Semiconductor device temperature characterization method and system

Abstract

The invention belongs to the technical field of temperature characterization, and discloses a semiconductor device temperature characterization method and system. The semiconductor device temperature characterization scheme provided by the invention comprises the following steps: bearing a semiconductor device and adjusting the position of the semiconductor device by using a device bearing and adjusting unit; respectively emitting detection laser and heating laser by using a detection laser emitting unit and a pumping laser emitting unit, and irradiating the detection laser and the heating laser to a test area of the semiconductor device; collecting and recording a temperature measurement signal reflected by the semiconductor device by using a temperature measurement unit; the device operation control unit is used for providing an electric signal for the semiconductor device and synchronously triggering the temperature measurement unit to record a temperature measurement signal so as to ensure the synchronization of online work and temperature measurement of the semiconductor device; and obtaining transient temperature characterization information of the semiconductor device based on the temperature measurement signal by using the main control unit. According to the invention, temperature characterization of nanosecond-level time and submicron-level spatial resolution of the semiconductor device can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of temperature characterization, and more particularly, to a semiconductor device temperature characterization method and system. BACKGROUND

[0002] With the wide application of gallium nitride (GaN) and gallium arsenide (GaAs) based microwave radio frequency (RF) and power semiconductor devices in the high frequency and high power fields, the thermal effect inside the device has evolved into a core bottleneck restricting its performance limit and long-term reliability. Accurately obtaining the channel temperature field distribution is not only a basic requirement for realizing precise thermal management, but also a core criterion for evaluating device failure mechanism and service life. In particular, under high power working conditions in the MHz to GHz frequency band, dynamic temperature monitoring is of decisive significance for revealing the performance of the device under high frequency and high power working conditions, and provides key data support for the optimization of new device structures and reliability design. It is worth noting that the channel gate length scale of typical GaN / GaAs microwave radio frequency and power devices is usually only microns, which requires the temperature detection technology to achieve sub-micron spatial resolution. In addition, such as GaN / GaAs high electron mobility transistors (HEMTs), the temperature peak (hot spot) is often distributed in the edge channel region near the gate drain, which requires the detection area to be as close to the channel surface as possible. The more severe challenge is that such devices often operate under high frequency (nanosecond transient process) working conditions, and the detection system needs to have nanosecond time resolution and dynamic response capability. Therefore, the development of online temperature detection technology with micro-nano scale spatial resolution and nanosecond transient time resolution has become a major technical demand in the field of wide bandgap semiconductor device research.

[0003] At present, the main channel junction temperature testing methods for high frequency and high power devices (such as GaN HEMT, GaAs HEMT) internationally include: junction temperature testing method based on electrical parameter characterization, infrared thermal imaging method, Raman thermal imaging method and thermal reflection imaging method.

[0004] The junction temperature testing method based on electrical parameter characterization obtains temperature by measuring temperature-related electrical parameters (saturated drain current, gate drain current and threshold voltage, etc.) of the device. This testing method does not have spatial resolution capability, and the test result represents the average temperature of the entire region of the device channel, so the electrical method usually underestimates the channel junction temperature.

[0005] The infrared thermal imaging method obtains temperature by measuring the infrared thermal radiation emitted by the device surface according to the Stefan-Boltzmann law, and the limit spatial resolution is in the range of 3um to 10um, which is insufficient in spatial resolution.

[0006] The Raman thermal imaging method obtains temperature by measuring the change of phonon frequency generated by the material with temperature change. The time resolution of this method reaches the level of 10 nanoseconds, and the spatial resolution can reach the sub-micron level. However, the detection light wavelength (532 / 488nm) used by this method is usually larger than the absorbable wavelength (365nm) of gallium nitride, and the detection light penetrates the gallium nitride layer, so that the test temperature is the average temperature of the gallium nitride layer. Therefore, the test result of the Raman method is usually lower than the actual temperature of the channel.

[0007] The current thermal reflection thermometry method is mainly in the form of thermal reflection imaging (TTI), which uses an LED light source as a detection light to irradiate the surface of the material, and detects the reflectivity change of the material surface through a charge coupled device (CCD) camera. However, the existing thermal reflection thermometry method cannot meet the nanosecond-level transient temperature detection requirement of high-frequency power devices. SUMMARY

[0008] The present application provides a semiconductor device temperature characterization method and system, which solves the problem that the prior art cannot realize nanosecond-level time and sub-micron-level spatial resolution temperature characterization of semiconductor devices.

[0009] The present application provides a semiconductor device temperature characterization system, which comprises: A device carrying and adjusting unit for carrying a semiconductor device and adjusting the position of the semiconductor device; A detection laser emitting unit for emitting detection laser and irradiating the test area of the semiconductor device; A pump laser emitting unit for emitting heating laser and irradiating the test area of the semiconductor device; A temperature measurement unit for collecting and recording the temperature measurement signal reflected by the semiconductor device; A device operation control unit for providing an electric signal to the semiconductor device and synchronously triggering the temperature measurement unit to record the temperature measurement signal, so as to ensure that the semiconductor device is online and the temperature measurement is synchronous; A master control unit for obtaining the transient temperature characterization information of the semiconductor device based on the temperature measurement signal.

[0010] Preferably, the device operation control unit comprises a waveform generator and / or a source table, and the device operation control unit is used to provide electric signals according to the working mode of different types of semiconductor devices.

[0011] Preferably, the device carrying and adjusting unit comprises a temperature control table and a displacement table, the semiconductor device is fixed on the temperature control table, the temperature control table is installed on the displacement table, the temperature control table is used to maintain the bottom temperature of the semiconductor device to a target temperature, and the displacement table is used to adjust the position of the semiconductor device.

[0012] Preferably, the device-carrying adjustment unit further comprises a white light auxiliary monitoring assembly; the white light auxiliary monitoring assembly comprises a white light source and a CCD camera, and the CCD camera is connected to the main control unit; the white light auxiliary monitoring assembly is used for monitoring the test area of the semiconductor device and the spot of the probe laser, and assisting the probe laser to focus on the test area of the semiconductor device.

[0013] Preferably, the probe laser emission unit comprises a wavelength-adjustable continuous laser, or the probe laser emission unit comprises a plurality of continuous lasers with different operating wavelengths.

[0014] Preferably, the semiconductor device temperature characterization system further comprises an incident guiding unit; the incident guiding unit is used for combining and coaxially converging the heating laser and the probe laser to the test area of the semiconductor device; the incident guiding unit comprises a beam splitter, a beam expander, a dichroic beam splitter in a beam combination path, and an objective lens; the heating laser after expansion by the beam expander and the probe laser after transmission by the beam splitter are incident to the dichroic beam splitter in the beam combination path, and the heating laser and the probe laser are combined and coaxially output after the dichroic beam splitter in the beam combination path, and then are focused by the objective lens to irradiate the test area of the semiconductor device; the reflected probe light formed by the reflection of the probe laser on the semiconductor device is transmitted to the temperature measurement unit after being incident to the beam splitter.

[0015] Preferably, the temperature measurement unit comprises a filter, a lens, a photodetector, and an oscilloscope; the filter is arranged on the reflected light path of the beam splitter, and the oscilloscope is connected to the device operation control unit; the filter is used for filtering out the heating laser reflected by the semiconductor device; the lens is used for converging the reflected probe light to the photodetector; the photodetector is used for collecting the reflected probe light; and the oscilloscope is used for displaying the temperature measurement signal and synchronously recording based on the trigger signal from the device operation control unit.

[0016] Preferably, the incident guiding unit further comprises at least one mirror for adjusting the incident light path; and the temperature measurement unit comprises at least one mirror for adjusting the temperature measurement light path.

[0017] Preferably, the probe laser emission unit can emit continuous laser with a wavelength of 200 nm to 1000 nm; the resolution of the objective lens is ≤1 μm; the time resolution of the photodetector is ≤4 ns, and the bandwidth of the photodetector is ≥100 MHz; the bandwidth of the oscilloscope is ≥500 MHz, the sampling rate is ≥1 GSa / s, and the number of channels is ≥2; and the bandwidth of the device operation control unit is ≥350 MHz, and the number of channels is ≥2.

[0018] In another aspect, the present application provides a semiconductor device temperature characterization method, comprising the following steps: Building a semiconductor device temperature characterization system as described above; Carrying the semiconductor device and adjusting the position of the semiconductor device by using the device carrying and adjusting unit; emitting and irradiating the probe laser to the test area of the semiconductor device by using the probe laser emitting unit; emitting and irradiating the heating laser to the test area of the semiconductor device by using the pump laser emitting unit; collecting and recording the temperature measurement signal reflected by the semiconductor device by using the temperature measurement unit; providing the electric signal for the semiconductor device by using the device operation control unit, and triggering the temperature measurement unit to record the temperature measurement signal synchronously, so as to ensure the synchronization of the online work of the semiconductor device and the temperature measurement; obtaining the transient temperature characterization information of the semiconductor device based on the temperature measurement signal by using the master control unit.

[0019] The one or more technical solutions provided in the present application have at least the following technical effects or advantages: The semiconductor device temperature characterization scheme provided by the present application comprises: carrying the semiconductor device and adjusting the position of the semiconductor device by using the device carrying and adjusting unit; emitting and irradiating the probe laser and the heating laser to the test area of the semiconductor device by using the probe laser emitting unit and the pump laser emitting unit, respectively; collecting and recording the temperature measurement signal reflected by the semiconductor device by using the temperature measurement unit; providing the electric signal for the semiconductor device by using the device operation control unit, and triggering the temperature measurement unit to record the temperature measurement signal synchronously, so as to ensure the synchronization of the online work of the semiconductor device and the temperature measurement; obtaining the transient temperature characterization information of the semiconductor device based on the temperature measurement signal by using the master control unit. The present application can not only characterize the temperature of the semiconductor device in the working state, but also can realize the temperature characterization of the semiconductor device with nanosecond-level time and sub-micron-level spatial resolution by combining the continuous laser, the high-bandwidth photoelectric detector, the high-bandwidth high-sampling-rate oscilloscope, the high-magnification objective lens and the high-bandwidth device operation control unit to cooperate with the signal test. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A schematic diagram of a semiconductor device temperature characterization system provided for embodiment 1 of the present application; Figure 2 A layout schematic diagram of GaN HEMT as a test object; Figure 3 A transient mode temperature rise diagram corresponding to the test area of GaN HEMT.

[0021] Wherein, 1-probe laser emitting unit, 2-first mirror, 3-white light source, 4-second mirror, 5-beam splitter, 6-pump laser emitting unit, 7-beam expander, 8-third mirror, 9-merging path dichroic beam splitter, 10-objective lens, 11-temperature control platform, 12-displacement platform, 13-filter, 14-fourth mirror, 15-lens, 16-photodetector, 17-oscilloscope, 18-waveform generator, 19-source table, 20-CCD camera, 21-master control unit. DETAILED DESCRIPTION

[0022] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the drawings and specific embodiments of the specification.

[0023] Embodiment 1: Embodiment 1 provides a semiconductor device temperature characterization system, mainly comprising: A device carrying and adjusting unit for carrying a semiconductor device and adjusting the position of the semiconductor device; A probe laser emitting unit for emitting probe laser and irradiating to the test area of the semiconductor device; A pump laser emitting unit for emitting heating laser and irradiating to the test area of the semiconductor device; A temperature measuring unit for collecting and recording the temperature measuring signal reflected by the semiconductor device; A device operation control unit for providing an electrical signal to the semiconductor device and synchronously triggering the temperature measuring unit to record the temperature measuring signal, ensuring that the semiconductor device is online and the temperature measurement is synchronized; A master control unit for obtaining the transient temperature characterization information of the semiconductor device based on the temperature measuring signal.

[0024] The above technical solutions will be described in detail below in conjunction with the drawings and specific embodiments of the specification. Figure 1 Each unit will be described respectively.

[0025] (1) Device carrying and adjusting unit.

[0026] The device carrying and adjusting unit comprises a temperature control platform 11 and a displacement platform 12; the semiconductor device is fixed on the temperature control platform 11, and the temperature control platform 11 is installed on the displacement platform 12; the temperature control platform 11 is used to maintain the bottom temperature of the semiconductor device to the target temperature; the displacement platform 12 is used to adjust the position of the semiconductor device.

[0027] The displacement platform 12 can adopt an electric three-dimensional displacement platform, and the x, y axis resolution of the electric three-dimensional displacement platform is ≤1um, and the z axis resolution is ≤5um.

[0028] The temperature control accuracy of the temperature control platform 11 is at least 0.1℃, the uniformity is at least 0.5℃, and the temperature control interval is at least room temperature to 200℃.

[0029] The device-carrying adjustment unit can further comprise a white light auxiliary monitoring assembly; the white light auxiliary monitoring assembly comprises a white light source 3 and a CCD camera 20 connected with the main control unit 21; the white light auxiliary monitoring assembly is used for monitoring the test area of the semiconductor device and the spot of the probe laser, and assisting the probe laser to focus on the test area of the semiconductor device.

[0030] (2) Probe laser emitting unit. The probe laser emitting unit 1 comprises a wavelength-tunable continuous laser, or the probe laser emitting unit 1 comprises a plurality of continuous lasers with different working wavelengths.

[0031] Whether the wavelength-tunable continuous laser or the plurality of continuous lasers with different working wavelengths is used, it is required to realize that the continuous laser with different wavelengths (200 nm to 1000 nm) can be emitted to detect the change of reflectivity of the surface of different materials of the semiconductor device. That is, the probe laser emitting unit 1 can emit the continuous laser with the wavelength of 200 nm to 1000 nm.

[0032] (3) Pump laser emitting unit.

[0033] The pump laser emitting unit 6 comprises a pump laser for emitting heating laser and irradiating to the surface of the semiconductor device to heat it, the working wavelength of the pump laser can be selected from the near ultraviolet to the near infrared band, the selection range is 300 nm to 1100 nm; the frequency range of the pump laser should not be greater than 100 kHz; the pulse width is selected between 1 nanosecond (ns) to 50 nanoseconds (ns), and the pulse shape is Gaussian.

[0034] (4) Temperature measuring unit.

[0035] The temperature measuring unit comprises a filter 13, a lens 15, a photodetector 16 and an oscilloscope 17.

[0036] The filter 13 is arranged on the reflected light path of the beam splitter 5, and the oscilloscope 17 is connected with the device operation control unit; the filter 13 is used for filtering all lights except the probe light wavelength; the lens 15 is used for converging the reflected probe light to the photodetector 16; the photodetector 16 is used for collecting the reflected probe light; and the oscilloscope 17 is used for displaying the temperature measuring signal and synchronously recording based on the trigger signal from the device operation control unit.

[0037] The photoelectric detector 16 corresponds to the detection wavelength, and its time resolution can be calculated by the formula (t=0.35 / bandwidth). In order to achieve nanosecond-level time resolution, the time resolution of the photoelectric detector 16 is ≤4ns, and the bandwidth of the photoelectric detector 16 is ≥100MHz.

[0038] The oscilloscope 17 is used to display the detection laser signal obtained by the transient thermal reflection test, the bandwidth of the oscilloscope 17 is ≥500MHz, the sampling rate is ≥1GSa / s, and the number of channels is ≥2. The temperature measurement unit can further include at least one mirror, for example Figure 1 The fourth mirror 14 in the fourth mirror 14 is used to adjust the temperature measurement light path.

[0039] (5) Device operation control unit.

[0040] The device operation control unit mainly includes a waveform generator 18, a source table 19 and other core devices that can provide accurate electrical signals. In addition, the device operation control unit can also include components for realizing reliable connection of electrical signals and semiconductor devices, such as probe seats, probes, and low-loss connectors. According to the working mode of different types of semiconductor devices, the device operation control unit provides electrical signals.

[0041] The bandwidth of the device operation control unit is ≥350MHz, and the number of channels is ≥2.

[0042] The device operation control unit is an important functional module for realizing “device online working + temperature measurement synchronization”. Its core design goal is to adapt to the working mode of different types of semiconductor devices, to provide accurate electrical signals, and to trigger the oscilloscope to record the reflected light signal synchronously, to ensure that the transient temperature test is highly matched with the actual working state of the device, and all the adapted working modes have transient signal test capability.

[0043] For example, for high-frequency pulse mode devices (such as GaN HEMT, GaAs HEMT, Si MOSFET, GaN MOSFET, etc.), the arbitrary waveform generator is the core of the electrical signal providing device. The selection needs to focus on meeting the high-frequency characteristics: bandwidth ≥ 350MHz (extensible to 1GHz to adapt to higher frequency devices), channel number ≥ 2 (used to output gate pulse driving signal), and needs to have channel coupling function (ensure the phase consistency of multiple channel signals, synchronous trigger oscilloscope recording, avoid signal time delay caused by working condition deviation); support output pulse period 10ns to 1s, duty cycle 1% to 99% high-frequency square wave, sawtooth wave and other pulse waveforms, match GaN HEMT high-frequency switching working characteristics; The source table needs to have fast current sampling capability (add bias to the drain), which is used to monitor the average working current and power consumption of the device under pulse working condition.

[0044] For example, for devices with complex dynamic working mode (such as GaN HEMT, GaAs HEMT self-defined waveform driving working condition), the arbitrary waveform generator selects a high flexibility type, in addition to meeting the bandwidth ≥ 350MHz, channel number ≥ 2, channel coupling function, it also needs to support user-defined waveform import (such as asymmetric pulse, amplitude modulation waveform based on actual application scene), waveform storage depth ≥ 1Mpts to ensure complete output of complex waveforms; The source table needs to have a wide range of self-adaptive adjustment capability, which can adjust the output voltage / current range in real time according to the dynamic working condition requirements of the device, and ensure the stable working of the device under complex dynamic bias.

[0045] For example, for devices with steady-state DC working mode (such as Si-based power devices with DC bias working condition), the source table is the core of the electrical signal providing device. The selection needs to meet: output voltage range covers 0V to 60V (adapt to medium and high voltage power devices), output current range covers 0A to 10A (adapt to large current devices), which is used to provide stable DC bias for the device while real-time sampling of the device working current and calculating the device power consumption; The arbitrary waveform generator selected needs to have basic functions, with bandwidth ≥ 350MHz, channel number ≥ 2, and channel coupling function, which can output small amplitude gate on / off trigger pulse to realize signal cooperative control with the source table.

[0046] For example, for Gate Turn-Off Thyristor (GTO) as a high-voltage and large-current semiconductor device, its operation depends on the cooperative control of gate positive pulse triggering conduction and gate negative pulse active turn-off, and the anode needs to withstand high-voltage and large-current bias. The core design goal of the device operation control unit is to adapt to this working mode, provide accurate gate pulse signals and anode high-voltage bias, support gate single pulse wave driving work synchronous trigger oscilloscope to record the reflected light signal under single pulse wave driving work, ensure that the transient temperature test is highly matched with the actual switching condition of GTO, and the corresponding arbitrary waveform generator needs to meet the bandwidth ≥ 350MHz (extensible to 1GHz to adapt to the high-frequency turn-off requirement of GTO), the channel number ≥ 2 and has the channel coupling function, supports the high-frequency square wave, sawtooth wave and other pulse waveforms with the pulse period of 10ns to 1s and the duty cycle of 1% to 99%, guarantees the steepness of the gate driving signal to meet the requirements of GTO fast conduction and turn-off, and the source table needs to be a high-voltage and large-current model (the specific voltage requirement is determined according to the device), has a fast current sampling capability of ≥ 1MHz, can provide stable bias for the anode of GTO, and can monitor the anode average working current and power consumption under pulse working condition in real time, and accurately feedback the energy loss state in the device switching process.

[0047] For example, Electro-Absorption Modulated Distributed Feedback Laser (EA-DFB) uses a composite working mode of "DFB chip continuous light output + EA modulator high-speed electrical signal modulation", needs to stabilize the direct current bias to ensure the DFB chip light emission, and high-frequency electrical pulse drives the EA modulator to realize optical signal modulation. Its transient temperature test needs to match "light emission stability + electrical modulation high speed", so the core design goal of the device operation control unit is to adapt to the composite mode, provide accurate DFB direct current bias and EA high-speed modulation electrical signal, trigger the oscilloscope to record the reflected light signal synchronously, and ensure that the test is highly consistent with the actual communication working condition of the EA-DFB. The corresponding arbitrary waveform generator needs to meet the bandwidth ≥ 350MHz (extensible to 2GHz to adapt to the high-speed demand), the channel number ≥ 2 and has the channel coupling function, 1 channel output adapts to the pulse waveform of the low-voltage driving characteristics of the EA modulator, supports high-frequency square wave / narrow pulse output with pulse period 10ns to 1s and duty cycle 1% to 90%, and the waveform storage depth ≥ 1Mpts to ensure the integrity of the long sequence waveform. The channel coupling function ensures that the modulation signal and the oscilloscope trigger signal are synchronous, and avoids timing deviation; the source table needs to adapt to the working interval of the DFB chip, provide stable direct current bias to ensure the stability of the optical output power, and has a fast current sampling capability of ≥ 1MHz, monitors the working current in real time and calculates the light emission power consumption, and feeds back the bias stability; in addition, the second channel of the arbitrary waveform generator can output a synchronous calibration pulse, which cooperates with the source table bias signal to ensure that the timing of the DFB chip light emission and the EA modulator driving signal is aligned, and ensures the effectiveness of the test.

[0048] (6) The main control unit.

[0049] The main control unit 1 can adopt a computer.

[0050] In addition, the semiconductor device temperature characterization system can further include an incident guiding unit.

[0051] (7) The incident guiding unit.

[0052] The incident guiding unit is used for combining and coaxially converging the heating laser and the detection laser to the test area of the semiconductor device.

[0053] The incidence guiding unit comprises a beam splitter 5, an expander 7, a dichroic beam splitter 9 of a beam combination path, and an objective lens 10; the heating laser beam expanded by the expander 7 and the probe laser beam transmitted by the beam splitter 5 are incident to the dichroic beam splitter 9 of the beam combination path, the heating laser beam and the probe laser beam are combined and coaxially output after passing through the dichroic beam splitter 9 of the beam combination path, and then are focused by the objective lens 10 to irradiate the test region of the semiconductor device; the reflected probe light formed by the reflection of the probe laser beam on the semiconductor device is transmitted to the temperature measuring unit after being incident to the beam splitter 5.

[0054] The objective lens 10 is adapted to the selected laser wavelength; and the resolution of the objective lens 10 is ≤1 μm.

[0055] In specific applications, the resolution can be determined according to applicable theories or technical specifications, for example, common calculation methods include Rayleigh criterion (d=0.61λ / NA) and Abbe limit theory (d=0.5λ / NA), wherein d represents the resolution of the objective lens, λ is the wavelength of the selected laser, and NA is the numerical aperture of the objective lens. If there are other formulas applicable to the resolution calculation of the objective lens (such as formulas provided by the supplier), the calculation results of the corresponding formulas shall be used as the criteria, and all need to meet the requirement of resolution ≤1 μm.

[0056] The incidence guiding unit can further comprise at least one mirror, for example Figure 1 the first mirror 2, the second mirror 4, and the third mirror 8 in FIG. 1, all of which are used to adjust the incidence light path.

[0057] Overall, the semiconductor device temperature characterization system provided in Embodiment 1 cooperates with continuous laser, high-bandwidth photodetector, high-bandwidth high-sampling-rate oscilloscope, high-magnification objective lens, and high-bandwidth device operation control unit to realize nanosecond-level time and sub-micron-level spatial resolution temperature characterization of the device.

[0058] Embodiment 2: Embodiment 2 provides a semiconductor device temperature characterization method, comprising the following steps: The semiconductor device temperature characterization system as described in Embodiment 1 is built; The device carrying and adjusting unit is used to carry and adjust the position of the semiconductor device; the probe laser emission unit is used to emit probe laser and irradiate the test region of the semiconductor device; the pump laser emission unit is used to emit heating laser and irradiate the test region of the semiconductor device; the temperature measuring unit is used to collect and record the temperature measurement signal reflected by the semiconductor device; the device operation control unit is used to provide an electrical signal for the semiconductor device and synchronously trigger the temperature measuring unit to record the temperature measurement signal, so as to ensure that the semiconductor device is online and the temperature measurement is synchronous; and the master control unit is used to obtain the transient temperature characterization information of the semiconductor device based on the temperature measurement signal.

[0059] Embodiment 2 provides a temperature characterization method corresponding to the semiconductor device temperature characterization system provided in Embodiment 1, and thus can be understood with reference to the description of Embodiment 1.

[0060] Embodiment 2 is further described below in combination with parameters.

[0061] The semiconductor device temperature characterization method provided in Embodiment 2 can have the following operations in application: S1, fixing a semiconductor device.

[0062] The semiconductor device is fixed on a temperature control table using a heat-conducting paste.

[0063] S2, selecting a probe laser.

[0064] The thermal reflectance coefficient C of the material of the test region of the semiconductor device is selected. th The wavelength light source has a large (|C th |>1E-4) and an absorption depth <100nm.

[0065] For example, for GaN HEMT channel (AlGaN / GaN), 320nm and 365nm wavelengths are selected; for GaAs HEMT channel (GaAs), 450nm and 532nm wavelengths are selected; for Si device channel (Si), 530nm wavelength is selected; for general device Au electrode, 532nm wavelength is selected; for Al electrode, 785nm wavelength is selected. The absorption depth can be calculated through literature or formula (δ=1 / α, α is the absorption coefficient of the material). For other materials, if |C th |>1E-4 and the penetration depth <100nm, the wavelength is appropriate.

[0066] Preferably, the thermal reflectance coefficient is calibrated.

[0067] The thermal reflectance coefficient C of the material of the test region of the semiconductor device is selected. th The calibration can be performed in combination with the pump-probe thermal reflectance method (TTR) and the transient temperature rise model. The maximum temperature rise ΔT max of the central region of the test region of the semiconductor device heated under the irradiation of the pump laser is calculated through the transient temperature rise model. max The maximum value ΔR / R max of the reflectivity change ratio of the probe light triggered by the pump laser is synchronously measured. max A series of the maximum temperature change ΔT th and the reflectivity change ratio maximum value ΔR / R th are linearly fitted to determine the C th of the sample.

[0068] The thermal reflectance coefficient Cth The calibration can also be calibrated by a conventional method, that is, fixing the material to be measured on a high-precision temperature control platform and installing a thermocouple temperature measuring device; synchronously monitoring the reflectivity change ΔR of the material under a preset temperature gradient; establishing a reflectivity-temperature mapping relationship according to the thermocouple collected temperature data and the corresponding ΔR change value; and obtaining the thermal reflectivity coefficient C based on the linear slope of the mapping relationship th Calibration parameters.

[0069] S3, focusing the probe light.

[0070] The bottom temperature of the semiconductor device is controlled by the temperature control console to be constant at the target temperature T0. The test area and the probe laser spot are detected by the white light auxiliary monitoring assembly. The exit light of the selected light source is focused on the test area by the objective lens and the displacement table.

[0071] During the process, the laser power can also be adjusted as needed by selecting a suitable power to make the light-induced current percentage <10%.

[0072] S4, measuring and recording the reflected light signals of the test area before and after the semiconductor device is powered on.

[0073] Measuring the reflected light signals of the test area before and after the semiconductor device is powered on includes two modes.

[0074] (1) Steady-state mode: Record the reflected light signal of the test area before power supply, read the voltage value from the oscilloscope, and record it as V0. Apply a steady voltage signal to the device using an arbitrary waveform generator and a DC source table. After the steady-state mode is powered on and the heat balance is waited, the reflected light signal of the test area is recorded, the voltage value is read using a photodetector and an oscilloscope, and recorded as V. The voltage and current readings of the DC source table are recorded as U1 and I1.

[0075] (2) Transient mode: Apply a periodic electrical signal (period T, duty cycle D) to the semiconductor device using an arbitrary waveform generator and a DC source table, so that the semiconductor device is in a periodic switching state. Use the channel coupling function to synchronize the semiconductor device periodic switching state type to the oscilloscope as a trigger signal. Record the reflected light transient signal V2(t) of the test area of the semiconductor device in the periodic switching state using a photodetector and an oscilloscope. Read the average voltage signal of the off period time ≤10% before the off period cutoff, and record it as V1. Record the voltage and current readings of the DC source table as U2 and I2.

[0076] S5, data processing.

[0077] (1) In the steady-state mode, the following formula is used for calculation:

[0078] When operating at a power of U1I1 (in W), the temperature of the test area of ​​the semiconductor device is T1.

[0079] (2) The following formula is used for calculation in transient mode sampling:

[0080] Under operating conditions with period T and duty cycle D, the transient temperature of the test area of ​​the semiconductor device is T2(t).

[0081] The following example illustrates the application of temperature measurement in the GaN HEMT channel layer for GaN device systems.

[0082] The electrode layout of the GaN HEMT used as the test object is as follows: Figure 2 As shown, the red circle represents the measured location.

[0083] The temperature characterization method for this device includes the following steps: S1, Fix the sample.

[0084] Use thermal paste to fix the GaN HEMT onto the temperature control panel.

[0085] S2, Select the detection laser.

[0086] Based on the material properties, select materials with good thermal reflectivity and C. th Larger wavelengths are used for temperature measurement to improve the accuracy and efficiency of thermal reflection temperature measurement. For GaN HEMT, a 320nm continuous laser is selected as the detection laser.

[0087] Among them, the thermal reflectance C of the test area was measured. th Calibration, calibration yields C th =1.36E-4.

[0088] S3, focusing of the probe light.

[0089] The bottom temperature of the semiconductor device was kept constant at 30°C using a temperature control stage. A white light auxiliary monitoring unit was used to monitor the test area and the probe light. The emitted light from the selected light source was focused onto the GaN HEMT channel region using a 20x ultraviolet objective lens (laser spot diameter of 0.8μm) and a displacement stage.

[0090] The laser output power was adjusted so that the laser power incident on the test area was 23 nW, and the laser power density was 10 nW / μm. 2 At this power, the percentage of photoinduced current is 3%.

[0091] S4. The light signal reflected from the area under test before and after the measuring and recording device is powered on.

[0092] Connect arbitrary waveform generator, source meter and device metal electrode by using probe, probe holder and related connecting line; further use displacement table to move 320nm probe laser to 1 micron away from the center of gate metal to channel layer (as shown in the middle circle of Figure 2 Figure 1) under the assistance of white light auxiliary monitoring unit.

[0093] Apply electrical signal to GaN HEMT device by using power supply includes two modes: (1) steady state mode: apply +3V voltage to GaN HEMT gate by using transient power supply, probe holder, probe, connecting line, etc., and apply +10V voltage to GaN HEMT gate by using DC source meter, probe holder, probe, connecting line, etc.

[0094] (2) transient mode: apply square wave with 200 microseconds period, 50% duty cycle, +3V high level voltage and -3.5V low level voltage to GaN HEMT gate by using transient power supply, probe holder, probe, connecting line, etc., and apply +10V voltage to GaN HEMT gate by using DC source meter, probe holder, probe, connecting line, etc.

[0095] In steady state mode, record the reflection light signal voltage of the measured area before power on as 77.29mV. After power on, use detector and oscilloscope to receive the reflection light signal of the measured area of GaN HEMT device after power on, read the voltage as 78.43mV, and record the DC source meter current value as 56mA.

[0096] In transient mode, input the square wave from transient power supply to device and oscilloscope at the same time, use the square wave as trigger signal (trigger when high level), use detector and oscilloscope to receive the reflection light signal of the measured area of device after power on, open the average mode of oscilloscope, after the average times >65535, record the transient reflection light signal V2(t) of the measured area of device, read the voltage value when the device is off as 79.26mV, and record the DC source meter current reading as 23mA.

[0097] S5, data processing; (1) in steady state mode, calculate by using the following formula:

[0098] Get the temperature of the measured area of semiconductor device as 149℃ under the working condition of power density of 5.6W / mm.

[0099] (2) in transient mode, calculate by using the following formula:

[0100] The transient temperature rise of the test area of the semiconductor device under the condition of a power density of 4.6 W / mm and a cycle of 200 microseconds, 100 microseconds on and 100 microseconds off is obtained as shown in FIG. 6. Figure 3

[0101] Other similar devices, such as GaAs, Si, InP, Ge-based devices, etc. also use the above method for semiconductor layer temperature characterization.

[0102] In summary, based on the heat reflection principle, the application proposes a multi-wavelength laser transient heat reflection temperature measurement technology, which cooperates with device operation control, and can realize high spatial resolution + high time resolution + online device different area (metal contact, channel, etc.) temperature measurement.

[0103] Finally, it should be explained that the above specific embodiments are only used to illustrate the technical solutions of the application and are not limited. Although the application is described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the application, which should be covered in the scope of the claims of the application.​

Claims

1. A semiconductor device temperature characterization system, comprising: The device includes: a device-carrying and adjusting unit for carrying and adjusting the position of a semiconductor device; a probe laser emitting unit for emitting probe laser and irradiating to the test area of the semiconductor device; a pump laser emitting unit for emitting heating laser and irradiating to the test area of the semiconductor device; a temperature measuring unit for collecting and recording the temperature measuring signal reflected by the semiconductor device; a device operation control unit for providing electrical signal to the semiconductor device and synchronously triggering the temperature measuring unit to record the temperature measuring signal, ensuring the synchronization of the on-line operation of the semiconductor device and the temperature measurement; a main control unit for obtaining the transient temperature characterization information of the semiconductor device based on the temperature measuring signal.

2. The semiconductor device temperature characterization system of claim 1, wherein, The device operation control unit includes a waveform generator and / or a source table, and the device operation control unit provides electrical signal according to the working mode of different types of semiconductor devices.

3. The semiconductor device temperature characterization system of claim 1, wherein, The device-carrying and adjusting unit includes a temperature control platform and a displacement platform, the semiconductor device is fixed on the temperature control platform, the temperature control platform is installed on the displacement platform, the temperature control platform is used to maintain the bottom temperature of the semiconductor device to the target temperature, and the displacement platform is used to adjust the position of the semiconductor device.

4. The semiconductor device temperature characterization system of claim 3, wherein, The device-carrying and adjusting unit further includes a white light auxiliary monitoring assembly, the white light auxiliary monitoring assembly includes a white light source and a CCD camera, the CCD camera is connected with the main control unit, and the white light auxiliary monitoring assembly is used to monitor the test area of the semiconductor device and the probe laser spot, and assist the focusing of the probe laser to the test area of the semiconductor device.

5. The semiconductor device temperature characterization system of claim 1, wherein, The probe laser emitting unit includes a wavelength-adjustable continuous laser, or the probe laser emitting unit includes a plurality of continuous lasers with different working wavelengths.

6. The semiconductor device temperature characterization system of claim 5, wherein, Further includes: an incident guiding unit; The incident guiding unit is used for combining and coaxially converging the heating laser and the probe laser to the test area of the semiconductor device; The incident guiding unit includes a beam splitter, a beam expander, a dichroic beam splitter in a beam combination path, and an objective lens, the heating laser expanded by the beam expander and the probe laser transmitted by the beam splitter are incident to the dichroic beam splitter in the beam combination path, the heating laser and the probe laser are combined and coaxially output after the dichroic beam splitter in the beam combination path, and then focused by the objective lens and irradiated to the test area of the semiconductor device; The reflected probe light formed by the reflection of the probe laser on the semiconductor device is transmitted to the temperature measuring unit after being incident to the beam splitter.

7. The semiconductor device temperature characterization system of claim 6, wherein, The temperature measuring unit includes a filter, a lens, a photodetector, and an oscilloscope, the filter is arranged on the reflected light path of the beam splitter, the oscilloscope is connected with the device operation control unit, the filter is used to filter out the heating laser reflected by the semiconductor device, the lens is used to converge the reflected probe light to the photodetector, the photodetector is used to collect the reflected probe light, and the oscilloscope is used to display the temperature measuring signal and synchronously record based on the trigger signal from the device operation control unit.

8. The semiconductor device temperature characterization system of claim 7, wherein, The incident guiding unit further comprises at least one mirror for adjusting the incident light path; the temperature measuring unit comprises at least one mirror for adjusting the temperature measuring light path.

9. The semiconductor device temperature characterization system of claim 7, wherein, The probe laser emitting unit can emit continuous laser with a wavelength of 200-1000 nm; the resolution of the objective lens is ≤1 μm; the time resolution of the photoelectric detector is ≤4 ns, the bandwidth of the photoelectric detector is ≥100 MHz; the bandwidth of the oscilloscope is ≥500 MHz, the sampling rate is ≥1 GSa / s, and the number of channels is ≥2; the bandwidth of the device operation control unit is ≥350 MHz, and the number of channels is ≥2.

10. A method of temperature characterization of a semiconductor device, the method comprising: The method comprises the following steps: building the semiconductor device temperature characterization system according to any one of claims 1-9; carrying and adjusting the position of the semiconductor device by the device carrying and adjusting unit; emitting probe laser to the test area of the semiconductor device by the probe laser emitting unit; emitting heating laser to the test area of the semiconductor device by the pump laser emitting unit; collecting and recording the temperature measuring signal reflected by the semiconductor device by the temperature measuring unit; providing electrical signal for the semiconductor device by the device operation control unit, and triggering the temperature measuring unit to record the temperature measuring signal synchronously to ensure the synchronization of the on-line operation of the semiconductor device and the temperature measurement; obtaining the transient temperature characterization information of the semiconductor device based on the temperature measuring signal by the master control unit.

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