CN116682846A - Defect barrier structure and method for silicon carbide epitaxial layer - Google Patents
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 125
- 229910010271 silicon carbide Inorganic materials 0.000 title claims abstract description 125
- 230000007547 defect Effects 0.000 title claims abstract description 91
- 230000004888 barrier function Effects 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 17
- 239000000758 substrate Substances 0.000 claims abstract description 34
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 37
- 229910052757 nitrogen Inorganic materials 0.000 claims description 19
- 238000006243 chemical reaction Methods 0.000 claims description 17
- 239000001257 hydrogen Substances 0.000 claims description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims description 11
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 claims description 10
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 239000013078 crystal Substances 0.000 claims description 3
- 150000002431 hydrogen Chemical class 0.000 claims description 3
- 230000000903 blocking effect Effects 0.000 claims description 2
- 238000005530 etching Methods 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 claims description 2
- 229910001873 dinitrogen Inorganic materials 0.000 claims 1
- 238000006073 displacement reaction Methods 0.000 abstract description 3
- 230000008859 change Effects 0.000 abstract description 2
- 230000008569 process Effects 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 244000000626 Daucus carota Species 0.000 description 1
- 235000002767 Daucus carota Nutrition 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000407 epitaxy Methods 0.000 description 1
- 238000001657 homoepitaxy Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
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- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
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- C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
- C30B25/02—Epitaxial-layer growth
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Abstract
The application discloses a defect barrier structure and a defect barrier method for a silicon carbide epitaxial layer, wherein the defect barrier structure comprises at least one silicon carbide buffer layer arranged between a silicon carbide substrate and the silicon carbide epitaxial layer, and at least one silicon carbide defect barrier layer grown between the silicon carbide substrate and the silicon carbide buffer layer. The doping concentration of the silicon carbide defect barrier layer is higher than that of the silicon carbide substrate, and the doping concentration of the silicon carbide defect barrier layer is 5E18/cm 3 ～7.5E18/cm 3 Between them; the thickness of the silicon carbide defect barrier layer is between 4 and 10 mu m. The defect barrier layer of the technical proposal can generate slight lattice distortion displacement, change the primary lattice vector of the vertical dislocation of the substrate, reduce the driving force of the vertical dislocation extending upwards to the epitaxial layer, thereby reducing the defect quantity in the epitaxial layer and on the surface, and leading the defect density of the epitaxial layer to be lower than 1/cm 2 And the performance and yield of the device are improved.
Description
The application is a divisional application of 2022, 02, 22, CN202210161021.6 and entitled defect barrier Structure and method for silicon carbide epitaxial layer.
Technical Field
The application belongs to the field of silicon carbide semiconductor devices, and particularly relates to a defect barrier structure and a defect barrier method for a silicon carbide epitaxial layer.
Background
The silicon carbide material is suitable for manufacturing electronic devices such as high temperature, high frequency, high power, radiation resistance, corrosion resistance and the like, has wide application prospect in the aspects of communication, automobiles, aviation, aerospace, oil exploitation, national defense and the like, and belongs to an international high-end advanced material. In order to realize the development of silicon carbide electronic devices, homoepitaxy must be performed on a silicon carbide substrate to grow the epitaxial structure required for the device.
The silicon carbide epitaxial layer produced in the prior art has the structure that a layer of concentration buffer layer is stacked on a high-concentration doped silicon carbide substrate, and epitaxial layers with different thicknesses and doping concentrations are grown on the buffer layer according to the pressure-resistant design. In general, the buffer layer has a direct effect on the number of surface defects of the epitaxial layer. The existing epitaxial technology can effectively control defects with larger surface size, such as triangular defects, carrot defects, linear defects, comet defects and the like, and the growth technology of the buffer layer is beneficial to different growth temperatures or different growth rate combinations so as to achieve the purpose of reducing the surface defects of the subsequent epitaxial layer. The defect density of the epitaxial layer grown by the above technique is about 1/cm 2 . For high voltage devices, the number of defect densities is still too high, which can easily affect device performance and reduce yield.
Disclosure of Invention
The application aims to: the application aims to provide a defect barrier structure of a silicon carbide epitaxial layer, which can simultaneously reduce the surface defects of the epitaxial layer and the stacking dislocation defect density in the epitaxial layer and produce the high-quality silicon carbide epitaxial layer.
Another object of the present application is to provide a method for forming a defect barrier for a silicon carbide epitaxial layer, which can obtain the above defect barrier structure and can reduce the defect density of the epitaxial layer to less than 1/cm 2 And the performance and yield of the device are improved.
The technical scheme is as follows: the defect barrier structure of the silicon carbide epitaxial layer comprises at least one silicon carbide buffer layer arranged between a silicon carbide substrate and the silicon carbide epitaxial layer, and at least one silicon carbide defect barrier layer grown between the silicon carbide substrate and the silicon carbide buffer layer; the nitrogen doping concentration of the silicon carbide defect barrier layer is higher than that of the silicon carbide substrate; the nitrogen doping concentration of the silicon carbide defect barrier layer is 5E18/cm 3 ～7.5E18/cm 3 Between them; the thickness of the silicon carbide defect barrier layer is between 4 and 10 mu m.
Preferably, the nitrogen doping concentration of the silicon carbide buffer layer is 9E17/cm 3 ～2E18/cm 3 Between them.
Preferably, the silicon carbide buffer layer has a thickness of between 0.5 μm and 2 μm.
The defect blocking method of the silicon carbide epitaxial layer comprises the following steps:
s1: growing a silicon carbide defect barrier layer on a silicon carbide substrate under the conditions that the temperature is higher than 1630 ℃ and the carbon-silicon ratio is between 1.2 and 1.0, and controlling the nitrogen doping concentration of the silicon carbide defect barrier layer to be between 5E18/cm 3 ～7.5E18/cm 3 The thickness is between 4 and 10 mu m;
s2: growing a silicon carbide buffer layer on the silicon carbide defect barrier layer at 1620-1630 ℃ and with a carbon-silicon ratio of 1.0-0.9, wherein the thickness of the silicon carbide buffer layer is 0.5-2 mu m, and the growth speed is increased to 1.3-1.5 times;
s3: and growing a silicon carbide epitaxial layer on the silicon carbide buffer layer under the conditions that the temperature is less than 1620 ℃ and the carbon-silicon ratio is between 1.0 and 0.9.
Preferably, the silicon carbide substrate comprises a 6 inch n-type (0001) silicon carbide substrate having its crystal plane(s) oriented 4 ° off-axis to the <11-20> direction.
Preferably, before the silicon carbide defect barrier layer grows on the silicon carbide substrate, the silicon carbide substrate is placed into a carrying inner base of a SiC epitaxial reaction chamber, hydrogen is introduced, the growth pressure range of the reaction chamber is controlled within 10-50kpa, the temperature of the reaction chamber is raised to 1625 ℃ in the hydrogen environment, the temperature of the reaction chamber is maintained for 10 minutes, and the surface of the silicon carbide substrate is etched.
Preferably, after growing the silicon carbide epitaxial layer on the silicon carbide buffer layer, maintaining the silicon carbide buffer layer in a hydrogen environment, stopping introducing carbon-silicon gas and nitrogen, stopping introducing hydrogen when the temperature is reduced to below 800 ℃, vacuumizing the reaction chamber to below 1Kpa, introducing argon to an atmospheric pressure, and opening the reaction chamber after circulation for 5 times, and taking out the epitaxial wafer.
The beneficial effects are that: compared with the prior art, the application has the following advantages: the defect barrier layer grown under different conditions can generate slight lattice distortion displacement, change the primary lattice vector of the vertical dislocation of the substrate, reduce the driving force of the vertical dislocation extending upwards to the epitaxial layer, and further reduce the number of defects in the epitaxial layer and on the surface.
Drawings
FIG. 1 is a schematic cross-sectional view of a defect barrier structure according to an embodiment of the present application;
FIG. 2 is a surface defect test chart of a silicon carbide epitaxial structure with barrier layer;
FIG. 3 is an internal defect test chart of a silicon carbide epitaxial structure with barrier layers;
FIG. 4 is a graph of the number of surface defects of a six inch silicon carbide epitaxial layer at different barrier layer doping concentrations;
FIG. 5 is a graph of the number of surface defects of six inch silicon carbide epitaxial layers at different barrier layer thicknesses;
FIG. 6 is a graph of the number of internal defects of a six inch silicon carbide epitaxial layer at different barrier layer doping concentrations;
FIG. 7 is a graph of the number of internal defects of a six inch silicon carbide epitaxial layer at different barrier layer thicknesses;
fig. 8 is a chart illustrating SIMS nitrogen doping content analysis of a silicon carbide epitaxial wafer according to an embodiment of the present application.
Detailed Description
The technical scheme of the application is further described below with reference to the accompanying drawings.
Referring to FIG. 1, a defect barrier structure of a silicon carbide epitaxial layer according to an embodiment of the present application comprises a silicon carbide buffer layer disposed between a silicon carbide substrate and the silicon carbide epitaxial layer, and a silicon carbide defect barrier layer grown between the silicon carbide substrate and the silicon carbide buffer layer, the silicon carbide defect barrier layer having a doping concentration higher than that of the silicon carbide substrate, the doping concentration of the silicon carbide defect barrier layer being 5E18/cm 3 ～1E19/cm 3 Between them.
According to the defect barrier structure of the silicon carbide epitaxial layer, the defect barrier layer grown under different conditions can generate slight lattice distortion displacement, the Berger vector of the vertical dislocation of the substrate is changed, the driving force of the vertical dislocation extending upwards to the epitaxial layer is reduced, and the defect quantity of the inside and the surface of the epitaxial layer is reduced.
In practice, the thickness of the silicon carbide defect barrier layer is preferably greater than 0.1 μm, and the doping concentration of the silicon carbide buffer layer is preferably 9E17/cm 3 ～2E18/cm 3 The thickness is preferably between 0.5 μm and 2. Mu.m.
In this embodiment, taking a 6 inch n-type substrate as an example, the defect barrier structure of the silicon carbide epitaxial layer can be manufactured by the following method:
1) Placing a silicon carbide substrate with a 6 inch n-type (0001) crystal face which is off-axis by 4 degrees towards the <11-20> direction into a carrying inner base of a SiC epitaxial reaction chamber;
2) Introducing hydrogen, controlling the growth pressure of the reaction cavity within 10-50kpa, heating to 1625 ℃ in the hydrogen environment, maintaining the temperature of the reaction chamber for 10 minutes, and etching the surface of the substrate;
3) On an n-type silicon carbide substrate, at a higher temperature>1630 ℃ and the carbon-silicon ratio of 1.2-1.0, growing a first layer of nitrogen doped silicon carbide defect barrier layer, wherein the nitrogen doping concentration is 5.5E18/cm 3 The barrier layer growth thickness is 4um;
4) Then growing a silicon carbide buffer layer with the thickness of 1um on the first layer of defect barrier layer, wherein the growth temperature is 1625 ℃, the ratio of carbon to silicon is 1.0-0.9, and the growth speed is increased to 1.3-1.5 times;
5) In the silicon carbide epitaxial layer part, the epitaxial layer grown under the growth condition that the growth temperature is reduced to be lower than 1620 ℃ and the carbon-silicon ratio is between 1.0 and 0.9 can have the advantages of high uniformity and low epitaxial defect. FIG. 8 is a chart of SIMS analysis of nitrogen atom concentration for an embodiment of the present silicon carbide epitaxial structure;
6) And (3) maintaining the reaction chamber in a hydrogen environment, stopping introducing carbon-silicon gas and nitrogen, stopping introducing hydrogen when the temperature is reduced to below 800 ℃, vacuumizing the reaction chamber to below 1Kpa, introducing argon to an atmospheric pressure, circulating for 5 times, opening the reaction chamber, taking out the epitaxial wafer, and detecting the surface of the epitaxial wafer by using a SICA88 surface defect detector of Lasertec company, wherein the detection result is shown in figures 2 and 3. As can be seen from the pictures, the process has a surface defect density of 1/cm on the epitaxial layer compared with a silicon carbide epitaxial wafer without a defect barrier layer obtained by the same method 2 Reduced to 0.3/cm 2 The defect density in the epitaxial layer is from 2.5/cm 2 Reduced to 0.5/cm 2 And the quality of the epitaxial layer is effectively improved.
In practice, the growth of dislocations can be further terminated by adjusting the ratio of the nitrogen doping concentration to the thickness in the process of epitaxy of the defect barrier layer, and the number of defects in the epitaxial layer and on the surface can be reduced.
FIGS. 4 and 6 are, respectively, 6 inch n-type SiC substrates with a SiC defect barrier layer thickness of 4 μm having a nitrogen doping concentration of 1E18/cm 3 、2E18/cm 3 、4E18/cm 3 、5E18/cm 3 、7.5E18/cm 3 And 1E19/cm 3 The number of epitaxial layer surface defects and the number of internal defects are shown in the figure, when the nitrogen doping concentration of the silicon carbide defect barrier layer is 5E18/cm 3 And 7.5E18/cm 3 During the process, the number of defects on the surface and the inside of the epitaxial layer is steadily smaller than that of other doping concentrations, so the nitrogen doping concentration of the silicon carbide defect barrier layer is preferably 5E18/cm 3 ～7.5E18/cm 3 Between them.
FIGS. 5 and 7 are, respectively, 6 inch n-type silicon carbide substrates with a nitrogen doping concentration of 5.1E18/cm in the silicon carbide defect barrier layer 3 When the thickness of the silicon carbide defect barrier layer is 1 μm, 2 μm, 4 μm, 5 μm, 7 μm and 10 μm, respectively, the number of defects on the surface and the number of defects in the epitaxial layer are increased, and when the thickness of the silicon carbide defect barrier layer is increased to 4 μm, the number of defects in the epitaxial layer is not significantly reduced, and when the thickness is increased to 10 μm, the number of defects on the surface of the epitaxial layer tends to increase, so the thickness of the silicon carbide defect barrier layer is preferably between 4 μm and 10 μm.
Claims (7)
1. A defect barrier structure for a silicon carbide epitaxial layer comprising at least one silicon carbide buffer layer disposed between a silicon carbide substrate and a silicon carbide epitaxial layer, characterized by further comprising at least one silicon carbide defect barrier layer grown between the silicon carbide substrate and the silicon carbide buffer layer; the nitrogen doping concentration of the silicon carbide defect barrier layer is higher than that of the silicon carbide substrate; the nitrogen doping concentration of the silicon carbide defect barrier layer is 5E18/cm 3 ～7.5E18/cm 3 Between them; the thickness of the silicon carbide defect barrier layer is between 4 and 10 mu m.
2. The defect-blocking structure of claim 1, wherein the silicon carbide buffer layer has a nitrogen doping concentration of 9E17/cm 3 ～2E18/cm 3 Between them.
3. The defect barrier structure of a silicon carbide epitaxial layer according to claim 1 or 2, wherein the silicon carbide buffer layer has a thickness of between 0.5 μm and 2 μm.
4. A method of defect blocking of a silicon carbide epitaxial layer, comprising the steps of:
s1: growing a silicon carbide defect barrier layer on a silicon carbide substrate under the conditions that the temperature is higher than 1630 ℃ and the carbon-silicon ratio is between 1.2 and 1.0, and controlling the nitrogen doping concentration of the silicon carbide defect barrier layer to be between 5E18/cm 3 ～7.5E18/cm 3 The thickness is between 4 and 10 mu m;
s2: growing a silicon carbide buffer layer on the silicon carbide defect barrier layer at 1620-1630 ℃ and with a carbon-silicon ratio of 1.0-0.9, wherein the thickness of the silicon carbide buffer layer is 0.5-2 mu m, and the growth speed is increased to 1.3-1.5 times;
s3: and growing a silicon carbide epitaxial layer on the silicon carbide buffer layer under the conditions that the temperature is less than 1620 ℃ and the carbon-silicon ratio is between 1.0 and 0.9.
5. The method of claim 4, wherein the silicon carbide substrate comprises a 6 inch n-type (0001) silicon carbide substrate with its crystal plane being offset by 4 ° from the <11-20> direction.
6. The method of claim 5, further comprising placing the silicon carbide substrate into a susceptor in a SiC epitaxial reaction chamber, introducing hydrogen, controlling the growth pressure of the reaction chamber to be within 10-50kpa, heating to 1625 ℃ in the presence of hydrogen, maintaining the temperature of the reaction chamber for 10 minutes, and etching the surface of the silicon carbide substrate.
7. The method of claim 4, further comprising maintaining the silicon carbide epitaxial layer on the silicon carbide buffer layer in a hydrogen atmosphere, stopping introducing the silicon carbide gas and nitrogen gas, stopping introducing hydrogen gas when the temperature is reduced to below 800 ℃, vacuumizing the reaction chamber to below 1Kpa, introducing argon gas to an atmospheric pressure, and opening the reaction chamber after 5 times of circulation, and taking out the epitaxial wafer.
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