Preparation method of N-type silicon carbide epitaxial wafer

Abstract

The invention relates to a preparation method of an N-type silicon carbide epitaxial wafer, in particular to the technical field of silicon carbide epitaxial growth, and the preparation method comprises the steps: carrying out the etching of a substrate, and sequentially carrying out the growth of an N-type buffer layer and an N-type drift layer, and obtaining the N-type silicon carbide epitaxial wafer; an N-type dopant used in the growth of the N-type drift layer comprises a cyanosilane compound. According to the preparation method provided by the invention, by adopting the specific N-type dopant cyanosilane compound, the memory effect of N in the reaction cavity can be remarkably reduced during growth of the N-type epitaxial layer, so that the doping uniformity of N-type SiC in different batches is improved, and stable N doping is favorably realized.

Description

Technical Field

[0001] The invention relates to the technical field of silicon carbide epitaxial growth, and in particular to a method for preparing an N-type silicon carbide epitaxial wafer. Background Art

[0002] At present, silicon carbide (SiC) has the characteristics of large bandgap, good thermal conductivity, high electron saturation drift velocity and excellent chemical stability, making it an important semiconductor material for manufacturing high-power devices, high-frequency devices, high-temperature devices and radiation-resistant devices.

[0003] The main technologies for SiC homoepitaxial growth include chemical vapor deposition (CVD), liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE). Currently, MOCVD has become the mainstream technology for SiC epitaxial growth. In comparison, it has many advantages, such as higher growth rate, precise thickness control, and SiC in-situ doping.

[0004] For example, CN102610500A discloses a method for preparing an N-type heavily doped silicon carbide thin film epitaxially, which mainly solves the problem that the prior art cannot achieve high-quality heavily doped silicon carbide. The implementation steps are: first, place a silicon carbide substrate into a reaction chamber; heat the reaction chamber in a hydrogen flow, and when the temperature reaches 1400°C, add C3H8 to the hydrogen flow; when the temperature reaches 1580°C, in-situ etch the substrate for 10-30 minutes; then maintain the reaction chamber temperature at 1580°C and the air pressure at 100-700mbar, add SiH4 with a flow rate of 15-24mL / min, C3H8 with a flow rate of 5-8mL / min and N2 with a flow rate of 2000mL / min to a hydrogen flow of 10-20L / min, and grow an epitaxial layer; after the growth is completed, cool in a hydrogen flow; and finally fill with argon.

[0005] However, during the epitaxial growth of N-type SiC, the doping uniformity of N-type SiC between different batches is poor. The main reason is that when growing SiC, not only SiC grows on the substrate, but also SiC deposits are attached to the dome and cover of the reaction chamber. These deposits have terminal dangling bonds, and the prior art uses N2 as a dopant. N2 has lone electron pairs that easily form complexes with dangling bonds. Therefore, there is a serious N memory effect in the reaction chamber, resulting in a high actual doping concentration of the N element during the subsequent epitaxial growth of N-type SiC, which affects the accuracy of the doping concentration and is not conducive to achieving stable N doping. Summary of the invention

[0006] In view of the problems existing in the prior art, an object of the present invention is to provide a method for preparing an N-type silicon carbide epitaxial wafer to solve the defect of unstable N doping concentration in the product due to the memory effect of N.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing an N-type silicon carbide epitaxial wafer, the preparation method comprising:

[0009] The substrate is etched, and then an N-type buffer layer and an N-type drift layer are grown in sequence to obtain an N-type silicon carbide epitaxial wafer;

[0010] The N-type dopant used in the growth of the N-type drift layer includes a cyanosilane compound.

[0011] The preparation method provided by the present invention can significantly reduce the memory effect of N in the reaction chamber when growing an N-type epitaxial layer by adopting a specific N-type dopant cyanosilane compound, thereby improving the doping uniformity of N-type SiC between different batches, which is conducive to achieving stable N doping.

[0012] As a preferred technical solution of the present invention, the substrate comprises a 4H-SiC substrate which is biased 4° towards the <11-20> direction.

[0013] Preferably, the concentration of N element in the substrate is 5×10 18 -1×10 19 atom / cm 3 .

[0014] As a preferred technical solution of the present invention, the gas used in the etching process includes hydrogen.

[0015] Preferably, the flow rate of the gas used in the etching process is 300-500 slm.

[0016] As a preferred technical solution of the present invention, the operating pressure of the etching process is 50-100 mbar.

[0017] Preferably, the operating temperature of the etching process is 1400-1650°C.

[0018] Preferably, the etching process takes 5-10 minutes.

[0019] As a preferred technical solution of the present invention, the flow rate of the carrier gas used for growing the N-type buffer layer is 100-800slm.

[0020] Preferably, the carrier gas used for growing the N-type buffer layer includes hydrogen.

[0021] Preferably, the silicon source gas used for growing the N-type buffer layer includes one or a combination of at least two of SiCl4, SiHCl3, SiH2C12 or SiH3Cl.

[0022] Preferably, the flow rate of the silicon source gas used for growing the N-type buffer layer is 300-600 sccm.

[0023] Preferably, the carbon source gas used for growing the N-type buffer layer includes C2H4 and / or C3H8.

[0024] Preferably, the flow rate of the carbon source gas used for growing the N-type buffer layer is 200-500 sccm.

[0025] Preferably, the N-type dopant used for growing the N-type buffer layer includes a cyanosilane compound and / or nitrogen.

[0026] Preferably, the flow rate of the N-type dopant used for growing the N-type buffer layer is 80-120 sccm.

[0027] As a preferred technical solution of the present invention, the growth pressure of the N-type buffer layer is 50-100 mbar.

[0028] Preferably, the growth temperature of the N-type buffer layer is 1580-1680°C.

[0029] As a preferred technical solution of the present invention, the thickness of the N-type buffer layer obtained by growing the N-type buffer layer is 0.9-1.1 μm.

[0030] Preferably, the concentration of N element in the N-type buffer layer obtained by growing the N-type buffer layer is 7×10 17 -1.3×10 18 atom / cm 3 .

[0031] As a preferred technical solution of the present invention, the carrier gas used for growing the N-type drift layer includes hydrogen.

[0032] Preferably, the flow rate of the carrier gas used for growing the N-type drift layer is 100-800 slm.

[0033] Preferably, the silicon source gas used for growing the N-type drift layer includes one or a combination of at least two of SiCl4, SiHCl3, SiH2C12 or SiH3Cl.

[0034] Preferably, the flow rate of the silicon source gas used for growing the N-type drift layer is 300-600 sccm.

[0035] Preferably, the carbon source gas used for growing the N-type drift layer includes C2H4 and / or C3H8.

[0036] Preferably, the flow rate of the carbon source gas used for growing the N-type drift layer is 200-500 sccm.

[0037] Preferably, the flow rate of the N-type dopant used for growing the N-type drift layer is 20-60 sccm.

[0038] As a preferred technical solution of the present invention, the growth pressure of the N-type drift layer is 50-100 mbar.

[0039] Preferably, the growth temperature of the N-type drift layer is 1580-1680°C.

[0040] As a preferred technical solution of the present invention, the thickness of the N-type drift layer obtained by growing the N-type drift layer is 10-200 μm.

[0041] Preferably, the concentration of N element in the N-type drift layer obtained by growing the N-type drift layer is 7×10 15 -8×10 15 atom / cm 3 .

[0042] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0043] Using cyanosilane compounds as N-type dopants can effectively dope N elements into the SiC lattice, reduce the residual nitrogen dopant in the growth environment, and thus effectively reduce the fluctuation of N element concentration in the epitaxial layer during the epitaxial growth of silicon carbide, which is beneficial to the precise control of the doping concentration and further ensures the stability of the doping concentration during the epitaxial growth process. DETAILED DESCRIPTION

[0044] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0045] This embodiment provides a method for preparing an N-type silicon carbide epitaxial wafer, the method comprising:

[0046] The substrate is etched, and then an N-type buffer layer and an N-type drift layer are grown in sequence to obtain an N-type silicon carbide epitaxial wafer;

[0047] The N-type dopant used in the growth of the N-type drift layer includes a cyanosilane compound.

[0048] In the present invention, the cyanosilane compound used includes: trimethylsilyl cyanide (CAS No.: 7677-24-9), difunctional chloromethylsilyl cyanide (CAS No.: 1964502-77-9) or difunctional vinylsilyl cyanide (CAS No.: 2069196-22-9) or a combination of at least two thereof.

[0049] Specifically, the substrate includes a 4H-SiC substrate with an angle of 4° toward the <11-20> direction.

[0050] Specifically, the concentration of N element in the substrate is 5×10 18 -1×10 19 atom / cm 3 , for example, it can be 5×10 18 atom / cm 3 , 5.5×10 18 atom / cm 3 , 6×10 18 atom / cm 3 , 6.5×10 18 atom / cm 3 ,7×10 18 atom / cm 3 , 7.5×10 18 atom / cm 3 , 8×10 18 atom / cm 3 , 8.5×10 18 atom / cm 3 ,9×10 18 atom / cm 3 , 9.5×10 18 atom / cm 3 or 1×10 9 atom / cm 3 The above values ​​are not limited to the above values. Other values ​​not listed in the above values ​​also meet the requirements.

[0051] In the present invention, atom / cm 3 Refers to the number of atoms contained in a unit volume.

[0052] Specifically, the gas used in the etching process includes hydrogen.

[0053] Specifically, the flow rate of the gas used in the etching process is 300-500slm, for example, it can be 300slm, 320slm, 340slm, 360slm, 380slm, 400slm, 420slm, 440slm, 460slm, 480slm or 500slm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0054] Specifically, the operating pressure of the etching process is 50-100 mbar, for example, it can be 50 mbar, 55 mbar, 60 mbar, 65 mbar, 70 mbar, 75 mbar, 80 mbar, 85 mbar, 90 mbar, 95 mbar or 100 mbar, etc., but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0055] Specifically, the operating temperature of the etching process is 1400-1650°C, for example, it can be 1400°C, 1420°C, 1440°C, 1460°C, 1480°C, 1500°C, 1520°C, 1540°C, 1560°C, 1580°C, 1600°C, 1620°C, 1640°C or 1650°C, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0056] Specifically, the etching treatment time is 5-10 minutes, for example, it can be 5 minutes, 5.5 minutes, 6 minutes, 6.5 minutes, 7 minutes, 7.5 minutes, 8 minutes, 8.5 minutes, 9 minutes, 9.5 minutes or 10 minutes, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0057] Specifically, the flow rate of the carrier gas used for growing the N-type buffer layer is 100-800slm, for example, it can be 100slm, 150slm, 200slm, 25slm, 300slm, 350slm, 400slm, 450slm, 500slm, 550slm, 600slm, 650slm, 700slm, 750slm or 800slm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0058] Specifically, the carrier gas used for growing the N-type buffer layer includes hydrogen.

[0059] Specifically, the silicon source gas used for growing the N-type buffer layer includes one or a combination of at least two of SiCl4, SiHCl3, SiH2C12 or SiH3Cl.

[0060] Specifically, the flow rate of the silicon source gas used for the growth of the N-type buffer layer is 300-600sccm, for example, it can be 300sccm, 320sccm, 340sccm, 360sccm, 380sccm, 400sccm, 420sccm, 440sccm, 460sccm, 480sccm, 500sccm, 520sccm, 540sccm, 560sccm, 580sccm or 600sccm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0061] Specifically, the carbon source gas used for growing the N-type buffer layer includes C2H4 and / or C3H8.

[0062] Specifically, the flow rate of the carbon source gas used for the growth of the N-type buffer layer is 200-500sccm, for example, it can be 200sccm, 220sccm, 240sccm, 260sccm, 280sccm, 300sccm, 320sccm, 340sccm, 360sccm, 380sccm, 400sccm, 420sccm, 440sccm, 460sccm, 480sccm or 500sccm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0063] Specifically, the N-type dopant used for growing the N-type buffer layer includes a cyanosilane compound and / or nitrogen.

[0064] Specifically, the flow rate of the N-type dopant used for growing the N-type buffer layer is 80-120sccm, for example, it can be 80sccm, 85sccm, 90sccm, 95sccm, 100sccm, 105sccm, 110sccm, 115sccm or 120sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0065] Specifically, the growth pressure of the N-type buffer layer is 50-100 mbar, for example, it can be 50 mbar, 55 mbar, 60 mbar, 65 mbar, 70 mbar, 75 mbar, 80 mbar, 85 mbar, 90 mbar, 95 mbar or 100 mbar, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0066] Specifically, the growth temperature of the N-type buffer layer is 1580-1680°C, for example, it can be 1580°C, 1590°C, 1600°C, 1610°C, 1620°C, 1630°C, 1640°C, 1650°C, 1660°C, 1670°C or 1680°C, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0067] Specifically, the thickness of the N-type buffer layer grown by the N-type buffer layer is 0.9-1.1μm, for example, it can be 0.9μm, 0.91μm, 0.92μm, 0.93μm, 0.94μm, 0.95μm, 0.96μm, 0.97μm, 0.98μm, 0.99μm, 1μm or 1.1μm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0068] Specifically, the concentration of N element in the N-type buffer layer obtained by growing the N-type buffer layer is 7×10 17 -1.3×1018 atom / cm 3 , for example, it can be 7×10 17 atom / cm 3 , 8×10 17 atom / cm 3 ,9×10 17 atom / cm 3 , 1×10 18 atom / cm 3 , 1.1×10 18 atom / cm 3 , 1.2×10 18 atom / cm 3 or 1.3 × 10 18 atom / cm 3 The above values ​​are not limited to the above values. Other values ​​not listed in the above values ​​also meet the requirements.

[0069] Specifically, the carrier gas used for growing the N-type drift layer includes hydrogen.

[0070] Specifically, the flow rate of the carrier gas used for growing the N-type drift layer is 100-800slm, for example, it can be 100slm, 200slm, 300slm, 400slm, 500slm, 600slm, 700slm or 800slm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0071] Specifically, the silicon source gas used for growing the N-type drift layer includes one or a combination of at least two of SiCl4, SiHCl3, SiH2C12 or SiH3Cl.

[0072] Specifically, the flow rate of the silicon source gas used for growing the N-type drift layer is 300-600sccm, for example, it can be 300sccm, 320sccm, 340sccm, 360sccm, 380sccm, 400sccm, 420sccm, 440sccm, 460sccm, 480sccm, 500sccm, 520sccm, 540sccm, 560sccm, 580sccm or 600sccm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0073] Specifically, the carbon source gas used for growing the N-type drift layer includes C2H4 and / or C3H8;

[0074] Specifically, the flow rate of the carbon source gas used for growing the N-type drift layer is 200-500sccm, for example, it can be 200sccm, 220sccm, 240sccm, 260sccm, 280sccm, 300sccm, 320sccm, 340sccm, 360sccm, 380sccm, 400sccm, 420sccm, 440sccm, 460sccm, 480sccm or 500sccm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0075] Specifically, the flow rate of the N-type dopant used for the growth of the N-type drift layer is 20-60sccm, for example, it can be 20sccm, 22sccm, 24sccm, 26sccm, 28sccm, 30sccm, 32sccm, 34sccm, 36sccm, 38sccm, 40sccm, 42sccm, 44sccm, 46sccm, 48sccm, 50sccm, 52sccm, 54sccm, 56sccm, 58sccm or 60sccm, but is not limited to the listed values, and other values ​​not listed in the range also meet the requirements.

[0076] Specifically, the growth pressure of the N-type drift layer is 50-100 mbar, for example, it can be 50 mbar, 55 mbar, 60 mbar, 65 mbar, 70 mbar, 75 mbar, 80 mbar, 85 mbar, 90 mbar, 95 mbar or 100 mbar, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0077] Specifically, the growth temperature of the N-type drift layer is 1580-1680°C, for example, it can be 1580°C, 1590°C, 1600°C, 1610°C, 1620°C, 1630°C, 1640°C, 1650°C, 1660°C, 1670°C or 1680°C, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0078] Specifically, the thickness of the N-type drift layer obtained by growing the N-type drift layer is 10-200 μm, for example, it can be 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm or 200 μm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0079] Specifically, the concentration of N element in the N-type drift layer obtained by growing the N-type drift layer is 7×10 15 -8×1015 atom / cm 3 , for example, it can be 7×10 15 atom / cm 3 , 7.1×10 15 atom / cm 3 , 7.2×10 15 atom / cm 3 , 7.3×10 15 atom / cm 3 , 7.4×10 15 atom / cm 3 , 7.5×10 15 atom / cm 3 , 7.6×10 15 atom / cm 3 , 7.7×10 15 atom / cm 3 , 7.8×10 15 atom / cm 3 ,7.9×10 15 atom / cm 3 or 8×10 15 atom / cm 3 The above values ​​are not limited to the above values. Other values ​​not listed in the above values ​​also meet the requirements.

[0080] Further, in order to illustrate the stable N-doping effect that can be achieved by the preparation provided by the present invention, the following practical examples are used for illustration, as follows:

[0081] Example 1

[0082] This embodiment provides a method for preparing an N-type silicon carbide epitaxial wafer, the preparation method comprising:

[0083] The substrate is etched, and then an N-type buffer layer and an N-type drift layer are grown in sequence to obtain an N-type silicon carbide epitaxial wafer;

[0084] The N-type dopants used in the growth of the N-type buffer layer and the growth of the N-type drift layer are both cyanosilane compounds (trimethylsilyl cyanide, CAS No.: 7677-24-9);

[0085] The substrate is a 4H-SiC substrate with a 4° orientation in the <11-20> direction; the concentration of N element in the substrate is 6×10 18 atom / cm 3 ;

[0086] The gas used in the etching process is hydrogen; the flow rate of the gas used in the etching process is 400 slm; the operating pressure of the etching process is 60 mbar; the operating temperature of the etching process is 1500° C.; the time of the etching process is 6 minutes;

[0087] The flow rate of the carrier gas used for the growth of the N-type buffer layer is 300slm; the carrier gas used for the growth of the N-type buffer layer is hydrogen; the silicon source gas used for the growth of the N-type buffer layer is SiCl4; the flow rate of the silicon source gas used for the growth of the N-type buffer layer is 400sccm; the carbon source gas used for the growth of the N-type buffer layer is C3H8; the flow rate of the carbon source gas used for the growth of the N-type buffer layer is 300sccm; the flow rate of the N-type dopant used for the growth of the N-type buffer layer is 100sccm; the growth pressure of the N-type buffer layer is 60mbar; the growth temperature of the N-type buffer layer is 1600℃; the thickness of the N-type buffer layer obtained by the growth of the N-type buffer layer is 1μm; the concentration of the N element in the N-type buffer layer obtained by the growth of the N-type buffer layer is 9×10 17 atom / cm 3 ;

[0088] The carrier gas used for growing the N-type drift layer is hydrogen; the flow rate of the carrier gas used for growing the N-type drift layer is 300slm; the silicon source gas used for growing the N-type drift layer is SiCl4; the flow rate of the silicon source gas used for growing the N-type drift layer is 400sccm; the carbon source gas used for growing the N-type drift layer is C3H8; the flow rate of the carbon source gas used for growing the N-type drift layer is 300sccm; the flow rate of the N-type dopant used for growing the N-type drift layer is 40sccm; the growth pressure of the N-type drift layer is 60mbar; the growth temperature of the N-type drift layer is 1600℃; the thickness of the N-type drift layer obtained by growing the N-type drift layer is 80μm.

[0089] Example 2

[0090] This embodiment provides a method for preparing an N-type silicon carbide epitaxial wafer, the preparation method comprising:

[0091] The substrate is etched, and then an N-type buffer layer and an N-type drift layer are grown in sequence to obtain an N-type silicon carbide epitaxial wafer;

[0092] The N-type dopants used in the growth of the N-type buffer layer and the growth of the N-type drift layer are both cyanosilane compounds (difunctional chloromethylsilane, CAS No.: 1964502-77-9);

[0093] The substrate is a 4H-SiC substrate with a 4° orientation in the <11-20> direction; the concentration of N element in the substrate is 8×10 18atom / cm 3 ;

[0094] The gas used in the etching process is hydrogen; the flow rate of the gas used in the etching process is 450slm; the operating pressure of the etching process is 80mbar; the operating temperature of the etching process is 1600°C; the time of the etching process is 8min;

[0095] The flow rate of the carrier gas used for the growth of the N-type buffer layer is 600slm; the carrier gas used for the growth of the N-type buffer layer is hydrogen; the silicon source gas used for the growth of the N-type buffer layer is SiH2C12; the flow rate of the silicon source gas used for the growth of the N-type buffer layer is 500sccm; the carbon source gas used for the growth of the N-type buffer layer is C2H4; the flow rate of the carbon source gas used for the growth of the N-type buffer layer is 400sccm; the flow rate of the N-type dopant used for the growth of the N-type buffer layer is 90sccm; the growth pressure of the N-type buffer layer is 80mbar; the growth temperature of the N-type buffer layer is 1620℃; the thickness of the N-type buffer layer obtained by the growth of the N-type buffer layer is 0.95μm; the concentration of the N element in the N-type buffer layer obtained by the growth of the N-type buffer layer is 1×10 18 atom / cm 3 ;

[0096] The carrier gas used for growing the N-type drift layer is hydrogen; the flow rate of the carrier gas used for growing the N-type drift layer is 600slm; the silicon source gas used for growing the N-type drift layer is SiH2C12; the flow rate of the silicon source gas used for growing the N-type drift layer is 500sccm; the carbon source gas used for growing the N-type drift layer is C2H4; the flow rate of the carbon source gas used for growing the N-type drift layer is 400sccm; the flow rate of the N-type dopant used for growing the N-type drift layer is 50sccm; the growth pressure of the N-type drift layer is 80mbar; the growth temperature of the N-type drift layer is 1620℃; the thickness of the N-type drift layer obtained by growing the N-type drift layer is 150μm.

[0097] Example 3

[0098] This embodiment provides a method for preparing an N-type silicon carbide epitaxial wafer, the preparation method comprising:

[0099] The substrate is etched, and then an N-type buffer layer and an N-type drift layer are grown in sequence to obtain an N-type silicon carbide epitaxial wafer;

[0100] The N-type dopant used in the growth of the N-type buffer layer is nitrogen; the N-type dopant used in the growth of the N-type drift layer is a cyanosilane compound (bifunctional vinyl cyanosilane, CAS No.: 2069196-22-9);

[0101] The substrate is a 4H-SiC substrate with a 4° orientation in the <11-20> direction; the concentration of N element in the substrate is 5×10 18 atom / cm 3 ;

[0102] The gas used in the etching process is hydrogen; the flow rate of the gas used in the etching process is 300 slm; the operating pressure of the etching process is 100 mbar; the operating temperature of the etching process is 1650° C.; the time of the etching process is 5 minutes;

[0103] The flow rate of the carrier gas used for the growth of the N-type buffer layer is 100 slm; the carrier gas used for the growth of the N-type buffer layer is hydrogen; the silicon source gas used for the growth of the N-type buffer layer is SiHCl3; the flow rate of the silicon source gas used for the growth of the N-type buffer layer is 300 sccm; the carbon source gas used for the growth of the N-type buffer layer is C2H4; the flow rate of the carbon source gas used for the growth of the N-type buffer layer is 500 sccm; the flow rate of the N-type dopant used for the growth of the N-type buffer layer is 80 sccm; the growth pressure of the N-type buffer layer is 100 mbar; the growth temperature of the N-type buffer layer is 1580°C; the thickness of the N-type buffer layer obtained by the growth of the N-type buffer layer is 1.1 μm; the concentration of the N element in the N-type buffer layer obtained by the growth of the N-type buffer layer is 7×10 17 atom / cm 3 ;

[0104] The carrier gas used for growing the N-type drift layer is hydrogen; the flow rate of the carrier gas used for growing the N-type drift layer is 100 slm; the silicon source gas used for growing the N-type drift layer is SiH3Cl; the flow rate of the silicon source gas used for growing the N-type drift layer is 300 sccm; the carbon source gas used for growing the N-type drift layer is C2H4; the flow rate of the carbon source gas used for growing the N-type drift layer is 500 sccm; the flow rate of the N-type dopant used for growing the N-type drift layer is 20 sccm; the growth pressure for growing the N-type drift layer is 100 mbar; the growth temperature for growing the N-type drift layer is 1580°C; the thickness of the N-type drift layer obtained by growing the N-type drift layer is 200 μm.

[0105] Example 4

[0106] This embodiment provides a method for preparing an N-type silicon carbide epitaxial wafer, the preparation method comprising:

[0107] The substrate is etched, and then an N-type buffer layer and an N-type drift layer are grown in sequence to obtain an N-type silicon carbide epitaxial wafer;

[0108] The N-type dopant used in the growth of the N-type buffer layer is nitrogen; the N-type dopant used in the growth of the N-type drift layer is a cyanosilane compound (trimethylsilyl cyanide, CAS No.: 7677-24-9);

[0109] The substrate is a 4H-SiC substrate with a 4° orientation in the <11-20> direction; the concentration of N element in the substrate is 1×10 19 atom / cm 3 ;

[0110] The gas used in the etching process is hydrogen; the flow rate of the gas used in the etching process is 500slm; the operating pressure of the etching process is 50mbar; the operating temperature of the etching process is 1400°C; the time of the etching process is 10min;

[0111] The flow rate of the carrier gas used for the growth of the N-type buffer layer is 800slm; the carrier gas used for the growth of the N-type buffer layer is hydrogen; the silicon source gas used for the growth of the N-type buffer layer is SiH3Cl; the flow rate of the silicon source gas used for the growth of the N-type buffer layer is 600sccm; the carbon source gas used for the growth of the N-type buffer layer is C3H8; the flow rate of the carbon source gas used for the growth of the N-type buffer layer is 200sccm; the flow rate of the N-type dopant used for the growth of the N-type buffer layer is 120sccm; the growth pressure of the N-type buffer layer is 50mbar; the growth temperature of the N-type buffer layer is 1680℃; the thickness of the N-type buffer layer obtained by the growth of the N-type buffer layer is 0.9μm; the concentration of the N element in the N-type buffer layer obtained by the growth of the N-type buffer layer is 1.3×10 18 atom / cm 3 ;

[0112] The carrier gas used for growing the N-type drift layer is hydrogen; the flow rate of the carrier gas used for growing the N-type drift layer is 800slm; the silicon source gas used for growing the N-type drift layer is SiH3Cl; the flow rate of the silicon source gas used for growing the N-type drift layer is 600sccm; the carbon source gas used for growing the N-type drift layer is C3H8; the flow rate of the carbon source gas used for growing the N-type drift layer is 200sccm; the flow rate of the N-type dopant used for growing the N-type drift layer is 60sccm; the growth pressure of the N-type drift layer is 50mbar; the growth temperature of the N-type drift layer is 1680℃; the thickness of the N-type drift layer obtained by growing the N-type drift layer is 10μm.

[0113] Example 5

[0114] The only difference from Example 1 is that the N-type dopant used in the growth of the N-type buffer layer is nitrogen.

[0115] Example 6

[0116] The only difference from Example 1 is that the N-type dopant used in the growth of the N-type drift layer is nitrogen and a cyanosilane compound in a volume ratio of 1:3.

[0117] Example 7

[0118] The only difference from Example 1 is that the N-type dopant used in the growth of the N-type drift layer is nitrogen and a silane cyanide compound in a volume ratio of 3:1.

[0119] Example 8

[0120] The only difference from Example 1 is that the N-type dopant used in the growth of the N-type drift layer is nitrogen.

[0121] Example 9

[0122] The only difference from Example 5 is that the N-type dopant used in the growth of the N-type drift layer is nitrogen.

[0123] Example 10

[0124] The only difference from Example 1 is that the N-type dopant used in the growth of the N-type drift layer is nitrogen and a cyanosilane compound in a volume ratio of 1:1.

[0125] The preparation process of the embodiment was used to continuously grow 42 batches, and the nitrogen doping concentration of the drift layer in the corresponding product was shown in Table 1.

[0126] Table 1

[0127]

[0128]

[0129]

[0130]

[0131] As can be seen from Table 1, the preparation method provided by the present invention, by adopting a specific N-type dopant cyanosilane compound, can significantly reduce the memory effect of N in the reaction chamber when growing an N-type epitaxial layer, thereby improving the doping uniformity of N-type SiC between different batches, which is conducive to achieving stable N doping.

[0132] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0133] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0134] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing an N-type silicon carbide epitaxial wafer, characterized in that: The preparation method comprises: The substrate is etched, and then an N-type buffer layer and an N-type drift layer are grown in sequence to obtain an N-type silicon carbide epitaxial wafer; The N-type dopant used in the growth of the N-type drift layer includes a cyanosilane compound.

2. The preparation method according to claim 1, characterized in that The substrate comprises a 4H-SiC substrate biased 4° in the <11-20> direction; Preferably, the concentration of N element in the substrate is 5×10 18 -1×10 19 atom / cm 3 .

3. The preparation method according to claim 1 or 2, characterized in that: The gas used in the etching process includes hydrogen; Preferably, the flow rate of the gas used in the etching process is 300-500 slm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The operating pressure of the etching process is 50-100 mbar; Preferably, the operating temperature of the etching process is 1400-1650°C; Preferably, the etching process takes 5-10 minutes.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The flow rate of the carrier gas used for growing the N-type buffer layer is 100-800slm; Preferably, the carrier gas used for growing the N-type buffer layer includes hydrogen; Preferably, the silicon source gas used for growing the N-type buffer layer includes one or a combination of at least two of SiCl4, SiHCl3, SiH2C12 or SiH3Cl; Preferably, the flow rate of the silicon source gas used for growing the N-type buffer layer is 300-600 sccm; Preferably, the carbon source gas used for growing the N-type buffer layer includes C2H4 and / or C3H8; Preferably, the flow rate of the carbon source gas used for growing the N-type buffer layer is 200-500 sccm; Preferably, the N-type dopant used for growing the N-type buffer layer includes a cyanosilane compound and / or nitrogen; Preferably, the flow rate of the N-type dopant used for growing the N-type buffer layer is 80-120 sccm.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The growth pressure of the N-type buffer layer is 50-100 mbar; Preferably, the growth temperature of the N-type buffer layer is 1580-1680°C.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The thickness of the N-type buffer layer obtained by growing the N-type buffer layer is 0.9-1.1 μm; Preferably, the concentration of N element in the N-type buffer layer obtained by growing the N-type buffer layer is 7×10 17 -1.3×10 18 atom / cm 3 .

8. The preparation method according to any one of claims 1 to 7, characterized in that: The carrier gas used for growing the N-type drift layer includes hydrogen; Preferably, the flow rate of the carrier gas used for growing the N-type drift layer is 100-800slm; Preferably, the silicon source gas used for growing the N-type drift layer includes one or a combination of at least two of SiCl4, SiHCl3, SiH2C12 or SiH3Cl; Preferably, the flow rate of the silicon source gas used for growing the N-type drift layer is 300-600 sccm; Preferably, the carbon source gas used for growing the N-type drift layer includes C2H4 and / or C3H8; Preferably, the flow rate of the carbon source gas used for growing the N-type drift layer is 200-500 sccm; Preferably, the flow rate of the N-type dopant used for growing the N-type drift layer is 20-60 sccm.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The growth pressure of the N-type drift layer is 50-100 mbar; Preferably, the growth temperature of the N-type drift layer is 1580-1680°C.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The thickness of the N-type drift layer obtained by growing the N-type drift layer is 10-200 μm; Preferably, the concentration of N element in the N-type drift layer obtained by growing the N-type drift layer is 7×10 15 -8×10 15 atom / cm 3 .

Images