SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas and method of fabrication

Abstract

This invention provides a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas, and its fabrication method. The SiC epitaxial structure includes, sequentially arranged, a Si-faced 3C-SiC barrier layer, a 2DHG, a Si-faced 4H-SiC channel layer, a Si-faced N-type 4H-SiC drift layer, a Si-faced N-type 4H-SiC buffer layer, a Si-faced conductive substrate, a C-faced N-type 4H-SiC buffer layer, a C-faced N-type 4H-SiC drift layer, a C-faced 4H-SiC channel layer, a 2DEG, and a C-faced 3C-SiC barrier layer. In this invention, the lattice mismatch between 3C-SiC and 4H-SiC in the (0001) plane is less than 0.1%, solving the problems of lattice mismatch and thermal mismatch, resulting in better device stability and reliability.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a SiC epitaxial structure having two-dimensional electron gas and two-dimensional hole gas and its preparation method. Background Technology

[0002] In gallium nitride high electron mobility transistor (GaN HEMT) devices, Si, SiC, or sapphire are typically chosen as the substrate for growing GaN. However, GaN exhibits lattice and thermal mismatches with these substrate materials, resulting in poor crystal quality and numerous defects in the grown GaN.

[0003] In AlGaN / GaN HEMT devices, increasing the Al composition or thickness in the AlGaN barrier layer can effectively increase the concentration of two-dimensional electron gas (2DEG). However, increasing the Al composition will increase the lattice mismatch between AlGaN and GaN, making relaxation more likely. Therefore, the thickness of the AlGaN layer must be limited.

[0004] The mobility of the two-dimensional electron gas also changes with the increase of Al composition or thickness. The increase in Al composition or thickness of the barrier layer leads to an increase in the density of the two-dimensional electron gas, a narrower distribution, and a closer proximity to the heterostructure interface, causing changes in various scattering mechanisms, which is the main reason for the decrease in the mobility of the two-dimensional electron gas. When the Al composition increases, the proportion of interface coarseness scattering and alloy disorder scattering in all scattering mechanisms becomes larger and larger, and they are the main factors affecting the mobility.

[0005] The performance of power semiconductors based on silicon materials has approached its physical limits and cannot meet the requirements of today's society for efficient energy conversion. To further improve the performance of power electronic devices, we need to turn to third-generation semiconductors with superior overall performance.

[0006] Third-generation semiconductor materials include wide-bandgap compound semiconductors such as gallium nitride (GaN) and silicon carbide (SiC). Among them, SiC possesses advantages such as low on-resistance, high frequency, high temperature resistance, and high voltage resistance, making it suitable for high-voltage environments exceeding 1200 volts. Compared to GaN, SiC is more resistant to high temperatures and high voltages, making it more suitable for harsh environments. Its applications are wide-ranging, including large transportation vehicles such as wind power and railways, as well as high-power applications such as solar inverters, uninterruptible power systems (UPS), smart grids, and power supplies.

[0007] Among SiC polymorphs, 3C-SiC, 4H-SiC, and 6H-SiC are the most widely used. Of these polymorphs, 3C-SiC exhibits the highest saturated electron drift velocity, electron mobility, and hole mobility, while 4H-SiC boasts the highest bandgap and critical breakdown field strength. Furthermore, 3C-SiC has a bandgap of 2.3 eV, while 4H-SiC has a bandgap as high as 3.2 eV, a difference of 0.9 eV. Due to this significant difference in bandgap, the heterojunction structure formed by 3C-SiC and 4H-SiC holds great potential in heterojunction devices.

[0008] Another important factor influencing the band structure of heterojunctions is the spontaneous polarization of wurtzite-structured SiC. Hexagonal SiC, such as 4H-SiC and 6H-SiC, exhibits spontaneous polarization due to its lower crystal symmetry and the different attraction of C and Si atoms to electrons. In contrast, cubic 3C-SiC, with its higher anisotropic symmetry, lacks spontaneous polarization. Considering the spontaneous polarization effect of SiC, the band structure of the heterojunction becomes more complex. Specifically, when growing 3C-SiC on a 4H-SiC substrate, epitaxy on the Si surface yields a two-dimensional hole gas, while epitaxy on the C surface yields a two-dimensional electron gas.

[0009] CN115346873A discloses a method for fabricating a silicon carbide (SiC) heterostructure normally closed high electron mobility transistor, comprising: selecting an unintentionally doped n-type 4H-SiC wafer as a substrate; isomorphically epitaxially growing a 4H-SiC transition layer on the surface of the substrate, and epitaxially growing a C-plane on the upper surface of the 4H-SiC transition layer; growing an unintentionally doped 3C-SiC well layer on the C-plane of the 4H-SiC transition layer; growing an n-type doped 4H-SiC barrier layer on the upper surface of the 3C-SiC well layer, and epitaxially growing a Si-plane on the upper surface of the 4H-SiC barrier layer; growing an unintentionally doped 3C-SiC cap layer on the Si-plane of the 4H-SiC barrier layer; fabricating electrodes and a protective film to obtain a 3C-SiC / 4H-SiC heterostructure normally closed single-channel high electron mobility transistor.

[0010] CN115440573A discloses a single-crystal SiC / Si wafer substrate, a heterostructure, and a method for fabricating the same. The single-crystal SiC / Si wafer substrate includes a Si substrate on which multiple patterned unit regions are formed. These unit regions are spaced apart by intervals, and each unit region includes a single-crystal SiC layer formed thereon. The heterostructure includes the aforementioned single-crystal SiC / Si and GaN layers. The fabrication method includes selectively growing a single-crystal SiC layer by reacting a carbon-containing material layer with the Si substrate exposed in a groove using an annealing process. Similarly, a single-crystal GaN layer is formed by reacting a nitrogen-containing gas and a gallium-containing vapor phase material on the patterned single-crystal SiC / Si wafer substrate using an MOCVD epitaxial growth process. The resulting single-crystal SiC and GaN structures within the unit regions exhibit high quality and low defect density.

[0011] CN114335135A discloses an enhancement-mode SiC heterojunction transistor epitaxial structure and its fabrication method. The enhancement-mode SiC heterojunction transistor epitaxial structure comprises, from bottom to top: a SiC substrate layer, an N-type heavily doped 4H-SiC buffer layer, an N-type lightly doped 4H-SiC buffer layer, a V-doped high-resistivity 4H-SiC buffer layer, a V-doped high-resistivity 4H-SiC drift layer, a 4H-SiC channel layer, a 3C-SiC barrier layer, and a P-type 3C-SiC layer. By growing P-type 3C-SiC on the depletion-mode basis of the 4H-SiC / 3C-SiC heterojunction, an enhancement-mode device is formed, thereby improving device reliability.

[0012] However, the aforementioned SiC heterojunction structure still suffers from lattice mismatch and thermal mismatch issues. Summary of the Invention

[0013] In view of the problems existing in the prior art, the present invention provides a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas and a preparation method thereof. Compared with the traditional AlGaN / GaN heterojunction structure, the heterojunction formed by 3C-SiC and 4H-SiC has negligible thermal matching and lattice matching, and has a better interface structure.

[0014] To achieve this objective, the present invention adopts the following technical solution:

[0015] In a first aspect, the present invention provides a SiC epitaxial structure having a two-dimensional electron gas and a two-dimensional hole gas, the SiC epitaxial structure comprising, sequentially arranged, a Si-faced 3C-SiC barrier layer, a 2DHG, a Si-faced 4H-SiC channel layer, a Si-faced N-type 4H-SiC drift layer, a Si-faced N-type 4H-SiC buffer layer, a Si-faced conductive substrate, a C-faced N-type 4H-SiC buffer layer, a C-faced N-type 4H-SiC drift layer, a C-faced 4H-SiC channel layer, a 2DEG, and a C-faced 3C-SiC barrier layer.

[0016] The 2DHG described in this invention is a two-dimensional cavitation gas, defined as follows: if the movement of a cavity in a three-dimensional solid is blocked (restricted) in a certain direction (such as the z direction), then the cavity can only move freely in the other two directions (x and y directions). Such a free cavity with two degrees of freedom is called a two-dimensional cavitation gas.

[0017] 2DEG is a two-dimensional electron gas. It is defined as follows: if the movement of electrons in a three-dimensional solid is blocked (restricted) in a certain direction (such as the z-direction), then the electrons can only move freely in the other two directions (x and y directions). Such free electrons with two degrees of freedom are called two-dimensional electron gas.

[0018] The SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas described in this invention forms a 2DHG between the Si-face 3C-SiC barrier layer and the Si-face 4H-SiC channel layer, and a 2DEG between the C-face 4H-SiC channel layer and the C-face 3C-SiC barrier layer. This solves the problems of lattice mismatch and thermal mismatch, giving the device better stability and reliability, and broad application prospects.

[0019] Preferably, the thickness of the Si-faceted N-type 4H-SiC buffer layer is 1–1.5 μm, for example, it can be 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.45 μm, or 1.5 μm, but it is not limited to the listed values; other unlisted values ​​within this range are also applicable; the N doping concentration is 1 × 10⁻⁶. 18 cm -3 ~1.5×10 18 cm -3 For example, it could be 1×10 18 cm -3 1.1×10 18 cm -3 1.2×10 18 cm -3 1.25×10 18 cm -3 1.3×10 18 cm -3 1.4×10 18 cm -3 Or 1.5×10 18 cm -3 This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0020] Preferably, the thickness of the Si-faceted N-type 4H-SiC drift layer is 5–10 μm, for example, it can be 5 μm, 5.5 μm, 6 μm, 7 μm, 8 μm, or 10 μm, but it is not limited to the listed values; other unlisted values ​​within this range are also applicable; the N doping concentration is 5 × 10⁻⁶. 15 cm -3 ~1.5×10 16 cm -3 For example, it could be 5×10 15 cm -3 6×10 15 cm -3 8×10 15 cm -3 1×10 16 cm -3 1.2×10 16 cm -3 Or 1.5×10 16 cm -3 This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0021] Preferably, the thickness of the Si-faced 4H-SiC channel layer is 1 to 2 μm, for example, it can be 1 μm, 1.2 μm, 1.3 μm, 1.5 μm, 1.7 μm or 2 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the thickness of the Si-faced 3C-SiC barrier layer is 50 to 100 μm, for example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] Preferably, the thickness of the Si-plane conductive substrate is 330-370 mm, for example, it can be 330 mm, 340 mm, 350 mm, 355 mm, 360 mm, 365 mm or 370 mm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the thickness of the C-side N-type 4H-SiC buffer layer is 1 to 1.5 μm, for example, it can be 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.45 μm or 1.5 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the N doping concentration is 1×10⁻⁶. 18 cm -3~1.5×10 18 cm -3 For example, it could be 1×10 18 cm -3 1.1×10 18 cm -3 1.2×10 18 cm -3 1.25×10 18 cm -3 1.3×10 18 cm -3 1.4×10 18 cm -3 Or 1.5×10 18 cm -3 This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0026] Preferably, the thickness of the C-plane N-type 4H-SiC drift layer is 5 to 10 μm, for example, it can be 5 μm, 5.5 μm, 6 μm, 7 μm, 8 μm or 10 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the N doping concentration is 5 × 10⁻⁶. 15 cm -3 ~1.5×10 16 cm -3 For example, it could be 5×10 15 cm -3 6×10 15 cm -3 8×10 15 cm -3 1×10 16 cm -3 1.2×10 16 cm -3 Or 1.5×10 16 cm -3 This applies to, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0028] Preferably, the thickness of the 4H-SiC channel layer on the C-side is 1 to 2 μm, for example, it can be 1 μm, 1.2 μm, 1.3 μm, 1.5 μm, 1.7 μm or 2 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the thickness of the 3C-SiC barrier layer on the C-side is 50 to 100 μm, for example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] In a second aspect, the present invention also provides a method for preparing a SiC epitaxial structure having a two-dimensional electron gas and a two-dimensional hole gas as described in the first aspect, the method comprising the following steps:

[0031] (1) In-situ etching is performed on a conductive Si-faced 4H-SiC substrate to sequentially grow a Si-faced N-type 4H-SiC buffer layer, a Si-faced N-type 4H-SiC drift layer, a Si-faced 4H-SiC channel layer and a Si-faced 3C-SiC barrier layer.

[0032] (2) Thin the 4H-SiC substrate, clean it and spin dry;

[0033] (3) In-situ etching is performed on a conductive C-side 4H-SiC substrate, and a C-side N-type 4H-SiC buffer layer, a C-side N-type 4H-SiC drift layer, a C-side 4H-SiC channel layer and a C-side 3C-SiC barrier layer are grown sequentially.

[0034] (4) The SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas was obtained by cooling to room temperature under hydrogen protection.

[0035] The preparation method is carried out in the order of steps (1)(2)(3)(4) or in the order of steps (3)(2)(1)(4).

[0036] The fabrication method described in this invention involves sequentially growing an N-type 4H-SiC buffer layer, an N-type 4H-SiC drift layer, a 4H-SiC channel layer, and a 3C-SiC barrier layer on both the Si and C faces of a conductive 4H-SiC substrate. The heterojunction formed by 3C-SiC and 4H-SiC has negligible thermal and lattice matching: the lattice mismatch between 3C-SiC and 4H-SiC on the (0001) face is less than 0.1%, resulting in a better interface structure and better device stability and reliability.

[0037] Preferably, the in-situ etching in step (1) selects a conductive Si-face 4H-SiC substrate with a bias of 4° or 8° in the <11-20> direction because this surface is a close-packed surface, and the crystal quality is the best compared to other surfaces.

[0038] Preferably, the in-situ etching in step (1) involves introducing H2 at a flow rate of 150 to 300 slm, for example, 150 slm, 180 slm, 200 slm, 250 slm, 270 slm, 290 slm or 300 slm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] HCl is introduced at a flow rate of 50 to 100 sccm, for example, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm, 95 sccm or 100 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] The pressure ranges from 50 to 500 mbar, for example, it can be 50 mbar, 100 mbar, 200 mbar, 300 mbar, 350 mbar, 400 mbar or 500 mbar, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] Temperatures range from 1600 to 1650°C, such as 1600°C, 1610°C, 1620°C, 1630°C, 1640°C, 1645°C, or 1650°C, but are not limited to the listed values. Other unlisted values ​​within this range also apply.

[0042] Etching time is 5 to 10 minutes, for example, 5 minutes, 5.5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the growth conditions for the Si-faced N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 50-300 slm, 80-200 sccm, 80-200 sccm and 5-30 sccm, respectively.

[0044] A flow rate of 50 to 300 slm is introduced into H2, for example, 50 slm, 80 slm, 100 slm, 150 slm, 180 slm, 200 slm or 300 slm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] A flow rate of 80–200 sccm is used to pass SiHCl3, for example, 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] A flow rate of 80–200 sccm is used to feed the carbon source. For example, the flow rate can be 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] A flow rate of 5 to 30 sccm is introduced into the nitrogen source, such as 5 sccm, 8 sccm, 10 sccm, 13 sccm, 15 sccm, 20 sccm or 30 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Temperatures range from 1580 to 1650℃, for example, 1580℃, 1590℃, 1600℃, 1610℃, 1620℃, 1630℃ or 1650℃, but are not limited to the listed values. Other unlisted values ​​within this range also apply.

[0049] Growth can be carried out under pressures of 50 to 500 mbar, such as 50 mbar, 100 mbar, 200 mbar, 300 mbar, 350 mbar, 400 mbar or 500 mbar, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the growth conditions of the Si-faced N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 50-300 slm, 80-200 sccm, 80-200 sccm and 30-60 sccm respectively, and the layer is grown at a temperature of 1580-1650℃ and a pressure of 50-500 mbar.

[0051] A flow rate of 50 to 300 slm is introduced into H2, for example, 50 slm, 80 slm, 100 slm, 200 slm, 270 slm, 290 slm or 300 slm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] A flow rate of 80–200 sccm is used to pass SiHCl3, for example, 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] A flow rate of 80–200 sccm is used to feed the carbon source. For example, the flow rate can be 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] A flow rate of 30 to 60 sccm is introduced into the nitrogen source, such as 30 sccm, 32 sccm, 35 sccm, 38 sccm, 40 sccm, 50 sccm or 60 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] Temperatures range from 1580 to 1650℃, for example, 1580℃, 1590℃, 1600℃, 1620℃, 1630℃, 1640℃ or 1650℃, but are not limited to the listed values. Other unlisted values ​​within this range also apply.

[0056] The pressure ranges from 50 to 500 mbar, for example, it can be 50 mbar, 100 mbar, 200 mbar, 300 mbar, 350 mbar, 400 mbar or 500 mbar, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] Preferably, the growth conditions of the Si-faced 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 50-300 slm, 80-200 sccm and 80-200 sccm respectively, and the layer is grown at a temperature of 1580-1650℃ and a pressure of 50-500 mbar.

[0058] A flow rate of 50 to 300 slm is introduced into H2, for example, 50 slm, 80 slm, 100 slm, 150 slm, 180 slm, 200 slm or 300 slm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] A flow rate of 80–200 sccm is used to pass SiHCl3, for example, 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0060] A flow rate of 80–200 sccm is used to feed the carbon source. For example, the flow rate can be 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0061] Temperatures range from 1580 to 1650℃, for example, 1580℃, 1590℃, 1600℃, 1620℃, 1630℃, 1640℃ or 1650℃, but are not limited to the listed values. Other unlisted values ​​within this range also apply.

[0062] The pressure ranges from 50 to 500 mbar, for example, it can be 50 mbar, 100 mbar, 200 mbar, 300 mbar, 350 mbar, 400 mbar or 500 mbar, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] Preferably, the growth conditions of the Si-faced 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 10-50 slm, 100-500 sccm, 80-150 sccm and 15-50 sccm respectively, and grown at a temperature of 1400-1500℃ and a pressure of 100-500 mbar.

[0064] A flow rate of 10 to 50 slm is introduced into H2, for example, 10 slm, 15 slm, 20 slm, 30 slm, 35 slm, 40 slm or 50 slm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0065] A flow rate of 100 to 500 sccm is fed into the silicon source, such as 100 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm or 500 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] A flow rate of 80–150 sccm is used to feed the carbon source. For example, it can be 80 sccm, 90 sccm, 100 sccm, 120 sccm, 130 sccm or 150 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0067] A flow rate of 15 to 50 sccm is introduced into N2, such as 15 sccm, 20 sccm, 25 sccm, 30 sccm, 40 sccm or 50 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0068] Temperatures range from 1400 to 1500℃, such as 1400℃, 1410℃, 1430℃, 1450℃, 1470℃, 1490℃, or 1500℃, but are not limited to the listed values. Other unlisted values ​​within this range also apply.

[0069] The pressure ranges from 100 to 500 mbar, for example, it can be 100 mbar, 200 mbar, 300 mbar, 350 mbar, 400 mbar or 500 mbar, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0070] Preferably, in step (2), the 4H-SiC substrate is thinned from 330-380 μm to 150-200 μm.

[0071] 330–380 μm, for example, it can be 330 μm, 340 μm, 350 μm, 360 μm, 370 μm, 375 μm or 380 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0072] 150–200 μm, for example, can be 150 μm, 155 μm, 160 μm, 165 μm, 170 μm, 180 μm, 190 μm or 200 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0073] Preferably, the in-situ etching in step (3) involves introducing H2 at a flow rate of 150 to 300 slm, for example, 150 slm, 180 slm, 200 slm, 250 slm, 270 slm, 290 slm or 300 slm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0074] HCl is introduced at a flow rate of 50 to 100 sccm, for example, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm, 95 sccm or 100 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0075] The pressure ranges from 10 to 50 mbar, for example, it can be 10 mbar, 15 mbar, 20 mbar, 30 mbar, 35 mbar, 40 mbar or 50 mbar, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0076] Temperatures of 1700–1750℃, such as 1700℃, 1710℃, 1720℃, 1730℃, 1740℃ or 1750℃, are not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0077] Etching time is 10 to 20 minutes, for example, 10 minutes, 12 minutes, 14 minutes, 15 minutes, 17 minutes, 19 minutes or 20 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0078] Preferably, the growth conditions of the C-face N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 50-300 slm, 80-200 sccm, 80-200 sccm and 5-30 sccm respectively, and grow at a temperature of 1650-1750℃ and a pressure of 10-50 mbar.

[0079] A flow rate of 50 to 300 slm is introduced into H2, for example, 50 slm, 80 slm, 100 slm, 150 slm, 180 slm, 200 slm or 300 slm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0080] A flow rate of 80–200 sccm is used to pass SiHCl3, for example, 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0081] A flow rate of 80–200 sccm is used to feed the carbon source. For example, the flow rate can be 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0082] A flow rate of 5 to 30 sccm is introduced into the nitrogen source, such as 5 sccm, 8 sccm, 10 sccm, 13 sccm, 15 sccm, 20 sccm or 30 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0083] Temperatures range from 1650 to 1750℃, such as 1650℃, 1660℃, 1670℃, 1700℃, 1720℃, 1740℃, or 1750℃, but are not limited to the listed values. Other unlisted values ​​within this range also apply.

[0084] Growth is carried out under pressures of 10–50 mbar, such as 10 mbar, 15 mbar, 20 mbar, 30 mbar, 35 mbar, 40 mbar, or 50 mbar, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0085] Preferably, the growth conditions of the C-plane N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 50-300 slm, 80-200 sccm, 80-200 sccm and 30-60 sccm respectively, and the layer is grown at a temperature of 1650-1750℃ and a pressure of 10-50 mbar.

[0086] A flow rate of 50 to 300 slm is introduced into H2, for example, 50 slm, 80 slm, 100 slm, 150 slm, 180 slm, 200 slm or 300 slm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0087] A flow rate of 80–200 sccm is used to pass SiHCl3, for example, 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0088] A flow rate of 80–200 sccm is used to feed the carbon source. For example, the flow rate can be 80 sccm, 100 sccm, 120 sccm, 140 sccm, 170 sccm, 190 sccm or 200 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0089] A flow rate of 30 to 60 sccm is introduced into the nitrogen source, such as 30 sccm, 35 sccm, 40 sccm, 50 sccm, 55 sccm, 58 sccm or 60 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0090] Temperatures range from 1650 to 1750℃, such as 1650℃, 1660℃, 1670℃, 1700℃, 1720℃, 1740℃, or 1750℃, but are not limited to the listed values. Other unlisted values ​​within this range also apply.

[0091] Growth is carried out under pressures of 10–50 mbar, such as 10 mbar, 15 mbar, 20 mbar, 30 mbar, 35 mbar, 40 mbar, or 50 mbar, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0092] Preferably, the growth conditions of the C-face 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 50-300 slm, 80-200 sccm and 80-200 sccm respectively, and the layer is grown at a temperature of 1650-1750℃ and a pressure of 10-50 mbar.

[0093] In this invention, the growth temperatures of the Si-faceted N-type 4H-SiC buffer layer, Si-faceted N-type 4H-SiC drift layer, and Si-faceted 4H-SiC channel layer are all lower than those of the C-faceted N-type 4H-SiC buffer layer, C-faceted N-type 4H-SiC drift layer, and C-faceted 4H-SiC channel layer, while the pressure is higher. This is because the critical supersaturated surface free energy of the C-face is lower than that of the Si-face, making nucleation easier on the C-face. Lowering the growth temperature or increasing the pressure on the C-face would prevent the normal growth of the C-faceted N-type 4H-SiC buffer layer, C-faceted N-type 4H-SiC drift layer, and C-faceted 4H-SiC channel layer.

[0094] Preferably, the growth conditions of the C-side 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 10-50 slm, 100-500 sccm, 80-150 sccm and 15-50 sccm respectively, and grown at a temperature of 1400-1500℃ and a pressure of 100-500 mbar.

[0095] A flow rate of 10 to 50 slm is introduced into H2, for example, 10 slm, 15 slm, 20 slm, 30 slm, 35 slm, 40 slm or 50 slm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0096] A flow rate of 100 to 500 sccm is fed into the silicon source, such as 100 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm or 500 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0097] A flow rate of 80–150 sccm is used to feed the carbon source. For example, it can be 80 sccm, 90 sccm, 100 sccm, 120 sccm, 130 sccm or 150 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0098] A flow rate of 15 to 50 sccm is introduced into N2, such as 15 sccm, 20 sccm, 25 sccm, 30 sccm, 40 sccm or 50 sccm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0099] Temperatures range from 1400 to 1500℃, such as 1400℃, 1410℃, 1430℃, 1450℃, 1470℃, 1490℃, or 1500℃, but are not limited to the listed values. Other unlisted values ​​within this range also apply.

[0100] The pressure ranges from 100 to 500 mbar, for example, it can be 100 mbar, 200 mbar, 300 mbar, 350 mbar, 400 mbar or 500 mbar, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0101] Preferably, the silicon source includes any one or a combination of at least two of SiH4, SiHCl3, SiH2Cl2 or SiH3Cl, wherein typical but non-limiting combinations include a combination of SiH4 and SiHCl3, a combination of SiH2Cl2 and SiH3Cl, or a combination of SiH4, SiH2Cl2 and SiH3Cl.

[0102] Preferably, the carbon source includes any one or a combination of at least two of C2H2, C2H4, or C3H8, wherein typical but non-limiting combinations include a combination of C2H2 and C2H4, a combination of C3H8 and C2H2, or a combination of C2H4, C3H8, and C2H2.

[0103] Preferably, the nitrogen source includes N2.

[0104] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0105] (1) In-situ etching is performed on a conductive Si-faced 4H-SiC substrate to sequentially grow a Si-faced N-type 4H-SiC buffer layer, a Si-faced N-type 4H-SiC drift layer, a Si-faced 4H-SiC channel layer, and a Si-faced 3C-SiC barrier layer; the in-situ etching is performed on a conductive Si-faced 4H-SiC substrate with a bias of 4° or 8° in the <11-20> direction; the in-situ etching is performed by introducing H2 at a flow rate of 150-300 slm and HCl at a flow rate of 50-100 sccm, and etching is performed at a pressure of 50-500 mbar and a temperature of 1600-1650 °C for 5-10 min.

[0106] The growth conditions for the Si-faced N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 50-300 slm, 80-200 sccm, 80-200 sccm and 5-30 sccm respectively, and grow at a temperature of 1580-1650℃ and a pressure of 50-500 mbar.

[0107] The growth conditions for the Si-faced N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source, and nitrogen source are introduced at flow rates of 50–300 slm, 80–200 sccm, 80–200 sccm, and 30–60 sccm, respectively, and the layer is grown at a temperature of 1580–1650 °C and a pressure of 50–500 mbar.

[0108] The growth conditions for the Si-faced 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 50-300 slm, 80-200 sccm and 80-200 sccm respectively, and the layer is grown at a temperature of 1580-1650℃ and a pressure of 50-500 mbar.

[0109] The growth conditions for the Si-faced 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 10-50 slm, 100-500 sccm, 80-150 sccm and 15-50 sccm respectively, and grown at a temperature of 1400-1500℃ and a pressure of 100-500 mbar.

[0110] (2) Thin the 4H-SiC substrate from 330-380 μm to 150-200 μm, clean and spin dry;

[0111] (3) In-situ etching is performed on a conductive C-side 4H-SiC substrate, and a C-side N-type 4H-SiC buffer layer, a C-side N-type 4H-SiC drift layer, a C-side 4H-SiC channel layer and a C-side 3C-SiC barrier layer are grown sequentially.

[0112] The in-situ etching process involves introducing H2 at a flow rate of 150–300 slm and HCl at a flow rate of 50–100 sccm, and etching for 10–20 min at a pressure of 10–50 mbar and a temperature of 1700–1750 °C.

[0113] The growth conditions for the C-plane N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 50-300 slm, 80-200 sccm, 80-200 sccm and 5-30 sccm respectively, and grow at a temperature of 1650-1750℃ and a pressure of 10-50 mbar.

[0114] The growth conditions for the C-plane N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 50-300 slm, 80-200 sccm, 80-200 sccm and 30-60 sccm respectively, and grown at a temperature of 1650-1750℃ and a pressure of 10-50 mbar.

[0115] The growth conditions for the C-side 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 50-300 slm, 80-200 sccm and 80-200 sccm respectively, and the layer is grown at a temperature of 1650-1750℃ and a pressure of 10-50 mbar.

[0116] The growth conditions for the C-side 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 10-50 slm, 100-500 sccm, 80-150 sccm and 15-50 sccm respectively, and grown at a temperature of 1400-1500℃ and a pressure of 100-500 mbar.

[0117] The silicon source includes any one or a combination of at least two of SiH4, SiHCl3, SiH2Cl2, or SiH3Cl; the carbon source includes any one or a combination of at least two of C2H2, C2H4, or C3H8; and the nitrogen source includes N2.

[0118] (4) The SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas was obtained by cooling to room temperature under hydrogen protection.

[0119] The preparation method is carried out in the order of steps (1)(2)(3)(4) or in the order of steps (3)(2)(1)(4).

[0120] Compared with the prior art, the present invention has at least the following beneficial effects:

[0121] The method for fabricating a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas provided by this invention is simple to operate. An N-type 4H-SiC buffer layer, an N-type 4H-SiC drift layer, a 4H-SiC channel layer, and a 3C-SiC barrier layer are sequentially grown on both the Si and C faces of a conductive 4H-SiC substrate. This results in a 2DHG between the 3C-SiC barrier layer and the 4H-SiC channel layer on the Si face, and a 2DEG between the 4H-SiC channel layer and the 3C-SiC barrier layer on the C face. The lattice mismatch between 3C-SiC and 4H-SiC on the (0001) plane is less than 0.1%, which solves the problems of lattice mismatch and thermal mismatch, and makes the device have better stability and reliability. Attached Figure Description

[0122] Figure 1 This is a schematic diagram of a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas provided in Example 1.

[0123] In the figure: 1-Si plane 3C-SiC barrier layer; 2-2DHG; 3-Si plane 4H-SiC channel layer; 4-Si plane N-type 4H-SiC drift layer; 5-Si plane N-type 4H-SiC buffer layer; 6-Si plane conductive substrate; 7-C plane N-type 4H-SiC buffer layer; 8-C plane N-type 4H-SiC drift layer; 9-C plane 4H-SiC channel layer; 10-2DEG; 11-C plane 3C-SiC barrier layer. Detailed Implementation

[0124] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0125] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0126] Example 1

[0127] This embodiment provides a method for preparing a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas, the preparation method comprising the following steps:

[0128] (1) In-situ etching is performed on a conductive Si-faced 4H-SiC substrate to sequentially grow a Si-faced N-type 4H-SiC buffer layer, a Si-faced N-type 4H-SiC drift layer, a Si-faced 4H-SiC channel layer, and a Si-faced 3C-SiC barrier layer; the in-situ etching is performed on a conductive Si-faced 4H-SiC substrate with a bias of 4° in the <11-20> direction; the in-situ etching is performed by introducing H2 at a flow rate of 200 slm and HCl at a flow rate of 80 sccm, and etching is performed at a pressure of 300 mbar and a temperature of 1600 °C for 8 min.

[0129] The growth conditions for the Si-faced N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 100 slm, 100 sccm, 100 sccm and 20 sccm respectively, and grow at a temperature of 1580℃ and a pressure of 100 mbar.

[0130] The growth conditions for the Si-faced N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 200 slm, 200 sccm, 200 sccm and 50 sccm respectively, and the layer is grown at a temperature of 1580℃ and a pressure of 100 mbar.

[0131] The growth conditions for the Si-face 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 200 slm, 200 sccm and 200 sccm respectively, and the layer is grown at a temperature of 1580℃ and a pressure of 100 mbar.

[0132] The growth conditions for the Si-faced 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 30 slm, 100 sccm, 100 sccm and 30 sccm respectively, and the layer is grown at a temperature of 1400℃ and a pressure of 300 mbar.

[0133] (2) Thin the 4H-SiC substrate from 350μm to 180μm, clean and spin dry;

[0134] (3) In-situ etching is performed on a conductive C-side 4H-SiC substrate, and a C-side N-type 4H-SiC buffer layer, a C-side N-type 4H-SiC drift layer, a C-side 4H-SiC channel layer and a C-side 3C-SiC barrier layer are grown sequentially.

[0135] The in-situ etching process involves introducing H2 at a flow rate of 200 slm and HCl at a flow rate of 100 sccm, and etching is performed for 10 min at a pressure of 20 mbar and a temperature of 1700 °C.

[0136] The growth conditions for the C-plane N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 200 slm, 200 sccm, 200 sccm and 30 sccm respectively, and grow at a temperature of 1750℃ and a pressure of 30 mbar.

[0137] The growth conditions for the C-plane N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 300 slm, 100 sccm, 100 sccm and 50 sccm respectively, and the layer is grown at a temperature of 1750℃ and a pressure of 30 mbar.

[0138] The growth conditions for the C-side 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 100 slm, 200 sccm and 80 sccm respectively, and the layer is grown at a temperature of 1750℃ and a pressure of 30 mbar.

[0139] The growth conditions for the C-side 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 50 slm, 500 sccm, 150 sccm and 50 sccm respectively, and grown at a temperature of 1500℃ and a pressure of 500 mbar.

[0140] The silicon source includes SiH4; the carbon source includes C2H2; the nitrogen source includes N2.

[0141] (4) The SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas was obtained by cooling to room temperature under hydrogen protection.

[0142] A schematic diagram of the SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas prepared in this embodiment is shown below. Figure 1 As shown; the thickness of the N-type 4H-SiC buffer layer on the Si surface is 1.3 μm, and the N doping concentration is 1.2 × 10⁻⁶. 18 cm -3 ;

[0143] The thickness of the Si-plane N-type 4H-SiC drift layer is 8 μm, and the N doping concentration is 8 × 10⁻⁶. 15 cm -3 ;

[0144] The thickness of the Si-faceted 4H-SiC channel layer is 1.3 μm;

[0145] The thickness of the Si-faced 3C-SiC barrier layer is 70 μm.

[0146] The thickness of the Si-faceted conductive substrate is 330 mm;

[0147] The thickness of the C-plane N-type 4H-SiC buffer layer is 1.3 μm, and the N doping concentration is 1.1 × 10⁻⁶. 18 cm -3 ;

[0148] The thickness of the C-plane N-type 4H-SiC drift layer is 7 μm, and the N doping concentration is 9 × 10⁻⁶. 15 cm -3 ;

[0149] The thickness of the 4H-SiC channel layer on the C-side is 1.2 μm;

[0150] The thickness of the 3C-SiC barrier layer on the C-side is 60 μm.

[0151] Example 2

[0152] This embodiment provides a method for preparing a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas, the preparation method comprising the following steps:

[0153] (1) In-situ etching is performed on a conductive C-side 4H-SiC substrate, and a C-side N-type 4H-SiC buffer layer, a C-side N-type 4H-SiC drift layer, a C-side 4H-SiC channel layer and a C-side 3C-SiC barrier layer are grown sequentially.

[0154] The in-situ etching process involves introducing H2 at a flow rate of 180 slm and HCl at a flow rate of 50 sccm, and etching is performed for 20 min at a pressure of 50 mbar and a temperature of 1750 °C.

[0155] The growth conditions for the C-side N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 50 slm, 80 sccm, 80 sccm and 10 sccm respectively, and grow at a temperature of 1650℃ and a pressure of 10 mbar.

[0156] The growth conditions for the C-plane N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 50 slm, 200 sccm, 200 sccm and 30 sccm respectively, and the layer is grown at a temperature of 1650℃ and a pressure of 10 mbar.

[0157] The growth conditions for the C-side 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 50 slm, 80 sccm and 80 sccm respectively, and the layer is grown at a temperature of 1650℃ and a pressure of 10 mbar.

[0158] The growth conditions for the C-side 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 50 slm, 100 sccm, 80 sccm and 15 sccm respectively, and grown at a temperature of 1400℃ and a pressure of 100 mbar.

[0159] (2) Thin the 4H-SiC substrate from 330μm to 150μm, clean and spin dry;

[0160] (3) In-situ etching is performed on a conductive Si-faced 4H-SiC substrate to sequentially grow a Si-faced N-type 4H-SiC buffer layer, a Si-faced N-type 4H-SiC drift layer, a Si-faced 4H-SiC channel layer, and a Si-faced 3C-SiC barrier layer; the in-situ etching is performed on a conductive Si-faced 4H-SiC substrate with a bias of 8° in the <11-20> direction; the in-situ etching is performed by introducing H2 at a flow rate of 150 slm and HCl at a flow rate of 50 sccm, and etching is performed at a pressure of 500 mbar and a temperature of 1650 °C for 5 min.

[0161] The growth conditions for the Si-faced N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 300 slm, 80 sccm, 80 sccm and 5 sccm respectively, and grow at a temperature of 1650℃ and a pressure of 500 mbar.

[0162] The growth conditions for the Si-faced N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 300 slm, 80 sccm, 80 sccm and 30 sccm respectively, and the layer is grown at a temperature of 1650℃ and a pressure of 500 mbar.

[0163] The growth conditions for the Si-face 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 300 slm, 80 sccm and 80 sccm respectively, and the layer is grown at a temperature of 1650℃ and a pressure of 500 mbar.

[0164] The growth conditions for the Si-faced 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 50 slm, 500 sccm, 150 sccm and 50 sccm respectively, and grown at a temperature of 1500℃ and a pressure of 500 mbar.

[0165] The silicon source includes SiH2Cl2; the carbon source includes C2H4; and the nitrogen source includes N2.

[0166] (4) The SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas was obtained by cooling to room temperature under hydrogen protection.

[0167] In this embodiment, the Si-face N-type 4H-SiC buffer layer with a two-dimensional electron gas and a two-dimensional hole gas SiC epitaxial structure was prepared with a thickness of 1 μm and an N doping concentration of 1.5 × 10⁻⁶. 18 cm -3 ;

[0168] The thickness of the Si-plane N-type 4H-SiC drift layer is 7.3 μm, and the N doping concentration is 1.5 × 10⁻⁶. 16 cm -3 ;

[0169] The thickness of the Si-faceted 4H-SiC channel layer is 1.4 μm;

[0170] The thickness of the Si-faceted 3C-SiC barrier layer is 62 μm.

[0171] The thickness of the Si-plane conductive substrate is 360 mm;

[0172] The thickness of the C-plane N-type 4H-SiC buffer layer is 1.3 μm, and the N doping concentration is 1.5 × 10⁻⁶. 18 cm -3 ;

[0173] The thickness of the C-plane N-type 4H-SiC drift layer is 5.5 μm, and the N doping concentration is 5 × 10⁻⁶. 15 cm -3 ;

[0174] The thickness of the 4H-SiC channel layer on the C-side is 1.3 μm;

[0175] The thickness of the 3C-SiC barrier layer on the C-side is 100 μm.

[0176] Example 3

[0177] This embodiment provides a method for preparing a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas, the preparation method comprising the following steps:

[0178] (1) In-situ etching is performed on a conductive Si-faced 4H-SiC substrate to sequentially grow a Si-faced N-type 4H-SiC buffer layer, a Si-faced N-type 4H-SiC drift layer, a Si-faced 4H-SiC channel layer, and a Si-faced 3C-SiC barrier layer; the in-situ etching is performed on a conductive Si-faced 4H-SiC substrate with a bias of 8° in the <11-20> direction; the in-situ etching is performed by introducing H2 at a flow rate of 300 slm and HCl at a flow rate of 100 sccm, and etching is performed at a pressure of 200 mbar and a temperature of 1610 °C for 7 min.

[0179] The growth conditions for the Si-faced N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 150 slm, 110 sccm, 120 sccm and 23 sccm respectively, and grow at a temperature of 1590℃ and a pressure of 160 mbar.

[0180] The growth conditions for the Si-faced N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 240 slm, 180 sccm, 110 sccm and 52 sccm respectively, and the layer is grown at a temperature of 1620℃ and a pressure of 450 mbar.

[0181] The growth conditions for the Si-faced 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 250 slm, 130 sccm and 170 sccm respectively, and the layer is grown at a temperature of 1630℃ and a pressure of 320 mbar.

[0182] The growth conditions for the Si-faced 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 41 slm, 360 sccm, 120 sccm and 30 sccm respectively, and grown at a temperature of 1480℃ and a pressure of 330 mbar.

[0183] (2) Thin the 4H-SiC substrate from 350μm to 190μm, clean and spin dry;

[0184] (3) In-situ etching is performed on a conductive C-side 4H-SiC substrate, and a C-side N-type 4H-SiC buffer layer, a C-side N-type 4H-SiC drift layer, a C-side 4H-SiC channel layer and a C-side 3C-SiC barrier layer are grown sequentially.

[0185] The in-situ etching was performed by introducing H2 at a flow rate of 210 slm and HCl at a flow rate of 63 sccm, and etching was carried out at a pressure of 18 mbar and a temperature of 1732 °C for 16 min.

[0186] The growth conditions for the C-plane N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 240 slm, 160 sccm, 110 sccm and 26 sccm respectively, and grow at a temperature of 1700℃ and a pressure of 16 mbar.

[0187] The growth conditions for the C-plane N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 260 slm, 120 sccm, 140 sccm and 35 sccm respectively, and the layer is grown at a temperature of 1680℃ and a pressure of 41 mbar.

[0188] The growth conditions for the C-side 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 130 slm, 130 sccm and 130 sccm respectively, and the layer is grown at a temperature of 1750℃ and a pressure of 22 mbar.

[0189] The growth conditions for the C-side 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 26 slm, 300 sccm, 120 sccm and 19 sccm respectively, and grown at a temperature of 1450℃ and a pressure of 320 mbar.

[0190] The silicon source includes SiH3Cl; the carbon source includes C3H8; and the nitrogen source includes N2.

[0191] (4) The SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas was obtained by cooling to room temperature under hydrogen protection.

[0192] In this embodiment, the thickness of the Si-face N-type 4H-SiC buffer layer with a two-dimensional electron gas and a two-dimensional hole gas in the SiC epitaxial structure is 1.31 μm, and the N doping concentration is 1.1 × 10⁻⁶. 18 cm -3 ;

[0193] The thickness of the Si-plane N-type 4H-SiC drift layer is 7 μm, and the N doping concentration is 1.1 × 10⁻⁶. 16 cm -3 ;

[0194] The thickness of the Si-faceted 4H-SiC channel layer is 1.4 μm;

[0195] The thickness of the Si-faceted 3C-SiC barrier layer is 80 μm.

[0196] The thickness of the Si-faceted conductive substrate is 338 mm;

[0197] The thickness of the C-plane N-type 4H-SiC buffer layer is 1.5 μm, and the N doping concentration is 1.3 × 10⁻⁶. 18 cm -3 ;

[0198] The thickness of the C-plane N-type 4H-SiC drift layer is 8.1 μm, and the N doping concentration is 1.5 × 10⁻⁶. 16 cm -3 ;

[0199] The thickness of the 4H-SiC channel layer on the C-side is 1.8 μm;

[0200] The thickness of the 3C-SiC barrier layer on the C-side is 88 μm.

[0201] Example 4

[0202] This embodiment provides a method for preparing a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas. Except for step (1), in which the in-situ etching is performed on a conductive Si-face 4H-SiC substrate biased 4° in the <1-100> direction, the preparation method is the same as in embodiment 1.

[0203] Example 5

[0204] This embodiment provides a method for preparing a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas. The preparation method is the same as in Example 1, except that the in-situ etching temperature of 1600℃ for the conductive Si-face 4H-SiC substrate is replaced with the same temperature of 1700℃ for the C-face 4H-SiC substrate.

[0205] Example 6

[0206] This embodiment provides a method for preparing a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas. The preparation method is the same as in Example 1, except that the growth temperature of 1580°C for the Si-face N-type 4H-SiC buffer layer, Si-face N-type 4H-SiC drift layer and Si-face 4H-SiC channel layer is replaced with the same growth temperature of 1750°C for the C-face N-type 4H-SiC buffer layer, C-face N-type 4H-SiC drift layer and C-face 4H-SiC channel layer.

[0207] Example 7

[0208] This embodiment provides a method for preparing a SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas. The preparation method is the same as in Example 1, except that the growth pressure of 100 mbar for the Si-face N-type 4H-SiC buffer layer, Si-face N-type 4H-SiC drift layer and Si-face 4H-SiC channel layer is replaced with the same growth pressure of 30 mbar for the C-face N-type 4H-SiC buffer layer, C-face N-type 4H-SiC drift layer and C-face 4H-SiC channel layer.

[0209] The surface roughness of the SiC epitaxial structures with two-dimensional electron gas and two-dimensional hole gas obtained in the above embodiments and comparative examples was tested using atomic force microscopy.

[0210] The defect density of the SiC epitaxial structures with two-dimensional electron gas and two-dimensional hole gas obtained in the above examples and comparative examples was tested using a Candela 8520 defect detector. The results are shown in Table 1.

[0211] Table 1

[0212]

[0213]

[0214] As can be seen from Table 1:

[0215] (1) As can be seen from Examples 1-3, the SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas prepared by the method of the present invention has excellent quality, low surface roughness (0.224-0.187 nm), and low defect density (0.25-0.12 / cm²). 2 ;

[0216] (2) Combining Examples 1 and 4, it can be seen that in Example 4, the in-situ etching of a conductive Si-faceted 4H-SiC substrate with a 4° offset in the <1-100> direction resulted in an increased surface roughness of the obtained SiC epitaxial structure to 0.236 nm and an increased defect density to 0.38 / cm². 2 ;

[0217] (3) It can be seen from the combined examples 1 and 5 to 7 that when the in-situ etching temperature of the Si surface and the growth temperature of the N-type 4H-SiC buffer layer, the N-type 4H-SiC drift layer and the 4H-SiC channel layer are high, or the growth pressure of the N-type 4H-SiC buffer layer, the N-type 4H-SiC drift layer and the 4H-SiC channel layer is low, the quality of the final SiC epitaxial structure will deteriorate, the surface roughness will increase, and the defect density will also increase.

[0218] This demonstrates that the method for fabricating SiC epitaxial structures with two-dimensional electron gas and two-dimensional hole gas provided by the present invention, through in-situ etching of a suitable biased conductive Si-face 4H-SiC substrate, and by using appropriate growth temperature and growth pressure to sequentially grow an N-type 4H-SiC buffer layer, an N-type 4H-SiC drift layer, and a 4H-SiC channel layer, yields a high-quality SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas, solving the problems of lattice mismatch and thermal mismatch, and enabling the device to have better stability and reliability.

[0219] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A SiC epitaxial structure having a two-dimensional electron gas and a two-dimensional hole gas, characterized by, The SiC epitaxial structure includes, sequentially arranged, a Si-face 3C-SiC barrier layer, a 2DHG, a Si-face 4H-SiC channel layer, a Si-face N-type 4H-SiC drift layer, a Si-face N-type 4H-SiC buffer layer, a Si-face conductive substrate, a C-face N-type 4H-SiC buffer layer, a C-face N-type 4H-SiC drift layer, a C-face 4H-SiC channel layer, a 2DEG, and a C-face 3C-SiC barrier layer; The thickness of the Si-faceted N-type 4H-SiC buffer layer is 1~1.5 μm, and the N doping concentration is 1×10⁻⁶. 18 cm -3 ~1.5×10 18 cm -3 ; The thickness of the Si-plane N-type 4H-SiC drift layer is 5~10 μm, and the N doping concentration is 5×10⁻⁶. 15 cm -3 ~1.5×10 16 cm -3 ; The thickness of the Si-faceted 4H-SiC channel layer is 1~2μm; The thickness of the Si-faceted 3C-SiC barrier layer is 50~100μm; The thickness of the Si-plane conductive substrate is 330~370mm; The thickness of the C-plane N-type 4H-SiC buffer layer is 1~1.5μm, and the N doping concentration is 1×10⁻⁶. 18 cm -3 ~1.5×10 18 cm -3 ; The thickness of the C-plane N-type 4H-SiC drift layer is 5~10 μm, and the N doping concentration is 5×10⁻⁶. 15 cm -3 ~1.5×10 16 cm -3 ; The thickness of the 4H-SiC channel layer on the C-side is 1~2μm; The thickness of the 3C-SiC barrier layer on the C-side is 50~100μm.

2. A method of producing a SiC epitaxial structure having a two-dimensional electron gas and a two-dimensional hole gas as claimed in claim 1, characterized in that, The preparation method includes the following steps: (1) In-situ etching is performed on a conductive Si-faced 4H-SiC substrate to sequentially grow a Si-faced N-type 4H-SiC buffer layer, a Si-faced N-type 4H-SiC drift layer, a Si-faced 4H-SiC channel layer, and a Si-faced 3C-SiC barrier layer. (2) Thin the 4H-SiC substrate, clean it, and spin dry; (3) In-situ etching is performed on a conductive C-side 4H-SiC substrate, and a C-side N-type 4H-SiC buffer layer, a C-side N-type 4H-SiC drift layer, a C-side 4H-SiC channel layer and a C-side 3C-SiC barrier layer are grown sequentially. (4) The SiC epitaxial structure with two-dimensional electron gas and two-dimensional hole gas was obtained by cooling to room temperature under hydrogen protection; The preparation method is carried out in the order of steps (1), (2), (3), and (4) or in the order of steps (3), (2), (1), and (4).

3. The production method according to claim 2, characterized by, In step (1), the in-situ etching is performed on a conductive Si-face 4H-SiC substrate with a bias of 4° or 8° in the <11-20> direction.

4. The preparation method according to claim 2, characterized in that, In step (1), the in-situ etching involves introducing H2 at a flow rate of 150-300 slm and HCl at a flow rate of 50-100 sccm, and etching for 5-10 minutes at a pressure of 50-500 mbar and a temperature of 1600-1650 °C.

5. The preparation method according to claim 2, characterized in that, The growth conditions for the Si-faced N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 50~300 slm, 80~200 sccm, 80~200 sccm and 5~30 sccm respectively, and grow at a temperature of 1580~1650℃ and a pressure of 50~500 mbar.

6. The preparation method according to claim 2, characterized in that, The growth conditions for the Si-faced N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 50~300 slm, 80~200 sccm, 80~200 sccm and 30~60 sccm respectively, and the layer is grown at a temperature of 1580~1650℃ and a pressure of 50~500 mbar.

7. The preparation method according to claim 2, characterized in that, The growth conditions for the Si-faced 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 50~300 slm, 80~200 sccm and 80~200 sccm respectively, and the layer is grown at a temperature of 1580~1650℃ and a pressure of 50~500 mbar.

8. The preparation method according to claim 2, characterized in that, The growth conditions for the Si-faced 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 10~50 slm, 100~500 sccm, 80~150 sccm and 15~50 sccm respectively, and grown at a temperature of 1400~1500℃ and a pressure of 100~500 mbar.

9. The method of claim 2, wherein, In step (2), the 4H-SiC substrate is thinned from 330~380μm to 150~200μm.

10. The method of claim 2, wherein, In step (3), the in-situ etching involves introducing H2 at a flow rate of 150-300 slm and HCl at a flow rate of 50-100 sccm, and etching for 10-20 min at a pressure of 10-50 mbar and a temperature of 1700-1750 °C.

11. The method of claim 2, wherein, The growth conditions for the C-side N-type 4H-SiC buffer layer are as follows: stop the HCl flow, and introduce H2, SiHCl3, carbon source and nitrogen source at flow rates of 50~300 slm, 80~200 sccm, 80~200 sccm and 5~30 sccm respectively, and grow at a temperature of 1650~1750℃ and a pressure of 10~50 mbar.

12. The preparation method according to claim 2, characterized in that, The growth conditions for the C-plane N-type 4H-SiC drift layer are as follows: H2, SiHCl3, carbon source and nitrogen source are introduced at flow rates of 50~300 slm, 80~200 sccm, 80~200 sccm and 30~60 sccm respectively, and the layer is grown at a temperature of 1650~1750℃ and a pressure of 10~50 mbar.

13. The preparation method according to claim 2, characterized in that, The growth conditions for the C-side 4H-SiC channel layer are as follows: the nitrogen source is turned off, and H2, SiHCl3 and carbon source are introduced at flow rates of 50~300 slm, 80~200 sccm and 80~200 sccm respectively, and the layer is grown at a temperature of 1650~1750℃ and a pressure of 10~50 mbar.

14. The method of claim 2, wherein, The growth conditions for the C-side 3C-SiC barrier layer are as follows: H2, silicon source, carbon source and N2 are introduced at flow rates of 10~50 slm, 100~500 sccm, 80~150 sccm and 15~50 sccm respectively, and grown at a temperature of 1400~1500℃ and a pressure of 100~500 mbar.

15. The production method according to claim 8 or 14, characterized by, The silicon source includes any one or a combination of at least two of SiH4, SiHCl3, SiH2Cl2, or SiH3Cl.

16. The method of any one of claims 5-8 or 11-14, wherein, The carbon source includes any one or a combination of at least two of C2H2, C2H4, or C3H8.

17. The method of any one of claims 5-7 or 11-13, wherein the method further comprises the step of: The nitrogen source includes N2. ​

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