Silicon carbide floating junction structure for improving switching characteristic along slope terminal P channel

Abstract

The invention provides a silicon carbide floating junction structure for improving switching characteristics along a slope terminal P channel, and relates to the technical field of semiconductor power devices. Comprising an N-type drift region formed on an N-type substrate; the plurality of first P-type floating junctions, the plurality of second P-type floating junctions and the plurality of P-type doped regions are all formed in the middle region of the N-type drift region, are arranged at intervals and are respectively and oppositely arranged up and down; the first P-type floating junction transition region is formed in the N-type drift region and surrounds the plurality of first P-type floating junctions; the second P-type floating junction transition region is formed in the N-type drift region and surrounds the plurality of second P-type floating junctions; the P-type transition region is formed in the N-type drift region and surrounds the plurality of P-type doped regions; and the inclined plane terminal P channels are formed on inclined planes at two ends of the N-type drift region, inclined planes at two ends of the first P-type floating junction transition region, inclined planes at two ends of the second P-type floating junction transition region and two ends of the P-type transition region. Therefore, the switching characteristic is relatively good, the process cost is relatively low, and the time cost is relatively low.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor power devices, and in particular to a silicon carbide floating junction structure with improved switching characteristics along a bevel terminal P channel. Background Art

[0002] In recent years, energy conservation, emission reduction and low-carbon development have become the mainstream development model. Semiconductor power devices are an important link in the energy generation-storage-distribution cycle, and are crucial to energy conservation, emission reduction and low-carbon development. Among them, silicon carbide power semiconductor devices are expected to become the next generation of mainstream high-power devices due to their high-voltage blocking capability, high-frequency switching characteristics, and high-temperature operation, and have been widely favored by researchers. Commercial silicon carbide devices have already appeared, and these commercial silicon carbide devices are an ideal choice to replace silicon power devices. However, due to the properties of silicon carbide materials, some mature silicon power devices still cannot be prepared using silicon carbide materials for commercial use. In order to make silicon power devices prepared using silicon carbide materials for commercial use, it is necessary to combine floating junction technology with silicon carbide, which can give full play to their respective advantages and break the one-dimensional limit of silicon carbide unipolar devices.

[0003] At present, power devices that break the one-dimensional limit of silicon carbide usually use silicon carbide floating junction junction barrier Schottky diodes (JBS). However, because the floating junction of the silicon carbide floating junction JBS diode greatly widens toward the drift region under reverse withstand voltage, when the bias voltage changes from reverse to forward, the floating junction depletion region widened under reverse bias lacks a channel, and minority carriers are difficult to be quickly extracted and depleted, which greatly affects the switching characteristics of the silicon carbide floating junction JBS diode; the silicon carbide floating junction JBS diode uses a field limiting ring terminal, which makes the number of ion implantations high, and thus makes the process cost and time cost high. Summary of the invention

[0004] The purpose of an embodiment of the present invention is to provide a silicon carbide floating junction structure with improved switching characteristics along the slope terminal P channel, so as to solve the problem that minority carriers are difficult to be quickly extracted and depleted, which greatly affects the switching characteristics of the silicon carbide floating junction JBS diode and causes high process costs and time costs.

[0005] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions:

[0006] A first aspect of the present invention provides a silicon carbide floating junction structure with improved switching characteristics along a bevel terminal P channel, comprising:

[0007] N-type substrate;

[0008] An N-type drift region is formed on an N-type substrate and both ends of the N-type drift region are inclined surfaces;

[0009] A plurality of first P-type floating junctions are formed in the middle region of the N-type drift region and are arranged at intervals;

[0010] A first P-type floating junction transition region is formed in the N-type drift region and surrounds a plurality of first P-type floating junctions, and both ends of the first P-type floating junction transition region are inclined surfaces;

[0011] A plurality of second P-type floating junctions are formed in the middle area of ​​the N-type drift region and are arranged at intervals, and the plurality of second P-type floating junctions are arranged vertically opposite to the plurality of first P-type floating junctions;

[0012] A second P-type floating junction transition region is formed inside the N-type drift region and surrounds a plurality of second P-type floating junctions, and both ends of the second P-type floating junction transition region are inclined surfaces;

[0013] A plurality of P-type doped regions are formed in the middle region of the N-type drift region and are arranged at intervals, and the plurality of P-type doped regions and the plurality of second P-type floating junctions are arranged vertically opposite to each other, and the upper surfaces of the plurality of P-type doped regions and the upper surface of the N-type drift region are in the same horizontal plane;

[0014] A P-type transition region is formed inside the N-type drift region and surrounds a plurality of P-type doped regions;

[0015] The sloped terminal P channel is formed on the slopes at both ends of the N-type drift region, the slopes at both ends of the first P-type floating junction transition region, the slopes at both ends of the second P-type floating junction transition region, and both ends of the P-type transition region.

[0016] In some modified implementations of the first aspect of the present invention, the silicon carbide floating junction structure for improving switching characteristics along the bevel terminal P channel further includes an ohmic contact metal and a Schottky contact metal;

[0017] Ohmic contact metal, formed on the lower surface of the N-type substrate;

[0018] The Schottky contact metal is formed on the N-type drift region, a plurality of P-type doped regions and a portion of the P-type transition region.

[0019] In some modified embodiments of the first aspect of the present invention, the implanted ions of the bevel terminal P channel are Al, the implantation energy range is 10 KeV-1000 KeV, and the doping concentration range is 1e15-1e18 cm -3 .

[0020] In some modified embodiments of the first aspect of the present invention, the inclination angles of the slopes at both ends of the N-type drift region, the slopes at both ends of the first P-type floating junction transition region, and the slopes at both ends of the second P-type floating junction transition region are all 30°.

[0021] In some modified embodiments of the first aspect of the present invention, the upper surface of the first P-type floating junction transition zone is at the same horizontal plane as the upper surfaces of multiple first P-type floating junctions, and the thickness of the first P-type floating junction transition zone is the same as the thickness of multiple first P-type floating junctions.

[0022] In some modified embodiments of the first aspect of the present invention, the upper surface of the second P-type floating junction transition zone is at the same horizontal plane as the upper surfaces of multiple second P-type floating junctions, and the thickness of the second P-type floating junction transition zone is the same as the thickness of multiple second P-type floating junctions.

[0023] In some modified embodiments of the first aspect of the present invention, the thickness of the plurality of first P-type floating junctions is the same as the thickness of the plurality of second P-type floating junctions.

[0024] In some modified embodiments of the first aspect of the present invention, the N-type substrate includes a first N-type substrate and a second N-type substrate, the second N-type substrate is formed on the first N-type substrate, the first N-type substrate is rectangular in shape, and the second N-type substrate is trapezoidal in shape.

[0025] A second aspect of the present invention provides a method for preparing a silicon carbide floating junction structure with improved switching characteristics along a bevel terminal P channel, comprising:

[0026] An N-type substrate is selected, and the material of the N-type substrate is silicon carbide;

[0027] Growing a first N-type drift region on a surface of the N-type substrate;

[0028] Performing ion implantation on the surface of the first N-type drift region to form a plurality of first P-type floating junctions and a first P-type floating junction transition region, so that the plurality of first P-type floating junctions are arranged at intervals and the first P-type floating junction transition region surrounds the plurality of first P-type floating junctions;

[0029] Growing a second N-type drift region on the surfaces of the plurality of first P-type floating junctions, the first P-type floating junction transition region and the first N-type drift region;

[0030] Performing ion implantation on the surface of the second N-type drift region to form a plurality of second P-type floating junctions and a second P-type floating junction transition region, so that the plurality of second P-type floating junctions are arranged at intervals and the second P-type floating junction transition region surrounds the plurality of second P-type floating junctions;

[0031] Growing a third N-type drift region on the surfaces of the plurality of second P-type floating junctions, the second P-type floating junction transition region and the second N-type drift region;

[0032] Performing ion implantation on the surface of the third N-type drift region to form a plurality of P-type doped regions and a P-type transition region, so that the plurality of P-type doped regions are arranged at intervals and the P-type transition region surrounds the plurality of second P-type floating junctions;

[0033] Depositing a SiO2 layer on the surfaces of the plurality of P-type doped regions, the P-type transition region and the third N-type drift region;

[0034] Forming a photoresist etching mask on the upper surface of the SiO2 layer, etching the SiO2 layer so that both ends of the SiO2 layer are inclined surfaces, and forming an etching mask of the SiO2;

[0035] Using the SiO2 etching mask as a mask, etching from the third N-type drift region to the N-type substrate to form an oblique angle sidewall;

[0036] Ion implantation is performed on the beveled sidewall to form a beveled terminal P channel;

[0037] Using magnetron sputtering or electron beam evaporation, Ni metal is deposited on the bottom of the N-type substrate, and rapid thermal annealing is performed to form an ohmic contact metal;

[0038] Metal is deposited on the surfaces of multiple P-type doped regions, the P-type transition region and the third N-type drift region, and Schottky contact metal is obtained by passivating the medium, performing patterning and selective etching.

[0039] Compared with the prior art, the present invention provides a silicon carbide floating junction structure with improved switching characteristics along a bevel terminal P channel, comprising an N-type substrate; an N-type drift region, formed on the N-type substrate and with both ends of the N-type drift region being bevels; a plurality of first P-type floating junctions, formed in the middle region of the N-type drift region and arranged at intervals; a first P-type floating junction transition region, formed in the N-type drift region and surrounding the plurality of first P-type floating junctions, with both ends of the first P-type floating junction transition region being bevels; a plurality of second P-type floating junctions, formed in the middle region of the N-type drift region and arranged at intervals, with the plurality of second P-type floating junctions being arranged vertically opposite to the plurality of first P-type floating junctions; and a plurality of second P-type floating junctions. A transition zone is formed inside the N-type drift zone and surrounds multiple second P-type floating junctions, and both ends of the second P-type floating junction transition zone are inclined surfaces; multiple P-type doped regions are formed in the middle area of ​​the N-type drift zone and are arranged at intervals, and the multiple P-type doped regions and the multiple second P-type floating junctions are arranged opposite to each other up and down, and the upper surfaces of the multiple P-type doped regions are in the same horizontal plane as the upper surface of the N-type drift zone; a P-type transition zone is formed inside the N-type drift zone and surrounds the multiple P-type doped regions; an inclined terminal P channel is formed on the inclined surfaces at both ends of the N-type drift zone, the inclined surfaces at both ends of the first P-type floating junction transition zone, the inclined surfaces at both ends of the second P-type floating junction transition zone, and on both ends of the P-type transition zone. In this way, a bevel terminal P channel can be formed on the bevels at both ends of the N-type drift region, the bevels at both ends of the first P-type floating junction transition region, the bevels at both ends of the second P-type floating junction transition region, and the two ends of the P-type transition region. The bevel terminal P channel accelerates the extraction speed of minority carriers, reduces the depletion region disappearance time, and reduces the overcharge voltage, so that the switching characteristics of the silicon carbide floating junction structure with improved switching characteristics along the bevel terminal P channel are better, and the turning on speed after being turned off and then turned on is faster; the bevel terminal P channel is formed on the bevel. Compared with the field limiting ring terminal, the introduction of the bevel terminal greatly reduces the number of ion implantations and the process difficulty, so that the process cost and time cost are lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] By reading the detailed description below with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0041] Figure 1 The structure diagram of the silicon carbide floating junction structure with improved switching characteristics along the slope terminal P channel is schematically shown;

[0042] Figure 2 A top view schematically shows a silicon carbide floating junction structure with improved switching characteristics along a bevel-terminated P-channel without depositing a Schottky contact metal;

[0043] Figure 3 A cross-sectional top view of a silicon carbide floating junction structure with improved switching characteristics along a bevel-terminated P-channel along a dotted line is schematically shown;

[0044] Figure 4 The flowchart of the method for preparing a silicon carbide floating junction structure with improved switching characteristics along a bevel-terminated P-channel is schematically shown.

[0045] Description of reference numerals:

[0046] 1. N-type substrate; 101. first N-type substrate; 102. second N-type substrate; 2. N-type drift region; 3. multiple first P-type floating junctions; 4. first P-type floating junction transition region; 5. multiple second P-type floating junctions; 6. second P-type floating junction transition region; 7. multiple P-type doped regions; 8. P-type transition region; 9. bevel terminal P channel; 10. ohmic contact metal; 11. Schottky contact metal. DETAILED DESCRIPTION

[0047] The following is a further detailed description of the embodiments of the present invention in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention. The present invention can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0048] A silicon carbide floating junction structure with improved switching characteristics along the sloped terminal P channel 9 in an embodiment of the present invention is described in detail below.

[0049] See also Figure 1 As shown, Figure 1 The structure diagram of the silicon carbide floating junction structure for improving the switching characteristics along the bevel terminal P channel 9 is schematically shown. The embodiment of the present invention proposes the structure diagram of the silicon carbide floating junction structure for improving the switching characteristics along the bevel terminal P channel 9, including:

[0050] N-type substrate 1;

[0051] An N-type drift region 2 is formed on an N-type substrate 1 and both ends of the N-type drift region 2 are inclined surfaces;

[0052] A plurality of first P-type floating junctions 3 are formed in the middle region of the N-type drift region 2 and are arranged at intervals;

[0053] A first P-type floating junction transition region 4 is formed in the N-type drift region 2 and surrounds a plurality of first P-type floating junctions 3, and both ends of the first P-type floating junction transition region 4 are inclined surfaces;

[0054] A plurality of second P-type floating junctions 5 are formed in the middle region of the N-type drift region 2 and arranged at intervals, and the plurality of second P-type floating junctions 5 are arranged vertically opposite to the plurality of first P-type floating junctions 3;

[0055] A second P-type floating junction transition region 6 is formed inside the N-type drift region 2 and surrounds a plurality of second P-type floating junctions 5, and both ends of the second P-type floating junction transition region 6 are inclined surfaces;

[0056] A plurality of P-type doping regions 7 are formed in the middle region of the N-type drift region 2 and are arranged at intervals, and the plurality of P-type doping regions 7 are arranged vertically opposite to the plurality of second P-type floating junctions 5, and the upper surfaces of the plurality of P-type doping regions 7 are in the same horizontal plane as the upper surface of the N-type drift region 2;

[0057] A P-type transition region 8 is formed inside the N-type drift region 2 and surrounds the plurality of P-type doped regions 7;

[0058] The sloped terminal P channel 9 is formed on the slopes at both ends of the N-type drift region 2 , the slopes at both ends of the first P-type floating junction transition region 4 , the slopes at both ends of the second P-type floating junction transition region 6 , and the two ends of the P-type transition region 8 .

[0059] Specifically, the N-type substrate 1 is a silicon carbide substrate. The reasons for selecting the silicon carbide substrate are: first, the production technology of silicon carbide substrates is mature and the device quality is good; second, silicon carbide has high thermal conductivity and good stability, and can be used in high-temperature growth processes; finally, silicon carbide has excellent physical and chemical properties and can realize high-performance high-power power electronic devices.

[0060] Inside the N-type drift region 2 , a plurality of second P-type floating junctions 5 are relatively arranged above the plurality of first P-type floating junctions 3 at a certain distance, and a plurality of P-type doping regions 7 are relatively arranged above the plurality of second P-type floating junctions 5 at a certain distance.

[0061] The implanted ions of the multiple first P-type floating junctions 3, the first P-type floating junction transition region 4, the multiple second P-type floating junctions 5, the second P-type floating junction transition region 6, the multiple P-type doped regions 7 and the P-type transition region 8 are all Al.

[0062] Multiple first P-type floating junctions 3 can be arranged at equal intervals or at unequal intervals, multiple second P-type floating junctions 5 can be arranged at equal intervals or at unequal intervals, and multiple P-type doped regions 7 can be arranged at equal intervals or at unequal intervals.

[0063] In the present invention, since two layers of P-type floating junctions and two layers of P-type floating junction transition regions are provided, the thickness of the N-type drift region 2 is increased, so that the withstand voltage is higher. The two layers of P-type floating junctions and two layers of P-type floating junction transition regions can increase the depletion region during reverse bias and enhance the withstand voltage.

[0064] In this embodiment, the silicon carbide floating junction structure for improving the switching characteristics along the slope terminal P channel 9 further includes an ohmic contact metal 10 and a Schottky contact metal 11;

[0065] An ohmic contact metal 10 is formed on the lower surface of the N-type substrate 1;

[0066] The Schottky contact metal 11 is formed on the N-type drift region 2 , the plurality of P-type doped regions 7 and a portion of the P-type transition region 8 .

[0067] Specifically, the ohmic contact metal 10 may be Ni metal, and the Schottky contact metal 11 may be Al, or Al doped with Si or Cu, or may be Ag or Cu. The Schottky contact metal 11 is not specifically limited.

[0068] In this embodiment, the implanted ions of the slope terminal P channel 9 are Al, the implantation energy range is 10Kev-1000Kev, and the doping concentration range is 1e15-1e18cm -3 .

[0069] In this embodiment, the inclination angles of the slopes at both ends of the N-type drift region 2 , the slopes at both ends of the first P-type floating junction transition region 4 , and the slopes at both ends of the second P-type floating junction transition region 6 are all 30°.

[0070] Specifically, the inclination angle of the inclined surfaces at both ends of the N-type drift region 2 is the included angle between the inclined surfaces at both ends of the N-type drift region 2 and the upper surface of the N-type substrate 1 , and the included angle is 30°.

[0071] The inclination angles of the slopes at both ends of the N-type drift region 2, the slopes at both ends of the first P-type floating junction transition region 4, and the slopes at both ends of the second P-type floating junction transition region 6 are all set to 30°, so that the electric field at the slope edge is smaller, the terminal withstand voltage is better, and the terminal efficiency is high.

[0072] In this embodiment, the upper surface of the first P-type floating junction transition zone 4 is at the same horizontal plane as the upper surfaces of the multiple first P-type floating junctions 3 , and the thickness of the first P-type floating junction transition zone 4 is the same as the thickness of the multiple first P-type floating junctions 3 .

[0073] In this embodiment, the upper surface of the second P-type floating junction transition zone 6 is at the same horizontal plane as the upper surfaces of the multiple second P-type floating junctions 5, and the thickness of the second P-type floating junction transition zone 6 is the same as the thickness of the multiple second P-type floating junctions 5.

[0074] The upper surfaces of the plurality of P-type doping regions 7 are on the same horizontal plane as the upper surface of the N-type drift region 2 , and the thickness of the plurality of P-type doping regions 7 is greater than the thickness of the P-type transition region 8 .

[0075] In this embodiment, the thickness of the plurality of first P-type floating junctions 3 is the same as the thickness of the plurality of second P-type floating junctions 5 .

[0076] Correspondingly, the thickness of the first P-type floating junction transition region 4 is the same as the thickness of the second P-type floating junction transition region 6 .

[0077] In this embodiment, the N-type substrate 1 includes a first N-type substrate 101 and a second N-type substrate 102 . The second N-type substrate 102 is formed on the first N-type substrate 101 . The first N-type substrate 101 is rectangular in shape, and the second N-type substrate 102 is trapezoidal in shape.

[0078] Specifically, the trapezoid may be an isosceles trapezoid, and the internal angle of the trapezoid is 30°.

[0079] The silicon carbide floating junction structure with improved switching characteristics along the slope terminal P channel 9 of the present invention solves the problem of turn-on speed when turning on again after being turned off, making it possible to realize a high-frequency and high-voltage silicon carbide floating junction diode, which can greatly expand the application scope of silicon carbide floating junction devices in the field of future power semiconductor devices.

[0080] Figure 2 The top view of the silicon carbide floating junction structure with improved switching characteristics along the sloped terminal P channel 9 without depositing the Schottky contact metal 11 is schematically shown, see Figure 2 As shown, the multiple P-type doped regions 7 arranged at intervals in the middle area are the source region, the rounded rectangular ring surrounding the multiple P-type doped regions 7 is the P-type transition region 8, the rounded rectangular ring surrounding the P-type transition region 8 is the bevel terminal P channel 9, the rounded rectangular ring surrounding the bevel terminal P channel 9 is the N-type substrate 1, and the N-type substrate 1 and the bevel terminal P channel 9 are bevel terminals.

[0081] Figure 3 The cross-sectional top view of the silicon carbide floating junction structure with improved switching characteristics along the bevel terminal P channel 9 along the dotted line is schematically shown, see Figure 3 As shown, the dotted line passes through multiple second P-type floating junctions 5, second P-type floating junction transition zone 6 and bevel terminal P channel 9 in the horizontal direction. Multiple second P-type floating junctions 5 are arranged at intervals in the middle area, the rounded rectangular ring surrounding the multiple second P-type floating junctions 5 is the second P-type floating junction transition zone 6, and the rounded rectangular ring surrounding the second P-type floating junction transition zone 6 is the bevel terminal P channel 9.

[0082] Based on the above Figure 1It can be seen from the implementation method that the silicon carbide floating junction structure with improved switching characteristics along the bevel terminal P channel 9 of the embodiment of the present invention includes an N-type substrate 1; an N-type drift region 2, formed on the N-type substrate 1 and both ends of the N-type drift region 2 are bevels; a plurality of first P-type floating junctions 3, formed in the middle area of ​​the N-type drift region 2 and arranged at intervals; a first P-type floating junction transition region 4, formed in the N-type drift region 2 and surrounding the plurality of first P-type floating junctions 3, both ends of the first P-type floating junction transition region 4 are bevels; a plurality of second P-type floating junctions 5, formed in the middle area of ​​the N-type drift region 2 and arranged at intervals, and the plurality of second P-type floating junctions 5 are arranged relative to the plurality of first P-type floating junctions 3 up and down; the second P-type floating junction transition region 4 A transition region 6 is formed inside the N-type drift region 2 and surrounds multiple second P-type floating junctions 5, and both ends of the second P-type floating junction transition region 6 are inclined surfaces; multiple P-type doped regions 7 are formed in the middle area of ​​the N-type drift region 2 and are arranged at intervals, and the multiple P-type doped regions 7 are arranged opposite to the multiple second P-type floating junctions 5 up and down, and the upper surfaces of the multiple P-type doped regions 7 are in the same horizontal plane as the upper surface of the N-type drift region 2; a P-type transition region 8 is formed inside the N-type drift region 2 and surrounds the multiple P-type doped regions 7; an inclined terminal P channel 9 is formed on the inclined surfaces at both ends of the N-type drift region 2, the inclined surfaces at both ends of the first P-type floating junction transition region 4, the inclined surfaces at both ends of the second P-type floating junction transition region 6, and the two ends of the P-type transition region 8. In this way, a bevel terminal P channel 9 can be formed on the bevels at both ends of the N-type drift region 2, the bevels at both ends of the first P-type floating junction transition region 4, the bevels at both ends of the second P-type floating junction transition region 6, and the two ends of the P-type transition region 8. The bevel terminal P channel 9 accelerates the extraction speed of minority carriers, reduces the depletion zone disappearance time, and reduces the overcharge voltage, so that the switching characteristics of the silicon carbide floating junction structure with improved switching characteristics along the bevel terminal P channel 9 are better, and the turning on speed after being turned off and then turned on is faster; the bevel terminal P channel 9 is formed on the bevel, and the introduction of the bevel terminal greatly reduces the number of ion implantations and the process difficulty compared to the field limiting ring terminal, so that the process cost and time cost are lower.

[0083] Figure 4 The flowchart of the method for preparing the silicon carbide floating junction structure with improved switching characteristics along the bevel terminal P channel 9 is schematically shown. Figure 4 As shown, a method for preparing a silicon carbide floating junction structure with improved switching characteristics along the bevel terminal P channel 9 may include:

[0084] S401 , selecting an N-type substrate 1 .

[0085] The material of the N-type substrate 1 is silicon carbide.

[0086] Specifically, since silicon carbide has a mature production technology and good device quality as the N-type substrate 1, silicon carbide has a high thermal conductivity and good stability, and can be used in high-temperature growth processes, silicon carbide has excellent physical and chemical properties, and can realize high-performance high-power power electronic devices, silicon carbide is selected as the material for the N-type substrate 1.

[0087] S402 , growing a first N-type drift region on the surface of the N-type substrate 1 .

[0088] The N-type drift region 2 includes a first N-type drift region, a second N-type drift region and a third N-type drift region.

[0089] Specifically, the N-type substrate 1 is an N+ substrate, and a first N-type drift region is grown on the surface of the N+ substrate by a chemical vapor deposition (CVD) method, with a growth temperature of 1600° C.-1900° C.

[0090] S403 , perform ion implantation on the surface of the first N-type drift region to form a plurality of first P-type floating junctions 3 and a first P-type floating junction transition region 4 , so that the plurality of first P-type floating junctions 3 are arranged at intervals and the first P-type floating junction transition region 4 surrounds the plurality of first P-type floating junctions 3 .

[0091] The implanted ions of the plurality of first P-type floating junctions 3 and the first P-type floating junction transition region 4 are all Al.

[0092] S404 , growing a second N-type drift region on the surfaces of the plurality of first P-type floating junctions 3 , the first P-type floating junction transition region 4 , and the first N-type drift region.

[0093] Specifically, a second N-type drift region is grown on the surfaces of the plurality of first P-type floating junctions 3, the first P-type floating junction transition region 4 and the first N-type drift region by a CVD method, and the growth temperature is 1600° C.-1900° C.

[0094] S405 , perform ion implantation on the surface of the second N-type drift region to form a plurality of second P-type floating junctions 5 and a second P-type floating junction transition region 6 , so that the plurality of second P-type floating junctions 5 are arranged at intervals and the second P-type floating junction transition region 6 surrounds the plurality of second P-type floating junctions 5 .

[0095] Specifically, the implanted ions of the plurality of second P-type floating junctions 5 and the second P-type floating junction transition region 6 are all Al.

[0096] S406 , growing a third N-type drift region on the surfaces of the plurality of second P-type floating junctions 5 , the second P-type floating junction transition region 6 , and the second N-type drift region.

[0097] Specifically, a third N-type drift region is grown on the surfaces of the plurality of second P-type floating junctions 5, the second P-type floating junction transition region 6 and the second N-type drift region by a CVD method, and the growth temperature is 1600°C-1900°C.

[0098] S407 , performing ion implantation on the surface of the third N-type drift region to form a plurality of P-type doping regions 7 and a P-type transition region 8 , so that the plurality of P-type doping regions 7 are arranged at intervals and the P-type transition region 8 surrounds the plurality of second P-type floating junctions 5 .

[0099] The implanted ions in the plurality of P-type doping regions 7 and the P-type transition region 8 are all Al.

[0100] The active region of the silicon carbide floating junction diode is formed through steps S402 to S407.

[0101] S408 , depositing a SiO 2 layer on the surfaces of the plurality of P-type doping regions 7 , the P-type transition region 8 and the third N-type drift region.

[0102] S409, forming a photoresist etching mask on the upper surface of the SiO2 layer, etching the SiO2 layer so that both ends of the SiO2 layer are inclined surfaces, and forming an etching mask of SiO2.

[0103] Both ends of the SiO2 layer are steep.

[0104] S410 , using the SiO 2 etching mask as a mask, etching from the third N-type drift region 2 to the N-type substrate 1 to form an oblique angle sidewall.

[0105] Specifically, dry etching is adopted to sequentially etch the third N-type drift region, the second P-type floating junction transition region 6, the second N-type drift region, the first P-type floating junction transition region 4, and the first N-type drift region until etching into the N-type substrate 1, and then the etching is stopped to form an angled sidewall.

[0106] After the above etching, both ends of the third N-type drift region, both ends of the second P-type floating junction transition region 6, both ends of the second N-type drift region, both ends of the first P-type floating junction transition region 4, both ends of the first N-type drift region and both ends of part of the N-type substrate 1 are all inclined surfaces.

[0107] The angle θ between the beveled side wall and the upper surface of the N-type substrate 1 is 30°.

[0108] S411 , ion implantation is performed on the beveled sidewall to form a beveled terminal P channel 9 .

[0109] Specifically, the implanted ions of the slope terminal P channel 9 are Al, the implantation energy range is 10Kev-1000Kev, and the doping concentration range is 1e15-1e18cm -3 .

[0110] S412 , depositing Ni metal on the bottom of the N-type substrate 1 by magnetron sputtering or electron beam evaporation, and performing rapid thermal annealing to form an ohmic contact metal 10 .

[0111] The ohmic contact metal 10 is a cathode metal layer.

[0112] S413, depositing metal on the surfaces of the plurality of P-type doped regions 7, the P-type transition region 8 and the third N-type drift region, and obtaining Schottky contact metal 11 by passivating the dielectric, performing patterning and selective etching.

[0113] Specifically, an anode metal layer is prepared on the surface of multiple P-type doped regions 7, P-type transition region 8 and the third N-type drift region, and the metal is deposited by a deposition method to form the required anode metal, wherein the anode metal can be Al, or Al doped with Si or Cu, or Ag or Cu; and the Schottky contact metal 117 is obtained by passivating the medium, performing patterning and selective etching.

[0114] Although some specific embodiments of the present invention have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It should be understood by those skilled in the art that the above embodiments may be modified or some technical features may be replaced by equivalents without departing from the scope and spirit of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there is no structural conflict.

[0115] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A silicon carbide floating junction structure with improved switching characteristics along a slope-terminated P-channel, characterized in that: The silicon carbide floating junction structure with improved switching characteristics along the slope terminal P channel includes: N-type substrate; An N-type drift region is formed on the N-type substrate and both ends of the N-type drift region are inclined surfaces; A plurality of first P-type floating junctions are formed in the middle region of the N-type drift region and are arranged at intervals; A first P-type floating junction transition region is formed in the N-type drift region and surrounds the plurality of first P-type floating junctions, and both ends of the first P-type floating junction transition region are inclined surfaces; A plurality of second P-type floating junctions are formed in the middle area of ​​the N-type drift region and are arranged at intervals, and the plurality of second P-type floating junctions are arranged vertically opposite to the plurality of first P-type floating junctions; A second P-type floating junction transition region is formed inside the N-type drift region and surrounds the plurality of second P-type floating junctions, and both ends of the second P-type floating junction transition region are inclined surfaces; A plurality of P-type doping regions are formed in the middle region of the N-type drift region and are arranged at intervals, and the plurality of P-type doping regions are arranged vertically opposite to the plurality of second P-type floating junctions, and the upper surfaces of the plurality of P-type doping regions are in the same horizontal plane as the upper surface of the N-type drift region; A P-type transition region formed inside the N-type drift region and surrounding the plurality of P-type doped regions; The sloped terminal P channel is formed on the slopes at both ends of the N-type drift region, the slopes at both ends of the first P-type floating junction transition region, the slopes at both ends of the second P-type floating junction transition region, and both ends of the P-type transition region.

2. The silicon carbide floating junction structure with improved switching characteristics along the slope-terminated P-channel according to claim 1, characterized in that: The silicon carbide floating junction structure for improving the switching characteristics along the slope terminal P channel also includes an ohmic contact metal and a Schottky contact metal; The ohmic contact metal is formed on the lower surface of the N-type substrate; The Schottky contact metal is formed on the N-type drift region, the plurality of P-type doping regions and a portion of the P-type transition region.

3. The silicon carbide floating junction structure with improved switching characteristics along the slope-terminated P-channel according to claim 1, characterized in that: The implanted ions of the slope terminal P channel are Al, the implantation energy range is 10Kev-1000Kev, and the doping concentration range is 1e15-1e18cm -3 .

4. The silicon carbide floating junction structure with improved switching characteristics along the slope-terminated P-channel according to claim 1, characterized in that: The inclination angles of the inclined surfaces at both ends of the N-type drift region, the inclined surfaces at both ends of the first P-type floating junction transition region, and the inclined surfaces at both ends of the second P-type floating junction transition region are all 30°.

5. The silicon carbide floating junction structure with improved switching characteristics along the slope-terminated P-channel according to claim 1, characterized in that: An upper surface of the first P-type floating junction transition zone is at the same level as upper surfaces of the multiple first P-type floating junctions, and a thickness of the first P-type floating junction transition zone is the same as a thickness of the multiple first P-type floating junctions.

6. The silicon carbide floating junction structure with improved switching characteristics along the slope-terminated P-channel according to claim 1, characterized in that: The upper surface of the second P-type floating junction transition zone is at the same horizontal plane as the upper surfaces of the multiple second P-type floating junctions, and the thickness of the second P-type floating junction transition zone is the same as the thickness of the multiple second P-type floating junctions.

7. The silicon carbide floating junction structure with improved switching characteristics along the slope-terminated P-channel according to claim 1, characterized in that: The thickness of the plurality of first P-type floating junctions is the same as the thickness of the plurality of second P-type floating junctions.

8. The silicon carbide floating junction structure with improved switching characteristics along the slope-terminated P-channel according to claim 1, characterized in that: The N-type substrate includes a first N-type substrate and a second N-type substrate, wherein the second N-type substrate is formed on the first N-type substrate, the first N-type substrate is in a rectangular shape, and the second N-type substrate is in a trapezoidal shape.

9. A method for preparing a silicon carbide floating junction structure with improved switching characteristics along a bevel-terminated P channel, characterized in that: The silicon carbide floating junction structure with improved switching characteristics along the bevel terminal P channel according to any one of claims 1 to 8 comprises: Selecting an N-type substrate, wherein the material of the N-type substrate is silicon carbide; Growing a first N-type drift region on the surface of the N-type substrate; Performing ion implantation on the surface of the first N-type drift region to form a plurality of first P-type floating junctions and a first P-type floating junction transition region, so that the plurality of first P-type floating junctions are arranged at intervals and the first P-type floating junction transition region surrounds the plurality of first P-type floating junctions; Growing a second N-type drift region on the surfaces of the plurality of first P-type floating junctions, the first P-type floating junction transition region and the first N-type drift region; Performing ion implantation on the surface of the second N-type drift region to form a plurality of second P-type floating junctions and a second P-type floating junction transition region, so that the plurality of second P-type floating junctions are arranged at intervals and the second P-type floating junction transition region surrounds the plurality of second P-type floating junctions; Growing a third N-type drift region on the surfaces of the plurality of second P-type floating junctions, the second P-type floating junction transition region and the second N-type drift region; Performing ion implantation on the surface of the third N-type drift region to form a plurality of P-type doped regions and a P-type transition region, so that the plurality of P-type doped regions are arranged at intervals and the P-type transition region surrounds the plurality of second P-type floating junctions; Depositing a SiO2 layer on the surfaces of the plurality of P-type doped regions, the P-type transition region and the third N-type drift region; Forming a photoresist etching mask on the upper surface of the SiO2 layer, etching the SiO2 layer so that both ends of the SiO2 layer are inclined surfaces, and forming an etching mask for the SiO2; Using the SiO2 etching mask as a mask, etching from the third N-type drift region to the N-type substrate to form an oblique angle sidewall; Performing ion implantation on the beveled sidewall to form a beveled terminal P channel; Depositing Ni metal on the bottom of the N-type substrate by magnetron sputtering or electron beam evaporation, and performing rapid thermal annealing to form an ohmic contact metal; Metal is deposited on the surfaces of the plurality of P-type doped regions, the P-type transition region and the third N-type drift region, and a Schottky contact metal is obtained by passivating a dielectric, performing patterning and selective etching.

10. The method for preparing a silicon carbide floating junction structure with improved switching characteristics along a bevel-terminated P channel according to claim 9, characterized in that: The implanted ions of the slope terminal P channel are Al, the implantation energy range is 10Kev-1000Kev, and the doping concentration range is 1e15-1e18cm -3 .

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