CN111257721A - Photoinduced current transient spectrum automatic analysis method and system - Google Patents
Photoinduced current transient spectrum automatic analysis method and system Download PDFInfo
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- CN111257721A CN111257721A CN202010093124.4A CN202010093124A CN111257721A CN 111257721 A CN111257721 A CN 111257721A CN 202010093124 A CN202010093124 A CN 202010093124A CN 111257721 A CN111257721 A CN 111257721A
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- 230000001052 transient effect Effects 0.000 title claims abstract description 17
- 238000001228 spectrum Methods 0.000 title claims abstract description 14
- 238000004458 analytical method Methods 0.000 title claims abstract description 11
- 239000000969 carrier Substances 0.000 claims abstract description 21
- 230000007547 defect Effects 0.000 claims abstract description 17
- 239000000463 material Substances 0.000 claims abstract description 17
- 239000004065 semiconductor Substances 0.000 claims abstract description 17
- 230000005284 excitation Effects 0.000 claims abstract description 15
- 230000005516 deep trap Effects 0.000 claims abstract description 12
- 230000031700 light absorption Effects 0.000 claims abstract description 6
- 238000005286 illumination Methods 0.000 claims abstract description 5
- 238000003949 trap density measurement Methods 0.000 claims abstract description 5
- 238000005070 sampling Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 4
- 230000001678 irradiating effect Effects 0.000 abstract description 2
- 239000000523 sample Substances 0.000 description 33
- 238000001514 detection method Methods 0.000 description 6
- 239000011521 glass Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 239000003990 capacitor Substances 0.000 description 2
- 229910003460 diamond Inorganic materials 0.000 description 2
- 239000010432 diamond Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 229910002601 GaN Inorganic materials 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000006399 behavior Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- AJNVQOSZGJRYEI-UHFFFAOYSA-N digallium;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Ga+3].[Ga+3] AJNVQOSZGJRYEI-UHFFFAOYSA-N 0.000 description 1
- 229910001195 gallium oxide Inorganic materials 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910003465 moissanite Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 238000010183 spectrum analysis Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
- G01N21/9501—Semiconductor wafers
- G01N21/9505—Wafer internal defects, e.g. microcracks
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/26—Testing of individual semiconductor devices
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Abstract
A photoinduced current transient spectrum automatic analysis method comprises the steps of adopting a laser with the wavelength less than 270nm, forming a 100 +/-50 HZ square wave excitation light source through modulation of a chopper, irradiating the square wave excitation light source on the surface of a detected sample, forming an excess carrier in a conduction band through light absorption between a material valence band and the conduction band of the detected sample, and driving the excess carrier to an external circuit in a space charge region to form photoinduced current; the excitation light source is in a square wave form, namely the sample in the first half period is in a light excitation state, and the sample in the second half period is not excited; under the condition of illumination excitation, excess carriers formed by light absorption can be captured by deep level trap defects in a semiconductor sample; when no light is emitted, the deep level trap defects release excessive carriers, the carriers are excessive carriers formed under the condition of no light, the excessive carriers are collected by an external circuit to form current, and the energy level position and trap density information of the deep level defects are obtained according to the change relation of the current intensity and the current with time.
Description
Technical Field
The invention relates to a photoinduced current transient spectrum automatic analysis method and a photoinduced current transient spectrum automatic analysis system, which are used for quantitative characterization and analysis of deep-level defects of wide-bandgap semiconductor materials.
Background
The wide-bandgap semiconductor material comprises SiC, GaN, diamond and the like, is a preferable material for the development of power electronic devices due to the larger bandgap and higher breakdown field strength, and has important application prospects in the fields of rail transit, automotive electronics, aerospace, smart power grids, new energy and weaponry. The formation of defects in semiconductors will affect the performance, stability and reliability of devices, so that the study of the type and energy level distribution of defects is crucial to the optimization of material quality and the preparation of devices. At present, for wide-bandgap semiconductor materials, the detection of impurity and defect energy levels mainly adopts a deep energy level transient spectrum technology, namely, the semiconductor material is made into a p-n junction, a Schottky junction or an MOS capacitor structure, a periodic transient voltage pulse is applied to a space charge region of the semiconductor material, and the transient change of a barrier capacitor of the space charge region is measured. The energy level position and the concentration of the deep energy level center are analyzed and obtained through the capacitance change under different temperature conditions. However, for wide band gap semiconductor materials, the band gap is larger than 3eV, and for example, in new semiconductor materials such as GaN, SiC, diamond, gallium oxide, etc., particularly in a high resistance state or a deep defect level, a voltage pulse cannot generate a sufficient number of carriers, and thus the change in capacitance is extremely small, and thus, the effective detection cannot be performed. In addition, the deep level transient spectrum technology cannot obtain important information such as the apparent ionization energy and the capture cross section of the deep level defect.
Disclosure of Invention
The invention aims to solve the problems that the existing deep energy level transient spectrum technology cannot measure a high-resistance wide-bandgap semiconductor material and cannot obtain important information such as the apparent ionization energy, the capture cross section and the like of a deep energy level defect.
The technical scheme adopted by the invention is as follows: an automatic analysis method for transient spectrum of photoinduced current is characterized by adopting a laser with short wavelength (the wavelength is less than 270nm and can cover the energy required for detection), forming a 100 +/-50 HZ square wave excitation light source through the modulation of a chopper, irradiating the square wave excitation light source on the surface of a detected sample, forming an excess carrier on a conduction band through the light absorption between the valence band and the conduction band of the detected sample material, and driving the excess carrier to an external circuit in a space charge region to form the photoinduced current.
Because the excitation light source is square wave type, the sample is in the optical excitation state in the first half period, and the sample is not in the optical excitation state in the second half period. Under the condition of illumination excitation, excess carriers formed by light absorption can be captured by deep level trap defects in a semiconductor sample; in the absence of illumination, the deep level trap defects release excess carriers, which are formed in the absence of illumination, and are also collected by an external circuit to form a current, and important information such as the level positions and trap densities of the deep level defects can be obtained through the relationship between the current intensity and the change of the current with time.
The photoinduced current transient spectrum automatic analysis system is characterized by comprising a computer (PC), a chopper, a laser, an oscilloscope, a cryostat and a temperature controller; the sample is placed on a sample table of a cryostat, the cryostat is provided with two joints, the first joint is externally connected with a temperature controller, an internal thermocouple and a temperature sensor, and the second joint is externally connected with an oscilloscope and internally connected with the sample; laser emitted by the laser passes through the chopper and then is struck on the surface of the sample; the PC computer is connected with the oscilloscope, the signal source and the temperature controller through a data line, and the computer controls the oscilloscope to acquire data and controls the temperature controller to heat and acquire data; in the measuring system, the excess current carriers flow through the sampling resistor through the second joint, voltage is generated at two ends of the resistor, current signals represented by the current carriers are converted into voltage signals at the moment, the PC controls the oscilloscope to collect the voltage signals, and the voltage values and the current temperature are stored in the PC.
The invention relates to an automatic photoinduced current transient spectrum analysis device, which comprises a PC, an oscilloscope, a temperature controller, a laser, a chopper and a low-temperature thermostat. The PC controls the oscilloscope and the temperature controller through the USB line, the temperature controller is connected with the thermocouple and the temperature sensor inside the cryostat through the first aviation connector, and the oscilloscope probe is connected with the sample on the sample table inside the cryostat through the second aviation connector. The laser emitted by the laser is modulated by the chopper and then is emitted to the surface of the sample in the cryostat. The method is mainly used for obtaining the deep energy level defect information of the high-impedance semiconductor material.
The method for obtaining the photoinduced current of the semiconductor material by adopting the laser chopper to provide the light source overcomes the defects that the traditional defect energy level detection method cannot effectively detect the high-resistance characteristic material and cannot obtain important information such as the apparent ionization energy, the capture cross section and the like of the deep energy level defect, thereby more deeply disclosing the characteristics of the semiconductor material and having great influence on the development and research of the semiconductor material. It is also possible to use LED light sources, especially uv LEDs with a strong light intensity, with subsequent signal processing, although it is more appropriate to use a laser in the light signal intensity.
Drawings
FIG. 1 is a schematic diagram of the internal structure and system architecture of a cryostat according to the present invention;
FIG. 2 is a schematic view of an aircraft joint of the present invention;
FIG. 3 is a schematic view of the detection step of the present invention;
FIG. 4 is a schematic diagram of the python script program of the present invention.
In fig. 1, 11 is a cryostat, 12 is a first aviation connector, 13 is a second aviation connector, 14 is a glass observation window, 15 is a temperature sensor, 16 is a thermocouple, 17 is a sample table, 18 is a sample, 19 is a light chopper, 20 is a laser.
Detailed Description
For a detailed description of the structural features and the specific operational steps of the present invention, reference will now be made to the preferred embodiments thereof in conjunction with the accompanying drawings.
As shown in figure 1 of the drawings, in which,
an automatic analysis system for transient spectrum of photoinduced current is composed of computer (PC), chopper, laser, oscilloscope, cryostat and temp controller. The sample is placed on a sample table of a cryostat, the cryostat is provided with two aviation connectors, the first aviation connector is externally connected with a temperature controller, an internal thermocouple and a temperature sensor, and the second aviation connector is externally connected with an oscilloscope and an internal sample. The laser emitted by the laser passes through the chopper and then strikes the surface of the sample. The PC computer is connected with the oscilloscope, the signal source and the temperature controller through a USB wire, and the python script is used for controlling the oscilloscope to collect data and controlling the temperature controller to rise. The circuit for collecting and forming current by the external circuit is that excessive current carriers flow through a 1K resistor through an electric connection joint, voltage is generated at two ends of a sampling resistor, current signals represented by the current carriers are converted into voltage signals at the moment, and the voltage values and the current temperature are correspondingly measured to obtain the energy level positions and trap densities of deep energy level defects.
The low-temperature thermostat is internally provided with a thermocouple, a temperature sensor, an aviation connector, a heating table, a sample, a transparent glass observation window, a thermocouple, a temperature sensor and an oscilloscope probe, wherein the aviation connector can be connected with an external instrument and an internal electronic component, the transparent glass observation window can be penetrated by laser, the thermocouple and the temperature sensor are connected to a temperature controller through a first aviation connector, and the sample is connected to the oscilloscope probe through a second aviation connector. The PC is an oscilloscope and a temperature controller controlled by a USB, and a cryostat 11. The temperature controller is connected with a temperature sensor 15 and a thermocouple 16 inside the cryostat 11 through a first aviation connector 12, and the oscilloscope is connected with a sample 18 on a heating table 17 inside the cryostat 11 through a second aviation connector 13. A laser 20, model MPL-F-266, emits laser light modulated by a chopper 19 and directed through a glass viewing window 14 onto the surface of a sample 18.
As shown in figure 2, the first aviation connector is internally connected with a thermocouple in a No. 1, a No. 2, a No. 3 and a No. 4 binding post, and is externally connected with a temperature controller, a temperature sensor in a No. 5 and a No. 6 binding post and is externally connected with the temperature controller. The second aviation connects 1, 2 terminal inscription sample external oscilloscope probe. The chopper can adopt a mechanical chopper and also can adopt an ultraviolet transparent photoswitch.
And the oscilloscope and the temperature controller are connected with the computer through a USB wire and controlled by the computer. The computer can adjust the temperature of the temperature controller, the temperature controller feeds the current temperature back to the computer, the computer controls the oscilloscope to sample, and the oscilloscope feeds the voltage value obtained by sampling back to the computer. The computer is internally provided with a python script, so that the behaviors of the temperature control instrument and the oscilloscope can be controlled in real time, the values fed back by the temperature control instrument and the oscilloscope are operated, and finally a voltage variation curve along with the temperature can be obtained. The laser emits laser, and square-wave-shaped current of the sample can be excited through modulation of the chopper.
As shown in FIG. 3, in the use of the present invention, the following detection steps can be taken:
1. the sample is fixed on the sample table, so that the sample is ensured to be in full contact with the sample table, and the heat conduction is full and rapid.
2. The oscilloscope, the temperature controller and the cryostat are connected together by an aviation connector.
3. And (3) running a python script, wherein the program schematic diagram of the script is shown in FIG. 4, at the moment, the whole device is driven by the program to operate correctly, and after the program is run, a voltage vs temperature curve is displayed, so that the related information of the semiconductor defects can be obtained.
As shown in FIG. 4, the python script is graphically executed, and can automatically complete data recording and drawing.
Claims (3)
1. The method for automatically analyzing the transient spectrum of the photoinduced current is characterized in that a laser with the wavelength less than 270nm is adopted, a square wave excitation light source with the wavelength of 100 +/-50 HZ is formed through modulation of a chopper and is irradiated on the surface of a detected sample, excess carriers are formed in a conduction band through light absorption between the valence band and the conduction band of a material of the detected sample, and the excess carriers are driven to an external circuit in a space charge area to form the photoinduced current; the excitation light source is in a square wave form, namely the sample in the first half period is in a light excitation state, and the sample in the second half period is not excited; under the condition of illumination excitation, excess carriers formed by light absorption can be captured by deep level trap defects in a semiconductor sample; when no light is emitted, the deep level trap defects release excessive carriers, the carriers are excessive carriers formed under the condition of no light, the excessive carriers are collected by an external circuit to form current, and the energy level position and trap density information of the deep level defects are obtained according to the change relation of the current intensity and the current with time.
2. The method of claim 1, wherein the external circuit collects the current by passing excess carriers through a sampling resistor via an electrical connector, generating a voltage across the sampling resistor, converting the current signal represented by the carriers into a voltage signal, and measuring the voltage value and the current temperature to obtain the energy level position and trap density of the deep level defect.
3. An automatic analysis system for transient spectrum of photoinduced current according to the automatic analysis method for transient spectrum of photoinduced current as claimed in any one of claims 1 to 2, characterized by comprising a PC computer, a light chopper, a laser, an oscilloscope, a cryostat, a temperature controller; the sample is placed on a sample table of a cryostat, the cryostat is provided with two joints, the first joint is externally connected with a temperature controller, an internal thermocouple and a temperature sensor, and the second joint is externally connected with an oscilloscope and internally connected with the sample; laser emitted by the laser passes through the chopper and then is struck on the surface of the sample; the PC computer is connected with the oscilloscope, the signal source and the temperature controller through a data line, and the PC computer controls the oscilloscope to acquire data and controls the temperature controller to heat and acquire data; in the measuring system, the excess current carrier flows through the sampling resistor through the second joint, voltage is generated at two ends of the resistor, at the moment, a current signal represented by the current carrier is converted into a voltage signal, the PC computer controls the oscilloscope to collect the voltage signal, and the voltage value and the current temperature are stored in the PC computer.
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| CN111766499A (en) * | 2020-07-28 | 2020-10-13 | 哈尔滨工业大学 | System and method for testing deep energy level transient spectrum of semiconductor material |
| CN111855704A (en) * | 2020-07-28 | 2020-10-30 | 哈尔滨工业大学 | Method for detecting ionization damage sensitive part of bipolar transistor |
| CN113970559A (en) * | 2021-10-25 | 2022-01-25 | 江苏华兴激光科技有限公司 | Semiconductor deep energy level defect detection device and detection method |
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| CN111855704A (en) * | 2020-07-28 | 2020-10-30 | 哈尔滨工业大学 | Method for detecting ionization damage sensitive part of bipolar transistor |
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