CN219675840U - Semiconductor heat conductivity coefficient testing device based on pumping detection Raman spectrum - Google Patents
Semiconductor heat conductivity coefficient testing device based on pumping detection Raman spectrum Download PDFInfo
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- 238000005086 pumping Methods 0.000 title claims abstract description 25
- 239000004065 semiconductor Substances 0.000 title claims abstract description 22
- 238000001514 detection method Methods 0.000 title claims abstract description 17
- 238000001237 Raman spectrum Methods 0.000 title claims abstract description 16
- 238000012360 testing method Methods 0.000 title claims description 6
- 230000003287 optical effect Effects 0.000 claims abstract description 27
- 238000005259 measurement Methods 0.000 claims abstract description 18
- 238000001069 Raman spectroscopy Methods 0.000 claims abstract description 14
- 230000005284 excitation Effects 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 9
- 238000001228 spectrum Methods 0.000 claims abstract description 9
- 239000002184 metal Substances 0.000 claims description 5
- 239000000463 material Substances 0.000 abstract description 6
- 238000010438 heat treatment Methods 0.000 abstract description 3
- 238000001579 optical reflectometry Methods 0.000 abstract description 2
- 239000000523 sample Substances 0.000 description 48
- 238000002310 reflectometry Methods 0.000 description 4
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000004093 laser heating Methods 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 238000005424 photoluminescence Methods 0.000 description 1
- 210000001747 pupil Anatomy 0.000 description 1
- 238000000985 reflectance spectrum Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
Abstract
The patent discloses a semiconductor thermal conductivity device based on pumping detection Raman spectrum. The device comprises a pumping source excitation and detection subsystem, a pumping laser spot adjusting subsystem, a temperature control subsystem of a sample and a reference plane, a Raman excitation and collection subsystem, a spectrum measurement subsystem, an optical element switching control component and a computer central control. The method uses the device to measure the excitation light reflectivity and the pumping-detection Raman spectrum, and can accurately acquire the semiconductor temperature change caused by pumping heating, thereby measuring the heat conductivity coefficient. The method has the advantages of convenience, no damage, non-contact and the like, and is very suitable for thermal property detection of micro-size photoelectric materials.
Description
Technical Field
The patent relates to a semiconductor heat conductivity testing technology and an experimental device, in particular to a method and a device for measuring semiconductor heat conductivity based on pump-detection Raman spectrum.
Background
The thermal conductivity of a semiconductor is an important thermal property parameter directly related to the heat dissipation and power handling capabilities of the resulting semiconductor device. Particularly with the development of high speed, high integration of microelectronic/optoelectronic devices, the dramatic decrease in cell size places high demands on the thermal conductivity from the semiconductor material. Measuring the thermal conductivity of microscale semiconductors is thus an important technical problem.
At present, the heat conductivity coefficient is mainly divided into indirect measurement and direct measurement. The former obtains the heat conductivity by measuring other physical quantities related to the heat conductivity, for example, a laser method is to obtain the diffusion coefficient of the material, and then calculate the heat conductivity by combining the density and the specific heat value of the material. The accuracy of the thermal conductivity is directly related to the measurement accuracy of these three physical quantities. The latter calculates the thermal conductivity by defining the heat and temperature gradient of the measured material according to the thermal conductivity, typically as in the steady state method, but suffers from the limitations of complex experimental conditions, thermal contact with the sample, etc. This makes it difficult to use for reliable measurement of micro-scale semiconductor thermal conductivity.
The semiconductor absorbs photons having energies greater than the forbidden bandwidth. Semiconductor photoluminescence is typically very inefficient, especially at near room temperature, with negligible photoluminescent radiant energy. Photons absorbed by the semiconductor are converted into heat, creating a heating effect for the sample. The anti-stokes peak to stokes peak intensity ratio of the raman spectrum is an important parameter reflecting the temperature of the sample. The temperature measurement by utilizing the characteristic is self-reference measurement, so that the influence of laser intensity fluctuation, a collection system and optical path calibration is avoided to a great extent.
Based on the characteristics, the patent discloses a semiconductor heat conductivity coefficient testing method and device based on pump-detection Raman spectrum. Specifically, by mode switching of the series optical element, the pump laser reflectance and raman spectrum variation at different pump powers of the semiconductor are measured, respectively, and a minute temperature variation due to laser heating is obtained, thereby calculating the thermal conductivity of the semiconductor.
Disclosure of Invention
The method has the advantages of convenience, no damage, non-contact and the like, and is very suitable for thermal property detection of micro-size photoelectric materials. The device comprises a pumping source excitation and detection subsystem, a pumping laser spot adjusting subsystem, a temperature control subsystem of a sample and a reference plane, a Raman excitation and collection subsystem, a spectrum measurement subsystem, an optical element switching control component and a computer central control. The method uses the device to measure the excitation light reflectivity and the pumping-detection Raman spectrum, and can accurately acquire the semiconductor temperature change caused by pumping heating, thereby measuring the heat conductivity coefficient. The device subsystem is specifically described as follows:
the pumping source excitation and detection subsystem 1 comprises a first continuous laser 101, a narrow-band pass filter 102, an optical beam expander 103, a right-angle plane mirror 104, an optical attenuation sheet 105 and a first photoelectric detector 106;
the pumping laser spot adjusting subsystem 2 comprises a laser reflector 201, a guide light path 202 and a laser focusing lens group 203 with adjustable focal length;
the temperature control subsystem 3 of the sample and the reference plane comprises an optical thermostat 301, a sample to be detected 302, a reference plane mirror 303, a high thermal conductivity metal sample holder 304, a temperature sensor 305 and a temperature display 306;
a raman excitation and collection subsystem 4 comprising a second continuous laser 401, a focusing lens 402, a parabolic mirror 403 with a small aperture in the focusing direction, a parabolic mirror 404, and a scattered light guiding light path 405;
the spectrum measurement subsystem 5 comprises a large-area plane reflection 501, a spectrometer 502 and a long-wave passA filter 503, a narrow band notch filter 504, and a second photodetector 505;
the optical element switching control section 6 controls the laser mirror 201, the metal sample holder 304, and the large-area plane mirror 501;
the computer central control 7 reads the first photodetector 106, the second photodetector 505 and the spectrometer 502 signals.
The photon energy emitted by the first continuous laser 101 is larger than the forbidden bandwidth of the sample to be detected, and the photon energy is used as pump light; the first photodetector 106 detects a wavelength band covering the laser wavelength range; the laser focusing lens group 203 has a focusing function; the sample 302 to be measured has a smooth and flat surface and has zero transmittance for pump light; the reference plane mirror 303 is equal in thickness with the sample 302 to be measured and has a reflectivity of approximately 100% at the wavelength of the pumping laser; the second continuous laser 401 generates photon energy smaller than the photon energy emitted by the first continuous laser (101); the spectrometer (502) covers raman scattered signal bands, which may be, but is not limited to, fourier transform infrared spectrometers and grating spectrometers; the cut-off wavelength of the long-wave pass filter (503) is positioned between the emergent wavelength of the first continuous laser (101) and the anti-Stokes scattered light wavelength; the narrow-band notch filter (504) corresponds to the emergent wavelength of the second continuous laser (401); the second photodetector (505) covers a raman scattered signal band.
According to the device, the patent provides a method for measuring the heat conductivity coefficient of a semiconductor, which comprises the following specific steps:
s1, mounting a sample (302) to be tested and a reference plane mirror (303) on a sample holder (304), and setting the temperature of a thermostat (301);
s2, setting a laser mirror (201) and a large-area plane mirror (501) to an off state through a switching control component (6);
s3, starting a first continuous laser (101), and adjusting the position of a sample holder (304) through a switching control component (6) to enable a pumping laser spot to completely fall on a reference plane mirror (303);
s4, recording an output signal of the first detector (106) through a computer central control (7);
s5, adjusting the position of the sample holder (304) to enable the pumping laser light spot to completely fall on the sample (302) to be detected, recording the output signal of the first detector (106) again, and obtaining the reflectivity of the sample (302) to be detected to the pumping laser according to the ratio of the two signal intensities;
s6, setting a laser reflector (201) and a large-area plane reflector (501) to be in an on state through a switching control component (6), adjusting a laser focusing lens group (203) to change a focusing focal length, enabling the size of a pumping light spot to just cover the surface of a sample (302) to be detected, and recording pumping light power at the moment;
s7, starting a second continuous laser (401) to irradiate laser to the surface of the sample (302) to be detected;
s8, starting a spectrometer (502) for scanning by a computer central control (7), obtaining a Raman spectrum by combining an output signal of a second detector (505), and calculating the current actual temperature of the sample (302) to be detected according to the Stokes and anti-Stokes scattering intensity ratio;
s9, changing the output power of the pump laser (101), performing spectrum scanning again to obtain a Raman spectrum, and calculating the current actual temperature of the sample (302) to be detected;
s10, calculating actual pump power change twice according to the pump laser reflectivity, and then calculating the heat conductivity coefficient of the sample (302) to be measured according to a heat conductivity coefficient definition formula by combining the actual temperature change.
The main advantages of this patent are:
1. the sample does not need pretreatment, and the nondestructive non-contact measurement belongs to nondestructive measurement;
2. the laser light spot can be focused to the micrometer scale, which is very beneficial to the measurement of the thermal characteristics of the micrometer-scale semiconductor;
3. the ratio of the anti-Stokes and Stokes scattering intensities of the Raman spectrum has high sensitivity to temperature changes, and is very favorable for small changes of temperature;
4. the thermal conductivity of the sample to be measured at different temperatures can be measured.
Drawings
Fig. 1 is a schematic diagram of a semiconductor thermal conductivity testing apparatus based on pump-probe raman spectroscopy.
Wherein 101 is a continuous laser with the energy of outgoing photons larger than the forbidden bandwidth of a sample to be detected, 102 is a narrow-band pass filter corresponding to the laser wavelength, 103 is a laser wavelength optical beam expander, 104 is a right-angle plane mirror, 105 is a laser wavelength optical attenuation sheet, and 106 is a photoelectric detector with the detection range covering the laser wavelength; 201 is an electrically movable laser reflector, which has two states of 'on' and 'off', 202 is a guiding light path composed of the laser reflector, 203 is a laser focusing lens group with adjustable focal length; 301 is an optical thermostat, 302 is a sample to be measured, 303 is a reference plane mirror with the same thickness as the sample to be measured, 304 is an electrically movable high-thermal-conductivity metal sample holder, 305 is a temperature sensor, and 306 is a temperature display connected with the sensor; 401 is a second continuous laser, 402 is a focusing lens, 403 is a parabolic mirror with an aperture along the focusing direction, 404 is a parabolic mirror, 405 is a scattered light guiding light path consisting of several planar mirrors; 501 is an electrically movable large-area planar mirror, which has two states of on and off, 502 is a spectrometer covering a raman scattering signal band, 503 is a long-wave pass filter, 504 is a narrow-band notch filter, and 505 is a second photodetector covering a raman scattering signal band; 6 is an optical element switching control part; and 7, computer central control.
Fig. 2 is a schematic flow chart of the measurement.
Detailed Description
Specific embodiments are shown in fig. 1 and 2. The following detailed description of the present patent refers to the accompanying drawings, which are included to provide a better understanding of the technical and functional aspects of the present patent, and are not intended to limit the scope of the present patent.
The optical and electrical components are first arranged according to the electro-optical logic of fig. 1. Defining an "on" state when mirrors 201 and 501 are placed in the optical path, and an "off" state when they leave the optical path. The optical element switching control section 6 controls the positional states of the plane mirrors 201 and 501 and the sample holder 304, respectively. The computer central control 7 reads the photodetectors 106 and 505 and the spectrum 502 information.
During measurement, the sample 302 to be measured and the reference plane mirror 303 are firstly mounted on the sample holder 304 of the optical thermostat 301, and the surfaces of the sample 302 to be measured and the reference plane mirror 303 are kept parallel. The inside of the thermostat 301 is in a vacuum state, and a temperature T0 required for measurement is set and the temperature of the sample holder 304 is kept stable. The temperature of sample holder 304 is monitored by temperature sensor 305 and displayed by temperature display 306.
Both mirrors 201 and 501 are set to the "off" state, and the first continuous laser 101 is activated. The beam expander 103 is adjusted so that the output spot diameter fills the equivalent pupil of the optical path as much as possible. The laser light is now focused into the thermostat 301 via the right angle planar mirror 104, the guiding light path 405 and the parabolic mirror 403.
The sample holder 304 is moved so that the laser spot falls completely on the reference plane mirror 303. The reflected laser light is now fed into the first photodetector 106 through the parabolic mirror 404, the guiding light path 405, the rectangular plane mirror 104 and the optical attenuation sheet 105. The computer 7 reads the detector 106 output signal Sg1.
Sample holder 304 is again moved so that the laser spot falls on the surface of sample 302 to be measured. The computer 7 reads the detector 106 output signal Sg2 at this moment. And calculating the reflectivity of the sample to be measured to the pump laser by using the Sg2/Sg 1.
Both mirrors 201 and 501 are set to the "on" state. At this time, the pump laser is irradiated to the surface of the sample 302 to be measured through the guide optical path 202 and the focusing lens group 203. The equivalent focal length of the focusing lens group 203 and the position of the sample holder 304 are adjusted in a combined way, so that the size of the pumping light spot just covers the surface of the sample 302 to be measured. After the stabilization, the pump light power P1 before entering the thermostat 301 at this time is recorded.
The second continuous laser 401 is turned on to emit laser light onto the surface of the sample 302 to be measured through the lens 402 and the small Kong Fuzhao of the parabolic mirror 403. The output power of laser 401 is as much smaller as possible than the output power of laser 101.
The spectrometer 502 is activated to spectrally scan the optical signal collected by the parabolic mirrors 403 and 404, and the signal is fed through a long pass filter 503 and a narrow band notch filter 504 to a second detector 505. The computer 7 picks up the spectrometer 502 and detector 505 signals simultaneously to obtain a raman spectrum from the sample 302 to be measured and containing stokes and anti-stokes scattering peaks.
The raman spectrum is extracted by the raman wavenumber delta, stokes peak intensity I S And anti-Stokes scattering intensity I AS . The current temperature T1 is calculated by the following formula,
wherein delta 0 Is the wavenumber of the laser light emitted from the second continuous laser 401, h is the planck constant, c is the vacuum light velocity, and k is the boltzmann constant.
The output power of the first continuous laser 101 is changed, and the pump light power P2 before entering the thermostat 301 at this time is recorded after stabilization. The raman spectrum is measured again and the temperature T2 of the sample to be measured at this time is calculated from the spectrum.
Since the thickness of the sample 302 to be measured is much larger than the pump laser wavelength, there is no pump light transmission. According to the definition, the thermal conductivity at the temperature T0 can be obtained,
where d is the sample thickness and A is the sample area. In the accurate measurement, the accuracy of the thermal conductivity measurement can be improved by measuring multiple groups of pump power and temperature and establishing a slope relation of power-temperature coordinates.
Claims (1)
1. The semiconductor heat conductivity coefficient testing device based on the pumping detection Raman spectrum comprises a pumping source excitation and detection subsystem (1), a pumping laser spot adjusting subsystem (2), a temperature control subsystem (3) of a sample and a reference plane, a Raman excitation and collection subsystem (4), a spectrum measurement subsystem (5), an optical element switching control component (6) and a computer central control (7); the method is characterized in that:
the pumping source excitation and detection subsystem (1) comprises a first continuous laser (101) with the energy of outgoing photons larger than the forbidden bandwidth of a sample to be detected, a narrow-band pass filter (102) which is arranged in front of the first continuous laser (101) and transmits a wave band corresponding to the laser wavelength, an optical beam expander (103) which sequentially passes through the corresponding laser wavelength, a right-angle plane mirror (104), an optical attenuation sheet (105) which is arranged at the corresponding laser wavelength and a first photoelectric detector (106) which covers the laser wavelength range;
the pumping laser spot adjusting subsystem (2) comprises a laser reflecting mirror (201) with an electric moving function, a guiding light path (202) formed by the laser reflecting mirror and a laser focusing lens group (203) with adjustable focal length;
the temperature control subsystem (3) of the sample and the reference plane comprises an optical thermostat (301), a sample to be measured (302) which is placed in the optical thermostat (301) and has a flat and smooth surface, a reference plane mirror (303) which is equal to the thickness of the sample to be measured, a high-heat-conductivity metal sample holder (304) with an electric movable function, a temperature sensor (305) placed on the sample holder and a temperature display (306) connected with the sensor;
the Raman excitation and collection subsystem (4) comprises a second continuous laser (401) which generates photon energy smaller than the photon energy emitted by the first continuous laser (101), a focusing lens (402) with a laser corresponding wavelength, a parabolic reflector (403) with a small hole along the focusing direction, a parabolic reflector (404) and a scattered light guiding light path (405) consisting of a plurality of plane reflectors;
the spectrum measurement subsystem (5) comprises a large-area plane reflecting mirror (501) with an electric moving function, a spectrometer (502) covering a Raman scattering signal wave band, a long-wave pass filter (503) with a cut-off wavelength between the emergent wavelength of the first continuous laser (101) and the anti-Stokes scattering light wavelength, a narrow-band notch filter (504) corresponding to the emergent wavelength of the second continuous laser (401) and a second photodetector (505) covering the Raman scattering signal wave band;
the pumping source excitation and detection subsystem (1) is optically connected with the pumping laser spot adjusting subsystem (2), the temperature control subsystem (3) of the sample and the reference plane, the Raman excitation and collection subsystem (4) and the spectrum subsystem (5);
the optical element switching control part (6) is electrically connected with the electrically movable laser reflecting mirror (201), the metal sample holder (304) and the large-area plane reflecting mirror (501);
the computer central control (7) is connected with the first photoelectric detector (106), the second photoelectric detector (505) and the spectrometer (502), and reads the detector and spectrometer signals.
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