Power device photon temperature sensing

Abstract

The invention provides power device photon temperature sensing. A power device sensor includes: a semiconductor thermo-optical element; circuitry including a light emitting diode that emits photons and a photodetector that detects the photons and alters a voltage output by the circuitry; and an optical waveguide in optical communication with the light emitting diode, the semiconductor thermo-optical element, and the photodetector.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to power electronics and semiconductor materials. BACKGROUND

[0002] Semiconductors are materials with an electrical conductivity that is intermediate between that of conductors (such as metals) and insulators (such as ceramics). This intermediate conductivity can be controlled by the addition of impurities, a process known as doping. Silicon has been the dominant semiconductor material due to its abundance, well-established manufacturing processes, and favorable electronic properties. However, as the demand for more efficient, higher power, and high-temperature electronic devices grows, the limitations of silicon become more apparent.

[0003] Silicon carbide (SiC) is a compound semiconductor composed of silicon and carbon atoms. It is known for its wide bandgap, the energy difference between a material’s valence band and conduction band. The wide bandgap allows SiC devices to operate at higher voltages, temperatures, and frequencies compared to silicon devices. Additionally, SiC has high thermal conductivity, meaning it can dissipate heat generated during operation efficiently. SUMMARY

[0004] A SiC power device includes a substrate, a SiC die mounted on the substrate, and a chip positioned on the SiC die. It also includes a semiconductor pyro-optic element in direct contact with the chip, a sensor with a light-emitting diode (LED) and a photodetector, and an optical waveguide. The optical waveguide is configured to establish optical communication between the semiconductor pyro-optic element, the LED, and the photodetector. Photons emitted by the LED and reflected by the semiconductor pyro-optic element are directed to the photodetector, thereby affecting the voltage output of the sensor.

[0005] A switching device has a SiC power device, a semiconductor pyro-optic element in direct contact with the power device, a sensor, and an optical waveguide. The optical waveguide facilitates optical communication between the semiconductor pyro-optic element and the sensor.

[0006] A power device sensor includes a semiconductor pyro-optic element designed to be placed in contact with a SiC power device. It also includes circuitry with an LED for emitting photons and a photodetector for detecting photons and modifying the voltage output of the circuitry. An optical waveguide is integrated to establish optical communication between the LED, the semiconductor pyro-optic element, and the photodetector. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a schematic diagram of a power device and sensor.

[0008] Figure 2 is Figure 1 a schematic diagram of a portion of the power device and sensor of DETAILED DESCRIPTION

[0009] This document describes embodiments. However, it should be understood that these embodiments are merely examples, and other embodiments may take various alternative forms. The drawings are not necessarily provided to scale, and some features may be enlarged or minimized to highlight particular parts. Therefore, the specific structural and functional details disclosed should not be construed as limiting, but rather as a representative basis for teaching those skilled in the art.

[0010] The combinations of features shown provide representative embodiments for typical applications. However, various combinations and modifications of these features consistent with the teachings of this disclosure may be desired for particular applications or implementations.

[0011] SiC power devices, with their material properties, have influenced the development of power electronics, making them ideal for high-power and high-temperature applications. SiC's wide bandgap (measured at 3.26 eV compared to 1.12 eV for silicon) allows these devices to operate at higher voltages, temperatures, and frequencies. This wide bandgap results in a higher breakdown voltage, allowing SiC devices to withstand larger electric fields and thus operate at elevated voltages without breaking down.

[0012] A potential advantage of SiC power devices is their high thermal conductivity, approximately three times higher than that of silicon. This characteristic facilitates more efficient heat dissipation, reducing the need for extensive cooling systems and improving overall system efficiency. Their ability to operate at higher temperatures, typically exceeding 200°C, extends their availability in harsh environments and high power density applications. Additionally, SiC devices benefit from higher electron mobility and lower on-resistance, enabling faster switching speeds. These properties result in reduced switching losses and allow for higher frequency operation, making it possible to design compact and efficient power converters.

[0013] SiC power devices include a variety of components such as SiC metal-oxide-semiconductor field-effect transistors (MOSFETs), SiC Schottky diodes, and SiC junction field-effect transistors (JFETs). Each of these components is constructed with specific design considerations to take advantage of the unique properties of SiC.

[0014] SiC MOSFETs have a gate oxide layer, typically silicon dioxide, constructed on top of a SiC substrate. The source and drain regions are heavily doped to form ohmic contacts, while the channel region is lightly doped to control current flow. The gate structure controls the channel conductivity, allowing the device to be turned on and off quickly. The thin gate oxide layer and SiC substrate facilitate high-voltage operation and fast switching.

[0015] SiC Schottky diodes are constructed with a metal-semiconductor junction instead of a traditional pn junction. This structure allows for a lower forward voltage drop and a faster recovery time, thereby reducing switching losses. The Schottky barrier height can be customized by selecting an appropriate metal, thus optimizing device performance for specific applications.

[0016] SiC JFETs are typically constructed with a vertical structure, in which current flows from the source to the drain through a channel controlled by the gate voltage. The vertical design minimizes on-resistance and maximizes current handling capability. The gate region is doped to form a junction that controls the conductivity of the channel, thereby allowing modulated current flow.

[0017] SiC power devices are used in electric vehicles. Inverters and on-board chargers benefit from the high-frequency operation and reduced thermal management requirements of SiC devices. Renewable energy systems, such as solar inverters and wind turbine converters, utilize the high efficiency and reliability of SiC devices to maximize energy conversion and minimize system losses. Industrial applications, including motor drives and power supplies, benefit from the robustness and high-temperature operation of SiC devices.

[0018] Accurately measuring the junction temperature of SiC devices remains a significant challenge. The lack of integrated on-die temperature sensors in most available products complicates direct junction temperature measurement. Some existing methods rely on indirect temperature measurements or algorithmic estimations, which can reduce accuracy, especially during dynamic events.

[0019] Inaccurate junction temperature measurement can sometimes hinder the efficient utilization of SiC power devices. Inaccurate temperature readings can affect power derating control and chip size optimization. Furthermore, inaccurate temperature measurements can impact device lifespan. Accurate junction temperature measurement can play a role in maximizing the performance and reliability of SiC power devices in electric vehicle applications. Therefore, an apparatus for directly measuring the junction temperature of SiC devices is described.

[0020] The thermo-optic effect is the phenomenon where the refractive index of a material changes in response to temperature variations. This effect is particularly pronounced in optical materials and devices where precise control of light propagation is required. The refractive index is a fundamental property of materials, determining how light travels through a medium. It is defined as the ratio of the speed of light in a vacuum to the speed of light within the material. As temperature changes, the atomic or molecular structure of a material can expand or contract, leading to changes in the material's density and electronic polarizability. These changes directly affect the refractive index.

[0021] Thermo-optic effects are evident in silicon and some other materials. Silicon has a relatively high thermo-optic coefficient, meaning its refractive index changes significantly with temperature.

[0022] The relationship between temperature and the refractive index of silicon is determined by the material's thermo-optic coefficient. For silicon, this coefficient is positive, indicating that the refractive index increases with increasing temperature. The magnitude of this change is influenced by factors such as the wavelength of light and the specific properties of the silicon used, including its doping level and crystal structure.

[0023] In practical applications, the thermo-optical effect in silicon and other materials can be used for temperature sensing. When integrated into a device, changes in temperature alter the refractive index of the silicon component. These changes can be detected by monitoring variations in the propagation characteristics of light, such as shifts in resonant frequencies or changes in light intensity.

[0024] Mechanical components made of silicon, gallium nitride, etc., are bonded to SiC dies using microfabrication techniques such as wafer bonding or silicon fusion bonding. As the die temperature changes, the silicon mechanical components also change temperature accordingly due to their direct thermal contact. This semiconductor thermo-optical element is positioned within a cavity-enhanced optical probe (such as a fiber optic duct) designed to guide light with minimal loss.

[0025] The thermo-optical effect in silicon mechanical components causes their refractive index to change linearly with temperature. Photons emitted by LEDs, quantum cascade lasers, etc., in the sensor travel through the optical cavity, are reflected from the surface of the mechanical component, and return to the photodetector within the sensor. LEDs can be adapted to operate at specific wavelengths (such as in the near-infrared range) that are highly sensitive to changes in refractive index.

[0026] The photodetector uses, for example, a photodiode or an avalanche photodiode to convert these returning photons into a voltage signal for higher sensitivity. This voltage signal is then transmitted to a processor, which uses calibration data to correlate the voltage signal with the temperature of the SiC die. This method allows the optical probe to detect the temperature of the SiC die with high accuracy.

[0027] This technology enables the direct measurement of hottest spots or multiple locations on a SiC chip with high spatial resolution and reliability. By plotting temperature changes across the entire chip, data is provided for thermal management and performance optimization.

[0028] Cavity-enhanced optical probes transmit photons precisely and reliably. They can be constructed from nanoscale reflective fibers or prisms, typically made of materials such as silica or sapphire, due to their optical clarity and durability. Their compact size and structure (typically less than a few millimeters in diameter) allow them to be positioned anywhere on a SiC device or across multiple locations when needed. The probes are characterized by robust mechanical structures that can be encapsulated in a protective cladding, and because they use photon resonance and intensity measurement instead of current and voltage like typical resistance thermometers, they are virtually unaffected by electromagnetic interference (EMI) from nearby electronics. This is particularly useful in high-power environments where EMI can be severe.

[0029] Photonic sensors (in some examples, photon-based quantum silicon devices) are sensitive to photon energy. They utilize the principle of photonic thermometry to analyze the unique spectral characteristics of mechanical components bonded to a SiC chip. By sensing the intensity of photons reflected from the mechanical components and carried through the probe, the sensor outputs an electrical signal that linearly corresponds to the junction temperature measurement. This signal is then relayed to a central control board, where it is used for real-time thermal management.

[0030] Figure 1 A SiC power device device 100 is shown. The device 100 includes a substrate 102, a SiC die 104, a chip 106, an optical waveguide 108, a sensing device 110, a silicon blank 112, a gate 114, and solder 116. The SiC die 104 is attached to the substrate 102 using solder 116. The silicon blank 112, positioned on top of the chip 106, is optically connected to the sensing device 110 via the optical waveguide 108.

[0031] Figure 2 Additional details are provided for the sensing device 110 and the optical waveguide 108. The sensing device 110 includes circuitry 118 comprising a power supply voltage 120, an output voltage 122, a ground 124, a first resistor 126, a second resistor 128, an LED 130, and a photodetector 132. The LED 130 emits photons 134, which are transmitted through the optical waveguide 108 to a silicon blank 112. The silicon blank 112 reflects the photons 134, and these reflected photons travel back through the optical waveguide 108 towards the sensing device 110, where they are detected by the photodetector 132. The photodetector 132 then generates an electrical signal corresponding to the intensity of the reflected photons 134, resulting in a corresponding change in the output voltage 122. This output voltage 122 is used to determine the temperature of the chip 106 at the location on the silicon blank 112.

[0032] As chip 106 heats up, silicon blank 112 also experiences a temperature change due to heat transfer. This temperature change in silicon blank 112 causes a change in its refractive index due to the thermo-optic effect. A higher refractive index results in more light being reflected by silicon blank 112 and less light being transmitted into the silicon blank. Therefore, when the refractive index of silicon blank 112 is higher, the intensity of the reflected photons 134 increases.

[0033] When current flows through LED 130, electrons recombine with electron-holes, thereby emitting photons 134. The intensity of the emitted photons 134 is directly related to the current flowing through LED 130.

[0034] The photodetector 132 can be of any type, such as a phototransistor or a photodiode. A phototransistor generates and amplifies a current when struck by a photon, where the current is proportional to the light intensity. Since the intensity of the reflected photon 134 is related to the temperature of the chip 106 at its location on the silicon blank 112, the current generated by the photodetector 132 in response to the photon 134 is also related to the chip's temperature. The change in current caused by the photodetector's response to the photon 134 will affect the output voltage 122 of the circuit 118. Therefore, the output voltage 122 can be used to accurately determine the temperature of the chip 106 at its location on the silicon blank 112.

[0035] While exemplary embodiments have been described above, these embodiments are not intended to cover all possible forms covered by the claims. The language used in this specification is descriptive rather than restrictive, and it should be understood that various modifications may be made without departing from the spirit and scope of this disclosure.

[0036] As previously described, features of various embodiments can be combined to produce other embodiments of the invention that may not be explicitly described or shown. While some embodiments may be described as offering advantages over other embodiments or prior art implementations in particular characteristics, or being preferred over other embodiments or prior art implementations, those skilled in the art will recognize that certain features or characteristics can be tailored to achieve desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, strength, durability, merchantability, appearance, packaging, size, maintainability, weight, manufacturability, and ease of assembly. Therefore, embodiments considered less desirable in one or more characteristics are not outside the scope of this disclosure and may be suitable for a particular application.

[0037] According to the present invention, a silicon carbide power device is provided, the silicon carbide power device comprising: a substrate; a silicon carbide die located on the substrate; a chip located on the silicon carbide die; a semiconductor thermo-optic element in direct contact with the chip; a sensor including a light-emitting diode and a photodetector; and an optical waveguide in optical communication with the semiconductor thermo-optic element, the photodiode, and the photodetector, such that photons emitted by the photodiode and reflected by the semiconductor thermo-optic element strike the photodetector and affect the voltage output by the sensor.

[0038] According to an embodiment, the semiconductor thermo-optical element is a silicon blank.

[0039] According to an embodiment, the optical waveguide is a fiber.

[0040] According to an embodiment, the optical waveguide is a prism.

[0041] According to an embodiment, the photodetector is a phototransistor.

[0042] According to an embodiment, the photodetector is a photodiode.

[0043] According to the present invention, a switching device is provided, the switching device comprising: a silicon carbide power device; a semiconductor thermo-optic element in direct contact with the silicon carbide power device; a sensor; and an optical waveguide in optical communication with the semiconductor thermo-optic element and the sensor.

[0044] According to an embodiment, the silicon carbide power device includes a chip, and the semiconductor thermo-optic element is in direct contact with the chip.

[0045] According to an embodiment, the sensor includes a light-emitting diode configured to emit photons and a photodetector configured to detect the photons.

[0046] According to an embodiment, the optical waveguide is configured to guide the photons.

[0047] According to an embodiment, the photodetector is arranged to influence the voltage output by the sensor.

[0048] According to an embodiment, the photodetector is a phototransistor or a photodiode.

[0049] According to an embodiment, the optical waveguide is a fiber or a prism.

[0050] According to the present invention, a power device sensor is provided, the power device sensor comprising: a semiconductor thermo-optic element configured to be placed in contact with a silicon carbide power device; a circuit system including a light-emitting diode configured to emit photons and a photodetector configured to detect the photons and change the voltage output by the circuit system; and an optical waveguide in optical communication with the light-emitting diode, the semiconductor thermo-optic element and the photodetector.

[0051] According to an embodiment, the semiconductor thermo-optical element is a silicon blank.

[0052] According to an embodiment, the optical waveguide is a fiber.

[0053] According to an embodiment, the optical waveguide is a prism.

[0054] According to an embodiment, the photodetector is a phototransistor.

[0055] According to an embodiment, the photodetector is a photodiode.

Claims

1. A silicon carbide power device, comprising: a substrate; a silicon carbide die on the substrate; a chip on the silicon carbide die; a semiconductor thermo-optic element in direct contact with the chip; a sensor comprising a light emitting diode and a photodetector; and an optical waveguide in optical communication with the semiconductor thermo-optic element, photodiode, and photodetector such that photons emitted by the photodiode and reflected by the semiconductor thermo-optic element impinge on the photodetector and affect a voltage output by the sensor.

2. The silicon carbide power device of claim 1, wherein the semiconductor thermo-optic element is a silicon blank.

3. The silicon carbide power device of claim 1, wherein the optical waveguide is a fiber.

4. The silicon carbide power device of claim 1, wherein the optical waveguide is a prism.

5. The silicon carbide power device of claim 1, wherein the photodetector is a phototransistor.

6. The silicon carbide power device of claim 1, wherein the photodetector is a photodiode.

7. A switching device, comprising: a silicon carbide power device; a semiconductor thermo-optic element in direct contact with the silicon carbide power device; a sensor; and an optical waveguide in optical communication with the semiconductor thermo-optic element and the sensor.

8. The switching device of claim 7, wherein the silicon carbide power device comprises a chip and the semiconductor thermo-optic element is in direct contact with the chip.

9. The switching device of claim 7, wherein the sensor comprises a light emitting diode configured to emit photons and a photodetector configured to detect the photons.

10. The switching device of claim 9, wherein the optical waveguide is configured to guide the photons.

11. The switching device of claim 9, wherein the photodetector is arranged to affect a voltage output by the sensor.

12. The switching device of claim 9, wherein the photodetector is a phototransistor or a photodiode.

13. The switching device of claim 7, wherein the optical waveguide is a fiber or a prism.

14. A power device sensor, comprising: a semiconductor thermo-optic element configured to be placed in contact with a silicon carbide power device; circuitry comprising a light emitting diode configured to emit photons and a photodetector configured to detect the photons and alter a voltage output by the circuitry; and an optical waveguide in optical communication with the light emitting diode, semiconductor thermo-optic element, and photodetector.

15. The power device sensor of claim 14, wherein the semiconductor thermo-optic element is a silicon blank. ​ ​ ​

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