Self-powered wireless telemetry for wafer temperature measurement

Abstract

A telemetry system is configured to monitor a temperature of a wafer disposed in a vacuum. The system may include a plurality of sensors configured to measure temperatures at a plurality of locations on the wafer. The system may also include a plurality of sensor signal conditioning circuits. Each sensor signal conditioning circuit may be coupled to a respective sensor of the plurality of sensors. The plurality of sensor signal conditioning circuits may be configured to convert a resistance from each of the plurality of sensors into low frequency sine waves defining respective frequencies proportional to the resistance. The system may also include a multiplexer configured to generate a composite modulated signal from the low frequency sine wave. The system may also include a frequency modulation (FM) transmitter configured to transmit the composite modulated signal to the outside of the vacuum.

Description

Background Technology

[0001] Various semiconductor applications require the measurement and monitoring of wafer temperatures during manufacturing. In various examples, wafers are exposed to extreme environments (e.g., temperatures around 650 degrees Celsius), which presents challenges in accurately measuring the temperature on the wafer. This invention recognizes that current methods for monitoring temperature typically utilize contact thermocouples, which are physically connected to a given wafer and hardwired to a temperature measurement system. Summary of the Invention

[0002] Embodiments of the present invention address and overcome one or more of the disadvantages or technical problems described herein by providing methods, systems, and apparatus for accurately and wirelessly measuring temperature on wafers in a variety of extreme environments.

[0003] In one example, a telemetry system is configured to monitor the temperature of a wafer placed in a vacuum. The system may include multiple sensors configured to measure the temperature at multiple locations on the wafer. The system may also include multiple sensor signal conditioning circuits. Each sensor signal conditioning circuit may be coupled to a corresponding sensor among the multiple sensors. The multiple sensor signal conditioning circuits may be configured to convert the resistance from each of the multiple sensors into a low-frequency sine wave, these low-frequency sine waves defining a corresponding frequency proportional to the resistance. The system may also include a multiplexer configured to generate a composite modulated signal from the low-frequency sine waves. The system may also include a frequency modulation (FM) transmitter configured to send or transmit the composite modulated signal outside the vacuum, wherein the composite modulated signal includes or indicates the temperature at each of the multiple locations on the wafer. In some examples, the system includes a molten salt cell inside the vacuum. The molten salt cell may be configured to provide power to the multiple signal conditioning circuits, the multiplexer, and the transmitter. In various examples, the vacuum defines a temperature of at least 500 degrees Celsius. The system may also include an FM receiver located outside the vacuum, wherein the FM receiver is configured to receive a composite modulated signal from an FM transmitter inside the vacuum. The FM transmitter may be configured to transmit the composite modulated signal at least 1 meter to the FM receiver outside the vacuum.

[0004] In this example, the plurality of sensors define a plurality of platinum resistance temperature devices. The system may also include a plurality of voltage-controlled oscillators (VCOs), each VCO coupled to a corresponding platinum resistance temperature device among the plurality of platinum resistance temperature devices. Each VCO can be configured to convert the resistance from the corresponding platinum resistance temperature device into a resistance-based frequency. Specifically, for example, each VCO can be configured to generate a corresponding waveform within a corresponding frequency range, which differs from the frequency ranges generated by the other VCOs among the plurality of VCOs. For example, each VCO can be configured to generate a corresponding waveform: at a first frequency when the platinum resistance temperature device is at a first resistance, and at a second frequency greater than the first frequency when the platinum resistance temperature device is at a second resistance greater than the first resistance. In this example, the first and second frequencies are within the frequency range corresponding to the respective VCO. Attached Figure Description

[0005] The above and other aspects of the invention will be best understood from the following detailed description when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, presently preferred embodiments are shown in the drawings; however, it should be understood that the invention is not limited to the specific means disclosed. The drawings include the following figures:

[0006] Figure 1 This is a block diagram of an example wafer according to an example implementation, the wafer including multiple locations where temperature can be monitored and measured.

[0007] Figure 2 This diagram illustrates a block diagram of an example frequency division multiplexing (FDM) telemetry system configured for use in manufacturing. Figure 1 The temperature of the wafer shown is measured simultaneously, wherein the FDM telemetry system defines the sensor multiplexing core and RF transmission circuitry.

[0008] Figure 3 This is a block diagram of a sensor multiplexing core and RF transmission circuit according to an example implementation.

[0009] Figure 4 This is a circuit diagram of an example voltage-controlled oscillator (VCO) according to an example implementation, which can be... Figure 3 The diagram shows a portion of the sensor multiplexing core and RF transmission circuit. Detailed Implementation

[0010] As a preliminary consideration, it is recognized in this invention that current methods for obtaining temperature measurement data from a wafer within a vacuum-sealed chamber during semiconductor manufacturing typically rely on sensors mounted on the wafer and hardwired to the outside of the chamber. For example, the wafer may be 300 millimeters (mm), and up to 64 sensors may be present on the wafer.

[0011] According to the various example implementations, refer to Figure 1 Temperature can be wirelessly monitored at multiple locations 102 on the wafer (e.g., wafer 100). In this example, the multiple locations 102 define 64 locations, but it should be understood that the number and arrangement of locations 102 can vary as desired, and all such alternative locations are contemplated to be within the scope of this disclosure. For example, in some cases, a subset of locations 102 (e.g., 16 locations in 102) may be sufficient to monitor the temperature on wafer 100. During temperature measurement, wafer 100 can be surrounded in a vacuum, such as a vacuum of about 5 millitors at a temperature of about 650 degrees Celsius (C).

[0012] It is recognized in this invention that, in various examples, monitoring wafers at high temperatures using analog methods can be performed more simply and reliably compared to digital systems. It should also be recognized in this invention that some advanced integrated circuits (e.g., operational amplifiers made of silicon carbide (SiC)) can operate at high temperatures, but they are typically limited to 500°C or lower in practical operation. Furthermore, it should be recognized in this invention that some transistors can operate at 550°C or even higher temperatures, for example, by using wide-bandgap electronics such as SiC and gallium nitride (GaN). Such transistors can include junction field-effect transistors (JFETs) and high electron mobility transistors (HEMTs), as well as some ceramic-based passive components for supporting active components.

[0013] In various example embodiments, high-temperature components (such as those mentioned above) are combined and arranged in such a manner as a 16-channel high-temperature wireless monitoring system defined for the wafer. (Refer to...) Figure 2 Example frequency division multiplexing (FDM) telemetry system 200 may include a sensor multiplexing core and a radio frequency (RF) transmission circuitry system 202 configured to perform frequency modulation (FM) of the RF carrier to wirelessly transmit data from a high-temperature vacuum environment 204 to an RF receiver system 206. In various examples, the RF receiver system 206 is at room temperature, for example, at about 25°C, while the RF transmission circuitry 202 is in a high-temperature environment 204, for example, at about 550°C to 650°C. The distance between the RF receiver 206 and the RF transmission circuitry 202 may be defined as several meters (m), for example, between 1 meter and 10 meters (e.g., 1.5 m), but it should be understood that the distance data travels from the RF transmission circuitry 202 and the RF receiver 206 can be alternatively configured, and all such alternative distances are contemplated within the scope of this disclosure.

[0014] Continue to refer to Figure 2System 200 (especially high-temperature vacuum environment 204) may include a wafer (which may be monitored at various locations on the wafer), such as wafer 100 (which may be monitored in a subset of multiple locations 102). In particular, for example, multiple temperature sensors 208 (such as platinum resistance temperature devices (RTDs) or other temperature-variable impedance devices) may be positioned at each location 102 in the subset of locations to be configured to measure the temperature at each subset of locations (e.g., 16 locations). For example, but not limitingly, sensor 208 may include other temperature-variable impedance devices (such as capacitors with a defined nonlinear temperature coefficient), whose capacitance typically decreases with increasing temperature over a given temperature range. It should be appreciated in this invention that most semiconductors (such as silicon) exhibit a negative temperature resistivity, such that the resistivity of the bulk semiconductor decreases with increasing temperature.

[0015] In various examples, system 200 may include a molten salt battery 210 configured to supply power to system 200, particularly to sensor 208 and the sensor multiplexing core and RF transmission circuitry 202. Battery 210 may be defined as having a high energy density and configured to operate at temperatures at which the salt melts, such as above 300°C. In particular, for example, a sodium sulfide molten salt battery that does not operate until the salt melts may operate above the temperature required for the salt to melt and for the electronics to operate (e.g., 300°C). Battery 210 may be configured to supply power for at least 100 hours, such as 1000 hours or more, depending on the specific chemistry and geometry of battery 210. Alternatively or additionally, system 200 may define a power source that wirelessly supplies power to the sensor multiplexing core and RF transmission circuitry 202. For example, power may be supplied wirelessly at radio frequency or optical frequencies. In some cases, system 200 defines a resonant inductive power system capable of transmitting and receiving electricity in order to wirelessly power the transmitter (RF transmission circuit 202) of sensor 208.

[0016] Continue to refer to Figure 2 In this example, wafer 100 can reside in a vacuum environment 204 at temperatures up to approximately 650°C. The sensor multiplexing core and RF transmission circuitry 202 can be communicatively coupled to multiple sensors 208 to define multiple sensor inputs. The sensor multiplexing core and RF transmission circuitry 202 can be configured to process multiple sensor inputs from the sensors 208, such as 16 sensor inputs. The sensor multiplexing core and RF transmission circuitry 202 can also be configured to wirelessly transmit data received from the sensors 208 (e.g., sensor inputs). In particular, the data can be transmitted several meters (e.g., 1.5 m) to an RF receiver 206 outside the vacuum environment 204.

[0017] See also Figure 3 The sensor multiplexing core and RF transmission circuitry 202 can define various circuits configured to process and transmit data from sensor 208. In particular, for example, the sensor multiplexing core and RF transmission circuitry 202 can include a signal conditioning system 302, a frequency division multiplexer 304, and an FM radio transmitter circuitry 306. The signal conditioning system 302 can include multiple sensor signal conditioning circuits 308. Each sensor signal conditioning circuit 308 can include a corresponding temperature sensor 208. In various examples, each temperature sensor 208 defines a platinum RTD or other temperature impedance device defining a resistor. The signal conditioning system 302 can convert the resistance of the RTD or temperature impedance device into a low-frequency sine wave that defines a frequency proportional to the resistance.

[0018] For example, refer to Figure 3 and Figure 4 Each sensor signal conditioning circuit 308 can define a voltage-controlled oscillator (VCO) 309. The VCO 309 can generate a signal 310 with an output frequency (f), which can be expressed as... Where L is the total inductance of the sensor signal conditioning circuit 308, and C is the total capacitance of the circuit 308. The sensor 208 (e.g., a platinum RTD) can be configured in a Wheatstone bridge 311 defined by the sensor signal conditioning circuit 308. The RTD can be excited by a bridge excitation voltage 313, such that a temperature change in the wafer 100 causes a resistance change in the sensor (RTD) 208. The resistance change in the RTD produces a voltage change across the bridge 311. In various examples, the sensor signal conditioning circuit 308 may include an instrumentation amplifier configured to amplify the voltage change across the bridge 311. The amplifier's output can be fed into a VCO 309, which can use the varying output voltage of the amplifier to drive a reverse-biased diode 402. In particular, for example, the varying voltage can produce a capacitance change in the reverse-biased diode 402, thereby changing the total capacitance of the LC circuit and the frequency (f) of the output 310 of the VCO 309.

[0019] For illustrative purposes, Figure 3Three sensor signal conditioning circuits 308 are shown, but it should be understood that the sensor conditioning system 302 may include additional sensor signal conditioning circuits 308 (e.g., 16 sensor signal conditioning circuits), and it is contemplated that all such sensor conditioning systems 302 with alternative numbers of sensor signal conditioning circuits 308 are within the scope of this disclosure. Each sensor conditioning circuit can generate a corresponding output 310, which can be input to a frequency division multiplexer 304. The frequency division multiplexer 304 can sum the outputs 310 together to generate a composite modulated signal 312 including data from the outputs 310. Therefore, the frequency division multiplexer 304 can modulate the signal 312 for wireless transmission based on the number of temperature sensors 208 being monitored. Each output 310 includes information from the corresponding sensor 208. Therefore, the composite modulated signal 312 can include information from each of the sensors 208 on wafer 100. The frequency division multiplexer 304 can feed the composite modulated signal 312 to an FM transmitter 306. The FM transmitter 306 can encode information from the composite modulation signal 312 to define an encoded signal 314. The FM transmitter 306 can wirelessly transmit the encoded signal outside the vacuum environment 204, for example, to the FM receiver 206.

[0020] Therefore, refer to again Figure 3 and Figure 4Each sensor 208 (platinum RTD) is part of a corresponding circuit 308 that converts the varying resistance of the corresponding RTD (attributed to the varying temperature of the wafer 100 (and thus the RTD)) into a waveform (output 310) of varying frequency. Specifically, a VCO 309 can convert the varying resistance from the corresponding sensor 208. In various examples, each VCO 309 is configured to output a frequency that varies according to the temperature (and thus resistance) of the RTD to which it is fed, and each VCO 309 is configured to output a frequency that varies within a separate range, such that the output 310 of each individual sensor corresponds to a unique frequency compared to each other. For example, but not limitingly, the first RTD 208 can feed its VCO 309 such that at 25°C, the frequency of its corresponding VCO 309's output 310 is 1 kHz, and at 600°C, the frequency of the same VCO 309's output 310 is 2 kHz. As a further example, the second RTD 208 can feed its VCO 309 such that at 25 °C, the frequency of its corresponding VCO 309 output 310 is 3 kHz, and at 600 °C, the frequency of the same VCO 309 output 310 is 4 kHz. Therefore, each VCO 309 can define its own frequency range, which differs from the other VCOs 309. It should be understood that 1 kHz is presented as an example range corresponding to a temperature range, and the corresponding output frequencies of the VCOs 309 can be varied as desired so that they differ from each other and based on the temperature of the respective sensor 208, and it is contemplated that all such frequency ranges are within the scope of this disclosure.

[0021] Still refer to Figure 3 Each output 310 of VCO 309, and consequently sensor 208, can be fed into frequency division multiplexer 304. Frequency division multiplexer 304 adds the individual outputs 310 together to form a single composite modulated signal 312. Signal 312 can be fed into FM radio transmitter circuitry 306, which defines the RF VCO. In various examples, the RF VCO generates a 70 MHz encoded signal 314 and wirelessly broadcasts signal 314 to receiver system 206, where signal 314 can be received, demodulated, stored, analyzed, etc. Specifically, refer to... Figure 3It should be understood that VCO309 is presented as an example, and each VCO may include capacitors and inductors that define values ​​suitable for alternatives (e.g., larger) to the sensor VCO, and it is contemplated that all such VCOs are within the scope of this disclosure. VCOs (such as example VCO 309) are capable of operating at various elevated temperatures (e.g., 650 °C). In particular, for example, VCO309 may include active devices made of wide-bandgap semiconductors (e.g., silicon carbide (SiC), gallium nitride (GaN), etc.). VCO309 may include a substrate using a ceramic thick film, resistors, capacitors, and inductors to limit the constructed and tested high-temperature co-fired ceramic (HTCC) circuit to the elevated temperature. In various examples, system 200 defines a high-temperature sensor transmitter system that continuously consumes power at a rate of less than 100 mW over a period of time (e.g., 12 hours to 24 hours). Furthermore, according to various embodiments, the system can continuously measure the temperature of wafer 100 and continuously process and wirelessly transmit related data and measured temperature information.

[0022] Figure 2An example environment in which embodiments of the present disclosure may be implemented is illustrated. System 200 may also include one or more processors for processing information. The processor may include one or more central processing units (CPUs), graphics processing units (GPUs), or any other processor known in the art. More generally, a processor as described herein is an apparatus for executing machine-readable instructions stored on a computer-readable medium for performing a task, and may include any one or a combination of hardware and firmware. The processor may also include memory storing machine-readable instructions executable for performing a task. The processor acts on information by manipulating, analyzing, modifying, transforming, or transmitting information for use by an executable program or information apparatus and / or by routing information to an output device. The processor may use or include the capabilities of, for example, a computer, controller, or microprocessor, and may be modulated using executable instructions to perform special functions not performed by a general-purpose computer. A processor can include any type of suitable processing unit, including but not limited to a central processing unit, microprocessor, reduced instruction set computer (RISC) microprocessor, complex instruction set computer (CISC) microprocessor, microcontroller, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), system-on-a-chip (SoC), digital signal processor (DSP), etc. Furthermore, a processor can have any suitable microarchitecture design, including any number of constituent parts, such as, for example, registers, multiplexers, arithmetic logic units, cache controllers for controlling read / write operations on cache memory, branch predictors, etc. The processor's microarchitecture design can be capable of supporting any instruction set from a variety of instruction sets. A processor can be coupled (electrically and / or including executable components) to any other processor to enable interaction and / or communication between them. A user interface processor or generator is a known element that includes an electronic circuit system or software, or a combination of both, for generating a display image or a portion thereof. The user interface includes one or more display images, thereby enabling user interaction with the processor or other devices.

[0023] While specific embodiments of this disclosure have been described, those skilled in the art will recognize that numerous other modifications and alternative embodiments are within the scope of this disclosure. For example, any functionality and / or processing capability described with respect to a particular device or component can be performed by any other device or component. Furthermore, while various illustrative implementations and architectures have been described according to embodiments of this disclosure, those skilled in the art will understand that numerous other modifications to the illustrative implementations and architectures described herein are also within the scope of this disclosure. Additionally, it should be understood that any operation, element, component, data, etc., described herein as being based on another operation, element, component, data, etc., may be additionally based on one or more other operations, elements, components, data, etc. Accordingly, the phrase "based on" or variations thereof should be interpreted as "at least partially based on".

[0024] Although embodiments have been described in language specific to structural features and / or methodological actions, it should be understood that this disclosure is not necessarily limited to the specific features or actions described. Rather, specific features and actions are disclosed in an illustrative form that implements the embodiments. Unless explicitly stated otherwise, or understood in the context of use, conditional language such as “can,” “may,” “may,” or “may” (and others) is generally intended to convey that some embodiments may include certain features, elements, and / or steps, while other embodiments do not. Therefore, such conditional language is not generally intended to imply that features, elements, and / or steps are required for one or more embodiments in any way, or that one or more embodiments necessarily include logic for (with or without user input or prompts) determining whether such features, elements, and / or steps are included or whether they are to be performed in any particular embodiment.

Claims

1. A telemetry system configured to monitor the temperature of a wafer placed in a vacuum, the system comprising: Multiple sensors are configured to measure the temperature at multiple locations on the wafer; Multiple sensor signal conditioning circuits, each coupled to a corresponding sensor among the multiple sensors, the multiple sensor signal conditioning circuits being configured to convert the resistance from each of the multiple sensors into a low-frequency sine wave, the low-frequency sine wave being defined based on a corresponding frequency of the resistance; A multiplexer is configured to generate a composite modulated signal from the low-frequency sine wave; as well as A frequency modulation (FM) transmitter is configured to transmit the composite modulation signal to the outside of the vacuum, wherein the composite modulation signal indicates the temperature at each of the plurality of locations on the wafer.

2. The telemetry system according to claim 1, further comprising: The vacuum contains a molten salt battery configured to provide power to multiple signal conditioning circuits, the multiplexer, and the transmitter.

3. The telemetry system according to claim 1, wherein, The vacuum is limited to a temperature of at least 500 degrees Celsius.

4. The telemetry system according to claim 1, further comprising: An FM receiver, located outside the vacuum, is configured to receive the composite modulated signal from an FM transmitter inside the vacuum.

5. The telemetry system according to claim 1, wherein, The FM transmitter is also configured to transmit the composite modulated signal to an FM receiver at least 1 meter outside the vacuum.

6. The telemetry system according to claim 1, wherein, The multiple sensors define multiple platinum resistance temperature devices.

7. The telemetry system according to claim 6, further comprising: Multiple voltage-controlled oscillators, each of which is coupled to a corresponding platinum resistance temperature device in the plurality of platinum resistance temperature devices.

8. The telemetry system according to claim 7, wherein, Each voltage-controlled oscillator is configured to convert the resistance from the corresponding platinum resistance temperature device into a frequency based on the resistance.

9. The telemetry system according to claim 8, wherein, Each voltage-controlled oscillator is configured to generate a corresponding waveform within a corresponding frequency range, which is different from the frequency range generated by the other voltage-controlled oscillators among the plurality of voltage-controlled oscillators.

10. The telemetry system according to claim 9, wherein, Each voltage-controlled oscillator is configured to generate its own corresponding waveform: at a first frequency when the platinum resistance temperature device is at a first resistance, and at a second frequency greater than the first frequency when the platinum resistance temperature device is at a second resistance greater than the first resistance.

11. The telemetry system according to claim 10, wherein, The first frequency and the second frequency are within the frequency range corresponding to the respective voltage-controlled oscillator.

12. A method for monitoring the temperature of a wafer placed in a vacuum, the method comprising: The resistance at various locations on the wafer is measured by each of a plurality of sensors. The resistance from each of the plurality of sensors is converted into a low-frequency sine wave, the low-frequency sine wave being defined based on a corresponding frequency of the respective resistance; A composite modulation signal is generated from the low-frequency sine wave; as well as The composite modulation signal is sent to the outside of the vacuum, wherein the composite modulation signal indicates the temperature at each of the plurality of locations on the wafer.

13. The method according to claim 12, wherein, The plurality of sensors are coupled to a plurality of voltage-controlled oscillators, and the method further includes: Each of the voltage-controlled oscillators generates a corresponding waveform within a corresponding frequency range, which is different from the frequency range generated by the other voltage-controlled oscillators in the plurality of voltage-controlled oscillators.

14. The method according to claim 13, further comprising: Each voltage-controlled oscillator generates its own corresponding waveform: at a first frequency when the sensor defines a first resistance, and at a second frequency greater than the first frequency when the sensor defines a second resistance greater than the first resistance.

15. The method according to claim 14, wherein, The first frequency and the second frequency are within the frequency range corresponding to the respective voltage-controlled oscillator.

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