System and method for calibrating a control system of an electrically heated appliance

Abstract

A method for calibrating a control system configured to control a two-wire heater includes providing power to a load electrically coupled to the control system; calibrating, by the control system and a controller, respectively, an initial measured characteristic and a calibrated measured characteristic of the load. The method further includes defining a calibrated measured reference based on a correlation of the initial measured characteristic and the calibrated measured characteristic. With the calibrated measured reference, the control system is further calibrated to define a resistance-temperature calibration reference for determining an operating temperature of the two-wire heater based on a measured resistance of the two-wire heater.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to and the benefit of U.S. Provisional Application 62 / 858,587, filed June 7, 2019. The disclosure of the above application is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to a control system that calibrates a control of an electric heater. BACKGROUND

[0004] The statements in this section merely provide background information related to the present disclosure and can not constitute prior art.

[0005] Heaters for semiconductor processing typically include a heater plate having a substrate and resistive heating elements disposed in the substrate for defining one or more heating zones. In some applications, the resistive heating elements function as both a heater and as a temperature sensor, having only two leads operably connected to the resistive heating elements instead of four (e.g., two for the heating element and two for a separate temperature sensor). In one form, such resistive heating elements can be defined by a relatively high temperature coefficient of resistance (TCR) material, and the temperature of the resistive heating elements can be determined based on the resistance of the heating elements.

[0006] In one application, the heater is controlled by a control system that measures the temperature of the resistive heating elements based on the resistance of the heating elements. To control the heater, the control system calculates the resistance based on measurements of voltage and / or current and determines the temperature of each zone based on the calculated resistance. While standardized information, such as a table correlating resistance values to temperature for a given resistive heater material, can be used, the heater can operate differently from one another even if the heater is of the same type. This can be caused by, for example, manufacturing variances, material lot variances, aging of the heater, number of cycles, and / or other factors, which results in inaccuracies in the calculated temperature. These and other issues associated with the use of two-wire resistive heaters are addressed by the present disclosure. SUMMARY

[0007] This section provides a general summary of the disclosure and not a comprehensive disclosure of its full scope or all of its features.

[0008] In one form, the disclosure relates to a method for calibrating a control system configured to control a two-wire heater operable to generate heat and function as a sensor for measuring electrical characteristics of the two-wire heater. The method includes providing, by the control system, power to a load electrically coupled to the control system; generating, by the control system, an initial measured characteristic of the load; and generating, by a controller coupled to the load, a calibrated measured characteristic of the load. The initial measured characteristic and the calibrated measured characteristic are indicative of an electrical characteristic of the load. The electrical characteristic of the load includes a voltage, a current, a resistance, or a combination thereof. The method further includes correlating the initial measured characteristic with the calibrated measured characteristic; and defining a calibrated measurement reference based on the correlation of the initial measured characteristic and the calibrated measured characteristic. The control system employs the calibrated measurement reference to provide accurate measurements for controlling the two-wire heater.

[0009] In another form, generating, by the control system, the initial measured characteristic further includes measuring, by the control system, an initial voltage and an initial current of the load. The initial measured characteristic includes the initial voltage and the initial current. Generating, by the controller coupled to the load, the calibrated measured characteristic further includes measuring, by the controller coupled to the load, a calibrated voltage and a calibrated current of the load. The calibrated measured characteristic includes the calibrated voltage and the calibrated current. The initial voltage and the calibrated voltage are measured simultaneously, and the initial current and the calibrated current are measured simultaneously.

[0010] In yet another form, the method further includes calculating an initial resistance of the load based on the initial voltage and the initial current of the load, and calculating a calibrated resistance of the load based on the calibrated voltage and the calibrated current of the load. The initial measured characteristic further includes the initial resistance and the calibrated measured characteristic further includes the calibrated resistance.

[0011] In one form, power is provided to the load at a plurality of power set points. For each of the plurality of power set points, the initial measured characteristic is generated by the control system and the calibrated measured characteristic is generated by the controller coupled to the load to provide a plurality of initial measured characteristics and a plurality of calibrated measured characteristics. The plurality of initial measured characteristics are correlated with the plurality of calibrated measured characteristics, and a calibrated measurement reference is defined based on the correlation of the plurality of initial measured characteristics and the plurality of calibrated measured characteristics.

[0012] In another form, the load is a controllable load having an adjustable resistance, and the method further includes setting the resistance of the load to a plurality of resistance set points, and for each of the plurality of resistance set points, generating an initial measurement characteristic by the control system and a calibrated measurement characteristic by the controller to provide a plurality of initial measurement characteristics and a plurality of calibrated measurement characteristics. The plurality of initial measurement characteristics are correlated to the plurality of calibrated measurement characteristics, and a calibrated measurement reference is defined based on the correlation of the plurality of initial measurement characteristics and the plurality of calibrated measurement characteristics.

[0013] In another form, where the control system is electrically coupled to the dual wire heater, the method further includes controlling, by the control system, the dual wire heater to a temperature set point from among a plurality of temperature set points, while acquiring, from the control system, a voltage and current (V-I) characteristic of the dual wire heater and acquiring, from the temperature sensor system, a temperature data set of the dual wire heater. The V-I characteristic and the temperature data set are acquired for each of the plurality of temperature set points. The method further includes determining, for each of the plurality of temperature set points, a resistance of the dual wire heater based on the acquired V-I characteristic and the calibrated measurement reference, calculating, for each of the plurality of temperature set points, temperature metrology data based on the acquired temperature data set, correlating the resistance of the dual wire heater and the temperature metrology data of the plurality of temperature set points, and defining, based on the measured resistance of the dual wire heater, a resistance-temperature calibration reference for determining an operating temperature of the dual wire heater.

[0014] In one form, acquiring, from the control system, the V-I of the dual wire heater and from the temperature sensor system, the temperature data set of the dual wire heater further includes measuring, by a sensor circuit of the control system, the V-I characteristic of the dual wire heater; and measuring, by the temperature sensor system, a plurality of temperature measurements of the dual wire heater at the temperature set point. The plurality of temperature measurements are provided as the temperature data set of the temperature set point.

[0015] In another form, the temperature metrology data includes an average temperature, a median temperature, a temperature variation, a standard deviation, a maximum temperature, a minimum temperature, a temperature range, a 3-sigma value, or a combination thereof.

[0016] In yet another form, the load is an active resistance bank having an adjustable resistance.

[0017] In one form, the disclosure relates to a method for calibrating a control system configured to operate a dual wire heater. The dual wire heater is operable to generate heat and function as a sensor for measuring a temperature of the dual wire heater. The method includes controlling, by the control system, the dual wire heater to a temperature setpoint from among a plurality of temperature setpoints while obtaining, from the control system, a voltage and current (V-I) characteristic of the dual wire heater and obtaining, from a temperature sensor system, a temperature data set of the dual wire heater. The V-I characteristic and the temperature data set are obtained for each of the plurality of temperature setpoints. The method further includes determining, based on the obtained V-I characteristic, a resistance of the dual wire heater for each of the plurality of temperature setpoints, calculating, based on the obtained temperature data set, a temperature metrology data for each of the plurality of temperature setpoints, correlating the resistance of the dual wire heater and the temperature metrology data of the plurality of temperature setpoints, and defining, based on the measured resistance of the dual wire heater, a resistance-temperature calibration reference for determining an operating temperature of the dual wire heater.

[0018] In another form, obtaining the V-I characteristic and the temperature data set of the dual wire heater further includes measuring, by a sensor circuit of the control system, the V-I characteristic of the dual wire heater, and measuring, by the temperature sensor system, a plurality of temperature measurements of the dual wire heater at the temperature setpoint. The plurality of temperature measurements are provided as the temperature data set of the temperature setpoint.

[0019] In yet another form, the temperature metrology data includes an average temperature, a median temperature, a temperature variation, a standard deviation, a maximum temperature, a minimum temperature, a temperature range, a 3-sigma value, or a combination thereof.

[0020] In one form, the dual wire heater includes a plurality of resistive heating elements defining a plurality of zones, the control system is configured to independently control each zone, the V-I characteristic of the dual wire heater obtained from the control system includes a V-I characteristic of each of the plurality of zones. The V-I characteristic of a zone from among the plurality of zones is provided as a zone characteristic. The temperature data set of the dual wire heater obtained from the temperature sensor system includes at least one temperature measurement of each of the plurality of zones.

[0021] In another form, controlling, by the control system, the dual wire heater to the temperature setpoint further includes providing power to the plurality of zones of the dual wire heater, obtaining a temperature of each of the plurality of zones of the dual wire heater, and adjusting the power to the plurality of zones in response to the temperature from one or more zones from among the plurality of zones not equaling the temperature setpoint.

[0022] In yet another form, the temperature sensor system includes a plurality of temperature sensors, and the method further includes, for each of the plurality of zones, associating one or more temperature sensors from among the plurality of temperature sensors with a respective zone. The one or more temperature sensors are configured to provide a temperature measurement of the respective zone.

[0023] In one form, each of the plurality of zones is associated with two or more temperature sensors from among the plurality of temperature sensors. The two or more temperature sensors are provided as a sensing group, and the method further includes, for each sensing group, performing a sensor diagnostic to identify a faulty temperature sensor from among the temperature sensors of the sensing group based on temperature measurements from the sensing group; in response to the sensor diagnostic identifying a faulty temperature sensor and when the number of identified faulty temperature sensors is less than a fault sensor threshold, discarding temperature measurements from the faulty temperature sensors; and in response to the sensor diagnostic identifying a faulty temperature sensor and when the number of identified faulty temperature sensors is greater than the fault sensor threshold, shutting off power to the dual wire heater.

[0024] In another form, each of the plurality of zones is associated with two or more temperature sensors from among the plurality of temperature sensors and the two or more temperature sensors are provided as a sensing group. The method further includes calculating zone temperature metrology data for each sensing group based on temperature measurements from the two or more temperature sensors of the respective sensing group.

[0025] In yet another form, the zone temperature metrology data includes an average temperature, a median temperature, a temperature variation, a standard deviation, a maximum temperature, a minimum temperature, a temperature range, a 3-sigma value, or a combination thereof.

[0026] In another form, in response to the sensor diagnostic not identifying a faulty temperature sensor, or when the number of identified faulty temperature sensors is less than a fault sensor threshold, the method further includes determining a resistance of the dual wire heater for each of the plurality of temperature set points based on the acquired V-I characteristics; calculating temperature metrology data for each of the plurality of temperature set points based on the temperature data set; correlating the resistance of the dual wire heater and the temperature metrology data of the plurality of temperature set points; and defining a resistance-temperature calibration reference for determining an operating temperature of the dual wire heater based on the measured resistance of the dual wire heater.

[0027] Further areas of application will become apparent from the description provided herein. It should be understood that the description and specific examples, while indicating embodiments of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0028] For a better understanding of the present disclosure, various forms thereof will now be described, by way of example only, with reference to the drawings in which:

[0029] Figure 1 is a block diagram of a thermal system having a multi-zone heater and control system in accordance with the present disclosure;

[0030] Figure 2 is a block diagram of a control system; Figure 1

[0031] Figure 3 is a block diagram of a calibration system for calibrating a control system Figure 1

[0032] Figure 4 is a block diagram of a calibration device for calibrating a multi-zone heater Figure 1

[0033] Figure 5 illustrates grouping of multiple thermocouples for a thermocouple wafer in accordance with the present disclosure;

[0034] Figure 6 illustrates a calibration device for calibrating a control system and a multi-zone heater in accordance with the present disclosure;

[0035] Figure 7 is a flowchart of an exemplary control system calibration routine; and

[0036] Figure 8 is a flowchart of an exemplary heater calibration control routine.

[0037] The drawings described herein are for purposes of illustration only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0038] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0039] A control system for a multi-zone heater having resistive heating elements operable as heaters and temperature sensors includes customizable feedback control for selectively adjusting a thermal profile of the heater based on measured electrical characteristics of the heater. To perform feedback control for a particular multi-zone heater, the control system is calibrated to accurately measure electrical characteristics (e.g., voltage, current, and / or resistance) of the heater over a wide voltage range (e.g., 1-240 V) and a wide current range (10-30 A).

[0040] ​​​More specifically, in one form, the control system simultaneously measures voltage and current (e.g., voltage and current measured within ± 140 μβ) and calculates resistance based on the measurements. In the event that the power waveform varies over time, the current and voltage measurements become closer and closer to each other to obtain an accurate resistance value (e.g., ± 0.005 ohms, ± 0.010 ohms, or other tolerance). Additionally, due to variations between similar heater types, the control system performs a calibration process to obtain resistance-temperature calibration data specific to the heater controlled by the control system to accurately calculate the temperature of the heater based on the resistance.

[0041] The present disclosure relates to calibration processes for calibrating the measurement capabilities of a control system and for generating resistance-temperature calibration data. Hereinafter, these processes are identified as: (I) calibration of control system measurements; and (II) calibration of resistance-temperature of a heater. In the figures, power lines are shown as dashed lines, while data signal lines are provided as solid lines.

[0042] To better understand the application of the two calibration processes, an example configuration of a thermal system having a heater (such as a multi-zone heater in one form) and a control system is first provided. Referring to Figure 1 and Figure 2 , the thermal system 100 includes a multi-zone susceptor heater 102 and a control system 104 having a heater controller 106 and a power converter system 108. In one form, the heater 102 includes a heating plate 110 and a support shaft 112 disposed at a bottom surface of the heating plate 110. The heating plate 110 includes a substrate 111 and a plurality of resistive heating elements (not shown) embedded in the substrate 111 or disposed along a surface of the substrate. The substrate 111 can be made of ceramic or aluminum. The resistive heating elements are independently controlled by the controller 106 and define a plurality of heating zones 114, as shown by the dotted lines in the figure. These heating zones 114 are merely exemplary and can take any configuration while still being within the scope of the present disclosure.

[0043] In one form, the heater 102 is a "two-wire" heater in which the resistive heating element functions as both a heater and as a temperature sensor, with only two leads operably connected to the heating element, rather than four. Such two-wire capability is disclosed, for example, in U.S. Patent No. 7,196,295, which is commonly assigned with the present application and is incorporated herein by reference in its entirety. Typically, in a two-wire system, the resistive heating element is defined by a material that exhibits a change in resistance with a change in temperature, such that the average temperature of the resistive heating element is determined based on the change in resistance of the heating element. In one form, the resistance of the resistive heating element is determined by first measuring the voltage across the heating element and the current through the heating element, and then using Ohm's Law to determine the resistance. The resistive heating element can be defined by a material with a relatively high temperature coefficient of resistance (TCR), a negative TCR material, or a material with a non-linear TCR.

[0044] The control system 104 controls the operation of the heater 102, and more specifically, is configured to independently control the power to each of the zones 114. In one form, the control system 104 is electrically coupled to the zones 114 via the channels 115, such that each zone 114 is coupled to a channel 115 having two terminals (not shown) for providing power and sensing temperature.

[0045] In one form, the control system 104 is electrically coupled to a computing device 117 (e.g., a computer having one or more human interface devices, such as a display, a keyboard, a mouse, a speaker, a touchscreen, etc.). In one form, the control system 104 is coupled to a power source 118 that provides an input voltage (e.g., 240V, 208V) to the power converter system 108 through an interlock 120. The interlock 120 controls the power flowing between the power source 118 and the power converter system 108 and is operable by the heater controller 106 as a safety mechanism to shut off power from the power source 118. Although shown in Figure 1 In one form, the control system 104 can not include the interlock 120.

[0046] The power converter system 108 is operable to regulate the input voltage to apply a desired power output (e.g., a desired output voltage (V OUT). In one form, the power converter system 108 includes a plurality of power converters 122 (122-1 through 122-N in the figure) operable to apply an adjustable power output to the resistive heating elements of a given zone 114 (114-1 through 114-N in the figure). One example of such a power converter system is described in co-pending application U.S. Serial No. 15 / 624,060, filed June 15, 2017, entitled "Power Converter for a Thermal System," which is commonly owned with the present application and the contents of which are incorporated herein by reference in their entirety. In this example, each power converter includes a buck converter operable by the heater controller to generate a desired output voltage less than or equal to the input voltage of the heating element(s) of a given zone 114. Thus, the power converter system is operable to provide a customizable amount of power (i.e., a desired power output) to each zone of the heater.

[0047] In the case of a two-wire heater, the control system 104 includes sensor circuitry 124 (i.e., 124-1 through 124-N in the figure) to measure the voltage and / or current of the resistive heating elements, which is then used to determine performance characteristics of the zones, such as resistance, temperature, and other suitable information. In one form, a given sensor circuit 124 is configured to measure the current flowing through the heating element(s) in a given zone 114 and the voltage applied to the heating element(s) in that given zone, as shown by the ammeter 126 and voltmeter 128 in the figure. Figure 2

[0048] In one form, the sensor circuitry 124 is provided as a power metering chip to measure the current and voltage simultaneously, regardless of the power applied to the heating elements. In another form, the voltage and / or current measurements can be taken at zero-crossing, as described in U.S. Patent No. 7,196,295. Figure 2 The sensor circuitry 124-1 through 124-N is shown, where each sensor circuit 124 is coupled to the circuit between a given power converter 122 and a given zone 114 to measure the electrical characteristics of the heating element(s) of the given zone. In one form, each ammeter 126 includes a shunt 130 to measure the current, and each voltmeter 128 includes a voltage divider 132 represented by resistors 132-1 and 132-2. Alternatively, the ammeters 126 can use a Hall effect sensor or a current transformer instead of the shunt 130 to measure the current.

[0049] In one form, the ammeters 126 and voltmeters 128 are provided as a power metering chip to measure the current and voltage simultaneously, regardless of the power applied to the heating elements. In another form, the voltage and / or current measurements can be taken at zero-crossing, as described in U.S. Patent No. 7,196,295.

[0050] ​Based on the current and voltage measurements, the heater controller 106 determines the resistance and, thus, the average temperature of the resistive heating element defining the zone 114. The heater controller 106 includes one or more microprocessors and memory for storing computer readable instructions executed by the microprocessors. The controller 106 is configured to execute one or more control processes in which the controller 106 determines a desired power to be applied to the zone, such as 100% of the input voltage, 90% of the input voltage, etc. An example control process is described in co-pending application U.S. Serial No. 15 / 624,060 and co-pending application U.S. Serial No. 16 / 100,585, filed August 10, 2018, and entitled “System and Method for Controlling Power to a Heater,” which is commonly owned with the present application and the contents of which are incorporated by reference herein in their entirety.

[0051] It should be readily appreciated that while particular components are shown and described, the thermal system can include other components while still being within the scope of the present disclosure. For example, in one form, the control system 104 can include electronic components that isolate low voltage components from high voltage components and still allow the components to exchange signals.

[0052] (I) Calibration of control system measurements

[0053] Referring to Figure 3 , the controller calibration system 200 is configured to calibrate the current and voltage measurements made by the control system 104. In Figure 3 , the channels 115 are not shown and the sensor circuit 124 is broadly represented as having a current meter 126 and a voltage meter 128 to facilitate showing the calibration process. The controller calibration system 200 includes a precision power supply 204, a controllable load 206, a high precision current meter 208, a high precision voltage meter 210, and a calibration controller 212. The precision power supply 204 is electrically connected to the control system 104 through a power supply input interface (not shown) to provide a stable and precise power supply to the control system 104 during the calibration process to suppress or reduce power variations (e.g., ±0.01 V). In one form, the precision power supply 204 is operable to provide a wide range of voltages and a wide range of currents to the control system 104 and can be one or more DC power supplies. For example, the precision power supply 204 can include a set of DC power supplies, such as CHROMA Model 62012 DC power supplies. The precision power supply 204 can also be one or more AC power supplies. It should be readily appreciated that the precision power supply 204 can be other suitable power supplies and should not be limited to CHROMA Model 62012 DC power supplies.

[0054] The controllable load 206 is electrically coupled to the control system 104 via a cable interface (not shown) to provide a stable current load that exhibits minimal to no variation during precision measurements. In an example application, the controllable load 206 is an active load bank (e.g., an electronic load bank) to generate a known load with zero to minimal error, such as a CHROMA Model 63600 load device. In one form, the controllable load 206 is controllable by the calibration controller 212 such that the calibration controller 212 sets the resistance of the load 206. In another form, the controllable load 206 can be a fixed resistance load and thus not controlled by the calibration controller 212. In such a form, the calibration controller 212 can not be connected to the controllable load 206. It should be readily understood that the controllable load 206 can be other suitable controllable loads and should not be limited to the CHROMA Model 63600 load device.

[0055] A high-precision (HP) ammeter 208 and a high-precision (HP) voltmeter 210 are configured to measure the current through the controllable load 206 and the voltage applied to the controllable load 206, respectively. In one form, the HP ammeter 208 measures the current through a shunt 214 based on the voltage across the shunt 214 and a known resistance of the shunt 214, although other types of ammeters 208 can be used while still within the scope of the present disclosure. In one form, the HP ammeter 208 and the HP voltmeter 210 are provided as multimeters having 7.5 digit resolution. For example, the HP ammeter 208 and the HP voltmeter 210 can be PXI-7 1 / 2 digital multimeters. In one form, the current measurement by the HP ammeter 208 is taken simultaneously with the current measurement by the ammeter 126 of the sensor circuit 124, and the voltage measurement by the HP voltmeter 210 is taken simultaneously with the voltage measurement by the voltmeter 128 of the sensor circuit 124 to calibrate the current and voltage measurements of the control system with the current and voltage measurements of the HP ammeter 208 and the HP voltmeter 210. The HP ammeter 208 and the HP voltmeter 210 can be collectively referred to herein as precision voltage-current (V-I) sensors 208 and 210.

[0056] In one form, the calibration controller 212 is a computer having one or more microprocessors and memory for storing computer readable instructions executed by the microprocessors. The calibration controller 212 is communicably coupled to one or more human interfaces (not shown), such as a monitor, mouse, keyboard, speaker, to communicate with a user performing the calibration.

[0057] The calibration controller 212 is communicably coupled to the precision power supply 204 to set the input voltage applied to the control system 104 and the precision V-I sensors 208 and 210 to obtain current and voltage measurements (i.e., precision current-voltage data or calibrated measurement characteristics). In one form, the calibration controller 212 is communicably coupled to the control system 104 to exchange data with the control system 104, such as measurements made by the sensor circuit(s) 124. In one form, the calibration controller 212 obtains voltage and current measurements from the precision V-I sensors 208 and 210 and the sensor circuit(s) 124 at approximately the same time (i.e., simultaneously). In another form, the calibration controller 212 obtains voltage measurements from the HP voltmeter 210 and the sensor circuit(s) 124 at the same time and current measurements from the HP ammeter 208 and the sensor circuit(s) 124 at a different time than the voltage measurements.

[0058] In one form, where the four measurements are obtained simultaneously, the calibration controller 212 is configured to determine the control system resistance based on the measurements from the sensor circuit 124 and the calibrated resistance based on the measurements from the precision V-I sensors 208 and 210. In one form, the control system 104 calculates resistance based on the root mean square (RMS) of the current and voltage measurements and can therefore include a true RMS converter that measures RMS current and RMS voltage simultaneously using a high sampling rate (e.g., 140 μβ or 7 kHz to allow for accurate observation of the power waveform). In another form, the control system 104 is configured to measure peak current and peak voltage simultaneously using the precision V-I sensors 208 and 210, which can sample, for example, once every 10 ms for 50 Hz and once every 8.3 ms for 60 Hz, respectively. The voltage current ratio provides resistance readings over a range of voltages and odd waveforms. This approach yields measurements that are substantially consistent with pure DC signals and AC signals of various shapes and mixed AC / DC systems.

[0059] Because the control system 104 measures the resistance of the plurality of zones 114 using a plurality of sensor circuits 124, the voltage and current measurements from each sensor circuit 124 are calibrated. The measurements from the sensor circuits 124 can be obtained one at a time, one after another, or even in groups. For example, in one configuration, each channel 115 is connected to a controllable load 206 and one set of precision V-I sensors 208 and 210 is configured to measure the current and voltage at each load 206. The control system 104 can then apply power to each load 206 via the power converter system 108 and obtain measurements from each sensor circuit 124. Further, the calibration controller 212 obtains measurements from each set of precision V-I sensors 208 and 210. Thus, measurements from all of the sensor circuits 124 can be obtained at one time. In another configuration, the measurements from the sensor circuits 124 are obtained one at a time or in groups based on the number of controllable loads 206 and sets of precision V-I sensors 208 and 210 available. For example, with one controllable load 206 and one set of precision V-I sensors 208 and 210, the controllable load 206 is connected to a selected channel 115 and the control system 104 is operable to transmit power to the selected channel 115 and obtain measurements from the sensor circuit 124 associated with the selected channel 115.

[0060] To distinguish between the electrical characteristic(s) measured by the control system 104 and the controller calibration system 200, the measurements made by the control system 104 can be referred to as initial measured characteristics of the load and can include an initial voltage, an initial current, and / or an initial resistance. The initial measured characteristics are indicative of the electrical characteristics of the load. Further, the measurements made by the controller calibration system 200 can be referred to as calibrated measured characteristics of the load and can include a calibrated voltage, a calibrated current, and / or a calibrated resistance. The calibrated measured characteristics are indicative of the electrical characteristics of the load.

[0061] Because the control system 104 is configured to calculate resistance over a wide range of power levels, the calibration controller 212 calibrates the control system 104 at different power levels (i.e., power set points). For example, the calibration controller 212 is configured to apply at least one low power amount (e.g., 10 V) and at least one high power amount (e.g., 130 V) via the precision power supply 204. In one form, the current is calibrated by holding the voltage constant and changing the programmable load to different resistive loads (i.e., resistance set points) to provide at least one low current point (such as 5 A) and at least one high current calibration point (such as 15 A). In yet another form, the calibration controller 212 can cause the control system 104 to apply a full power amount (e.g., 100% of the input voltage) or a reduced power amount (e.g., 90% or 75% of the input voltage) to the load 206 via the power converter system 108.

[0062] In one form, the calibration controller 212 correlates the measurements from the control system 104 with the measurements from the precision V-I sensors 208 and 210 to calibrate the measurements made by the control system 104. In particular, the calibration controller 212 defines correlation data (or in other words a calibrated measurement reference) that maps the measurements from the control system 104 (i.e., the initial measurement characteristic(s)) with the measurements from the precision V-I sensors 208 and 210 (i.e., the calibrated measurement characteristic(s)) to improve the accuracy and control of the heater. The correlation data can also include a resistance calculated based on the measurements (i.e., the control system resistance and / or the calibrated resistance). In one form, the correlation data can be provided as a statistical relationship (e.g., a linear model), an algorithm, or other suitable correlation stored by the heater controller 106. In another form, the correlation data can be a table that correlates the measurements from the precision V-I sensors 208 and 210 with the measurements made by the sensor circuit 124. The table can also include the resistance(s) calculated by the calibration controller 212. Thus, in one form, the calibrated measurement reference is based on a correlation of the initial measurement characteristic(s) from the control system 104 and the calibrated measurement characteristic(s) from the controller calibration system 200. In another form, instead of the calibration controller 212 generating the correlation data, the control system 104 is configured to generate the correlation data. For example, the calibration controller 212 can provide data, such as the measurements from the precision V-I sensors 208 and 210, to the control system 104, and the heater controller 106 of the control system 104 uses these measurements and the measurements from the sensor circuit 124 to generate the correlation data.

[0063] Instead of a DC power supply, the calibration system can include an AC power supply. In such a configuration, the AC power supply is provided to a low temperature coefficient resistor that is capable of operating at high currents (e.g., 20 amps) and is actively cooled. The control system 104 and the calibration controller 212 measure the known resistance over the AC voltage range (e.g., 1 to 208 V) and the power modulation range (e.g., 0 to 100%) of the control system 104.

[0064] The control system 104 for the multi-zone heater 102 operates as both a power delivery device and a high precision ohmmeter. An ohmmeter typically provides only a small amount of power to the resistance being measured without disturbing the system, but enough to get a good signal. Here, the control system 104 delivers a large amount of power and also senses the resistance of the resistive heating elements being driven with the same precision as a precision ohmmeter, while delivering the power in the form of high current and high voltage. Calibration and sensing under these conditions is a significant challenge. The calibration system of the present disclosure: (1) provides controllable electrical stimulus to a known load via the control system 104 at low voltage(s) and high voltage(s); (2) for each power setpoint, acquires the electrical characteristics of the load from the control system 104 and measures the electrical characteristics of the load using high precision current and voltage meters; and (4) correlates the measurements made by the high precision meters with the measurements of the control system 104 to calibrate the measurements of the control system 104. Thus, the current and voltage measurements, and hence the resistance measured by the control system 104, are calibrated to achieve high precision resistance measurements (e.g., ±0.005 ohms or better).

[0065] (II) Resistance-temperature calibration of dual wire heater

[0066] With a two-wire heater, the control system 104 determines the temperature of a zone 114 based on the resistance of the resistive heating element of the given zone 114. To determine the temperature, the control system 104 includes resistance-temperature calibration data (i.e., a resistance-temperature calibration reference) that associates a plurality of resistances with corresponding temperature measurements. As described herein, the control system 104 is configured to perform heater calibration control to generate and store this calibration data, which is used during standard operation to measure the temperature of the zones and control the power to the resistive heating elements. The heater calibration control of the present disclosure can be performed for a two-wire heater having one or more zones, and should not be limited to a multi-zone heater.

[0067] Referring to Figure 4 The thermal system 100, including the control system 104 and the heater 102, is calibrated using a temperature sensor system 300 that measures the temperature of the zones 114 of the heater 102 and outputs the measurements to the control system 104.

[0068] In one form, the temperature sensor system 300 is a thermocouple (TC) wafer 302 having a wafer 304 and a plurality of TCs 308 distributed along the wafer 304. During calibration, the TC wafer 302 is positioned on the multi-zone heater 102 and secured to the surface using various methods, such as generating a negative pressure in a chamber that houses the heater 102 and the TC wafer 302, bonding the TC wafer 302 to the heater 102, or by gravity. The temperature sensor system 300 can be other suitable sensor(s) and should not be limited to a thermocouple wafer. For example, the temperature sensor system 300 can be provided as a TC clamp that probes the surface of the heater 102 with a TC spring-loaded sensor array. In another example, the temperature sensor system 300 is an infrared camera that captures thermal images of the surface of the heater 102.

[0069] In one form, the TCs of the TC wafer are configured in a plurality of groups that correspond to the thermal control zones 114 of the heater 102. For example, in Figure 5 , the TC wafer 350 includes 26 TCs (indicated by arrows) distributed around the TC wafer 350. The TCs are arranged in six groups, with group 1 having 6 TCs and groups 2, 3, 4, 5, and 6 each having 4 TCs. Group 1 is associated with a zone disposed at a central region of the heater 102 and groups 2-6 are associated with one or more zones disposed along an outer ring of the heater 102. The TCs of the TC wafer can be grouped in various suitable ways to associate with the zones of the heater 102 and should not be limited to the configuration shown in Figure 5 .

[0070] The control system 104 includes an input / output interface (not shown) for connecting to the TC wafer 302. For example, Figure 6 An example configuration is shown in which the susceptor heater 400 will receive a TC wafer 402. The TC wafer includes a plurality of TC sensors having a plurality of leads extending from the TC sensors. In one form, the TC sensors are connected to a control system 404 through a TC scanner system 406 for monitoring measurements from the TC sensors. The TC sensors can be connected to the control system 404 in other suitable ways and should not be limited to the TC scanner system 406. Through a wired connection, a heater controller of the control system 404 receives temperature measurements, such as an average temperature of a zone, a discrete temperature measurement from each TC, a standard deviation of the TCs from the TC wafer 402, etc. The heater 400 and the control system 404 are similar to the heater 102 and the control system 104, respectively.

[0071] Reference is made to Figure 4In one form, the heater calibration controller 310 maps the TC sensors 308 to their respective temperature measurements and maps the temperature measurements to their physical locations on the TC wafer 302 based on a wired connection between the TC wafer 302 and the control system 104. Thus, the temperature measurements are further associated with defined groups corresponding to the thermal control zones on the heater 102, and thus the sensor groups are identified for a given zone of the heater 102.

[0072] In one form, the heater calibration controller 310 heats the heater to a plurality of temperature set points such that the heater 102 has a uniform heat distribution. For each temperature set point, the heater calibration controller 310 receives temperature measurements from the TC sensors 308 and electrical characteristic (e.g., voltage and / or current) measurements from the sensor circuit 124. Based on the temperature measurements (i.e., a temperature data set), the heater calibration controller 310 generates temperature metrology data for each group for a given set point, which can include at least one of: an average temperature corresponding to an average temperature of the respective heater zone associated with the group; a median temperature; a variation in temperature corresponding to a variation in the respective heater zone; a standard deviation in temperature corresponding to a standard deviation in the respective heater zone; a maximum temperature; a minimum temperature; a temperature range; a 3-sigma value; and indices of the minimum, maximum, and median sensors in the group. Although specific metrology data is listed, other metrology data can be computed by the heater calibration controller 310 based on the temperature measurements.

[0073] In addition to determining metrology data for each group, the heater calibration controller 310 computes metrology data for the entire TC wafer 302, and thus the heater 102 as a whole. For example, average temperatures, median temperatures, maximum temperatures, minimum temperatures, and other metrology data are computed based on all of the temperature measurements. These metrics are used to monitor and control the heater 102 to provide a uniform heat distribution across the surface of the heater 102, and not just a single zone.

[0074] In one form, the heater calibration controller 310 correlates the mean (average) temperature of a given group to the average temperature of the corresponding zone. Based on the voltage and / or current measured for the zone at the time of temperature measurement, the heater calibration controller 310 determines the resistance of the resistive heating element of the zone and correlates the resistance of the zone to the average temperature of the corresponding group. In one form, the heater calibration controller 310 employs a calibrated measurement reference in determining the electrical characteristics (i.e., voltage, current, and / or resistance). The resistance of the resistive heating element is saved for each zone at each set point as part of the resistance-temperature calibration data. With the resistance-temperature calibration data, the control system 104 can use the resistance as a direct representation of the true temperature to precisely control the zones via the temperature it senses. Instead of or in addition to the average temperature, other measures can alternatively be used as the control source, such as the range, median, minimum, and maximum.

[0075] The heater calibration controller 310 can further perform diagnostics on the temperature sensor system 300 to identify possible faulty sensors using one or more of the measures of data. That is, sensors can fail for various reasons, such as normal wear and tear, overuse, and environmental conditions, and abnormal readings from the sensors skew the temperature calibration, resulting in poor uniformity. In one form, to detect a faulty sensor in a given group, the heater calibration controller 310 compares the temperature measurements from the sensors to the median temperature of the given group. If the temperature reading deviates from the median value by a predetermined amount (i.e., ±10°C), the heater calibration controller 310 identifies the sensor outputting the erroneous temperature reading as faulty. The temperature variation tolerance can be predetermined and determined based on experimental testing of the model heater and control system. The heater calibration controller 310 identifies the faulty sensors and excludes the faulty sensors in calculating one or more of the measures of data (e.g., average temperature).

[0076] As part of the diagnostics, the heater calibration controller 310 limits the maximum number of faulty sensors allowable per zone before the temperature sensor system 300 is deemed defective. For example, for a group with 4 TC sensors, the group is allowed to have one faulty sensor before being deemed defective, and for a group with 5 TC sensors, the group is allowed to have two faulty sensors. Thus, if any of the sensor groups has exceeded the number of allowable faulty sensors, the heater calibration controller 310 then stops the calibration process (e.g., shuts off power to the heater 102) and notifies the user of the faulty temperature sensor system 300. The number of allowable faulty sensors is predetermined and can be based on the number of sensors in the group and the level of precision provided for the heater 102.

[0077] Using temperature measurements from the TC sensors and voltage and current measurements from the sensor circuit, the heater controller is configured to self-calibrate via the sensor array using an algorithm, such as direct control temperature. That is, in one form, the heater is controlled to an average temperature determined by the heater controller based on measurements from the TC sensors. The heater can also be controlled to a nominal temperature measured by the resistive heating element of the heater based on data from previous heaters of the same class as the heater being tested. Such data can be close, but not exact for each unique base produced.

[0078] In operation, heater calibration control performed by the control system can begin when the temperature sensor system is set up (e.g., positioned and secured to the heater and communicably coupled to the controller). In one form, the heater calibration controller controls the heater at a plurality of set points, such as temperature set points. For each set point, the heater is held at the set point until the heater and / or TC die is in equilibrium, and the control system measures and records the resistance of each of the zones based on data from the sensor circuit and obtains temperature measurements from the temperature sensor system. The control system then calculates a sum of each zone as a gauge data of the heater as a whole, such as an average temperature. One or more of the defined set points, measured resistances, and / or gauge data can be stored as resistance-temperature calibration data and provided in various suitable ways, such as a table. During calibration, the control system can perform sensor diagnostics described herein to verify that the temperature sensor system is operating within set parameters.

[0079] In one form, the control system can display one or more graphical user interfaces for displaying information to a user and receiving commands from the user. For example, in one form, the control system can display plots of the calibration data, heating patterns of the heater, and / or gauge data of each zone and the heater as a whole. This information can allow the zones to be optimized to match a desired temperature profile and allow the heater and control system to work together to achieve optimal uniformity.

[0080] Using the resistance-temperature calibration data, the control system measures the temperature of each zone of the multi-zone heater without the need for discrete temperature sensors at the zones and provides closed loop / servo control of all zones with precise accuracy. As described herein, the calibration process is automated, so the operator does not need to understand the calibration in detail other than how to install the temperature sensor system and begin the calibration stored in the control system. In one form, the thermal system can implement one or both of the calibration processes of the present disclosure.

[0081] References Figure 7, an example control system calibration routine 500 is provided. The control system calibration routine is performed by the controller calibration system of the present disclosure. At 502, the system provides power to a load via a control system, and at 504, the system generates an initial measured characteristic of the load from the control system and a calibrated measured characteristic of the load from the controller calibration. In one form, once generated, the power to the load can be turned off. The initial measured characteristic and the calibrated measured characteristic are indicative of an electrical characteristic of the load including voltage, current, and / or resistance. More specifically, in one form, to generate the initial measured characteristic, an initial voltage and an initial current of the load are measured by the control system, and to generate the calibrated measured characteristic, a calibrated voltage and a calibrated current of the load are measured by the controller calibration system. In one form, the initial voltage and the calibrated voltage are measured simultaneously, and the initial current and the calibrated current are measured simultaneously. In another form, the initial voltage, the initial current, the calibrated voltage, and the calibrated current are measured simultaneously. In one form, an initial resistance of the load is calculated based on the initial voltage and the initial current, and is also provided as the initial measured characteristic, and a calibrated resistance of the load is calculated based on the calibrated voltage and the calibrated current of the load, and is also provided as the calibrated measured characteristic.

[0082] At 506, the system correlates the initial measured characteristic with the calibrated measured characteristic to calibrate the measurements made by the control system. At 508, the system defines a calibrated measurement reference based on the correlation of the initial measured characteristic and the calibrated measured characteristic.

[0083] The routine 500 is merely one example routine for performing heater control calibration and can be configured in various suitable ways. For example, in one form, the calibrated measurement reference can be defined for multiple power set points of the load and / or multiple known resistances (i.e., load resistances). For each power and / or load resistance, the initial measured characteristic and the calibrated measured characteristic are generated and then correlated to define the calibrated measurement reference.

[0084] Referring to Figure 8An example heater calibration control routine 600 performed by a control system is provided. The routine 600 can be performed when a temperature sensor system is connected to the control system to provide temperature measurements of a heater. At 602, the heater is controlled to a temperature setpoint from among a plurality of temperature setpoints. At 604, a voltage and current (V-I) characteristic and a temperature dataset of the heater are acquired. The V-I characteristic and temperature dataset are acquired for each temperature setpoint. At 606, the control system determines a resistance of the heater for each temperature setpoint based on the V-I characteristic acquired for the temperature setpoint. At 608, the control system determines temperature metrology data based on the temperature dataset acquired for the temperature setpoint. In one form, the temperature metrology data includes an average temperature, a median temperature, a temperature variation, a standard deviation, a maximum temperature, a minimum temperature, a temperature range, and / or a 3-sigma value. At 610, the control system correlates the resistance of the heater and the temperature metrology data of the temperature setpoint. At 612, the control system defines a resistance-temperature calibration reference for determining an operating temperature of the heater based on the measured resistance of the heater.

[0085] If the heater is a multi-zone heater, power is provided to and controlled for each of the zones such that the temperatures of the zones are substantially equal to the temperature setpoint. In addition, the V-I characteristic and temperature measurements are also captured for each of the zones. The temperature dataset of the heater from the temperature sensor system includes at least one temperature measurement for each of the zones.

[0086] The routine 600 is merely one example routine for performing heater control calibration and can be configured in various suitable ways. For example, in one form, the routine can perform a diagnostic on the temperature sensor system to identify possible faulty sensors. More particularly, in one form, each zone of a multi-zone heater is associated with two or more temperature sensors from among the temperature sensors of the temperature sensor system (i.e., a sensing group). For each sensing group, a sensor diagnostic is performed to identify a faulty temperature sensor from among the temperature sensors of the sensing group based on the temperature measurements from the sensing group. When the sensor diagnostic identifies a number of faulty temperature sensors less than a faulty sensor threshold, the temperature measurements from the faulty temperature sensors are discarded prior to determining the temperature metrology data. When the number of faulty temperature sensors is greater than the faulty sensor threshold, power to the heater is turned off. In addition, all numerical values representing tolerances, temperatures, voltages, currents, or other characteristics are provided as examples. Thus, it should be readily understood that other numerical values can be used while still remaining within the scope of the present disclosure.

[0087] Unless specifically stated otherwise as apparent from the foregoing disclosure, all percentages, all amounts, all ratios, all percentages, all amounts, all ratios, and all other quantities, used herein are understood to be modified by the word "about," unless otherwise specifically noted. It is understood that the total numerical values of all components in a composition will not exceed 100% unless otherwise specifically stated herein.

[0088] 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 the non-exclusive logical OR, and it should not be construed to mean "at least one of A and at least one of B and at least one of C."

[0089] In this application, the term "controller" can be replaced by the term "circuit." The term "controller" can 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 combination of combinational logic circuits; 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.

[0090] The term code can include software, firmware, and / or microcode, and when the code includes a procedure, a function, a class, a data structure, and / or an object, the code can be referred to as a process, a routine, a function, a class, a data structure, and / or an object. 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 propagating signals or electromagnetic waves propagating through a medium, such as on a carrier; thus, the term computer-readable medium can be considered tangible and non-transitory.

[0091] The description of the present disclosure is merely exemplary in nature and, thus, variations that do not depart from the essence of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.

Claims

1. A method for calibrating a control system configured to control a two-wire heater operable to generate heat and function as a sensor for measuring an electrical characteristic of the two-wire heater, the method comprising: providing, by the control system, power to a load electrically coupled to the control system, generating, by the control system, an initial measured characteristic of the load, wherein the initial measured characteristic is indicative of an electrical characteristic of the load, wherein the electrical characteristic of the load comprises a voltage, a current, a resistance, or a combination thereof; generating, by a controller calibration system coupled to the load, a calibrated measured characteristic of the load indicative of the electrical characteristic of the load, wherein the controller calibration system is separate from the control system, and wherein the calibrated measured characteristic is generated simultaneously with the initial measured characteristic; correlating the initial measured characteristic with the calibrated measured characteristic; and defining a calibrated measurement reference based on the correlation of the initial measured characteristic and the calibrated measured characteristic, wherein the control system employs the calibrated measurement reference to provide accurate measurements for controlling the two-wire heater.

2. The method of claim 1, wherein: generating, by the control system, the initial measured characteristic further comprises measuring, by the control system, an initial voltage and an initial current of the load, wherein the initial measured characteristic comprises the initial voltage and the initial current, and generating, by the controller calibration system coupled to the load, the calibrated measured characteristic further comprises measuring, by the controller calibration system, a calibrated voltage and a calibrated current of the load, wherein the calibrated measured characteristic comprises the calibrated voltage and the calibrated current, wherein the initial voltage and the calibrated voltage are measured simultaneously, and the initial current and the calibrated current are measured simultaneously.

3. The method of claim 2, further comprising: calculating an initial resistance of the load based on the initial voltage and the initial current of the load, wherein the initial measured characteristic further comprises the initial resistance; and calculating a calibrated resistance of the load based on the calibrated voltage and the calibrated current of the load, wherein the calibrated measured characteristic further comprises the calibrated resistance.

4. The method of claim 1, wherein: power is provided to the load at a plurality of power set points, for each of the plurality of power set points, the initial measured characteristic is generated by the control system and the calibrated measured characteristic is generated by the controller calibration system to provide a plurality of initial measured characteristics and a plurality of calibrated measured characteristics, the plurality of initial measured characteristics are correlated with the plurality of calibrated measured characteristics, and the calibrated measurement reference is defined based on the correlation of the plurality of initial measured characteristics and the plurality of calibrated measured characteristics.

5. The method of claim 1, wherein, the load is a controllable load having an adjustable resistance, wherein the method further comprises: setting the resistance of the load to a plurality of resistance set points, wherein, for each of the plurality of resistance set points, the initial measurement characteristic is generated by the control system and the calibrated measurement characteristic is generated by the controller calibration system to provide a plurality of initial measurement characteristics and a plurality of calibrated measurement characteristics, the plurality of initial measurement characteristics are correlated with the plurality of calibrated measurement characteristics, and a calibrated measurement reference is defined based on the correlation of the plurality of initial measurement characteristics and the plurality of calibrated measurement characteristics.

6. The method of claim 1, wherein, the control system is electrically coupled to the two-wire heater, the method further comprising: controlling, by the control system, the two-wire heater to a temperature set point from a plurality of temperature set points; simultaneously acquiring, from the control system, a voltage and current (V-I) characteristic of the two-wire heater and a temperature data set of the two-wire heater from a temperature sensor system, wherein the V-I characteristic and the temperature data set are acquired for each of the plurality of temperature set points; determining, based on the acquired V-I characteristic, a resistance of the two-wire heater for each of the plurality of temperature set points; calculating, based on the acquired temperature data set, temperature metrology data for each of the plurality of temperature set points; correlating the resistance of the two-wire heater and the temperature metrology data of the plurality of temperature set points; and defining, based on the measured resistance of the two-wire heater, a resistance-temperature calibration reference for determining an operating temperature of the two-wire heater.

7. The method of claim 6, wherein, the temperature metrology data comprises an average temperature, a median temperature, a temperature variation, a standard deviation, a maximum temperature, a minimum temperature, a temperature range, a 3-sigma value, or a combination thereof.

8. A method for calibrating a control system configured to operate a two-wire heater, the two-wire heater being operable to generate heat and to function as a sensor for measuring a temperature of the two-wire heater, the two-wire heater comprising a plurality of resistive heating elements defining a plurality of zones, the control system being configured to independently control each zone, the method comprising: controlling, by the control system, the two-wire heater to a temperature set point from a plurality of temperature set points; simultaneously acquiring, from the control system, a voltage and current (V-I) characteristic of the two-wire heater and a temperature data set of the two-wire heater from a temperature sensor system, wherein the V-I characteristic and the temperature data set are acquired for each of the plurality of temperature set points, wherein the V-I characteristic of the two-wire heater comprises a V-I characteristic of each of the plurality of zones and a V-I characteristic of the two-wire heater as a whole, and the temperature data set of the two-wire heater acquired from the temperature sensor system comprises at least one temperature measurement of each of the plurality of zones; determining, based on the acquired V-I characteristic, a resistance of the two-wire heater for each of the plurality of temperature set points; calculating, based on the acquired temperature data set, temperature metrology data for each of the plurality of temperature set points; correlating the resistance of the dual wire heater and the temperature metrology data of the plurality of temperature setpoints; and defining, based on the measured resistance of the dual wire heater, a resistance-temperature calibration reference for determining an operating temperature of the dual wire heater.

9. The method of claim 8, wherein, acquiring the V-I characteristics of the dual wire heater and the temperature data set further comprises: measuring, by a sensor circuit of the control system, the V-I characteristics of the dual wire heater; and measuring, by the temperature sensor system, a plurality of temperature measurements of the dual wire heater at the temperature setpoints, wherein the plurality of temperature measurements are provided as a temperature data set for the temperature setpoints.

10. The method of claim 8, wherein, The temperature metrology data comprises an average temperature, a median temperature, a temperature variation, a standard deviation, a maximum temperature, a minimum temperature, a temperature range, a 3-sigma value, or a combination thereof.

11. The method of claim 8, wherein, controlling, by the control system, the dual wire heater to the temperature setpoint further comprises: providing power to a plurality of zones of the dual wire heater; obtaining a temperature of each of the plurality of zones of the dual wire heater; and adjusting the power to the plurality of zones in response to a temperature from one or more of the plurality of zones not equaling the temperature setpoint.

12. The method of claim 8, wherein, The temperature sensor system comprises a plurality of temperature sensors, wherein the method further comprises, for each of the plurality of zones, associating one or more of the plurality of temperature sensors with the respective zone, wherein the one or more temperature sensors are configured to provide temperature measurements of the respective zone.

13. The method of claim 12, wherein, Each of the plurality of zones is associated with two or more temperature sensors from the plurality of temperature sensors, the two or more temperature sensors are provided as a sensing group, and the method further comprises: for each sensing group, performing a sensor diagnostic to identify a faulty temperature sensor from the temperature sensors of the sensing group based on temperature measurements from the sensing group; in response to the sensor diagnostic identifying the faulty temperature sensor and when a number of identified faulty temperature sensors is less than a faulty sensor threshold, discarding the temperature measurements from the faulty temperature sensors; and in response to the sensor diagnostic identifying the faulty temperature sensor and when a number of identified faulty temperature sensors is greater than the faulty sensor threshold, shutting off power to the dual wire heater.

14. The method of claim 13, wherein, in response to the sensor diagnostic not identifying the faulty temperature sensor or when a number of identified faulty temperature sensors is less than the faulty sensor threshold, the method further comprises: determining, for each of the plurality of temperature setpoints, a resistance of the dual wire heater based on the acquired V-I characteristics; calculating, for each of the plurality of temperature setpoints, temperature metrology data based on the temperature data set; correlating the resistance of the dual wire heater and the temperature metrology data of the plurality of temperature setpoints; and defining, based on the measured resistance of the dual wire heater, a resistance-temperature calibration reference for determining an operating temperature of the dual wire heater.

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