Epitaxial structure for MOSFET and preparation method and application thereof

Abstract

The invention relates to an epitaxial structure for an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) and a preparation method and application thereof, in particular to the field of power devices, and the epitaxial structure comprises a buffer layer, a first drift layer, a second drift layer, an AlN layer, a first NO-doped 3C-SiC layer, an O-doped 3C-SiC layer and a second NO-doped 3C-SiC layer which are sequentially arranged on a substrate. According to the epitaxial structure provided by the invention, the epitaxial structure is designed, and the specific design of the first NO-doped 3C-SiC layer, the O-doped 3C-SiC layer and the second NO-doped 3C-SiC layer is adopted, so that the defects of low channel mobility and over-low threshold voltage caused by poor SiO2 / SiC interface quality and high interface state are overcome; therefore, the obtained power device has excellent channel mobility and reasonable threshold voltage.

Description

Technical Field

[0001] The present invention relates to the field of power devices, and in particular to an epitaxial structure for MOSFET and a preparation method and application thereof. Background Art

[0002] At present, SiC power MOSFET, as an important SiC power device, is widely used in power electronic systems due to its advantages such as simple gate drive circuit, high operating frequency, high power density and high conversion efficiency.

[0003] For example, 4H-SiC MOSFET has made remarkable progress in research at home and abroad. For example, CN109616523A discloses a 4H-SiC MOSFET power device and its manufacturing method, which includes: source, SiO2 interlayer dielectric, gate, gate oxide layer, P+ contact region, N+ source region, P well, additionally injected P-type region, N-type epitaxial layer, N- epitaxial layer, buffer layer, N+ substrate and drain.

[0004] However, 4H-SiC MOSFET devices still need further adjustments in terms of SiO2 / SiC interface quality, gate voltage stability, high-reliability terminal structure design, more reliable ohmic contact preparation process and higher parameter device design requirements. This is because after SiC oxidation, there are C residues. These interface traps will introduce fixed position energy levels in the bandgap of SiC, resulting in poor SiO2 / SiC interface quality, high interface states, low channel mobility and too low threshold voltage. Summary of the invention

[0005] In view of the problems existing in the prior art, the object of the present invention is to provide an epitaxial structure for MOSFET and a preparation method and use thereof, so as to solve the defects of poor SiO2 / SiC interface quality, high interface state leading to low channel mobility and too low threshold voltage.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides an epitaxial structure for a MOSFET, the epitaxial structure comprising: a buffer layer, a first drift layer, a second drift layer, an AlN layer, a first NO-doped 3C-SiC layer, an O-doped 3C-SiC layer and a second NO-doped 3C-SiC layer, which are sequentially arranged on a substrate.

[0008] The epitaxial structure provided by the present invention solves the defects of low channel mobility and too low threshold voltage caused by poor SiO2 / SiC interface quality and high interface state, thereby ensuring that the obtained power device has excellent channel mobility and reasonable threshold voltage, by designing the epitaxial structure and adopting a specific first NO-doped 3C-SiC layer, an O-doped 3C-SiC layer and a second NO-doped 3C-SiC layer.

[0009] As a preferred technical solution of the present invention, the thickness of the buffer layer is 0.9-1.1 μm.

[0010] Preferably, the N-type doping concentration of the buffer layer is 7×10 17 -1.3×10 18 atom / cm 3 .

[0011] As a preferred technical solution of the present invention, the thickness of the first drift layer is 5-20 μm.

[0012] Preferably, the N-type doping concentration of the first drift layer is 0.7×10 16 -1×10 16 atom / cm 3 .

[0013] Preferably, the second drift layer has a thickness of 1-2 μm.

[0014] Preferably, the N-type doping concentration of the second drift layer is 2×10 16 -2.5×10 16 atom / cm 3 .

[0015] As a preferred technical solution of the present invention, the thickness of the AlN layer is 10-300 nm.

[0016] As a preferred technical solution of the present invention, the thickness of the first NO-doped 3C-SiC layer is 0.1-0.5 nm.

[0017] Preferably, the NO doping concentration of the first NO-doped 3C-SiC layer is 1×10 16 -1×10 19 atom / cm 3 .

[0018] Preferably, the O-doped 3C-SiC layer has a thickness of 0.1-0.5 nm.

[0019] Preferably, the O-doping concentration of the O-doped 3C-SiC layer is 1×10 16 -1×10 19 atom / cm 3.

[0020] Preferably, the thickness of the second NO-doped 3C-SiC layer is 0.1-0.5 nm.

[0021] Preferably, the NO doping concentration of the second NO-doped 3C-SiC layer is 1×10 16 -1×10 19 atom / cm 3 .

[0022] In a second aspect, the present invention provides a method for preparing the epitaxial structure according to the first aspect, the preparation method comprising:

[0023] The substrate is sequentially subjected to buffer layer growth, first drift layer growth, second drift layer growth, AlN layer growth, first NO-doped 3C-SiC layer growth, O-doped 3C-SiC layer growth and second NO-doped 3C-SiC layer growth.

[0024] 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.

[0025] Preferably, the flow rate of the carrier gas used in the growth of the buffer layer is 100-800 slm.

[0026] Preferably, the flow rate of the silicon source gas used in the growth of the buffer layer is 300-600 sccm.

[0027] Preferably, the flow rate of the carbon source gas used in the growth of the buffer layer is 200-500 sccm.

[0028] Preferably, the flow rate of the N-type dopant used in the growth of the buffer layer is 80-120 sccm.

[0029] Preferably, the growth temperature of the buffer layer is 1580-1680°C.

[0030] Preferably, the growth pressure of the buffer layer is 50-100 mbar.

[0031] As a preferred technical solution of the present invention, the flow rate of the carrier gas used in the growth of the first drift layer is 100-800slm.

[0032] Preferably, the flow rate of the silicon source gas used in the growth of the first drift layer is 300-600 sccm.

[0033] Preferably, the flow rate of the carbon source gas used in the growth of the first drift layer is 200-500 sccm.

[0034] Preferably, the flow rate of the N-type dopant used in the growth of the first drift layer is 20-60 sccm.

[0035] Preferably, the growth temperature of the first drift layer is 1580-1680°C.

[0036] Preferably, the growth pressure of the first drift layer is 50-500 mbar.

[0037] Preferably, the flow rate of the carrier gas used in the growth of the second drift layer is 100-800 slm.

[0038] Preferably, the flow rate of the silicon source gas used in the growth of the second drift layer is 300-600 sccm.

[0039] Preferably, the flow rate of the carbon source gas used in the growth of the second drift layer is 200-500 sccm.

[0040] Preferably, the flow rate of the N-type dopant used in the growth of the second drift layer is 20-60 sccm.

[0041] Preferably, the growth temperature of the second drift layer is 1580-1680°C.

[0042] Preferably, the growth pressure of the second drift layer is 50-500 mbar.

[0043] As a preferred technical solution of the present invention, the flow rate of the carrier gas used in the growth of the AlN layer is 10-50slm.

[0044] Preferably, the flow rate of the aluminum source used in the growth of the AlN layer is 50-100 sccm.

[0045] Preferably, the flow rate of the nitrogen source used in the growth of the AlN layer is 80-200 sccm.

[0046] Preferably, the growth temperature of the AlN layer is 700-1200°C.

[0047] Preferably, the growth pressure of the AlN layer is 100-500 mbar.

[0048] Preferably, the flow rate of the carrier gas used in the growth of the first NO-doped 3C-SiC layer is 10-50 slm.

[0049] Preferably, the flow rate of the silicon source gas used in the growth of the first NO-doped 3C-SiC layer is 100-500 sccm.

[0050] Preferably, the flow rate of the carbon source gas used in the growth of the first NO-doped 3C-SiC layer is 80-150 sccm.

[0051] Preferably, the flow rate of NO used in the growth of the first NO-doped 3C-SiC layer is 15-50 sccm.

[0052] Preferably, the growth temperature of the first NO-doped 3C-SiC layer is 1350-1400°C.

[0053] Preferably, the growth pressure of the first NO-doped 3C-SiC layer is 100-500 mbar.

[0054] Preferably, the flow rate of the carrier gas used in the growth of the O-doped 3C-SiC layer is 10-50 slm.

[0055] Preferably, the flow rate of the silicon source gas used in the growth of the O-doped 3C-SiC layer is 100-500 sccm.

[0056] Preferably, the flow rate of the carbon source gas used in the growth of the O-doped 3C-SiC layer is 80-150 sccm.

[0057] Preferably, the flow rate of the oxygen source gas used in the growth of the O-doped 3C-SiC layer is 15-50 sccm.

[0058] Preferably, the growth temperature of the O-doped 3C-SiC layer is 1350-1400°C.

[0059] Preferably, the growth pressure of the O-doped 3C-SiC layer is 100-500 mbar.

[0060] Preferably, the flow rate of the carrier gas used in the growth of the second NO-doped 3C-SiC layer is 10-50 slm.

[0061] Preferably, the flow rate of the silicon source gas used in the growth of the second NO-doped 3C-SiC layer is 100-500 sccm.

[0062] Preferably, the flow rate of the carbon source gas used in the growth of the second NO-doped 3C-SiC layer is 80-150 sccm.

[0063] Preferably, the flow rate of NO used in the growth of the second NO-doped 3C-SiC layer is 15-50 sccm.

[0064] Preferably, the growth temperature of the second NO-doped 3C-SiC layer is 1350-1400°C.

[0065] Preferably, the growth pressure of the second NO-doped 3C-SiC layer is 100-500 mbar.

[0066] In a third aspect, the present invention provides a use of the epitaxial structure according to the first aspect, the use comprising:

[0067] The epitaxial structure for MOSFET is used to prepare a MOSFET device.

[0068] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0069] The epitaxial structure provided by the present invention designs the epitaxial structure of MOSFET and adopts the synergistic effect of the first NO-doped 3C-SiC layer, the O-doped 3C-SiC layer and the second NO-doped 3C-SiC layer, so that the epitaxial structure has a higher channel mobility and threshold voltage, and the channel mobility is ≥214cm 2 / V·s, threshold voltage ≤12V. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a schematic diagram of an epitaxial structure for MOSFET provided by an embodiment of the present invention.

[0071] In the figure: 1-substrate, 2-buffer layer, 3-first drift layer, 4-second drift layer, 5-AlN layer, 6-first NO-doped 3C-SiC layer, 7-O-doped 3C-SiC layer, 8-second NO-doped 3C-SiC layer.

[0072] The present invention is further described in detail below. However, the following examples are only 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 shall be subject to the claims. DETAILED DESCRIPTION

[0073] 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:

[0074] This embodiment provides an epitaxial structure for MOSFET, such as Figure 1 As shown, the epitaxial structure includes: a buffer layer 2, a first drift layer 3, a second drift layer 4, an AlN layer 5, a first NO-doped 3C-SiC layer 6, an O-doped 3C-SiC layer 7 and a second NO-doped 3C-SiC layer 8 which are sequentially arranged on a substrate 1.

[0075] Among them, the thickness of the buffer layer 2 is 0.9-1.1μm, for example, it can be 0.9μm, 0.92μm, 0.94μm, 0.96μm, 0.98μm, 1μm, 1.02μm, 1.04μm, 1.06μm, 1.08μm or 1.1μm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0076] The N-type doping concentration of the buffer layer 2 is 7×10 17 -1.3×10 18 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.

[0077] The thickness of the first drift layer 3 is 5-20 μm, for example, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0078] The N-type doping concentration of the first drift layer 3 is 0.7×10 16 -1×10 16 atom / cm 3 , for example, it can be 0.7×10 16 atom / cm 3 , 0.75×10 16 atom / cm 3 , 0.8×10 16 atom / cm 3 , 0.85×10 16 atom / cm 3 , 0.9×10 16 atom / cm 3 , 0.95×10 16 atom / cm 3 or 1×10 16 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.

[0079] The thickness of the second drift layer 4 is 1-2 μm, for example, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm or 2 μm, but is not limited to the listed values, and other values ​​not listed in the range also meet the requirements.

[0080] The N-type doping concentration of the second drift layer 4 is 2×10 16 -2.5×10 16 atom / cm 3 , for example, it can be 2×10 16 atom / cm 3 , 2.05×10 16 atom / cm 3 , 2.1×10 16 atom / cm 3 , 2.15×10 16 atom / cm 3 , 2.2×10 16 atom / cm 3 , 2.25×10 16 atom / cm 3 , 2.3×10 16 atom / cm 3 , 2.35×10 16 atom / cm 3 , 2.4×10 16 atom / cm 3 , 2.45×10 16 atom / cm 3 or 2.5 × 10 16 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.

[0081] The thickness of the AlN layer 5 is 10-300 nm, for example, 10 nm, 20 nm, 40 nm, 60 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm or 300 nm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0082] Among them, the thickness of the first NO-doped 3C-SiC layer 6 is 0.1-0.5nm, for example, it can be 0.1nm, 0.15nm, 0.2nm, 0.25nm, 0.3nm, 0.35nm, 0.4nm, 0.45nm or 0.5nm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0083] The NO doping concentration of the first NO-doped 3C-SiC layer 6 is 1×10 16 -1×10 19 atom / cm 3 , for example, it can be 1×10 16 atom / cm 3 , 2×10 16 atom / cm 3 , 3×10 16 atom / cm 3 , 4×10 16 atom / cm 3 , 5×10 16 atom / cm 3 , 6×10 16 atom / cm 3 ,7×10 16 atom / cm 3 , 8×10 16 atom / cm 3 ,9×10 16 atom / cm 3 , 1×10 17 atom / cm 3 , 2×10 17 atom / cm 3 , 4×10 17 atom / cm 3 , 6×10 17 atom / cm 3 , 8×10 17 atom / cm 3 , 1×10 18 atom / cm 3 , 2×10 18 atom / cm 3 , 4×10 18 atom / cm 3 , 6×10 18 atom / cm 3 , 8×10 18 atom / cm 3 or 1×10 19 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.

[0084] The thickness of the O-doped 3C-SiC layer 7 is 0.1-0.5 nm, for example, 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm or 0.5 nm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0085] The O-doping concentration of the O-doped 3C-SiC layer 7 is 1×10 16 -1×10 19 atom / cm 3 , for example, it can be 1×10 16 atom / cm 3 , 2×10 16 atom / cm 3 , 3×10 16 atom / cm 3 , 4×10 16 atom / cm 3 , 5×10 16 atom / cm 3 , 6×10 16 atom / cm 3 ,7×10 16 atom / cm 3 , 8×10 16 atom / cm 3 ,9×10 16 atom / cm 3 , 1×10 17 atom / cm 3 , 2×10 17 atom / cm 3 , 4×10 17 atom / cm 3 , 6×10 17 atom / cm 3 , 8×10 17 atom / cm 3 , 1×10 18 atom / cm 3 , 2×10 18 atom / cm 3 , 4×10 18 atom / cm 3 , 6×10 18 atom / cm 3 , 8×10 18 atom / cm 3 or 1×10 19 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.

[0086] The thickness of the second NO-doped 3C-SiC layer 8 is 0.1-0.5 nm, for example, 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm or 0.5 nm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0087] The NO doping concentration of the second NO-doped 3C-SiC layer 8 is 1×10 16 -1×10 19 atom / cm 3 , for example, it can be 1×10 16 atom / cm 3 , 2×10 16 atom / cm 3 , 3×10 16 atom / cm 3 , 4×10 16 atom / cm 3 , 5×10 16 atom / cm 3 , 6×10 16 atom / cm 3 ,7×10 16 atom / cm 3 , 8×10 16 atom / cm 3 ,9×10 16 atom / cm 3 , 1×10 17 atom / cm 3 , 2×10 17 atom / cm 3 , 4×10 17 atom / cm 3 , 6×10 17 atom / cm 3 , 8×10 17 atom / cm 3 , 1×10 18 atom / cm 3 , 2×10 18 atom / cm 3 , 4×10 18 atom / cm 3 , 6×10 18 atom / cm 3 , 8×10 18 atom / cm 3 or 1×10 19 atom / cm 3The above values ​​are not limited to the above values. Other values ​​not listed in the above values ​​also meet the requirements.

[0088] Furthermore, the present invention provides a method for preparing an epitaxial structure for MOSFET, the preparation method comprising:

[0089] The substrate is sequentially subjected to buffer layer growth, first drift layer growth, second drift layer growth, AlN layer growth, first NO-doped 3C-SiC layer growth, O-doped 3C-SiC layer growth and second NO-doped 3C-SiC layer growth.

[0090] The substrate comprises a 4H-SiC substrate with an angle of 4° in the <11-20> direction.

[0091] Among them, the flow rate of the carrier gas used in the growth of the buffer 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.

[0092] Among them, the flow rate of the silicon source gas used in the growth of the buffer layer is 300-600sccm, for example, it can be 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, 550sccm or 600sccm, but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0093] Among them, the flow rate of the carbon source gas used in the growth of the buffer layer is 200-500sccm, for example, it can be 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm or 500sccm, but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0094] Among them, the flow rate of the N-type dopant used in the growth of the buffer layer is 80-120sccm, for example, it can be 80sccm, 85sccm, 90sccm, 95sccm, 100sccm, 105sccm, 110sccm, 115sccm or 120sccm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0095] Among them, the growth temperature of the buffer layer is 1580-1680℃, for example, it can be 1580℃, 1590℃, 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃, 1660℃, 1670℃ or 1680℃, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0096] The growth pressure of the buffer layer is 50-100 mbar, for example, 50 mbar, 60 mbar, 70 mbar, 80 mbar, 90 mbar or 100 mbar, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0097] Among them, the flow rate of the carrier gas used in the growth of the first 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.

[0098] Among them, the flow rate of the silicon source gas used in the growth of the first drift layer is 300-600sccm, for example, it can be 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, 550sccm or 600sccm, but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0099] Among them, the flow rate of the carbon source gas used in the growth of the first drift layer is 200-500sccm, for example, it can be 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm or 500sccm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0100] Among them, the flow rate of the N-type dopant used in the growth of the first drift layer is 20-60sccm, for example, it can be 20sccm, 25sccm, 30sccm, 35sccm, 40sccm, 45sccm, 50sccm, 55sccm or 60sccm, but is not limited to the listed values. Other values ​​not listed in this range also meet the requirements.

[0101] Among them, the growth temperature of the first drift layer is 1580-1680℃, for example, it can be 1580℃, 1590℃, 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃, 1660℃, 1670℃ or 1680℃, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0102] The growth pressure of the first drift layer is 50-500 mbar, for example, it can be 50 mbar, 60 mbar, 80 mbar, 100 mbar, 150 mbar, 200 mbar, 250 mbar, 300 mbar, 350 mbar, 400 mbar, 450 mbar or 500 mbar, but is not limited to the listed values, and other values ​​not listed in this range also meet the requirements.

[0103] The flow rate of the carrier gas used in the growth of the second drift layer is 100-800slm, for example, 100slm, 200slm, 300slm, 400slm, 500slm, 600slm, 700slm or 800slm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0104] Among them, the flow rate of the silicon source gas used in the growth of the second drift layer is 300-600sccm, for example, it can be 300sccm, 350sccm, 400sccm, 450sccm, 500sccm, 550sccm or 600sccm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0105] Among them, the flow rate of the carbon source gas used in the growth of the second drift layer is 200-500sccm, for example, it can be 200sccm, 250sccm, 300sccm, 350sccm, 400sccm, 450sccm or 500sccm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0106] Among them, the flow rate of the N-type dopant used in the growth of the second drift layer is 20-60sccm, for example, it can be 20sccm, 25sccm, 30sccm, 35sccm, 40sccm, 45sccm, 50sccm, 55sccm or 60sccm, but is not limited to the listed values. Other values ​​not listed in this range also meet the requirements.

[0107] Among them, the growth temperature of the second drift layer is 1580-1680℃, for example, it can be 1580℃, 1590℃, 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, 1650℃, 1660℃, 1670℃ or 1680℃, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0108] The growth pressure of the second drift layer is 50-500 mbar, for example, it can be 50 mbar, 60 mbar, 80 mbar, 100 mbar, 150 mbar, 200 mbar, 250 mbar, 300 mbar, 350 mbar, 400 mbar, 450 mbar or 500 mbar, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0109] The flow rate of the carrier gas used in the growth of the AlN layer is 10-50 slm, for example, 10 slm, 20 slm, 30 slm, 40 slm or 50 slm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0110] The flow rate of the aluminum source used in the growth of the AlN layer is 50-100 sccm, for example, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm or 100 sccm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0111] Among them, the flow rate of the nitrogen source used in the growth of the AlN layer is 80-200sccm, for example, it can be 80sccm, 100sccm, 120sccm, 140sccm, 160sccm, 180sccm or 200sccm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0112] The growth temperature of the AlN layer is 700-1200°C, for example, 700°C, 800°C, 900°C, 1000°C, 1100°C or 1200°C, but is not limited to the listed values, and other values ​​not listed in the range also meet the requirements.

[0113] The growth pressure of the AlN layer is 100-500 mbar, for example, 100 mbar, 150 mbar, 200 mbar, 250 mbar, 300 mbar, 350 mbar, 400 mbar, 450 mbar or 500 mbar, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0114] Among them, the flow rate of the carrier gas used in the growth of the first NO-doped 3C-SiC layer is 10-50slm, for example, it can be 10slm, 20slm, 30slm, 40slm or 50slm, but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0115] Among them, the flow rate of the silicon source gas used in the growth of the first NO-doped 3C-SiC layer is 100-500sccm, for example, it can be 100slm, 200slm, 300slm, 400slm or 500slm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0116] Among them, the flow rate of the carbon source gas used in the growth of the first NO-doped 3C-SiC layer is 80-150sccm, for example, it can be 80sccm, 100sccm, 120sccm, 140sccm or 150sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0117] Among them, the flow rate of NO used in the growth of the first NO-doped 3C-SiC layer is 15-50sccm, for example, it can be 15sccm, 20sccm, 25sccm, 30sccm, 35sccm, 40sccm, 45sccm or 50sccm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0118] Among them, the growth temperature of the first NO-doped 3C-SiC layer is 1350-1400°C, for example, it can be 1350°C, 1360°C, 1370°C, 1380°C, 1390°C or 1400°C, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0119] Among them, the growth pressure of the first NO-doped 3C-SiC layer is 100-500mbar, for example, it can be 100mbar, 150mbar, 200mbar, 250mbar, 300mbar, 350mbar, 400mbar, 450mbar or 500mbar, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0120] The flow rate of the carrier gas used in the growth of the O-doped 3C-SiC layer is 10-50 slm, for example, 10 slm, 20 slm, 30 slm, 40 slm or 50 slm, but is not limited to the listed values, and other values ​​not listed within the range also meet the requirements.

[0121] Among them, the flow rate of the silicon source gas used in the growth of the O-doped 3C-SiC layer is 100-500sccm, for example, it can be 100slm, 200slm, 300slm, 400slm or 500slm, but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0122] Among them, the flow rate of the carbon source gas used in the growth of the O-doped 3C-SiC layer is 80-150sccm, for example, it can be 80sccm, 100sccm, 120sccm, 140sccm or 150sccm, but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0123] Among them, the flow rate of the oxygen source gas used in the growth of the O-doped 3C-SiC layer is 15-50sccm, for example, it can be 15sccm, 20sccm, 25sccm, 30sccm, 35sccm, 40sccm, 45sccm or 50sccm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0124] Among them, the growth temperature of the O-doped 3C-SiC layer is 1350-1400°C, for example, it can be 1350°C, 1360°C, 1370°C, 1380°C, 1390°C or 1400°C, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0125] Among them, the growth pressure of the O-doped 3C-SiC layer is 100-500 mbar, for example, it can be 100 mbar, 150 mbar, 200 mbar, 250 mbar, 300 mbar, 350 mbar, 400 mbar, 450 mbar or 500 mbar, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0126] Among them, the flow rate of the carrier gas used in the growth of the second NO-doped 3C-SiC layer is 10-50slm, for example, it can be 10slm, 20slm, 30slm, 40slm or 50slm, but is not limited to the listed values, and other unlisted values ​​within this range also meet the requirements.

[0127] Among them, the flow rate of the silicon source gas used in the growth of the second NO-doped 3C-SiC layer is 100-500sccm, for example, it can be 100slm, 200slm, 300slm, 400slm or 500slm, etc., but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0128] Among them, the flow rate of the carbon source gas used in the growth of the second NO-doped 3C-SiC layer is 80-150sccm, for example, it can be 80sccm, 100sccm, 120sccm, 140sccm or 150sccm, etc., but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0129] Among them, the flow rate of NO used in the growth of the second NO-doped 3C-SiC layer is 15-50sccm, for example, it can be 15sccm, 20sccm, 25sccm, 30sccm, 35sccm, 40sccm, 45sccm or 50sccm, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0130] Among them, the growth temperature of the second NO-doped 3C-SiC layer is 1350-1400°C, for example, it can be 1350°C, 1360°C, 1370°C, 1380°C, 1390°C or 1400°C, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0131] Among them, the growth pressure of the second NO-doped 3C-SiC layer is 100-500mbar, for example, it can be 100mbar, 150mbar, 200mbar, 250mbar, 300mbar, 350mbar, 400mbar, 450mbar or 500mbar, but is not limited to the listed values, and other unlisted values ​​within the range also meet the requirements.

[0132] In the present invention, the silicon source gas used includes one or a combination of at least two of SiCl4, SiHCl3, SiH2C12 or SiH3Cl.

[0133] In the present invention, the carbon source gas used includes C2H4 and / or C3H8.

[0134] In the present invention, the carrier gas used includes hydrogen.

[0135] In the present invention, the N-type dopant used includes nitrogen.

[0136] In the present invention, the aluminum source used includes TMAl.

[0137] In the present invention, the oxygen source gas used includes oxygen.

[0138] Furthermore, the present invention provides a use of the epitaxial structure for MOSFET as described above, the use comprising:

[0139] The epitaxial structure for MOSFET is used to prepare a MOSFET device.

[0140] Example 1

[0141] This embodiment provides an epitaxial structure for MOSFET, the epitaxial structure comprising: a buffer layer, a first drift layer, a second drift layer, an AlN layer, a first NO-doped 3C-SiC layer, an O-doped 3C-SiC layer, and a second NO-doped 3C-SiC layer sequentially disposed on a substrate;

[0142] The thickness of the buffer layer is 1 μm; the N-type doping concentration of the buffer layer is 1×10 18 atom / cm 3 ;

[0143] The thickness of the first drift layer is 10 μm; the N-type doping concentration of the first drift layer is 0.8×10 16 atom / cm 3 ;

[0144] The thickness of the second drift layer is 1.5 μm; the N-type doping concentration of the second drift layer is 2.2×10 16 atom / cm 3 ;

[0145] The thickness of the AlN layer is 100 nm;

[0146] The thickness of the first NO-doped 3C-SiC layer is 0.2 nm; the NO doping concentration of the first NO-doped 3C-SiC layer is 1×10 17 atom / cm 3 ;

[0147] The thickness of the O-doped 3C-SiC layer is 0.3 nm; the O-doping concentration of the O-doped 3C-SiC layer is 1×10 18 atom / cm 3 ;

[0148] The thickness of the second NO-doped 3C-SiC layer is 0.4 nm; the NO doping concentration of the second NO-doped 3C-SiC layer is 1×10 17 atom / cm 3 .

[0149] The preparation process is as follows:

[0150] The substrate is sequentially subjected to buffer layer growth, first drift layer growth, second drift layer growth, AlN layer growth, first NO-doped 3C-SiC layer growth, O-doped 3C-SiC layer growth and second NO-doped 3C-SiC layer growth.

[0151] The substrate is a 4H-SiC substrate with a 4° bias toward the <11-20> direction;

[0152] The flow rate of the carrier gas used in the growth of the buffer layer is 300 slm, the flow rate of the silicon source gas used is 400 sccm, the flow rate of the carbon source gas used is 300 sccm, the flow rate of the N-type dopant used is 100 sccm, the growth temperature is 1600° C., and the growth pressure is 60 mbar;

[0153] The flow rate of the carrier gas used in the growth of the first drift layer is 300slm, the flow rate of the silicon source gas used is 400sccm, the flow rate of the carbon source gas used is 300sccm, the flow rate of the N-type dopant used is 40sccm, the growth temperature is 1600°C, and the growth pressure is 300mbar; the flow rate of the carrier gas used in the growth of the second drift layer is 300slm, the flow rate of the silicon source gas used is 400sccm, the flow rate of the carbon source gas used is 300sccm, the flow rate of the N-type dopant used is 40sccm, the growth temperature is 1600°C, and the growth pressure is 300mbar;

[0154] The flow rate of the carrier gas used in the growth of the AlN layer is 20 slm, the flow rate of the aluminum source used is 60 sccm, the flow rate of the nitrogen source used is 100 sccm, the growth temperature is 800° C., and the growth pressure is 300 mbar;

[0155] The flow rate of the carrier gas used in the growth of the first NO-doped 3C-SiC layer is 30 slm, the flow rate of the silicon source gas used is 300 sccm, the flow rate of the carbon source gas used is 100 sccm, the flow rate of NO used is 30 sccm, the growth temperature is 1380° C., and the growth pressure is 300 mbar;

[0156] The flow rate of the carrier gas used in the growth of the O-doped 3C-SiC layer is 30 slm, the flow rate of the silicon source gas used is 300 sccm, the flow rate of the carbon source gas used is 120 sccm, the flow rate of the oxygen source gas used is 40 sccm, the growth temperature is 1380° C., and the growth pressure is 300 mbar;

[0157] The carrier gas flow rate used in the growth of the second NO-doped 3C-SiC layer is 30 slm, the silicon source gas flow rate is 300 sccm, the carbon source gas flow rate is 100 sccm, the NO flow rate is 30 sccm, the growth temperature is 1380°C, and the growth pressure is 300 mbar.

[0158] In this embodiment, the silicon source gas used is SiH3Cl; the carbon source gas used is C2H4; the carrier gas used is hydrogen; the N-type dopant used is nitrogen; the aluminum source used is TMAl; and the oxygen source gas used is oxygen.

[0159] Example 2

[0160] This embodiment provides an epitaxial structure for MOSFET, the epitaxial structure comprising: a buffer layer, a first drift layer, a second drift layer, an AlN layer, a first NO-doped 3C-SiC layer, an O-doped 3C-SiC layer, and a second NO-doped 3C-SiC layer sequentially disposed on a substrate;

[0161] The thickness of the buffer layer is 1.05 μm; the N-type doping concentration of the buffer layer is 1.1×10 18 atom / cm 3 ;

[0162] The thickness of the first drift layer is 15 μm; the N-type doping concentration of the first drift layer is 0.9×10 16 atom / cm 3 ;

[0163] The thickness of the second drift layer is 1.8 μm; the N-type doping concentration of the second drift layer is 2.4×10 16 atom / cm 3 ;

[0164] The thickness of the AlN layer is 200 nm;

[0165] The thickness of the first NO-doped 3C-SiC layer is 0.3 nm; the NO doping concentration of the first NO-doped 3C-SiC layer is 1×10 18 atom / cm 3 ;

[0166] The thickness of the O-doped 3C-SiC layer is 0.5 nm; the O-doping concentration of the O-doped 3C-SiC layer is 1×10 17 atom / cm 3 ;

[0167] The thickness of the second NO-doped 3C-SiC layer is 0.2 nm; the NO doping concentration of the second NO-doped 3C-SiC layer is 1×10 18 atom / cm 3 .

[0168] The preparation process is as follows:

[0169] The substrate is sequentially subjected to buffer layer growth, first drift layer growth, second drift layer growth, AlN layer growth, first NO-doped 3C-SiC layer growth, O-doped 3C-SiC layer growth and second NO-doped 3C-SiC layer growth.

[0170] The substrate is a 4H-SiC substrate with a 4° bias toward the <11-20> direction;

[0171] The flow rate of the carrier gas used in the growth of the buffer layer is 500 slm, the flow rate of the silicon source gas used is 500 sccm, the flow rate of the carbon source gas used is 400 sccm, the flow rate of the N-type dopant used is 90 sccm, the growth temperature is 1630° C., and the growth pressure is 80 mbar;

[0172] The flow rate of the carrier gas used in the growth of the first drift layer is 500slm, the flow rate of the silicon source gas used is 500sccm, the flow rate of the carbon source gas used is 400sccm, the flow rate of the N-type dopant used is 50sccm, the growth temperature is 1630°C, and the growth pressure is 400mbar; the flow rate of the carrier gas used in the growth of the second drift layer is 500slm, the flow rate of the silicon source gas used is 500sccm, the flow rate of the carbon source gas used is 400sccm, the flow rate of the N-type dopant used is 50sccm, the growth temperature is 1630°C, and the growth pressure is 400mbar;

[0173] The flow rate of the carrier gas used in the growth of the AlN layer is 30 slm, the flow rate of the aluminum source used is 80 sccm, the flow rate of the nitrogen source used is 150 sccm, the growth temperature is 1000° C., and the growth pressure is 400 mbar;

[0174] The flow rate of the carrier gas used in the growth of the first NO-doped 3C-SiC layer is 40 slm, the flow rate of the silicon source gas used is 400 sccm, the flow rate of the carbon source gas used is 120 sccm, the flow rate of NO used is 40 sccm, the growth temperature is 1360° C., and the growth pressure is 400 mbar;

[0175] The flow rate of the carrier gas used in the growth of the O-doped 3C-SiC layer is 40 slm, the flow rate of the silicon source gas used is 40 sccm, the flow rate of the carbon source gas used is 100 sccm, the flow rate of the oxygen source gas used is 30 sccm, the growth temperature is 1360° C., and the growth pressure is 400 mbar;

[0176] The carrier gas flow rate used in the growth of the second NO-doped 3C-SiC layer is 40 slm, the silicon source gas flow rate is 400 sccm, the carbon source gas flow rate is 120 sccm, the NO flow rate is 40 sccm, the growth temperature is 1360°C, and the growth pressure is 400 mbar.

[0177] In this embodiment, the silicon source gas used is SiCl4; the carbon source gas used is C3H8; the carrier gas used is hydrogen; the N-type dopant used is nitrogen; the aluminum source used is TMAl; and the oxygen source gas used is oxygen.

[0178] Example 3

[0179] This embodiment provides an epitaxial structure for MOSFET, the epitaxial structure comprising: a buffer layer, a first drift layer, a second drift layer, an AlN layer, a first NO-doped 3C-SiC layer, an O-doped 3C-SiC layer, and a second NO-doped 3C-SiC layer sequentially disposed on a substrate;

[0180] The thickness of the buffer layer is 0.9 μm; the N-type doping concentration of the buffer layer is 7×10 17 atom / cm 3 ;

[0181] The thickness of the first drift layer is 20 μm; the N-type doping concentration of the first drift layer is 1×10 16 atom / cm 3 ;

[0182] The thickness of the second drift layer is 1 μm; the N-type doping concentration of the second drift layer is 2×10 16 atom / cm 3 ;

[0183] The thickness of the AlN layer is 10 nm;

[0184] The thickness of the first NO-doped 3C-SiC layer is 0.1 nm; the NO doping concentration of the first NO-doped 3C-SiC layer is 1×10 16 atom / cm 3 ;

[0185] The thickness of the O-doped 3C-SiC layer is 0.5 nm; the O-doping concentration of the O-doped 3C-SiC layer is 1×10 19 atom / cm 3 ;

[0186] The thickness of the second NO-doped 3C-SiC layer is 0.1 nm; the NO doping concentration of the second NO-doped 3C-SiC layer is 1×10 19 atom / cm 3 .

[0187] The preparation process is as follows:

[0188] The substrate is sequentially subjected to buffer layer growth, first drift layer growth, second drift layer growth, AlN layer growth, first NO-doped 3C-SiC layer growth, O-doped 3C-SiC layer growth and second NO-doped 3C-SiC layer growth.

[0189] The substrate is a 4H-SiC substrate with a 4° bias toward the <11-20> direction;

[0190] The flow rate of the carrier gas used in the growth of the buffer layer is 100 slm, the flow rate of the silicon source gas used is 600 sccm, the flow rate of the carbon source gas used is 200 sccm, the flow rate of the N-type dopant used is 120 sccm, the growth temperature is 1580° C., and the growth pressure is 100 mbar;

[0191] The flow rate of the carrier gas used in the growth of the first drift layer is 100 slm, the flow rate of the silicon source gas used is 600 sccm, the flow rate of the carbon source gas used is 200 sccm, the flow rate of the N-type dopant used is 60 sccm, the growth temperature is 1580°C, and the growth pressure is 500 mbar; the flow rate of the carrier gas used in the growth of the second drift layer is 100 slm, the flow rate of the silicon source gas used is 600 sccm, the flow rate of the carbon source gas used is 200 sccm, the flow rate of the N-type dopant used is 60 sccm, the growth temperature is 1580°C, and the growth pressure is 500 mbar;

[0192] The flow rate of the carrier gas used in the growth of the AlN layer is 50 slm, the flow rate of the aluminum source used is 100 sccm, the flow rate of the nitrogen source used is 80 sccm, the growth temperature is 700° C., and the growth pressure is 500 mbar;

[0193] The flow rate of the carrier gas used in the growth of the first NO-doped 3C-SiC layer is 10 slm, the flow rate of the silicon source gas used is 500 sccm, the flow rate of the carbon source gas used is 150 sccm, the flow rate of NO used is 50 sccm, the growth temperature is 1400° C., and the growth pressure is 100 mbar;

[0194] The flow rate of the carrier gas used in the growth of the O-doped 3C-SiC layer is 10 slm, the flow rate of the silicon source gas used is 500 sccm, the flow rate of the carbon source gas used is 150 sccm, the flow rate of the oxygen source gas used is 15 sccm, the growth temperature is 1400° C., and the growth pressure is 100 mbar;

[0195] The carrier gas flow rate used in the growth of the second NO-doped 3C-SiC layer is 50 slm, the silicon source gas flow rate is 100 sccm, the carbon source gas flow rate is 150 sccm, the NO flow rate is 50 sccm, the growth temperature is 1350°C, and the growth pressure is 500 mbar.

[0196] In this embodiment, the silicon source gas used is SiHCl3; the carbon source gas used is C2H4; the carrier gas used is hydrogen; the N-type dopant used is nitrogen; the aluminum source used is TMAl; and the oxygen source gas used is oxygen.

[0197] Example 4

[0198] This embodiment provides an epitaxial structure for MOSFET, the epitaxial structure comprising: a buffer layer, a first drift layer, a second drift layer, an AlN layer, a first NO-doped 3C-SiC layer, an O-doped 3C-SiC layer, and a second NO-doped 3C-SiC layer sequentially disposed on a substrate;

[0199] The thickness of the buffer layer is 1.1 μm; the N-type doping concentration of the buffer layer is 1.3×10 18 atom / cm 3 ;

[0200] The thickness of the first drift layer is 5 μm; the N-type doping concentration of the first drift layer is 0.7×10 16 atom / cm 3 ;

[0201] The thickness of the second drift layer is 2 μm; the N-type doping concentration of the second drift layer is 2.5×10 16 atom / cm 3 ;

[0202] The thickness of the AlN layer is 300 nm;

[0203] The thickness of the first NO-doped 3C-SiC layer is 0.5 nm; the NO doping concentration of the first NO-doped 3C-SiC layer is 1×10 19 atom / cm 3 ;

[0204] The thickness of the O-doped 3C-SiC layer is 0.1 nm; the O-doping concentration of the O-doped 3C-SiC layer is 1×10 16 atom / cm 3 ;

[0205] The thickness of the second NO-doped 3C-SiC layer is 0.5 nm; the NO doping concentration of the second NO-doped 3C-SiC layer is 1×10 16 atom / cm 3 .

[0206] The preparation process is as follows:

[0207] The substrate is sequentially subjected to buffer layer growth, first drift layer growth, second drift layer growth, AlN layer growth, first NO-doped 3C-SiC layer growth, O-doped 3C-SiC layer growth and second NO-doped 3C-SiC layer growth.

[0208] The substrate is a 4H-SiC substrate with a 4° bias toward the <11-20> direction;

[0209] The flow rate of the carrier gas used in the growth of the buffer layer is 800 slm, the flow rate of the silicon source gas used is 300 sccm, the flow rate of the carbon source gas used is 500 sccm, the flow rate of the N-type dopant used is 80 sccm, the growth temperature is 1680° C., and the growth pressure is 50 mbar;

[0210] The flow rate of the carrier gas used in the growth of the first drift layer is 800slm, the flow rate of the silicon source gas used is 300sccm, the flow rate of the carbon source gas used is 500sccm, the flow rate of the N-type dopant used is 20sccm, the growth temperature is 1680°C, and the growth pressure is 50mbar; the flow rate of the carrier gas used in the growth of the second drift layer is 800slm, the flow rate of the silicon source gas used is 300sccm, the flow rate of the carbon source gas used is 500sccm, the flow rate of the N-type dopant used is 20sccm, the growth temperature is 1580°C, and the growth pressure is 500mbar;

[0211] The flow rate of the carrier gas used in the growth of the AlN layer is 10 slm, the flow rate of the aluminum source used is 50 sccm, the flow rate of the nitrogen source used is 200 sccm, the growth temperature is 1200° C., and the growth pressure is 100 mbar;

[0212] The flow rate of the carrier gas used in the growth of the first NO-doped 3C-SiC layer is 50 slm, the flow rate of the silicon source gas used is 100 sccm, the flow rate of the carbon source gas used is 80 sccm, the flow rate of NO used is 15 sccm, the growth temperature is 1350° C., and the growth pressure is 500 mbar;

[0213] The flow rate of the carrier gas used in the growth of the O-doped 3C-SiC layer is 50 slm, the flow rate of the silicon source gas used is 100 sccm, the flow rate of the carbon source gas used is 80 sccm, the flow rate of the oxygen source gas used is 50 sccm, the growth temperature is 1350° C., and the growth pressure is 500 mbar;

[0214] The carrier gas flow rate used in the growth of the second NO-doped 3C-SiC layer is 10 slm, the silicon source gas flow rate is 500 sccm, the carbon source gas flow rate is 80 sccm, the NO flow rate is 15 sccm, the growth temperature is 1400°C, and the growth pressure is 100 mbar.

[0215] In this embodiment, the silicon source gas used is SiH2C12; the carbon source gas used is C3H8; the carrier gas used is hydrogen; the N-type dopant used is nitrogen; the aluminum source used is TMAl; and the oxygen source gas used is oxygen.

[0216] Example 5

[0217] The only difference from Example 1 is that no AlN layer is provided.

[0218] Example 6

[0219] The only difference from Embodiment 1 is that the first drift layer is not provided.

[0220] Example 7

[0221] The only difference from Embodiment 1 is that no second drift layer is provided.

[0222] Example 8

[0223] The only difference from Example 1 is that the first NO-doped 3C—SiC layer is not provided.

[0224] Example 9

[0225] The only difference from Example 1 is that no O-doped 3C-SiC layer is provided.

[0226] Example 10

[0227] The only difference from Example 1 is that the second NO-doped 3C—SiC layer is not provided.

[0228] Embodiment 11

[0229] The only difference from Embodiment 1 is that the positions of the first drift layer and the second drift layer are interchanged, that is, the second drift layer is arranged first, and then the first drift layer is arranged.

[0230] Example 12

[0231] The only difference from Example 1 is that the arrangement order of the first NO-doped 3C-SiC layer, the O-doped 3C-SiC layer and the second NO-doped 3C-SiC layer is replaced by arranging the first NO-doped 3C-SiC layer, the second NO-doped 3C-SiC layer and the O-doped 3C-SiC layer in sequence.

[0232] Example 12

[0233] The only difference from Example 1 is that the arrangement order of the first NO-doped 3C-SiC layer, the O-doped 3C-SiC layer and the second NO-doped 3C-SiC layer is replaced by arranging the O-doped 3C-SiC layer, the first NO-doped 3C-SiC layer and the second NO-doped 3C-SiC layer in sequence.

[0234] Embodiment 13

[0235] The only difference from Example 1 is that the arrangement order of the first NO-doped 3C-SiC layer, the O-doped 3C-SiC layer and the second NO-doped 3C-SiC layer is replaced by sequentially arranging the second NO-doped 3C-SiC layer, the O-doped 3C-SiC layer and the first NO-doped 3C-SiC layer.

[0236] Embodiment 14

[0237] The only difference from Example 1 is that the AlN layer is replaced by an AlGaN layer of equal thickness.

[0238] Embodiment 15

[0239] The only difference from Example 1 is that the three-layer structure of the first NO-doped 3C-SiC layer, the O-doped 3C-SiC layer and the second NO-doped 3C-SiC layer is replaced by a 4H-SiC layer with a thickness of 0.3 μm.

[0240] The epitaxial structure for MOSFET obtained in the above embodiment is subjected to performance testing, and the threshold voltage is tested according to GB / T29332-2012;

[0241] The channel mobility is tested according to the following process: the epitaxial structure is assembled into a power device, and the process includes: after the bare chip is cleaned, the alignment mark is made, and then three ion implantation processes are made, which are ion implantation of P-well, N+ and P+ regions, wherein the P-well and P+ regions are P-type doped, using Al ion implantation, and the maximum ion implantation energy is 350keV and 90keV respectively; the N+ region is N-type implanted, using N ion implantation, and the maximum implantation energy is 80keV. All ion implantations are carried out at 500℃. After the ion implantation is completed, a carbon film (thickness of 50nm) is sputtered on the surface, and then ion implantation activation annealing is carried out at a temperature of 1650℃ for 30min. After removing the carbon film, the gate oxide layer is grown, and at a temperature of 1250℃, NO annealing is first carried out on the surface of the sample for 1h, then oxidation is carried out in dry oxygen, and finally annealing is carried out in NO for 1h. The thickness of the final gate oxide layer is 60nm through CV testing. Next, a layer of Al metal is deposited, and then a gate pattern is formed through a photolithography etching process. The metal used for the drain ohmic contact is Ni (200nm), and the drain ohmic contact is formed by rapid thermal annealing at 1000℃ / 3min. The metal used for the source ohmic contact is Ti / Al / N (50nm / 100nm / 43nm), and the source ohmic contact is formed by rapid thermal annealing at 900℃ / 5min. The next step is to deposit a layer of interlayer dielectric, etch a through hole, and form the source and gate pads by depositing a thick layer of Al (4μm). Finally, a layer of PI glue was passivated to complete the device fabrication. The key structural parameters are as follows: (1) JFET region width WJFET = 1.8 μm, (2) channel length Wch = 0.5 μm, (3) overlap area between Polysilicon and N+ source region W = 0.5 μm, (4) spacing between Polysilicon and source electrode W = 0.8 μm, (5) length of N+ source region covered by source electrode W = 0.5 μm, (6) length of P+ ohmic contact region W = 1.0 μm. The obtained device was tested for channel mobility using MCV530L from semilab. The results are shown in Table 1.

[0242] Table 1

[0243]

[0244]

[0245] As can be seen from Table 1, the epitaxial structure provided by the present invention solves the defects of poor SiO2 / SiC interface quality and high interface state resulting in low channel mobility and too low threshold voltage by designing the epitaxial structure and adopting a specific first NO-doped 3C-SiC layer, an O-doped 3C-SiC layer and a second NO-doped 3C-SiC layer, thereby ensuring that the obtained power device has excellent channel mobility and a reasonable threshold voltage.

[0246] 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.

[0247] 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.

[0248] 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. An epitaxial structure for MOSFET, characterized in that: The epitaxial structure comprises: a buffer layer, a first drift layer, a second drift layer, an AlN layer, a first NO-doped 3C-SiC layer, an O-doped 3C-SiC layer and a second NO-doped 3C-SiC layer which are sequentially arranged on a substrate.

2. The epitaxial structure according to claim 1, characterized in that The thickness of the buffer layer is 0.9-1.1 μm; Preferably, the N-type doping concentration of the buffer layer is 7×10 17 -1.3×10 18 atom / cm 3 .

3. The epitaxial structure according to claim 1 or 2, characterized in that: The thickness of the first drift layer is 5-20 μm; Preferably, the N-type doping concentration of the first drift layer is 0.7×10 16 -1×10 16 atom / cm 3 ; Preferably, the thickness of the second drift layer is 1-2 μm; Preferably, the N-type doping concentration of the second drift layer is 2×10 16 -2.5×10 16 atom / cm 3 .

4. The epitaxial structure according to any one of claims 1 to 3, characterized in that: The thickness of the AlN layer is 10-300 nm.

5. The epitaxial structure according to any one of claims 1 to 4, characterized in that: The thickness of the first NO-doped 3C-SiC layer is 0.1-0.5 nm; Preferably, the NO doping concentration of the first NO-doped 3C-SiC layer is 1×10 16 -1×10 19 atom / cm 3 ; Preferably, the thickness of the O-doped 3C-SiC layer is 0.1-0.5 nm; Preferably, the O-doping concentration of the O-doped 3C-SiC layer is 1×10 16 -1×10 19 atom / cm 3 ; Preferably, the thickness of the second NO-doped 3C-SiC layer is 0.1-0.5 nm; Preferably, the NO doping concentration of the second NO-doped 3C-SiC layer is 1×10 16 -1×10 19 atom / cm 3 .

6. A method for preparing an epitaxial structure according to any one of claims 1 to 5, characterized in that: The preparation method comprises: The substrate is sequentially subjected to buffer layer growth, first drift layer growth, second drift layer growth, AlN layer growth, first NO-doped 3C-SiC layer growth, O-doped 3C-SiC layer growth and second NO-doped 3C-SiC layer growth.

7. The preparation method according to claim 6, characterized in that: The substrate comprises a 4H-SiC substrate biased 4° in the <11-20> direction; Preferably, the flow rate of the carrier gas used in the growth of the buffer layer is 100-800slm; Preferably, the flow rate of the silicon source gas used in the growth of the buffer layer is 300-600 sccm; Preferably, the flow rate of the carbon source gas used in the growth of the buffer layer is 200-500 sccm; Preferably, the flow rate of the N-type dopant used in the growth of the buffer layer is 80-120 sccm; Preferably, the growth temperature of the buffer layer is 1580-1680°C; Preferably, the growth pressure of the buffer layer is 50-100 mbar.

8. The preparation method according to claim 6 or 7, characterized in that: The flow rate of the carrier gas used in the growth of the first drift layer is 100-800slm; Preferably, the flow rate of the silicon source gas used in the growth of the first drift layer is 300-600 sccm; Preferably, the flow rate of the carbon source gas used in the growth of the first drift layer is 200-500 sccm; Preferably, the flow rate of the N-type dopant used in the growth of the first drift layer is 20-60 sccm; Preferably, the growth temperature of the first drift layer is 1580-1680°C; Preferably, the growth pressure of the first drift layer is 50-500 mbar; Preferably, the flow rate of the carrier gas used in the growth of the second drift layer is 100-800slm; Preferably, the flow rate of the silicon source gas used in the growth of the second drift layer is 300-600 sccm; Preferably, the flow rate of the carbon source gas used in the growth of the second drift layer is 200-500 sccm; Preferably, the flow rate of the N-type dopant used in the growth of the second drift layer is 20-60 sccm; Preferably, the growth temperature of the second drift layer is 1580-1680°C; Preferably, the growth pressure of the second drift layer is 50-500 mbar.

9. The preparation method according to any one of claims 6 to 9, characterized in that: The flow rate of the carrier gas used in the growth of the AlN layer is 10-50slm; Preferably, the flow rate of the aluminum source used in the growth of the AlN layer is 50-100 sccm; Preferably, the flow rate of the nitrogen source used in the growth of the AlN layer is 80-200 sccm; Preferably, the growth temperature of the AlN layer is 700-1200°C; Preferably, the growth pressure of the AlN layer is 100-500 mbar; Preferably, the flow rate of the carrier gas used in the growth of the first NO-doped 3C-SiC layer is 10-50 slm; Preferably, the flow rate of the silicon source gas used in the growth of the first NO-doped 3C-SiC layer is 100-500 sccm; Preferably, the flow rate of the carbon source gas used in the growth of the first NO-doped 3C-SiC layer is 80-150 sccm; Preferably, the flow rate of NO used in the growth of the first NO-doped 3C-SiC layer is 15-50 sccm; Preferably, the growth temperature of the first NO-doped 3C-SiC layer is 1350-1400° C.; Preferably, the growth pressure of the first NO-doped 3C-SiC layer is 100-500 mbar; Preferably, the flow rate of the carrier gas used in the growth of the O-doped 3C-SiC layer is 10-50 slm; Preferably, the flow rate of the silicon source gas used in the growth of the O-doped 3C-SiC layer is 100-500 sccm; Preferably, the flow rate of the carbon source gas used in the growth of the O-doped 3C-SiC layer is 80-150 sccm; Preferably, the flow rate of the oxygen source gas used in the growth of the O-doped 3C-SiC layer is 15-50 sccm; Preferably, the growth temperature of the O-doped 3C-SiC layer is 1350-1400° C.; Preferably, the growth pressure of the O-doped 3C-SiC layer is 100-500 mbar; Preferably, the flow rate of the carrier gas used in the growth of the second NO-doped 3C-SiC layer is 10-50 slm; Preferably, the flow rate of the silicon source gas used in the growth of the second NO-doped 3C-SiC layer is 100-500 sccm; Preferably, the flow rate of the carbon source gas used in the growth of the second NO-doped 3C-SiC layer is 80-150 sccm; Preferably, the flow rate of NO used in the growth of the second NO-doped 3C-SiC layer is 15-50 sccm; Preferably, the growth temperature of the second NO-doped 3C-SiC layer is 1350-1400° C.; Preferably, the growth pressure of the second NO-doped 3C-SiC layer is 100-500 mbar.

10. Use of the epitaxial structure according to any one of claims 1 to 5, characterized in that: The uses include: The epitaxial structure for MOSFET is used to prepare a MOSFET device.

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