RF voltage or may simply connect the showerheads to a ground reference. The second RF generator 126 and the second RF matching network 129 may each or collectively be referred to as a power source and provide a RF / bias voltage to the substrate supports. In oneembodiment, the first RF generator 125 and the first RF matching network 127 provide power that ionizes gas and drives plasma. In another embodiment, the second RF generator 126 and the second RF matching network 129 provide power that ionizes gas and drives plasma. One of the RF generators 125, 126 may be a high-power RF generator producing, for example, 6-10 kilowatts (kW) of power or more.

[0045] A gas delivery system 131 includes one or more substance sources 132-1 , 132-2,..., and 132-N (collectively substance sources 132), where N is an integer greater than zero. The substance sources 132 supply one or more precursors and substance mixtures thereof. The substance sources 132 may also supply etch gas, carrier gas and / or purge gas. The substance sources 132 are connected by valves 134-1 , 134-2, ..., and 134-N (collectively valves 134) and mass flow controllers 136-1 , 136-2, ..., and 136-N (collectively mass flow controllers 136) to a manifold and valve assembly 140. Outputs of the manifold and valve assembly 140 are fed respectively to the showerheads 110.

[0046] A valve 156 and pump 158 may be used to evacuate reactants from the substrate processing chamber 108. The system controller 122 may control components of the substrate processing system including controlling supplied RF power levels, pressures and flow rates of supplied gases, RF matching, etc. The system controller 122 controls states of the valve 156 and the pump 158. A robot 164 may be used to deliver substrates into and remove substrates from the processing stations 109. For example, the robot 164 may transfer substrates between the substrate supports and a load lock 166. The robot 164 may be controlled by the system controller 122. The system controller 122 may control operation of the load lock 166. The valves, gas and / or coolant pumps, power sources, RF generators, etc. may be referred to as actuators.

[0047] The substrate processing system further includes a power source 170 that may supply power to the system controller 122, the lift pin actuator assemblies 114 and motors 172. The motor 172 rotates a spindle 174 and move the spindle 174 and hub 148 in a Z direction (or vertically). The power source 170 may be controlled by the system controller 122. The system controller 122 may control supply of power from the power source 170 to the motors 172 and / or to the RF generating system 121 .

[0048] The lift pin actuator assemblies 114 raise and lower the lift pins 116. The lift pin actuator assemblies 1114 may include electrical and / or pneumatic actuators foradjusting positions of the lift pins 116. One of the motors 172 rotates a spindle 174, which is connected to and thus rotates the hub 148 about a vertical center axis 175. The hub 148 is connected to either the substrate indexing arms 119, which extend laterally from the hub 148. Top and / or bottom planar surfaces of the substrate indexing arms 119 may be parallel to bottom planar surfaces of the showerheads 110 and / or top planar surfaces of the substrate supports 112 when attached to the hub.

[0049] During substrate processing, the substrate indexing arms 119 are rotated to position the substrates 118 over the substrate supports 112. The lift pins 116 are raised to lift the substrates 118 off the substrate indexing arms 119 and the substrate indexing arms 119 are rotated out of the way to stowed positions. The lift pins 116 are then lowered to set the substrates 118 on the substrate supports 112. One or more processing operations (e.g., etch, deposition, or clean operation) are then performed on the substrates 118. Subsequently, the lift pins 116 are raised to lift the substrates off of the substrate supports 112 and the substrate indexing arms 119 are rotated to be between the substrate supports 112 and the substrates 118. The lift pins 116 are then lowered to set the substrates 118 back on the substrate indexing arms 119. This process may be repeated and the substrates 118 may be moved from processing station-to-processing station in this manner. Each of the processing stations 109 may perform a different set of processing operations.

[0050] The lift pins 116 may also be used to allow delivery and removal of the substrates 118 from the substrate processing chamber 108 using a robot arm of the robot 164. Upper ends of the lift pins 116 may be located flush with or below upper surfaces of the substrate supports 112 when stowed. During substrate delivery, removal and / or transfer, the lift pins are raised relative to the upper surfaces of the substrate supports 112 to lift the substrates 118 and provide clearance between the substrates 118 and the substrate supports 112. The clearance between the substrates 118 and the substrate supports 112 allows (i) an end effector of the robot arm to be inserted or removed, and (ii) the substrate transfer paddles 119 to be moved between the substrates 118 and the substrate supports 112.

[0051] The temperature control system 102 may further include a coolant source 180, a pump 182, lower manifolds 184, and upper manifolds 186. In an embodiment, the pump 182 is not included and the coolant source supplies and receives coolant directly to and from the lower manifolds 184. The pump 182 may circulate coolant to and fromthe coolant source 180 and through the manifolds 184, 186, the proportional valves 104, 105 and the plates 106, 107. The lower manifolds 184 may include a lower supply manifold and a lower return manifold, examples of which are shown in FIG. 3. The upper manifolds 186 may include an upper supply manifold and an upper return manifold, examples of which are shown in FIG. 3. The system controller 122 may control the pump 182. The system controller 122 controls the states of the proportional valves as further described below based on temperatures of the plates 106, 107.

[0052] FIG. 2A shows a top plate 200 including a cooling channel 202. The coolant channel 202 extends throughout the top plate 200 in a predetermined pattern. In the example shown, the cooling channel 202 extends around areas 204 above processing stations (e.g., the processing stations 109 of FIG. 1 ). The cooling channel 202 may be in various patterns. The top plate may also include holes or recessed areas 210 for receiving heaters 212. In an embodiment, the heaters 212 are cylindrical-shaped cartridge heaters. The heaters 212 may be implemented as heating elements that extend through and / or are embedded in respective portions of the top plate 200. The top plate 200 may include one or more temperature sensors such as one or more thermocouples to detect temperatures of the top plate 200. One thermocouple 220 is shown. Although the top plate 200 is shown having a single coolant channel, the top plate 200 may have multiple coolant channels. Flow through each of the coolant channels may be controlled via a respective proportional valve and corresponding circuitry as disclosed herein.

[0053] FIG. 2B shows a bottom plate 250 including a cooling channel 252. The cooling channel 252 extends throughout the bottom plate 250 in a predetermined pattern. In the example shown, the cooling channel 252 extends around areas 254 above processing stations (e.g., the processing stations 109 of FIG. 1 ). The cooling channel 252 may be in various patterns. The bottom plate may also include holes or recessed areas 260 for receiving heaters 262. In an embodiment, the heaters 262 are cylindrical-shaped cartridge heaters. The heaters 262 may be implemented as heating elements that extend through and / or are embedded in respective portions of the bottom plate 250. The bottom plate 250 may include one or more temperature sensors such as one or more thermocouples to detect temperatures of the bottom plate 250. One thermocouple 270 is shown. Although the bottom plate 250 is shown having a single coolant channel, the bottom plate 250 may have multiple coolant channels. Flow through each of thecoolant channels may be controlled via a respective proportional valve and corresponding circuitry as disclosed herein.

[0054] FIG. 3 shows a cooling circuit 300 including proportional valves 302, 304. States of the proportional valves 302, 304 are controlled to control flow of coolant (e.g., plant cooling water (PCW)) through channels of a top plate 306 and a bottom plate 308 of a substrate processing chamber 310. The cooling circuit 300 may include a lower supply manifold 320, an upper supply manifold 322, an upper return manifold 324, and a lower return manifold 326.

[0055] The lower supply manifold 320 supplies coolant to the first proportional valve 302 via the upper supply manifold 322, and to the second proportional valve 304. The first proportional valve controls flow of coolant to the top plate 306. The second proportional valve controls flow of coolant to the bottom plate 308. The lower supply manifold 320 receives coolant from a facilities supply line 327. The lower return manifold 326 returns coolant to a facilities return line 329.

[0056] Coolant out of the top plate 306 flows through the upper return manifold 324 to the lower return manifold 326. Coolant out of the bottom plate 308 flows to the lower return manifold 326. A first flow sensor 330 detects flow of coolant through the coolant channel in the top plate 306. An example of the coolant channel of the top plate 306 is shown in FIG. 2A. A second flow sensor 332 detects flow of coolant through the coolant channel in the bottom plate 308. An example of the coolant channel of the bottom plate 308 is shown in FIG. 2B.

[0057] FIG. 4 shows a control circuit 400 for controlling operation of proportional valves 402, 404, top plate heaters 406, and bottom plate heaters 408. The control circuit 400 further includes a system controller 410, a local power box (a first portion 412 and second portion 414 of which are shown), and PWM to analog converters 416, 418. The system controller 410 may replace the system controller 122 of FIG. 1 and generates PWM signals PWM1 , PWM2 based on detected temperatures of a top plate and a bottom plate of a substrate processing chamber (e.g., the substrate processing chamber 108) of FIG. 1. In an embodiment, the system controller 410 operates as a proportional integral derivative (PID) controller when generating the PWM signals PWM1 , PWM2. The PWM signals PWM1 , PWM2 may cycle between a HIGH voltage (e.g., 24 V) and LOW voltage (e.g., 0 V) at selected duty cycles. The temperatures may be detected via temperature sensors (e.g., the temperature sensors 220, 270 in FIGs.2A-2B) in the top and bottom plates. Temperature signals TEMPI , TEMP2 from thermocouples (TCs) of top and bottom plates are shown and provided to the system controller 410. Other and / or additional temperature sensors may be included and monitored by the system controller 410. For example, the plates of the TCs may each include multiple temperature sensors, which are monitored by the system controller 410 and based on which the system controller 410 generates the PWM signals PWM1 , PWM2.

[0058] The system controller 410 provides the signals PWM1 , PWM2 respectively to the PWM to analog converters 416, 418, which convert the signals PWM1 , PWM2 to control signals CtrH , Ctrl2 to control states of the proportional valves 402, 404. The signals PWM1 , PWM2 are digital signals with respective duty cycles, which are set by the system controller 410. The proportional valves 402, 404 control flow of coolant through cooling channels of the top and bottom plates. The control signals CtrH , Ctrl2 are generated based on the duty cycles of the signals PWM1 , PWM2. The PWM to analog converters 416, 418 supply power signals PWR (e.g., a 24 volt (V)) to power the proportional valves 402, 404. Return lines RTN are connected between the system controller 410 and the PWM to analog converters 416, 418. Power return PWR RTN and control return Ctrl RTN lines are connected between the PWM to analog converters 416, 418 and the proportional valves 402, 404.

[0059] The local power box may include a first solid-state relay (SSR) 430, a second SSR 432, and an alternating current (AC)-to-direct current (DC) converter 434. The system controller 410 controls states of the SSRs 430, 432 based on the temperature signals TEMPI , TEMP2. The SSRs 430, 432 have contactors 436, 438, which are closed by supplying power to the SSRs 430, 432. When closed, power from utility lines L1 and L2 is supplied to the heaters 406, 408. As an example, the lines L1 and L2 may supply a high AC voltage (e.g., 208V AC) to the heaters 406, 408. The AC-to-DC converter 434 may convert a voltage of one of the lines L1 , L2 or a voltage across lines L1 , L2 to a DC voltage (e.g., 24V), which is supplied to the PWM to analog converters 416, 418. The power signals PWR may be at the same voltage as the DC voltage supplied to the PWM to analog converters 416, 418.

[0060] FIG. 5 shows a PWM to analog converter 500. The PWM to analog converters 416, 418 of FIG. 4 may each be configured as the PWM to analog converter 500 of FIG. 5. The PWM to analog converter 500 may include a counter 502, a parallel inparallel out (PIPO) shift register 504, and a digital-to-analog converter 506. The counter 502, PIPO shift register 504, digital-to-analog converter 506, and the clock generator 508 may each receive a supply voltage Vcc (e.g., 5V, 10V, or other supply voltage). The supply voltage Vcc may be supplied by a voltage regulator 510 based on a power signal PWR (e.g., 24V). The voltage regulator 510 regulates the supply voltage Vcc.

[0061] As an example, the counter 502 may be a 12-bit counter that is configured to count clock cycles of a clock signal CLK received by a clock generator 508. The counter 502 counts cycles of the clock signal CLK for a duration of a HIGH pulse of a PWM signal 512. In an embodiment, the PWM signal has a set time period T (e.g., 1 second). The frequency of the clock signal is (2A12) / T (e.g., 4096 Hertz or 4096 pulses per second). When the time period T is 1 second, the counter 502 counts from 0 and up to 4095 clock pulses depending on the ON duration of a cycle of the PWM signal, and after which the counter 502 resets itself. The counter 502 updates the count value when the PWM signal is HIGH and / or when the PWM signal transitions from HIGH to LOW. The counter 502 outputs binary signals 513 to the PIPO shift register 504. The binary signals 513 may provide a count value in binary, where each bit representing the count is provided via a respective one of the binary signals 513. As an example, the count may be represented as a 12-bit binary value, where 12 binary signals are provided respectively for the 12 bits to the PIPO shift register 504.

[0062] The PWM signal 512 may be generated by a system controller (e.g., the system controller 410 of FIG. 4). The PWM signal 512 is supplied to the counter 502 and to an inverter 514, which outputs an inverted PWM signal to the PIPO shift register 504 to control when a count stored in the PIPO shift register 504 is provided to the digital-to-analog converter 506. The digital-to-analog converter 506 converts the digital count value to an analog voltage (or control signal Ctrl), which is supplied to a proportional valve (e.g., one of the proportional valves 402, 404 of FIG. 4). In an embodiment, the digital-to-analog converter 506 is a 12-bit binary to analog converter.

[0063] As an example, the PWM signal may be a digital signal transitioning between 0 V and 24 V and the analog signal Ctrl may be an analog 0-10 V signal, where the analog voltage of Ctrl is equal to ten times the duty cycle of the PWM signal. The duty cycle refers to a ratio between an ON duration of the PWM signal during a cycle T of the PWM signal. As another example, the analog signal Ctrl may be a 0-5 V signal, where the analog voltage of Ctrl is equal to 5 times the duty cycle. In yet anotherembodiment, the analog signal Ctrl is a current signal instead of a voltage signal. In an embodiment, the current signal is a 4-20 milli-ampere (mA) signal, where 4 mA corresponds to a 0% duty cycle of the PWM signal and 20 mA is a 100% duty cycle of the PWM signal. Thus, an analog voltage signal or an analog current signal may be provided to the proportional valve to set an open percentage of the proportional valve.

[0064] The digital-to-analog converter 506 may have a gain pin 520 and receive a gain voltage. The gain voltage may be used to provide an analog output voltage that is greater than the supply voltage Vcc. For example, the supply voltage Vcc may be 5 V and the analog output voltage may vary between 0-10V. In an embodiment, the supply voltage Vcc and the gain voltage are provided by the voltage regulator 510.

[0065] FIG. 6 shows a plot of an example PWM input signal 600 and an analog output signal 602 of a PWM to analog converter (e.g., the PWM to analog converter 500 of FIG. 5. The PWM signal is shown switching from a first duty cycle (e.g., 80%) to a second duty cycle (e.g., 60%). The analog output signal 602 is shown switching from a first voltage V1 (e.g., 8V) to a second voltage (e.g., 6V) due to the change in the duty cycle. The analog output signal 602 is directly related to the duty cycle. Table 1 provides example analog output voltages provided for given duty cycles.Table 1 - PWM-to-Analog Conversion

[0066] FIG. 7 shows a temperature control method for a cooling plate of substrate processing chamber. This method may be performed for each cooling plate and corresponding proportional valve. The following operations may be iteratively performed. At 700, a system controller detects a temperature of a plate (e.g., a top plate or a bottom plate of a substrate processing chamber) via a corresponding thermocouple.

[0067] At 702, the system controller determines if the temperature is in a target range. If yes, operation 700 is performed, otherwise operation 704 is performed.

[0068] At 704, the system controller determines whether the temperature is greater and thus outside of the target range. If yes, operation 706 is performed, otherwise operation 714 is performed.

[0069] At 706, the system controller determines if one or more heaters of the plate are ON. If yes, operation 708 is performed, otherwise operation 710 is performed.

[0070] At 708, the system controller turns OFF one or more heaters. The heaters that are turned OFF may be the same or different than the heaters for which current is reduced. This may include opening contactors of one or more SSRs of the one or more heaters being turned OFF.

[0071] At 710, the system controller generates a PWM signal based on the temperature and the target temperature range including turning ON the corresponding proportional valve if not already ON. The system controller may adjust the open state of the proportional valve based on the temperature.

[0072] At 712, the system controller ramps up the duty cycle of the PWM signal to ramp up an opening percentage of the proportional valve based on the temperature and the target temperature range. In an embodiment, the duty cycle is gradually increasedto gradually increase the opening percentage such that there is not a large temperature gradient in a short period thereby preventing cooling channel fatigue. The duty cycle is ramped up from a first percentage to a second percentage. If operation 712 is iteratively performed, then during each subsequent iteration, the current first duty cycle is a previous second duty cycle and the current second duty cycle is set to a percentage greater than the current first duty cycle. Operation 700 may be performed subsequent to operation 712. Operations 710, 712 may also be based on feedback from a flow sensor, such as one of the flow sensors 330, 332 of FIG. 3 and a target flow rate. The target flow rate may be set based on a difference between the detected temperature and the target temperature range and / or a target temperature.

[0073] At 714, the system controller determines whether the corresponding proportional valve is ON and at least partially open. If yes, operation 716 is performed, otherwise operation 718 is performed.

[0074] At 716, the system controller may ramp down the duty cycle of the PWM signal to gradually decrease the duty cycle and the open percentage of the proportional valve. The duty cycle is reduced from a current duty cycle to a reduced duty cycle that is less than the current duty cycle. In an iteration of operation 716, this may include reducing the duty cycle to 0% and turning OFF the proportional valve. Operation 716 may also be based on feedback from a flow sensor, such as one of the flow sensors 330, 332 of FIG. 3 and a target flow rate. The target flow rate may be set based on a difference between the detected temperature and the target temperature range and / or a target temperature.

[0075] At 718, the system controller turns ON one or more heaters of plate if the one or mor heaters are OFF. Operation 700 may be performed subsequent to operation 718.

[0076] FIG. 8 shows a method of operating a PWM to analog converter to control state of a proportional valve. The following operations may be iteratively performed. At 800, a clock generator (e.g., the clock generator 508 of FIG.5) generates a clock signal.

[0077] At 802, a system controller, such as one of the system controllers disclosed herein, generates a PWM signal. At 804, a counter (e.g., the counter 502 of FIG. 5), based on the clock signal, counts clock cycles associated with an ON pulse (or duty cycle) of the PWM signal. The counter generates binary counter signals indicative of the count.

[0078] At 806, a PIPO shift register (e.g., the PIPO shift register 504 of FIG. 5) receives the binary counter signals and stores the count. At 808, a digital-to-analog converter (e.g., the digital-to-analog converter 506) converts the stored count to an analog signal. At 810, the analog signal is supplied as a control signal to the proportional valve to adjust cooling of a plate of a substrate processing chamber.

[0079] The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and / or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.

[0080] Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

[0081] In some implementations, a controller is part of a system, which may be part of the above-described examples. Such systems can comprise semiconductor processingequipment, including a processing tool or tools, chamber or chambers, a platform or platforms for processing, and / or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems. The controller, depending on the processing requirements and / or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and / or load locks connected to or interfaced with a specific system.

[0082] Broadly speaking, the controller may be defined as electronics having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system. The operational parameters may, in some embodiments, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or dies of a wafer.

[0083] The controller, in some implementations, may be a part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the “cloud” or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality offabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start a new process. In some examples, a remote computer (e.g., a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and / or settings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus, as described above, the controller may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.

[0084] Without limitation, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and / or manufacturing of semiconductor wafers.

[0085] As noted above, depending on the process step or steps to be performed by the tool, the controller might communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of wafers to and from tool locations and / or load ports in a semiconductor manufacturing factory.

Claims

CLAIMSWhat is claimed is:1 . A temperature control system for a first plate of a substrate processing chamber, the temperature control system comprising: a first proportional valve configured to adjust flow of coolant through a first cooling channel of the first plate; a controller configured to generate a first pulse width modulation (PWM) signal, the first PWM signal having a first duty cycle; and a first PWM to analog converter configured to, based on the first duty cycle, convert the first PWM signal to a first analog signal and supply the first analog signal to the first proportional valve to adjust an opening percentage of the first proportional valve.

2. The temperature control system of claim 1 , wherein the first PWM to analog converter supplies a power signal to the first proportional valve to power ON the first proportional valve.

3. The temperature control system of claim 1 , wherein the controller is configured to at least one of ramp up or ramp down the first duty cycle to at least one of ramp up or ramp down an opening percentage of the first proportional valve.

4. The temperature control system of claim 1 , wherein the first PWM to analog converter comprises: a counter configured to generate a count value based on the first PWM signal; a shift register configured to store the count value; and a digital-to-analog converter configured to convert the count value to the first analog signal.

5. The temperature control system of claim 4, wherein the counter is configured to generate the count value based on a clock signal and the first duty cycle of the first PWM signal.

6. The temperature control system of claim 4, wherein the shift register is configured to store the count value from the counter based on an inverted version of the first PWM signal.

7. The temperature control system of claim 4, wherein the counter is a 12-bit counter.

8. The temperature control system of claim 1 , further comprising: a second proportional valve configured to adjust flow of coolant through a second cooling channel of a second plate of the substrate processing chamber, wherein the controller is configured to generate a second PWM signal, the second PWM signal has a second duty cycle; and a second PWM to analog converter configured to, based on the first duty cycle, convert the second PWM signal to a second analog signal and supply the second analog signal to the second proportional valve to adjust an opening percentage of the second proportional valve.

9. The temperature control system of claim 8, wherein the second PWM to analog converter comprises: a counter configured to generate a count value based on the second PWM signal; a shift register configured to store the count value; and a digital-to-analog converter configured to convert the count value to the second analog signal.

10. The temperature control system of claim 8, further comprising the first plate and the second plate, wherein: the first plate is a top plate of the substrate processing chamber; and the second plate is a bottom plate of the substrate processing chamber.11 . The temperature control system of claim 1 , further comprising a temperature sensor configured to detect a temperature of the first plate, wherein the system controller is configured to at least one of set and adjust the first duty cycle based on the temperature.

12. The temperature control system of claim 11 , wherein the system controller is configured to turn ON and OFF one or more heaters in the first plate based on the temperature.

13. The temperature control system of claim 1 , further comprising a thermocouple configured to detect a temperature of the first plate, wherein the system controller is configured to at least one of set and adjust the first duty cycle based on the temperature.

14. The temperature control system of claim 1 , further comprising a flow sensor configured to detect a flow rate of the first plate, wherein the system controller is configured to at least one of set and adjust the first duty cycle based on the flow rate.

15. A method of controlling temperature of a first plate of a substrate processing chamber, the method comprising: generating a first pulse width modulation (PWM) signal having a first duty cycle; and based on the first duty cycle, converting the first PWM signal to a first analog signal and supplying the first analog signal to a first proportional valve to adjust an opening percentage of the first proportional valve, wherein the first proportional valve configured to adjust flow of coolant through a first cooling channel of the first plate.

16. The method of claim 15, further comprising supplying a power signal to the first proportional valve to power ON the first proportional valve.

17. The method of claim 15, further comprising at least one of ramping up or ramping down the first duty cycle to at least one of ramping up or ramping down an opening percentage of the first proportional valve.

18. The method of claim 15, wherein converting the first PWM signal to the first analog signal comprises: generating a count value based on the first PWM signal; storing the count value; and converting the count value to the first analog signal.

19. The method of claim 18, wherein the count value is generated based on a clock signal and the first duty cycle of the first PWM signal.

20. The method of claim 18, wherein the count value is stored based on an inverted version of the first PWM signal.

21. The method of claim 18, wherein the count value is generated by a 12-bit counter.

22. The method of claim 15, further comprising: generating a second PWM signal having a second duty cycle; and based on the second duty cycle, converting the second PWM signal to a second analog signal and supplying the second analog signal to a second proportional valve to adjust an opening percentage of the second proportional valve, wherein the second proportional valve is configured to adjust flow of coolant through a second cooling channel of a second plate of the substrate processing chamber.

23. The method of claim 22, wherein converting the second PWM signal to the second analog signal comprises: generating a count value based on the second PWM signal; storing the count value; and converting the count value to the second analog signal.

24. The method of claim 15, further comprising: detecting the temperature of the first plate; and at least one of setting and adjusting the first duty cycle based on the temperature.

25. The method of claim 24, further comprising turning ON and OFF one or more heaters in the first plate based on the temperature.

26. The method of claim 15, further comprising: detecting a flow rate of the first plate; and at least one of setting and adjusting the first duty cycle based on the flow rate.

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