CN117276313A - High-voltage-resistant GaN-based epitaxial structure based on Si substrate and preparation method thereof - Google Patents

High-voltage-resistant GaN-based epitaxial structure based on Si substrate and preparation method thereof Download PDF

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CN117276313A
CN117276313A CN202311194715.0A CN202311194715A CN117276313A CN 117276313 A CN117276313 A CN 117276313A CN 202311194715 A CN202311194715 A CN 202311194715A CN 117276313 A CN117276313 A CN 117276313A
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epitaxial structure
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王洪
刘玉琪
王楷
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South China University of Technology SCUT
Zhongshan Institute of Modern Industrial Technology of South China University of Technology
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Zhongshan Institute of Modern Industrial Technology of South China University of Technology
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Abstract

The invention discloses a high-voltage-resistant GaN-based epitaxial structure based on a Si substrate and a preparation method thereof. The device epitaxial structure comprises: si substrate, alN nucleation layer, step AlGaN buffer layer, gaN nucleation layer the GaN-based semiconductor device comprises a GaN high-resistance layer, a GaN channel layer, an AlGaN barrier layer and a GaN cap layer. The adoption of the step AlGaN buffer layer can effectively compensate stress mismatch of the Si substrate and the GaN material, promote bending and annihilation of dislocation, improve crystal quality of the GaN epitaxial film, and effectively improve breakdown voltage of the GaN epitaxial film by adopting a C self-doping technology to epitaxially grow the GaN high-resistance layer. The high-voltage-resistant GaN-based epitaxial structure based on the Si substrate and the preparation method thereof have the characteristics of simple manufacturing process and good repeatability, and are suitable for high-voltage high-power electronic devices and the like.

Description

High-voltage-resistant GaN-based epitaxial structure based on Si substrate and preparation method thereof
Technical Field
The invention belongs to the technical field of semiconductor materials and devices, and particularly relates to a high-voltage-resistant GaN-based epitaxial structure based on a Si substrate and a preparation method thereof.
Background
GaN is used as a typical material of a third-generation semiconductor, has the advantages of high electron mobility, high thermal conductivity, high electric field strength and the like, and enables a GaN-based HEMT to have great advantages in the fields of high-frequency, high-voltage and high-power electronic devices. The silicon substrate has obvious advantages in the aspects of cost, large-size preparation and the like, becomes an ideal substrate for commercial application of GaN material epitaxial growth, and becomes an important research field for epitaxially growing a GaN epitaxial film with good crystal quality and pressure resistance on the large-size silicon substrate.
The Si substrate and the GaN material have huge lattice mismatch (17 percent) and thermal mismatch (116 percent), the lattice mismatch can cause high dislocation density to generate, so that the quality of GaN epitaxial thin film crystal is poor, the thermal mismatch can cause the GaN epitaxial thin film to bear extremely large tensile stress in the MOCVD growth cooling process, so that cracks are easy to generate on the surface of the GaN epitaxial thin film, and the high-density dislocation and the cracks can reduce the electrical property of the GaN-based HEMT. In addition, gaN materials have a wider forbidden bandwidth than conventional Si materials, and theoretically have a larger critical breakdown field strength. However, the unintentionally doped GaN material grown epitaxially by MOCVD typically has n-type conductivity, which can lead to vertical leakage of the epitaxial buffer layer, limiting the withstand voltage performance of the GaN-based HEMT device. The GaN epitaxial film growth with no crack on the upper surface of the large-size silicon substrate and good crystal quality and pressure resistance is important for the application of the GaN-based HEMT in the field of power electronic devices.
Aiming at the problem of stress mismatch between the substrate and the epitaxial material, a superlattice structure such as AlN/AlGaN is inserted between the Si substrate and the GaN layer to exert compressive stress so as to balance tensile stress (Shen X Q, takahashi T, ide T, et al high-quality GaN film and AlGaN/GaN HEMT grown on 4-inch Si (110) substrates by MOCVD using an ultra-thin AlN/GaN superlattice layer.physical states solid (b), 2014) which causes cracks. However, superlattice structures such as AlN/AlGaN require frequent switching of MO sources during growth, and the preparation process is complex and has poor repeatability. The step AlGaN buffer layer structure can effectively compensate huge stress mismatch between the Si substrate and the GaN material, prevent the generation of cracks on the surface of the GaN epitaxial film, promote bending and annihilation of dislocation, and improve the crystal quality of the GaN epitaxial film (Yu X, ni J, li Z, et al, reduction in leakage current in AlGaN/GaN HEMT with three Al-rotation step-graded AlGaN buffer layers on silicon, japanese Journal of Applied Physics, 2014). However, for the growth of a GaN film with a larger thickness, reasonable design is required for the number of layers, thickness and Al composition of the stepped AlGaN buffer layer to achieve good stress control, so as to obtain a crack-free GaN epitaxial film.
And a GaN high-resistance layer is epitaxially grown on the step AlGaN buffer layer, so that the leakage current of the GaN epitaxial buffer layer can be effectively reduced, and the vertical breakdown voltage of the GaN-based HEMT is increased. Mg, fe and C doping techniques are typically used to achieve the high resistance of GaN materials, where Mg and Fe doping have a memory Effect, i.e., after the doping of the doping source is turned off, there is still a continued incorporation of the doping agent remaining on the wall cavity of the tube into the GaN material (Choi Y C, pophoric M, cha H Y, et al, effect of an Fe-doped GaN Buffer on off-State Breakdown Characteristics in AlGaN/GaN HEMTs on Si substrate.ieee Transactions on Electron Devices, 2006). The C-doped impurities can be divided into active C-doped impurities and automatic C-doped impurities, and the active C-doped impurities need to introduce additional C sources, so that the cost is increased; the automatic C doping can change the C doping concentration by changing the epitaxial growth condition, but can influence the crystal quality of the GaN material, and the high resistance and the crystal quality of the GaN film need to be comprehensively considered to obtain proper epitaxial growth conditions.
Disclosure of Invention
The invention aims to solve the problems of poor crystal quality and low withstand voltage of a GaN epitaxial film on a large-size Si substrate, and provides a high withstand voltage GaN-based epitaxial structure based on the Si substrate from the perspective of epitaxial growth of a GaN material and a preparation method thereof, so that the crystal quality of the GaN epitaxial material on the large-size Si substrate is improved, the process difficulty is reduced, and the vertical breakdown voltage of a GaN-based HEMT device is improved.
The object of the invention is achieved by at least one of the following technical solutions.
The high-withstand voltage GaN-based epitaxial structure based on the Si substrate comprises the Si substrate, an AlN nucleation layer, a stepped AlGaN buffer layer, a GaN nucleation layer, a GaN high-resistance layer, a GaN channel layer, an AlGaN barrier layer and a GaN cap layer which are sequentially stacked from bottom to top.
Further, the AlN nucleation layer, the step AlGaN buffer layer, the GaN nucleation layer, the GaN high-resistance layer, the GaN channel layer, the AlGaN barrier layer and the GaN cap layer are all grown by adopting a metal organic chemical vapor deposition technology.
Further, the thickness of the Si substrate is 970-1030 mu m, the resistivity is 0.001-0.005 ohm cm, the crystal direction is 4-6inch.
Further, the AlN nucleation layer has a thickness of 150-200nm.
Further, the step AlGaN buffer layer comprises 7 layers of AlxGayN buffer layers, al components in each layer of AlxGayN buffer layer are sequentially reduced from bottom to top, and values of x and y are 0-1, so that the relation of x+y=1 is satisfied; the thickness h of each AlxGayN buffer layer is increased from bottom to top in sequence, and the relation that the thickness h is more than or equal to 1500nm and more than or equal to 100nm is satisfied.
Further, the thickness of the GaN nucleation layer is 200-300nm, a flat nucleation surface is provided for the growth of the GaN high-resistance layer, and the crystal quality of the GaN high-resistance layer is improved.
Further, the thickness of the GaN high-resistance layer is 1.0-1.5 mu m, the growth temperature is smaller than that of the GaN nucleation layer, and the high-resistance performance is realized by adopting a C self-doping technology, so that the leakage current of the buffer layer is reduced, and the breakdown voltage of the GaN-based HEMT device is improved.
Further, the thickness of the GaN channel layer is 200-300nm, the thickness of the AlGaN barrier layer is 20-30nm, the Al component value range of the AlGaN barrier layer is 0.2-0.5, and two-dimensional electron gas is formed at the interface of the GaN channel layer and the AlGaN barrier layer.
Further, the GaN cap layer is positioned on the AlGaN barrier layer, and the thickness of the GaN cap layer is 1-3nm.
The preparation method of the high-voltage-resistant GaN-based epitaxial structure based on the Si substrate comprises the following steps:
s1, carrying out high-temperature annealing treatment on a Si substrate in a reaction chamber of metal organic chemical vapor epitaxy equipment to remove magazines and oxide layers on the surface of the substrate, wherein the annealing temperature is 1090 ℃ and the annealing time is 10min;
s2, pre-paving Al on the surface of the Si substrate, and inhibiting the formation of polycrystalline SiNx so as to improve the surface morphology and crystallization quality of a GaN film grown on the Si substrate;
s3, growing an AlN nucleation layer on the Si substrate pre-paved with Al, and providing a smooth nucleation surface for the epitaxial growth of the further step AlGaN buffer layer;
s4, growing a step AlGaN buffer layer on the AlN nucleation layer to compensate stress mismatch of the Si substrate and the GaN material, promoting bending and annihilation of dislocation, improving crystal quality and breakdown voltage of the GaN epitaxial film, and dividing the step AlGaN buffer layer into 7 layers for growth, wherein Al components of the step AlGaN buffer layer are gradually reduced from bottom to top, and the thickness of the step AlGaN buffer layer is gradually increased from bottom to top;
s5, growing a GaN nucleation layer on the step AlGaN buffer layer to provide a smooth nucleation surface for further growth of the GaN high-resistance layer;
s6, growing a GaN high-resistance layer on the GaN nucleation layer, and adopting a C self-doping technology to realize the high-resistance performance of the GaN high-resistance layer so as to reduce the leakage current of the buffer layer and improve the breakdown voltage of the device;
s7, growing a GaN channel layer on the GaN high-resistance layer;
s8, growing an AlGaN barrier layer on the GaN channel layer, wherein the Al component of the AlGaN barrier layer is in a range of 0.2-0.5;
and S9, growing a GaN cap layer on the AlGaN barrier layer to improve the two-dimensional electron gas mobility and reduce the grid leakage current.
Compared with the prior art, the invention has the following advantages and technical effects:
aiming at the problems of poor quality and low pressure resistance of GaN epitaxial thin film crystals on a large-size Si substrate, the invention provides a high pressure resistance GaN-based epitaxial structure based on the Si substrate from the aspect of epitaxial growth of GaN materials and a preparation method thereof. On one hand, the step AlGaN buffer layer effectively introduces pre-stress to compensate the tensile stress caused by thermal mismatch between the Si substrate and the GaN material, so that the growth of a crack-free GaN thick film is realized, the bending and annihilation of dislocation are promoted by the multi-layer AlGaN hetero interface, and the crystal quality and the electrical property of the GaN epitaxial thin film are improved. On the other hand, on the step AlGaN buffer layer, a GaN high-resistance layer with high resistance characteristic is epitaxially grown by using a C self-doping technology, so that the leakage current of the GaN epitaxial buffer layer is effectively reduced, and the vertical breakdown voltage of the GaN-based HEMT is improved. The high-voltage-resistant GaN-based epitaxial structure based on the Si substrate and the preparation method thereof have the characteristics of simple manufacturing process and good repeatability, and are suitable for high-voltage high-power electronic devices and the like.
Drawings
Fig. 1 is a schematic structural diagram of a high withstand voltage GaN-based epitaxial structure based on a Si substrate in an embodiment of the present invention;
FIG. 2 is a schematic diagram of a layered structure of a step AlGaN buffer layer (3) according to an embodiment of the invention;
FIG. 3 is an X-ray diffraction (XRD) contrast pattern of a Si substrate-based high withstand voltage GaN-based epitaxial structure according to the present invention obtained in example 1 and a conventional structure;
fig. 4 is a graph showing comparison of current-voltage curves of a high withstand voltage GaN-based epitaxial structure based on a Si substrate and a conventional structure according to the present invention obtained in example 1.
Detailed Description
For a further understanding of the present invention, embodiments of the present invention are further described below with reference to specific examples, but are not limited thereto, and it should be noted that the following processes or process parameters, if any, are not specifically described in detail, can be implemented by those skilled in the art with reference to the prior art.
As shown in fig. 1, the high withstand voltage GaN-based epitaxial structure based on Si substrate includes: a Si substrate 1, an AlN nucleation layer 2, a stepped AlGaN buffer layer 3, a GaN nucleation layer 4, a GaN high-resistance layer 5, a GaN channel layer 6, an AlGaN barrier layer 7 and a GaN cap layer 8.
Example 1
The preparation method of the high-voltage-resistant GaN-based epitaxial structure based on the Si substrate comprises the following steps:
step one, carrying out high-temperature annealing treatment on a Si substrate 1 in an H2 atmosphere, wherein the annealing temperature is 1090 ℃ and the annealing time is 10min;
step two, pre-paving Al on the Si substrate 1 after annealing treatment for 10s, wherein the temperature of the cavity is 1025 ℃;
step three, the AlN nucleation layer 2 is epitaxially grown on the Si substrate 1, the growth thickness is 150nm, and the growth temperature is 1065 ℃;
step four, epitaxially growing a step AlGaN buffer layer 3 on the AlN nucleation layer 2, wherein the step AlGaN buffer layer 3 is divided into 7 layers altogether, al components in the AlGaN buffer layers of all layers from bottom to top are gradually reduced by matching with stress control, the Al components are sequentially 0.8, 0.7, 0.6, 0.5, 0.4, 0.2 and 0.1 from bottom to top, and the layering thicknesses are gradually increased, and are sequentially 150nm, 300nm, 450nm, 600nm, 900nm and 1200nm from bottom to top;
step five, a GaN nucleation layer 4 grows on the step AlGaN buffer layer 3, the growth thickness is 200nm, and the growth temperature is 1020 ℃;
step six, a GaN high-resistance layer 5 grows on the GaN nucleation layer 4, the growth thickness is 1000nm, and the growth temperature is 950 ℃;
step seven, a GaN channel layer 6 grows on the GaN high resistance 5, the growth thickness is 200nm, and the growth temperature is 1055 ℃;
step eight, an AlGaN barrier layer 7 grows on the GaN channel 6, the thickness is 25nm, the Al component is 0.25, and the growth temperature is 1055 ℃;
step nine, a GaN cap layer 8 is grown on the AlGaN barrier layer 7, the thickness is 2nm, and the growth temperature is 1055 ℃.
Example 2:
the preparation method of the high-voltage-resistant GaN-based epitaxial structure based on the Si substrate comprises the following steps:
step one, carrying out high-temperature annealing treatment on a Si substrate 1 in an H2 atmosphere, wherein the annealing temperature is 1090 ℃ and the annealing time is 10min;
step two, pre-paving Al on the Si substrate 1 after annealing treatment for 10s, wherein the temperature of the cavity is 1025 ℃;
step three, the AlN nucleation layer 2 is epitaxially grown on the Si substrate 1, the growth thickness is 200nm, and the growth temperature is 1065 ℃;
step four, the step AlGaN buffer layer 3 is epitaxially grown on the AlN nucleation layer 2, as shown in FIG. 2, the step AlGaN buffer layer 3 is divided into 7 layers altogether, al components in the AlGaN buffer layers of all layers from bottom to top are gradually reduced, the Al components are sequentially 0.8, 0.7, 0.6, 0.5, 0.4, 0.2 and 0.1, the layering thickness is gradually increased, and the layering thicknesses are sequentially 150nm, 300nm, 450nm, 600nm, 900nm and 1200nm from bottom to top;
step five, a GaN nucleation layer 4 grows on the step AlGaN buffer layer 3, the growth thickness is 300nm, and the growth temperature is 1020 ℃;
step six, growing a GaN high-resistance layer 5 on the GaN nucleation layer 4, wherein the growth thickness is 1500nm, and the growth temperature is 950 ℃;
step seven, a GaN channel layer 6 grows on the GaN high resistance 5, the growth thickness is 200nm, and the growth temperature is 1055 ℃;
step eight, an AlGaN barrier layer 7 grows on the GaN channel 6, the thickness is 25nm, the Al component is 0.25, and the growth temperature is 1055 ℃;
step nine, a GaN cap layer 8 is grown on the AlGaN barrier layer 7, the thickness is 2nm, and the growth temperature is 1055 ℃.
Fig. 3 is a graph showing the comparison of XRD test results of the GaN-based HEMT epitaxial structure prepared under the condition of example 1 with that of the conventional structure, and the ordinate in fig. 3 represents the diffraction intensity in cps; the abscissa is omega, which indicates that when X-ray diffraction test is carried out, the position of an XRD detector is fixed, then a test sample is rotated within a certain omega angle range, diffraction information is obtained, the unit is arcsec, and the result shows that the half-height width of the 002 face of the GaN epitaxial film prepared under the condition of embodiment 1 is smaller than that of the conventional structure by 35%, and the quality of the GaN epitaxial film crystal is obviously improved. Fig. 4 is a graph showing comparison of current-voltage test results of the GaN-based HEMT epitaxial structure prepared under the condition of example 1 and the conventional structure, and the result shows that the leakage current of the GaN-based HEMT epitaxial wafer prepared under the condition of example 1 is significantly reduced and the breakdown voltage is significantly improved.
The above-described embodiments are only preferred examples of the present invention and do not constitute any limitation of the present invention, and it will be apparent to those skilled in the art that various modifications and changes in form and details can be made according to the method of the present invention without departing from the principle and scope of the invention, but these modifications and changes based on the present invention remain within the scope of the appended claims.

Claims (10)

1. The high withstand voltage GaN-based epitaxial structure based on the Si substrate is characterized in that: comprises a Si substrate (1), an AlN nucleation layer (2), a step AlGaN buffer layer (3), a step AlGaN buffer layer, and a step AlGaN buffer layer, which are sequentially laminated from bottom to top the GaN-based semiconductor device comprises a GaN nucleation layer (4), a GaN high-resistance layer (5), a GaN channel layer (6), an AlGaN barrier layer (7) and a GaN cap layer (8).
2. The Si substrate based high withstand voltage GaN based epitaxial structure of claim 1, wherein: the AlN nucleation layer (2), the step AlGaN buffer layer (3), the GaN nucleation layer (4), the GaN high-resistance layer (5), the GaN channel layer (6), the AlGaN barrier layer (7) and the GaN cap layer (8) are grown by adopting a Metal Organic Chemical Vapor Deposition (MOCVD) technology.
3. The Si substrate based high withstand voltage GaN based epitaxial structure of claim 1, wherein: the thickness of the Si substrate (1) is 970-1030 mu m, the resistivity is 0.001-0.005 ohm cm, the crystal direction is (111), and the size is 4-6inch.
4. The Si substrate based high withstand voltage GaN based epitaxial structure of claim 1, wherein: the AlN nucleation layer (2) has a thickness of 150-200nm.
5. The Si substrate based high withstand voltage GaN based epitaxial structure of claim 1, wherein: the step AlGaN buffer layer (3) comprises 7 layers of AlxGayN buffer layers, al components in each layer of AlxGayN buffer layers are sequentially reduced from bottom to top, and values of x and y are 0-1, so that the relation of x+y=1 is satisfied; the thickness h of each AlxGayN buffer layer is increased from bottom to top in sequence, and the relation that the thickness h is more than or equal to 1500nm and more than or equal to 100nm is satisfied.
6. The Si substrate based high withstand voltage GaN based epitaxial structure of claim 1, wherein: the thickness of the GaN nucleation layer (4) is 200-300nm.
7. The Si substrate based high withstand voltage GaN based epitaxial structure of claim 1, wherein: the thickness of the GaN high-resistance layer (5) is 1.0-1.5 mu m, the growth temperature is smaller than that of the GaN nucleation layer (4), and the high-resistance performance is realized by adopting a C self-doping technology, so that the leakage current of the buffer layer is reduced, and the breakdown voltage of the GaN-based HEMT device is improved.
8. The Si substrate based high withstand voltage GaN based epitaxial structure of claim 1, wherein: the thickness of the GaN channel layer (6) is 200-300nm, the thickness of the AlGaN barrier layer (7) is 20-30nm, the Al component value range of the AlGaN barrier layer is 0.2-0.5, and a two-dimensional electron gas (2 DEG) is formed at the interface of the GaN channel layer (6) and the AlGaN barrier layer (7).
9. The Si substrate based high withstand voltage GaN based epitaxial structure of claim 1, wherein: the GaN cap layer (8) is positioned on the AlGaN barrier layer (7) and has a thickness of 1-3nm.
10. The method for producing a high withstand voltage GaN-based epitaxial structure based on Si substrate according to any one of claims 1 to 9, characterized by comprising the steps of:
s1, carrying out high-temperature annealing treatment on a Si substrate (1) in a reaction chamber of Metal Organic Chemical Vapor Deposition (MOCVD) equipment to remove magazines and oxide layers on the surface of the substrate, wherein the annealing temperature is 1090 ℃ and the annealing time is 10min;
s2, pre-paving Al on the surface of the Si substrate (1) to inhibit the formation of polycrystalline SiNx so as to improve the surface morphology and the crystallization quality of a GaN film grown on the Si substrate (1);
s3, growing an AlN nucleation layer (2) on the Si substrate (1) pre-paved with Al, and providing a flat nucleation surface for the epitaxial growth of the further step AlGaN buffer layer (3);
s4, growing a step AlGaN buffer layer (3) on the AlN nucleation layer (2) to compensate stress mismatch of the Si substrate and the GaN material, promoting bending and annihilation of dislocation, improving crystal quality and breakdown voltage of the GaN epitaxial film, wherein the step AlGaN buffer layer (3) is divided into 7 layers for growth, al components of the step AlGaN buffer layer are gradually reduced from bottom to top, and thickness of the step AlGaN buffer layer is gradually increased from bottom to top;
s5, growing a GaN nucleation layer (4) on the step AlGaN buffer layer (3);
s6, growing a GaN high-resistance layer (5) on the GaN nucleation layer (4), and realizing the high-resistance performance by adopting a C self-doping technology so as to reduce the leakage current of the buffer layer and improve the breakdown voltage of the device;
s7, growing a GaN channel layer (6) on the GaN high-resistance layer (5);
s8, growing an AlGaN barrier layer (7) on the GaN channel layer (6), wherein the Al component of the AlGaN barrier layer ranges from 0.2 to 0.5;
and S9, growing a GaN cap layer (8) on the AlGaN barrier layer (7) to improve the two-dimensional electron gas mobility and reduce the grid leakage current.
CN202311194715.0A 2023-09-15 2023-09-15 High-voltage-resistant GaN-based epitaxial structure based on Si substrate and preparation method thereof Pending CN117276313A (en)

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