CN116825620A - Method for reducing surface defects of silicon carbide epitaxial wafer - Google Patents

Method for reducing surface defects of silicon carbide epitaxial wafer Download PDF

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CN116825620A
CN116825620A CN202310336236.1A CN202310336236A CN116825620A CN 116825620 A CN116825620 A CN 116825620A CN 202310336236 A CN202310336236 A CN 202310336236A CN 116825620 A CN116825620 A CN 116825620A
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gas
silicon carbide
epitaxial
silicon
flow rate
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陈威佑
蔡清富
蔡长祐
胡智威
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Nanjing Baishi Electronic Technology Co ltd
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Nanjing Baishi Electronic Technology Co ltd
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Abstract

The invention discloses a method for reducing surface defects of a silicon carbide epitaxial wafer, which relates to the technical field of reducing the surface defects of the silicon carbide epitaxial wafer and comprises three stages of surface etching, buffer layer growth and epitaxial growth; in the process of buffer layer growth, chlorine-containing gas with a certain ratio range is introduced to improve the bonding stability of silicon gas molecules and carbon gas molecules in the epitaxial reaction process, so as to avoid the reaction of non-silicon carbide bonding, reduce the surface and crystal defects formed by the non-silicon carbide bonding in the epitaxial process, and simultaneously improve the epitaxial growth rate to obtain the high-quality silicon carbide epitaxial layer.

Description

Method for reducing surface defects of silicon carbide epitaxial wafer
Technical Field
The invention relates to the technical field of reducing surface defects of silicon carbide epitaxial wafers, in particular to a method for reducing the surface defects of the silicon carbide epitaxial wafers.
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 adopts a stepped doping concentration as a layered structure or adopts a combination of different growth rates to reduce the surface defects of the subsequent epitaxial layer. The defect density of the epitaxial layer grown by the above technique is about 0.8-1/cm 2. For high voltage devices, the number of defect densities is still too high, which can easily affect device performance and reduce yield.
The defect density of the epitaxial layer grown by the prior art is about 0.8-1/cm 2. For high withstand voltage devices, the number of defect densities is still too high, which tends to reduce device yield.
In the prior art, the defect density of the epitaxial surface is still too high, which is unfavorable for device application.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for reducing the surface defects of a silicon carbide epitaxial wafer aiming at the defects of the background technology, and the method effectively improves and reduces the surface defects of the silicon carbide epitaxial wafer by utilizing the ratio of the introduced chlorine-containing reaction gas in the growth process.
The invention adopts the following technical scheme for solving the technical problems:
a method for reducing surface defects of a silicon carbide epitaxial wafer comprises three stages of surface etching, buffer layer growth and epitaxial growth;
wherein, surface etching: etching the surface of the silicon carbide substrate by utilizing hydrogen at the temperature of more than 1600 ℃;
buffer layer growth: introducing a reaction gas containing a silicon source and a carbon source and a chlorine-containing gas with a certain proportion range to grow a buffer layer with proper thickness and doping concentration;
and (3) epitaxial growth: and continuing the gas used for the growth of the buffer layer, adjusting the gas flow and the ratio of chlorine-containing gas, and performing epitaxial layer growth at the growth rate and the epitaxial time.
As a further preferable mode of the method for reducing the surface defects of the silicon carbide epitaxial wafer, the growth step of the buffer layer
In the section, the flow rate of the buffer layer is in a ratio range of Cl/Si=10-20.
As a further preferable scheme of the method for reducing the surface defects of the silicon carbide epitaxial wafer, in the epitaxial growth stage, the flow rate of the epitaxial layer is in a range of Cl/Si=10-15.
As a further preferred embodiment of the method for reducing surface defects in silicon carbide epitaxial wafers of the present invention, the source gases of silicon and carbon are mainly silane and propane during the buffer layer growth stage.
As a further preferred embodiment of the method for reducing surface defects in silicon carbide epitaxial wafers of the present invention, nitrogen and trimethylaluminum are used as the source of doping concentration gases during the epitaxial growth phase.
As a further preferable scheme of the method for reducing the surface defects of the silicon carbide epitaxial wafer, the method specifically comprises the following steps:
step 1, placing a silicon carbide substrate with a 6 inch n-type (0001) crystal face which is deviated by 4 degrees from an axis towards a <11-20> direction into a carrying inner base a of a SiC epitaxial reaction chamber;
step 2, introducing hydrogen, wherein the pressure range is 10-28kpa, heating to 1625 ℃ in the hydrogen environment, maintaining the temperature of the reaction chamber for 10 minutes, and etching the surface of the substrate;
step 3, growing a buffer layer, namely introducing carbon-silicon gas, doping gas nitrogen and chlorine-containing gas in a mode that the flow rate is gradually increased along with the set time under the condition that the temperature and the pressure are kept unchanged, wherein the flow rate ratio of the carbon-silicon gas is 0.2-0.4, the flow rate of a silicon source gas is 5% -8% of the flow rate ratio of the chlorine-containing gas, the flow rate range of the nitrogen is 100-200 sccm, growing a first buffer layer, the thickness is 0.5-1 um, the doping concentration is 1e18cm & lt-3 & gt, and the reaction temperature is maintained for 5-10min;
step 4, under the condition that the temperature and the pressure are kept unchanged, introducing carbon silicon gas, doping gas nitrogen and chlorine-containing gas in a mode that the flow rate is increased along with the set time, adjusting the flow rate ratio range of the carbon silicon gas to be 0.4-0.6, simultaneously increasing the flow rate ratio of the silicon source gas to the chlorine-containing gas to be 8-10%, keeping the flow rate range of the nitrogen to be 1-200 sccm, growing silicon carbide epitaxy, and keeping the reaction temperature for 5-30 min;
and 5, maintaining the environment of hydrogen, 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, opening the reaction chamber after circulation for 5 times, taking out the epitaxial wafer, and detecting the surface of the epitaxial wafer by adopting a SICA88 surface defect detector of Lasertec company.
Compared with the prior art, the technical scheme provided by the invention has the following technical effects:
1. according to the method for reducing the surface defects of the silicon carbide epitaxial wafer, in an environment filled with hydrogen, the temperature is raised to more than 1600 ℃, reaction gases containing a silicon source and a carbon source are introduced for epitaxy, the source gases of silicon and carbon are mainly silane and propane, nitrogen and trimethylaluminum are used as the gas sources of doping concentration, chlorine-containing gases with a certain proportion range are introduced to improve the bonding stability of silicon gas molecules and carbon gas molecules in the epitaxial reaction process except the reaction gases in the buffer layer growth process, and the reaction of non-silicon carbide bonding is avoided, so that the surface and crystal defects formed by the non-silicon carbide bonding in the epitaxy are reduced, and meanwhile, the epitaxial growth rate is improved, so that a high-quality silicon carbide epitaxial layer is obtained;
2. according to the invention, chlorine-containing gases with different duty ratio ranges are respectively introduced into the buffer layer and the epitaxial layer, the index is the duty ratio of silicon source gas in the chlorine-containing gases, the duty ratio range of the buffer layer flow is Cl/Si=10-20, the duty ratio range of the epitaxial layer flow is Cl/Si=10-15, the epitaxial growth condition in the range can effectively improve the bonding stability of crystal atoms, improve the epitaxial growth rate, avoid the reaction of non-silicon carbide bonding, reduce the surface defects formed by the non-silicon carbide bonding in the epitaxial process, and obtain the high-quality silicon carbide epitaxial layer.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is evident that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art.
FIG. 1 is a schematic diagram of the epitaxial growth temperature profile of silicon carbide according to the present invention;
FIG. 2 is a schematic view of the surface defect density of an epitaxial wafer before the process is not used in the present invention;
fig. 3 is a schematic view of the surface defect density of the epitaxial wafer after the process is used in the present invention.
Detailed Description
The technical scheme of the invention is further described in detail below with reference to the accompanying drawings:
in order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in figure 1, the epitaxial growth temperature curve of silicon carbide is mainly divided into three main stages of surface etching, buffer layer growth and epitaxial growth, the temperature is raised to above 1600 ℃ in the environment full of hydrogen, reaction gases containing silicon source and carbon source are introduced for epitaxy, the source gases of silicon and carbon are mainly silane and propane, nitrogen and trimethylaluminum are used as the gas sources of doping concentration, chlorine-containing gas with a certain ratio range is introduced in the process of buffer layer growth except the reaction gases to improve the bonding stability of silicon gas molecules and carbon gas molecules in the epitaxial reaction process, and the reaction of non-silicon carbide bonding is avoided, so that the surface and crystal defects formed by the non-silicon carbide bonding in the epitaxial process are reduced, and meanwhile, the epitaxial growth rate is improved, so that a high-quality silicon carbide epitaxial layer is obtained.
Examples are as follows:
a method for reducing surface defects of a silicon carbide epitaxial wafer comprises three stages of surface etching, buffer layer growth and epitaxial growth;
wherein, surface etching: etching the surface of the silicon carbide substrate by utilizing hydrogen at the temperature of more than 1600 ℃;
buffer layer growth: introducing a reaction gas containing a silicon source and a carbon source and a chlorine-containing gas with a certain proportion range to grow a buffer layer with proper thickness and doping concentration;
and (3) epitaxial growth: and continuing the gas used for the growth of the buffer layer, adjusting the gas flow and the ratio of chlorine-containing gas, and performing epitaxial layer growth at the growth rate and the epitaxial time.
Chlorine-containing gases with different duty ratio ranges are respectively led into the buffer layer and the epitaxial layer, the index is the duty ratio of silicon source gases in the chlorine-containing gases, the flow of the buffer layer is in the duty ratio range of Cl/Si=10-20, the flow of the epitaxial layer is in the duty ratio range of Cl/Si=10-15, the epitaxial growth condition in the range can effectively improve the bonding stability of crystal atoms, improve the epitaxial growth rate, avoid the reaction of non-silicon carbide bonding, reduce the surface defects formed by the non-silicon carbide bonding in the epitaxial process, and obtain the high-quality silicon carbide epitaxial layer.
The method specifically comprises the following steps:
step 1, placing a silicon carbide substrate with a 6 inch n-type (0001) crystal face which is deviated by 4 degrees from an axis towards a <11-20> direction into a carrying inner base a of a SiC epitaxial reaction chamber;
step 2, introducing hydrogen, wherein the pressure range is 10-28kpa, heating to 1625 ℃ in the hydrogen environment, maintaining the temperature of the reaction chamber for 10 minutes, and etching the surface of the substrate;
step 3, growing a buffer layer, namely introducing carbon-silicon gas, doping gas nitrogen and chlorine-containing gas in a mode that the flow rate is gradually increased along with the set time under the condition that the temperature and the pressure are kept unchanged, wherein the flow rate ratio of the carbon-silicon gas is 0.2-0.4, the flow rate of a silicon source gas is 5% -8% of the flow rate ratio of the chlorine-containing gas, the flow rate range of the nitrogen is 100-200 sccm, growing a first buffer layer, the thickness is 0.5-1 um, the doping concentration is 1e18cm & lt-3 & gt, and the reaction temperature is maintained for 5-10min;
step 4, under the condition that the temperature and the pressure are kept unchanged, introducing carbon silicon gas, doping gas nitrogen and chlorine-containing gas in a mode that the flow rate is increased along with the set time, adjusting the flow rate ratio range of the carbon silicon gas to be 0.4-0.6, simultaneously increasing the flow rate ratio of the silicon source gas to the chlorine-containing gas to be 8-10%, keeping the flow rate range of the nitrogen to be 1-200 sccm, growing silicon carbide epitaxy, and keeping the reaction temperature for 5-30 min;
and 5, maintaining the environment of hydrogen, 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, opening the reaction chamber after circulation for 5 times, taking out the epitaxial wafer, and detecting the surface of the epitaxial wafer by adopting a SICA88 surface defect detector of Lasertec company. The picture shows that the process reduces the surface defect density of the epitaxial layer from 0.8/cm < 2 > (figure 2) to 0.22/cm < 2 > (figure 3), and effectively improves the surface quality of the epitaxial layer.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereto, and any modification made on the basis of the technical scheme according to the technical idea of the present invention falls within the protection scope of the present invention. The embodiments of the present invention have been described in detail, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present invention.

Claims (6)

1. A method for reducing surface defects of a silicon carbide epitaxial wafer is characterized by comprising the following steps: comprises three stages of surface etching, buffer layer growth and epitaxial growth;
wherein, surface etching: etching the surface of the silicon carbide substrate by utilizing hydrogen at the temperature of more than 1600 ℃;
buffer layer growth: introducing a reaction gas containing a silicon source and a carbon source and a chlorine-containing gas with a certain proportion range to grow a buffer layer with proper thickness and doping concentration;
and (3) epitaxial growth: and continuing the gas used for the growth of the buffer layer, adjusting the gas flow and the ratio of chlorine-containing gas, and performing epitaxial layer growth at the growth rate and the epitaxial time.
2. The method for reducing surface defects of a silicon carbide epitaxial wafer according to claim 1, wherein the method comprises the steps of: in the buffer layer growth stage, the buffer layer flow rate is in the range of Cl/Si=10-20.
3. The method for reducing surface defects of a silicon carbide epitaxial wafer according to claim 1, wherein the method comprises the steps of: in the epitaxial growth stage, the flow rate of the epitaxial layer is in a range of Cl/Si=10-15.
4. The method for reducing surface defects of a silicon carbide epitaxial wafer according to claim 1, wherein the method comprises the steps of: the source gases for silicon and carbon are mainly silane and propane during the buffer layer growth phase.
5. The method for reducing surface defects of a silicon carbide epitaxial wafer according to claim 1, wherein the method comprises the steps of: during the epitaxial growth phase, nitrogen and trimethylaluminum are used as the source of the doping concentration gas.
6. The method for reducing surface defects of a silicon carbide epitaxial wafer according to claim 1, wherein the method comprises the steps of: the method specifically comprises the following steps:
step 1, placing a silicon carbide substrate with a 6 inch n-type (0001) crystal face which is deviated by 4 degrees from an axis towards a <11-20> direction into a carrying inner base a of a SiC epitaxial reaction chamber;
step 2, introducing hydrogen, wherein the pressure range is 10-28kpa, heating to 1625 ℃ in the hydrogen environment, maintaining the temperature of the reaction chamber for 10 minutes, and etching the surface of the substrate;
step 3, growing a buffer layer, namely introducing carbon-silicon gas, doping gas nitrogen and chlorine-containing gas in a mode that the flow rate is gradually increased along with the set time under the condition that the temperature and the pressure are kept unchanged, wherein the flow rate ratio of the carbon-silicon gas is 0.2-0.4, the flow rate of a silicon source gas is 5% -8% of the flow rate ratio of the chlorine-containing gas, the flow rate range of the nitrogen is 100-200 sccm, growing a first buffer layer, the thickness is 0.5-1 um, the doping concentration is 1e18cm & lt-3 & gt, and the reaction temperature is maintained for 5-10min;
step 4, under the condition that the temperature and the pressure are kept unchanged, introducing carbon silicon gas, doping gas nitrogen and chlorine-containing gas in a mode that the flow rate is increased along with the set time, adjusting the flow rate ratio range of the carbon silicon gas to be 0.4-0.6, simultaneously increasing the flow rate ratio of the silicon source gas to the chlorine-containing gas to be 8-10%, keeping the flow rate range of the nitrogen to be 1-200 sccm, growing silicon carbide epitaxy, and keeping the reaction temperature for 5-30 min;
and 5, maintaining the environment of hydrogen, 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, opening the reaction chamber after circulation for 5 times, taking out the epitaxial wafer, and detecting the surface of the epitaxial wafer by adopting a SICA88 surface defect detector of Lasertec company.
CN202310336236.1A 2023-03-31 2023-03-31 Method for reducing surface defects of silicon carbide epitaxial wafer Pending CN116825620A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117293015A (en) * 2023-11-23 2023-12-26 希科半导体科技(苏州)有限公司 Growth method of silicon carbide epitaxial layer of silicon substrate and silicon-based silicon carbide epitaxial wafer

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117293015A (en) * 2023-11-23 2023-12-26 希科半导体科技(苏州)有限公司 Growth method of silicon carbide epitaxial layer of silicon substrate and silicon-based silicon carbide epitaxial wafer
CN117293015B (en) * 2023-11-23 2024-02-20 希科半导体科技(苏州)有限公司 Growth method of silicon carbide epitaxial layer of silicon substrate and silicon-based silicon carbide epitaxial wafer

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