WO2020023295A1

WO2020023295A1 - Substrate support temperature sensing systems and methods

Info

Publication number: WO2020023295A1
Application number: PCT/US2019/042532
Authority: WO
Inventors: Steven GARRISON; John Pease
Original assignee: Lam Research Corporation
Priority date: 2018-07-25
Filing date: 2019-07-19
Publication date: 2020-01-30
Also published as: TW202018841A

Abstract

A substrate support for a plasma system includes: a first layer; a temperature sensor, a light receiver, and a temperature module. The temperature sensor is configured to measure a temperature of the substrate support, and to, based on the measured temperature, transmit light through the first layer. The light receiver is configured to receive light through the first layer and to generate an output signal based on the light received through the first layer. The temperature module is configured to determine the measured temperature based on the output signal.

Description

SUBSTRATE SUPPORT TEMPERATURE SENSING SYSTEMS AND METHODS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Patent Application No. 62/703,206, filed on July 25, 2018. The entire disclosure of the application referenced above is incorporated herein by reference

FIELD

[0002] The present disclosure relates to substrate supports of processing chambers, and more particularly to systems and methods for measuring temperature at various locations of a substrate support.

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] Substrate processing systems may be used to treat substrates such as semiconductor wafers. Example processes that may be performed on a substrate include, but are not limited to, chemical vapor deposition (CVD), atomic layer deposition (ALD), conductor etch, and/or other etch, deposition, or cleaning processes. A substrate may be arranged on a substrate support, such as a pedestal, an electrostatic chuck (ESC), etc. in a processing chamber of the substrate processing system. During etching, gas mixtures may be introduced into the processing chamber and plasma may be used to initiate chemical reactions.

[0005] The substrate support may include a ceramic layer arranged to support a substrate. For example, the wafer may be electrostatically clamped to the ceramic layer during processing.

SUMMARY

[0006] In a feature, a substrate support for a plasma system is described. The substrate support includes: a first layer; a temperature sensor, a light receiver, and a temperature module. The temperature sensor is configured to measure a temperature of the substrate support, and to, based on the measured temperature, transmit light through the first layer. The light receiver is configured to receive light through the first layer and to generate an output signal based on the light received through the first layer. The temperature module is configured to determine the measured temperature based on the output signal.

[0007] In further features, the substrate support further includes a second layer that is made of a ceramic, where the second layer is disposed above the first layer, and where the temperature sensor is in contact with the second layer.

[0008] In further features, the temperature sensor includes: a sensing element configured to vary an output based on the measured temperature; an analog to digital (A/D) converter configured to generate a digital value based on the output of the sensing element; a light source configured to transmit light through the first layer; and a light driver configured to control the light source based on the digital value.

[0009] In further features, the light driver is configured to: determine a pattern for controlling the light source based on the digital value; and control the light source according to the pattern.

[0010] In further features, the light source is a light emitting diode (LED).

[0011] In further features, the light receiver is configured to: set the output signal to a first state when the light source is on; and set the output signal to a second state when the light source is off.

[0012] In further features, the substrate support further includes: a thermal control element embedded within the second layer; and a temperature controller configured to selectively apply power to the thermal control element based on the measured temperature.

[0013] In further features, the substrate support further includes a temperature controller configured to control coolant flow through coolant channels in the first layer based on the measured temperature.

[0014] In further features, the temperature sensor is located within a recess in the second layer.

[0015] In further features, the substrate support further includes: first wires that extend through the first layer and that are connected to a power source; and second wires that are embedded within the second layer and that connect the temperature sensor to the first wires.

[0016] In further features, the substrate support further includes an optical diffuser layer that is located between the first layer and the second layer and that is configured to direct light through an aperture through the first layer.

[0017] In further features, the substrate support further includes a through hole in the first layer, where the temperature sensor transmits light through the through hole based on the measured temperature, and where the light receiver receives the light through the through hole.

[0018] In further features, the light receiver is a phototransistor.

[0019] In further features, the temperature module is configured to determine a pattern in the output signal and to determine the measured temperature based on the pattern.

[0020] In further features, the pattern further includes a unique identifier corresponding to the temperature sensor and, the temperature module is configured to identify the temperature sensor based on the unique identifier.

[0021] In further features, the substrate support further includes a plurality of additional temperature sensors configured to measure respective temperatures at corresponding locations of the substrate support, and to, based on the measured temperatures, transmit light through the first layer.

[0022] In further features, the substrate support further includes: a plurality of additional light receivers configured to receive light from the corresponding additional temperature sensors through the first layer and to generate respective output signals based on light received from the plurality of additional temperature sensors through the first layer, where the temperature module is further configured to determine the respective measured temperatures based on the respective output signals from the plurality of additional light receivers.

[0023] In further features, the substrate support further includes: a plurality of thermal control elements embedded within a second layer; and a temperature controller configured to: selectively apply power to the plurality of thermal control elements based on the temperatures measured by the temperature sensor and the plurality of additional temperature sensors. [0024] In further features, the substrate support further includes an optical diffuser layer configured to direct the light from the plurality of additional temperature sensors to the light receiver.

[0025] In further features, the light receiver is located within a recess in the first layer.

[0026] In further features, the first layer includes a baseplate.

[0027] In a feature, an electrostatic chuck for a plasma system is described. The electrostatic chuck includes: a ceramic layer; a baseplate; a thermal control element that is embedded in the ceramic layer; and a temperature sensor. The temperature sensor is configured to: measure a temperature of the ceramic layer; and, through a through hole in the baseplate, transmit light indicative of the measured temperature.

[0028] In further features, a circuit board is attached to the baseplate, and the circuit board includes: a light receiver configured to receive the light transmitted by the temperature sensor; a temperature module configured determine the measured temperature based on the received light; and a temperature controller is configured to control the thermal control element based on the measured temperature.

[0029] In further features, the temperature sensor includes: a sensing element configured to vary an output based on the measured temperature; an analog to digital (A/D) converter configured to generate a digital value based on the output of the sensing element; a light source configured to transmit light through the through hole; and a light driver configured to control the light source based on the digital value.

[0030] In further features, the light driver is configured to: determine a pattern for controlling the light source based on the digital value; and control the light source according to the pattern.

[0031] In further features, the temperature sensor is located within a recess in the ceramic layer.

[0032] In further features, the electrostatic chuck further includes: first wires that extend through the baseplate and that are connected to a power source; and second wires that are embedded within the ceramic layer and that connect the temperature sensor to the first wires.

[0033] In further features, the electrostatic chuck further includes an optical diffuser layer that is located between the baseplate and the ceramic layer and that is configured to direct light through the through hole. [0034] In further features, the electrostatic chuck further includes a plurality of additional temperature sensors configured to measure a plurality of additional temperatures of the ceramic layer, respectively, and to transmit light indicative of the additional measured temperatures.

[0035] In further features, the electrostatic chuck further includes an optical diffuser layer configured to direct the light from the plurality of additional temperature sensors through the through hole.

[0036] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0038] FIG. 1 is a functional block diagram of an example processing chamber;

[0039] FIG. 2 is a cross-sectional view of a portion of an example substrate support;

[0040] FIG. 3 is a functional block diagram including an example implementation of a temperature control system of a substrate support including one temperature sensor;

[0041] FIG. 4 is a cross-sectional view of a portion of an example substrate support; and

[0042] FIG. 5 is a flowchart depicting an example method of measuring one temperature using one temperature sensor of a substrate support and, based on the temperature, controlling at least one of heating and cooling of the substrate support.

[0043] In the drawings, reference numbers may be reused to identify similar and/or identical elements.

DETAILED DESCRIPTION

[0044] A substrate support, such as an electrostatic chuck, supports a substrate in a substrate processing chamber. A substrate is arranged on a ceramic portion of the substrate support during processing. A plurality of thermal control elements are embedded in the ceramic portion. [0045] A plurality of temperature sensors are also embedded in the ceramic portion. For example, one temperature sensor may be provided near each of the electric heating elements. The temperature sensors measure temperatures at their respective locations.

[0046] The temperature sensors communicate the measured temperatures optically to a temperature controller. Based on the measured temperatures, the temperature controller controls heating and/or cooling of the substrate support.

[0047] By optically transmitting the measured temperatures, the number of wires connected to the temperature sensors through the substrate support is minimized. For example, inter integrated circuit (I2C) temperature sensors may include four wires connected through the substrate support. The measured temperatures can be transmitted optically through the substrate support using only two wires connected. Minimizing the number of wires connected to the temperature sensors through the substrate support may decrease a cost of the substrate support and increase a lifetime of the substrate support.

[0048] Referring now to FIG. 1 , an example substrate processing system 100 is shown. For example only, the substrate processing system 100 may be used for performing etching using a radio frequency (RF) plasma.

[0049] The substrate processing system 100 includes a processing chamber 102 that encloses other components of the substrate processing system 100 and that contains the RF plasma. The processing chamber 102 includes an upper electrode 104 and a substrate support 106, such as an electrostatic chuck (ESC).

[0050] During operation, a substrate 108 is arranged on the substrate support 106. An example of the substrate processing system 100 and the processing chamber 102 is shown. Flowever, the present disclosure is also applicable to other types of substrate processing systems and processing chambers, such substrate processing systems that generate plasma in-situ, substrate processing systems that implement remote plasma generation and delivery (e.g., using a plasma tube, a microwave tube), etc.

[0051] The upper electrode 104 may include a gas distribution device, such as a showerhead 109, that introduces and distributes process gases within the processing chamber 102. The showerhead 109 may include a stem portion including one end connected to a top surface of the processing chamber 102. A base portion of the showerhead 109 is generally cylindrical and extends radially outwardly from an opposite end of the stem portion at a location that is spaced from the top surface of the processing chamber 102. A substrate-facing surface, or faceplate, of the base portion of the showerhead 109 includes a plurality of holes through which process gas or purge gas flows. Alternatively, the upper electrode 104 may include a conducting plate and the process gases may be introduced in another manner.

[0052] The substrate support 106 includes an electrically conductive baseplate 110 that acts as a lower electrode. The baseplate 110 supports a ceramic layer 112. One or more other layers, such as an optical diffuser layer 114 may be arranged between the ceramic layer 112 and the baseplate 110. The baseplate 110 may include one or more coolant channels 116 for flowing coolant through the baseplate 110. In some examples, a protective seal 176 may be provided.

[0053] An RF generating system 120 generates and outputs an RF voltage to one of the upper electrode 104 and the lower electrode (e.g., the baseplate 110 of the substrate support 106) to strike and maintain plasma within the processing chamber 102. The other one of the upper electrode 104 and the baseplate 110 may be direct current (DC) grounded, alternating current (AC) grounded, or floating. For example only, the RF generating system 120 may include an RF voltage generator 122 that generates the RF voltage that is fed by a matching and distribution network 124 to the upper electrode 104 or the baseplate 110.

[0054] A gas delivery system 130 includes one or more gas sources 132-1 , 132-2, ... , and 132-N (collectively gas sources 132), where N is an integer greater than zero. The gas sources 132 supply one or more etch gases, carrier gases, inert gases, precursor gases, and mixtures thereof. The gas sources 132 may also supply purge gas and other types of gas.

[0055] The gas 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 140. An output of the manifold 140 is fed to the processing chamber 102. For example only, the output of the manifold 140 is fed to the showerhead 109 and output to the processing chamber 102 from the showerhead 109.

[0056] A temperature controller 142 is connected to an array of heating elements, such as thermal control elements (TCEs) 144 arranged in the ceramic layer 112. For example, the TCEs 144 may include, but are not limited to, macro heating elements corresponding to respective zones in a multi-zone heating plate and/or an array of micro heating elements disposed across multiple zones of a multi-zone heating plate. The TCEs 144 may be, for example, (electrically) resistive heaters that generate heat when power is applied to the heaters, respectively, or another suitable type of heating element. In various implementations, a total of 144 TCEs or another suitable number of TCEs may be implemented throughout the ceramic layer 112.

[0057] The temperature controller 142 controls the application of power to the TCEs 144 to control temperatures at various locations on the substrate support 106 and the substrate 108. For example, the temperature controller 142 may control respective switches to connect and disconnect the TCEs 144 to and from power.

[0058] The temperature controller 142 may communicate with a coolant assembly 146 to control coolant flow through the coolant channels 116. For example, the coolant assembly 146 may include a coolant pump and reservoir. The temperature controller 142 operates the coolant assembly 146 to selectively flow the coolant through the coolant channels 116 to cool the substrate support 106. The temperature controller 142 may control the TCEs 144 together with the coolant assembly 146, for example, to achieve one or more target temperatures.

[0059] A valve 150 and pump 152 may be used to evacuate reactants from the processing chamber 102. A system controller 160 may control components of the substrate processing system 100. Although shown as separate controllers, the temperature controller 142 may be implemented within the system controller 160.

[0060] A robot 170 may deliver substrates onto, and remove substrates from, the substrate support 106. For example, the robot 170 may transfer substrates between the substrate support 106 and a load lock 172.

[0061] In some examples, the substrate support 106 includes an edge ring 180. The edge ring 180 may be moveable (e.g., moveable upward and downward in a vertical direction) relative to the substrate 108. For example, movement of the edge ring 180 may be controlled via an actuator responsive to the system controller 160. In some examples, a user may input control parameters to the system controller 160 via a user interface 184, which may include one or more input devices (e.g., keyboard, mouse, touchscreen), a display, etc. [0062] FIG. 2 includes a cross-sectional view of a portion of an example implementation of the substrate support 106. The TCEs 144 are embedded in the ceramic layer 112. A plurality of temperature sensors 204 are also embedded in the ceramic layer 112. Each of the temperature sensors 204 is spaced apart from each other one of the temperature sensors 204. In various implementations, the ceramic layer 112 may include one temperature sensor per TCE. The temperature sensors 204 may be located proximate to (e.g., within a predetermined distance of) the TCEs 144, respectively. For example, the temperature sensors 204 may be located between the TCEs 144, respectively, and the baseplate 110. The temperature sensors 204 measure temperatures at their respective locations.

[0063] The TCEs 144 are controlled by the temperature controller 142. The temperature controller 142 may control the application of power to the TCEs 144 individually. For example, switches may be connected in series with the TCEs 144, respectively, and the temperature controller 142 may control the switches to control the application of power to the TCEs 144, respectively. In various implementations, the temperature controller 142 may control the application of power to groups of two or more of the TCEs 144. For example, switches may be connected in series with groups of two or more the TCEs 144, and the temperature controller 142 may control the switches to control the application of power to the groups, respectively.

[0064] A first through hole 208 is formed through the baseplate 110 and the optical diffuser layer 114. The temperature sensors 204 are powered (e.g., by the temperature controller 142) via wires 212 that extend through the first through hole 208. One of the wires 212 is connected to a ground reference potential, and the other one of the wires 212 is connected to another reference potential.

[0065] For example, the temperature sensors 204 may be connected (e.g., in parallel) to two electrically conductive pads 214 located on a lower surface of the ceramic layer 112. The wires 212 may each be connected to one of the two electrically conductive pads 214. The temperature sensors 204 are connected to the electrically conductive pads 214 via wires embedded in or on the ceramic layer 112.

[0066] While the example of the first through hole 208 is provided, in various implementations, other ones of the temperature sensors 204 may be powered via wires extending through one or more other through holes through the baseplate 110. Also, while the example of connecting three of the temperature sensors 204 through the first through hole 208 is provided, a greater or lesser number of the temperature sensors 204 may be powered through the first through hole 208.

[0067] A second through hole 220 is also formed through the baseplate 110. At least one of the temperature sensors 204 optically transmits its measured temperature to the temperature controller 142 through the second through hole 220. In the example of two or more of the temperature sensors 204 optically transmitting their respective measured temperatures through the second through hole 220, the optical diffuser layer 114 includes features (e.g., mirrors, reflectors, baffles) 228 configured to direct (e.g., reflect) the light output by at least one of the two or more temperature sensors through the second through hole 220.

[0068] The temperature sensors 204 are fixed within recesses 224 in a lower surface of the ceramic layer 112. The temperature controller 142 may be implemented on a circuit board 232 that is fixed within a recess 236 in a lower surface of the baseplate 110. While the example of the second through hole 220 is provided, the baseplate 110 may be a multiple-piece baseplate and the temperature sensors 204 may optically transmit their measured temperatures through a space between different pieces of the baseplate 110.

[0069] FIG. 3 is a functional block diagram including an example implementation of a temperature control system of the substrate support 106 including one of the temperature sensors 204. As stated above, the temperature sensors 204 are fixed within the recesses 224 in lower surface of the ceramic layer 112.

[0070] The temperature sensors 204 each include a sensing element 304, a controller 308, and a first light source 312. The sensing element 304 may be, for example, a resistance temperature detector (RTD) or another suitable type of temperature sensor. The first light source 312 may be, for example, a light emitting diode (LED), a laser, or another suitable type of light source.

[0071] The sensing element 304 may directly contact the ceramic layer 112 or indirectly contact the ceramic layer 112. In the example of indirect contact, the sensing element 304 may contact the ceramic layer 112, for example, via a thermally conductive material (e.g., a thermally conductive paste).

[0072] The sensing element 304 and the controller 308 receive power via the wires 212 and the wires embedded in the ceramic layer 112. A temperature of the sensing element 304 varies as the temperature of the ceramic layer 112 at the location of the sensing element 304 changes. The sensing element 304 generates an output (e.g., voltage or current) based on the temperature of the sensing element 304. The sensing element 304 varies the output as the temperature of the sensing element 304 changes. For example, a resistance of the sensing element 304 may vary as temperature changes, and changes in the resistance of the sensing element 304 may vary the output of the sensing element 304.

[0073] The controller 308 may include a first clock 316, an analog to digital (A/D) converter 320, and a first light driver 324. The first clock 316 selectively generates a first clock signal. The first clock 316 may generate the first clock signal, for example, each first predetermined period or each predetermined number of received light pulses as further described below. Each time that the first clock 316 generates the first clock signal, the A/D converter 320 samples the (analog) output of the sensing element 304 and converts the sample into a digital value using A/D conversion.

[0074] Each predetermined number of times that the first clock signal is generated, the first light driver 324 turns the first light source 312 on and off in a pattern indicative of the temperature measured by the sensing element 304 at that time. The first light driver 324 determines the pattern based on the digital value, for example, using one of a function and a mapping that relates digital values to unique patterns of turning the first light source 312 on and off.

[0075] The first light driver 324 may determine the predetermined number, for example, based on a predetermined unique identifier of the one of the temperature sensors 204. The predetermined unique identifier may be, for example, a unique address of the one of the temperature sensors 204. The predetermined unique identifier of the one of the temperature sensors 204 may be stored in memory of the one of the temperature sensors 204.

[0076] The temperature sensors 204 may each have a different predetermined unique identifier such that the temperature sensors 204 each turn their respective lights on and off according to their respective patterns at different times. The temperature sensors 204 may each have a different predetermined unique identifier, for example, when two, more than two, or all of the temperature sensors 204 optically transmit their respective measure temperatures through the second through hole 220. In various implementations, each of the temperature sensors 204 may generate light at a different wavelength. The temperature sensors 204 can therefore be identified and distinguished from one another based on the wavelength and/or time when light is generated.

[0077] When the first light source 312 is on, light 328 from the first light source 312 travels through the second through hole 220. The light 328 may also travel through the optical diffuser layer 114. A first light receiver 332 is implemented on the circuit board 232 and receives light through the second through hole 220. The first light receiver 332 may be, for example, a phototransistor or another suitable type of light receiving device.

[0078] The first light receiver 332 generates a first output signal based on the light received. For example, the first light receiver 332 may set the first output signal to a first state when the light is received and set the first output signal to a second state when no light is received. The state of the first output signal of the first light receiver 332 therefore reflects the pattern that the first light source 312 is turned on and off.

[0079] A temperature module 336 receives the first output signal from the first light receiver 332 and determines the pattern included in the first output signal. The temperature module 336 determines the temperature measured by the one of the temperature sensors 204 based on the pattern in the first output signal. The temperature module 336 transmits the determined measured temperature and the identity of the corresponding temperature sensor 204 that measured the temperature to the temperature controller 142.

[0080] The temperature module 336 may determine which one of the temperature sensors 204 measured the temperature, for example, based on a predetermined order in which the temperature sensors 204 transmit their respective temperatures. The predetermined order is set based on the predetermined unique identifiers of the temperature sensors 204. Based on the predetermined unique identifiers, the temperature sensors 204 transmit their respective temperatures in the predetermined order.

[0081] In various implementations, the first light driver 324 may also turn the first light source 312 on and off to transmit the predetermined unique identifier (e.g., a string of binary values) of the corresponding temperature sensor 204. The first light driver 324 may turn the first light source 312 on and off to transmit the predetermined unique identifier before or after turning the first light source 312 on and off according to the pattern. The temperature module 336 may determine which one of the temperature sensors 204 measured the temperature based on the predetermined unique identifier included in the output signal of the first light receiver 332.

[0082] The temperature controller 142 receives from the temperature module 336 the temperatures measured respectively by the temperature sensors 204. The temperature controller 142 controls at least one of the TCEs 144 and the coolant assembly 146 based on the measured temperatures. For example, the temperature controller 142 may control one or more of the TCEs 144 to adjust the temperature measured by one of the temperature sensors 204 associated with the corresponding TCE 144 toward a target temperature. The temperature controller 142 may do the same for each other one of the TCEs 144 based on the temperatures measured respectively by the other temperature sensors 204 and other target temperatures, respectively.

[0083] In various implementations, each of the temperature sensors 204 may transmit light through a respective second through hole in the baseplate 110. In this example, the optical diffuser layer 114 may be omitted. One light receiver, such as the first light receiver 332, is included for each second through hole. FIG. 4 includes a cross- sectional view of a portion of an example implementation of the substrate support 106 where each of the temperature sensors 204 transmits light through a respective second through hole.

[0084] In various implementations, a second light source 340 may be used to trigger the temperature sensors 204 to transmit the respective measured temperatures. For example, the second light source 340 implemented on the circuit board 232 and transmit light through the second through hole 220. A second light receiver 344 may be implemented in the lower surface of the ceramic layer 112. Each of the temperature sensors 204 may include a second light receiver, such as the second light receiver 344. The optical diffuser layer 114 may reflect light to the second light receivers of other ones of the temperature sensors 204.

[0085] A second clock 346 selectively generates a second clock signal. The second clock 346 may generate the second clock signal, for example, each second predetermined period. Each time that the second clock 346 generates the second clock signal, a second light driver 347 may turn the second light source 340 on for a predetermined duration.

[0086] When the second light source 340 is on, light 348 from the second light source 340 travels through the second through hole 220. The light 348 may also travel through the optical diffuser layer 114. In various implementations, the optical diffuser layer 114 may reflect the light 348 to other ones of the temperature sensors 204. The second light receiver 344 receives light through the second through hole 220. The second light receiver 344 may be, for example, a phototransistor or another suitable type of light receiving device.

[0087] The second light receiver 344 generates a second output signal based on the light received. For example, the second light receiver 344 may set the second output signal to a first state when light is received and set the second output signal to a second state when no light is received. The state of the second output signal of the second light receiver 344 therefore reflects whether the second light source 340 is on and off.

[0088] The first clock 316 may generate the first clock signal each predetermined number of times that the second output signal of the second light receiver 344 transitions from the second state to the first state. As such, the temperature sensor 204 will transmit its measured temperature each predetermined number of times that the second output signal transitions from the second state to the first state.

[0089] Each of the temperature sensors 204 may have a different predetermined number such that the temperature sensors 204 transmit light at different times. For example, a first one of the temperature sensors 204 may transmit its measured temperature each first predetermined number of times that the second light source 340 is turned on, a second one of the temperature sensors 204 may transmit its measured temperature each second predetermined number of times that the second light source 340 is turned on, and so on.

[0090] As another example, the second clock signal can be transmitted to the temperature sensors 204 by wire and the second clock 346, the second light driver 347, the second light source 340 may be omitted. The temperature sensors 204 may transmit their respective measured temperatures each predetermined number of times that the second clock signal is generated. Each of the temperature sensors 204 may have a different predetermined number such that the temperature sensors 204 transmit light at different times.

[0091] As yet another alternative, the temperature sensors 204 may be electrically connected in parallel to power. The temperature sensors 204 (e.g., the controller 308) may each measure a power (e.g., voltage) applied to the temperature sensors 204. Each of the temperature sensors 204 may detect that one of the temperature sensors 204 is transmitting its measured temperature when the power applied to the temperature sensors 204 decreases relative to a predetermined power. Each of the temperature sensors 204 may transmit its respective measured temperature each predetermined number of times that one of the temperature sensors 204 is transmitting its measured temperature. Each of the temperature sensors 204 may have a different predetermined number such that the temperature sensors 204 transmit light at different times. The temperature sensors 204 may wait a predetermined delay period after transmission ends before beginning to transmit their respective measured temperatures.

[0092] FIG. 5 includes a flowchart depicting an example method of measuring one temperature using one of the temperature sensors 204 and, based on the temperature, controlling at least one of heating and cooling. Control begins with 504 where the A/D converter 320 determines whether the first clock signal has been generated by the first clock 316. If 504 is true, control continues with 508. If 504 is false, control remains at 504.

[0093] At 508, the A/D converter 320 of the one of the temperature sensors 204 samples the output of the sensing element 304 of the one of the temperature sensors 204 and digitizes the sample. As stated above, the output of the sensing element 304 varies with temperature. The first light driver 324 of the one of the temperature sensors 204 increments a counter value at 508. For example, the first light driver 324 may set the counter value equal to the (previous) counter value plus one.

[0094] At 512, the first light driver 324 determines whether the counter value is less than the predetermined number. The first light driver 324 may determine the predetermined number based on the predetermined unique identifier of the one of the temperature sensors 204. If 512 is true, control may return to 504. If 512 is false, control may continue with 520.

[0095] Based on the digital value from the A/D converter 320, the first light driver 324 determines the pattern for turning the first light source 312 on and off at 520. The first light driver 324 may determine the pattern, for example, using one of a function and a mapping that relates digital values to patterns of turning the first light source 312 on and off. At 524, the first light driver 324 turns the first light source 312 of the one of the temperature sensors 204 on and off according to the pattern. The first light driver 324 turns the first light source 312 on by applying power to the first light source 312. The first light driver 324 turns the first light source 312 off by disconnecting the first light source 312 from power. When on, the first light source 312 outputs light that is transmitted through the second through hole 220. The first light source 312 may transmit light directly through the second through hole 220, or the light output by the first light source 312 may be directed through the second through hole 220 via the optical diffuser layer 114.

[0096] At 528, the first light receiver 332 generates the output signal to indicate whether the first light source 312 is on or off. At 532, based on the output signal from the first light receiver 332, the temperature module 336 determines the pattern at which the first light source 312 was turned on and off. At 536, the temperature module 336 determines the temperature measured by the sensing element 304 of the one of the temperature sensors 204 based on the pattern. At 540, the temperature controller 142 controls at least one of the TCEs 144 and/or the coolant assembly 146 based on adjusting the temperature toward a target temperature, and control returns to 504. While the example of one of the temperature sensors 204 is provided, the example of FIG. 5 may be performed for each of the temperature sensors 204.

[0097] 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.

[0098] 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.”

[0099] In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A.

[0100] In this application, including the definitions below, the term“module” or the term “controller” may be replaced with the term“circuit.” The term“module” may refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

[0101] The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces that are connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules that are connected via interface circuits. For example, multiple modules may allow load balancing. In a further example, a server (also known as remote, or cloud) module may accomplish some functionality on behalf of a client module.

[0102] The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, data structures, and/or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that, in combination with additional processor circuits, executes some or all code from one or more modules. References to multiple processor circuits encompass multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that, in combination with additional memories, stores some or all code from one or more modules.

[0103] The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are nonvolatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random access memory circuit or a dynamic random access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

[0104] The apparatuses and methods described in this application may be partially or fully implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications, which can be translated into the computer programs by the routine work of a skilled technician or programmer. [0105] The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs may also include or rely on stored data. The computer programs may encompass a basic input/output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0106] The computer programs may include: (i) descriptive text to be parsed, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation) (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code for execution by an interpreter, (v) source code for compilation and execution by a just-in-time compiler, etc. As examples only, source code may be written using syntax from languages including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.

Claims

CLAIMS What is claimed is:

1. A substrate support for a plasma system, the substrate support comprising:

a first layer;

a temperature sensor configured to measure a temperature of the substrate support, and to, based on the measured temperature, transmit light through the first layer;

a light receiver configured to receive light through the first layer and to generate an output signal based on the light received through the first layer; and

a temperature module configured to determine the measured temperature based on the output signal.

2. The substrate support of claim 1 further comprising:

a second layer that is made of a ceramic,

wherein the second layer is disposed above the first layer, and

wherein the temperature sensor is in contact with the second layer.

3. The substrate support of claim 2 wherein the temperature sensor includes:

a sensing element configured to vary an output based on the measured temperature;

an analog to digital (A/D) converter configured to generate a digital value based on the output of the sensing element;

a light source configured to transmit light through the first layer; and

a light driver configured to control the light source based on the digital value.

4. The substrate support of claim 3 wherein the light driver is configured to:

determine a pattern for controlling the light source based on the digital value; and

control the light source according to the pattern.

5. The substrate support of claim 3 wherein the light source is a light emitting diode (LED).

6. The substrate support of claim 3 wherein the light receiver is configured to: set the output signal to a first state when the light source is on; and set the output signal to a second state when the light source is off.

7. The substrate support of claim 2 further comprising:

a thermal control element embedded within the second layer; and

a temperature controller configured to selectively apply power to the thermal control element based on the measured temperature.

8. The substrate support of claim 2 further comprising:

a temperature controller configured to control coolant flow through coolant channels in the first layer based on the measured temperature.

9. The substrate support of claim 2 wherein the temperature sensor is located within a recess in the second layer.

10. The substrate support of claim 2 further comprising:

first wires that extend through the first layer and that are connected to a power source; and

second wires that are embedded within the second layer and that connect the temperature sensor to the first wires.

11. The substrate support of claim 2 further comprising an optical diffuser layer that is located between the first layer and the second layer and that is configured to direct light through an aperture through the first layer.

12. The substrate support of claim 1 further comprising a through hole in the first layer,

wherein the temperature sensor transmits light through the through hole based on the measured temperature, and

wherein the light receiver receives the light through the through hole.

13. The substrate support of claim 1 wherein the light receiver is a phototransistor.

14. The substrate support of claim 1 wherein the temperature module is configured to determine a pattern in the output signal and to determine the measured temperature based on the pattern.

15. The substrate support of claim 14 wherein the pattern further includes a unique identifier corresponding to the temperature sensor and,

wherein the temperature module is configured to identify the temperature sensor based on the unique identifier.

16. The substrate support of claim 1 further comprising:

a plurality of additional temperature sensors configured to measure respective temperatures at corresponding locations of the substrate support, and to, based on the measured temperatures, transmit light through the first layer.

17. The substrate support of claim 16 further comprising:

a plurality of additional light receivers configured to receive light from the corresponding additional temperature sensors through the first layer and to generate respective output signals based on light received from the plurality of additional temperature sensors through the first layer,

wherein the temperature module is further configured to determine the respective measured temperatures based on the respective output signals from the plurality of additional light receivers.

18. The substrate support of claim 16 further comprising:

a plurality of thermal control elements embedded within a second layer; and a temperature controller configured to:

selectively apply power to the plurality of thermal control elements based on the temperatures measured by the temperature sensor and the plurality of additional temperature sensors.

19. The substrate support of claim 16 further comprising an optical diffuser layer configured to direct the light from the plurality of additional temperature sensors to the light receiver.

20. The substrate support of claim 1 wherein the light receiver is located within a recess in the first layer.

21. The substrate support of claim 1 wherein the first layer includes a baseplate.

22. An electrostatic chuck for a plasma system, the electrostatic chuck comprising: a ceramic layer;

a baseplate;

a thermal control element that is embedded in the ceramic layer; and

a temperature sensor configured to:

measure a temperature of the ceramic layer; and,

through a through hole in the baseplate, transmit light indicative of the measured temperature.

23. The electrostatic chuck of claim 22 wherein a circuit board is attached to the baseplate, and the circuit board includes:

a light receiver configured to receive the light transmitted by the temperature sensor;

a temperature module configured determine the measured temperature based on the received light; and

a temperature controller is configured to control the thermal control element based on the measured temperature.

24. The electrostatic chuck of claim 22 wherein the temperature sensor includes: a sensing element configured to vary an output based on the measured temperature;

a light source configured to transmit light through the through hole; and a light driver configured to control the light source based on the digital value.

25. The electrostatic chuck of claim 24 wherein the light driver is configured to:

control the light source according to the pattern.

26. The electrostatic chuck of claim 22 wherein the temperature sensor is located within a recess in the ceramic layer.

27. The electrostatic chuck of claim 22 further comprising:

first wires that extend through the baseplate and that are connected to a power source; and

second wires that are embedded within the ceramic layer and that connect the temperature sensor to the first wires.

28. The electrostatic chuck of claim 22 further comprising an optical diffuser layer that is located between the baseplate and the ceramic layer and that is configured to direct light through the through hole.

29. The electrostatic chuck of claim 22 further comprising:

a plurality of additional temperature sensors configured to measure a plurality of additional temperatures of the ceramic layer, respectively, and to transmit light indicative of the additional measured temperatures.

30. The electrostatic chuck of claim 29 further comprising an optical diffuser layer configured to direct the light from the plurality of additional temperature sensors through the through hole.