CN108336152A - Groove-shaped silicon carbide SBD device with floating junction and its manufacturing method - Google Patents

Abstract

The invention relates to a trench-type silicon carbide SBD device with a floating junction and a manufacturing method thereof, belonging to the technical field of semiconductor devices, comprising a silicon carbide substrate (101), a first epitaxial layer (201), and a P-type ion implantation region ( 203), the second epitaxial layer (301), the trench structure (302), the terminal area insulating dielectric isolation layer (401), the Schottky metal layer (501) and the metal electrode (502); the silicon carbide substrate ( 101), the first epitaxial layer (201), the second epitaxial layer (301) and the Schottky metal layer (501) are stacked sequentially from bottom to top, and the P-type ion implantation region (203) is embedded in a certain interval On the upper surface of the first epitaxial layer (201), the P-type ion implantation region (203) is flush with the upper surface of the first epitaxial layer (201) and in contact with the lower surface of the second epitaxial layer (301). The invention has the advantage of maximally improving the reverse breakdown voltage of the existing Schottky barrier diode structure without affecting the conduction current of the device.

Description

Trench-type silicon carbide SBD device with floating junction and manufacturing method thereof

technical field

The invention belongs to the technical field of semiconductor devices, and relates to a trench type silicon carbide SBD device with a floating junction and a manufacturing method thereof.

Background technique

Bipolar devices have lower on-resistance due to conductivity modulation by minority carriers, but also have lower switching frequencies due to the presence of excess carriers in their structure And higher switching losses limit the application of bipolar devices in high switching frequency occasions. However, the switching frequency of unipolar devices is much higher than that of bipolar devices because there are no minority carriers in its structure to modulate the conductivity, and it is widely used in high switching frequency circuits.

For silicon material, due to its lower band gap and thermal conductivity, it is suitable for lower voltage circuit system. Silicon carbide material has the advantages of larger bandgap (about 3 times that of Si), stronger critical breakdown electric field (about 10 times that of Si), and higher thermal conductivity (about 3 times that of Si). The field of power electronics has greater application advantages. The leakage current of devices made of silicon carbide materials is several orders of magnitude smaller than that of silicon, so silicon carbide devices can work in high temperature environments above 500°C and have good radiation resistance. Since the silicon carbide material has a larger band gap than silicon, the drift region length of the silicon carbide device is smaller than that of silicon under the same withstand voltage, which greatly reduces the on-resistance of the device. The greater thermal conductivity of silicon carbide material also makes the device have better heat dissipation. Even if it works in a high temperature environment, no additional heat dissipation device is needed, which greatly reduces the size and cost of the system. Therefore, silicon carbide materials are ideal materials for manufacturing high-temperature, high-power, high-voltage, and low-power electronic devices, and have broad application scenarios in power electronics.

Silicon carbide materials are usually grown using epitaxial technology. Due to the particularity of the material, the current growth technology of silicon carbide materials is far less mature than that of silicon materials, and the silicon carbide materials obtained during growth are relatively thin. Thick silicon carbide materials are due to technical reasons. There are usually more defects, which seriously affect the performance of the device. Introducing a floating junction structure into the device can nearly double the withstand voltage of the device under the same doping concentration and thickness, which is the key to solving the above problems, and has received extensive attention in the field of power devices in recent years.

Floating junction silicon carbide Schottky diodes not only have the characteristics of low dropout and high current of traditional Schottky diodes, but also have higher reverse breakdown voltage than traditional Schottky diodes. It is noted that in the "trenched floating junction silicon carbide SBD device and its manufacturing method based on epitaxial process" proposed by the patent application number "201410166386.3", although the structure also uses a floating junction + trench structure SBD device, but Its design flaws are obvious. This invention uses metal to fill the trench above the floating island. Although it can increase the electrode contact area, the existence of the floating island limits the current path area, so this design cannot increase the on-current of the device. At the same time, when the trench is filled with metal, the metal in the trench and the silicon carbide material only form a Schottky contact, and the Schottky barrier is the same as that formed by the metal on the upper surface of the trench and the silicon carbide material. , which is equivalent to reducing the thickness of the drift layer of the silicon carbide material, thereby reducing the reverse withstand voltage of the device.

Contents of the invention

In view of this, the object of the present invention is to provide a trench type silicon carbide SBD device with a floating junction and a manufacturing method thereof, to solve the problem of maximizing the existing Schottky SBD without affecting the conduction current of the device. The reverse breakdown voltage of a barrier diode structure.

To achieve the above object, the present invention provides the following technical solutions:

A trench-type silicon carbide SBD device with a floating junction, the device includes a silicon carbide substrate 101, a first epitaxial layer 201, a P-type ion implantation region 203, a second epitaxial layer 301, a trench structure 302, and a terminal area insulating dielectric isolation Layer 401, Schottky metal layer 501 and metal electrode 502;

The silicon carbide substrate 101, the first epitaxial layer 201, the second epitaxial layer 301 and the Schottky metal layer 501 are stacked sequentially from bottom to top, and the P-type ion implantation region 203 is embedded in the first epitaxial layer at a certain interval. The upper surface of the layer 201, the P-type ion implantation region 203 is flush with the upper surface of the first epitaxial layer 201 and is in contact with the lower surface of the second epitaxial layer 301;

The outer surfaces on both sides of the second epitaxial layer 301 are flush with the outer surfaces on both sides of the silicon carbide substrate 101 and the first epitaxial layer 201, and the groove structure 302 is embedded in the second epitaxial layer at a certain distance. The upper surface of the layer 301, and the position of the trench structure 302 corresponds to the position of the P-type ion implantation region 203;

The inner wall of the trench structure 302 is provided with an insulating dielectric layer 304, and the insulating dielectric layer 304 is filled with a conductive material 305. The upper surfaces of the trench structure 302, the insulating dielectric layer 304, and the conductive material 305 are all connected to the second The upper surface of the epitaxial layer 301 is flush;

The terminal region insulating dielectric isolation layer 401 is disposed on both sides of the upper surface of the second epitaxial layer 301, and the terminal region insulating dielectric isolation layer 401 on both sides is in contact with at least one upper surface of the trench structure 302 respectively. , the metal electrode 502 is bonded to the upper surface of the Schottky metal layer 501 and the insulating dielectric isolation layer 401 in the terminal area, and the surfaces on both sides of the metal electrode 502 do not exceed the insulating dielectric isolation layer 401 in the terminal area surfaces on both sides.

Further, the silicon carbide substrate 101 is an N ⁺ -type silicon carbide conductive substrate, and its doping concentration is 1×10 ¹⁹ -1×10 ²⁰ cm ⁻³ .

Further, both the first epitaxial layer 201 and the second epitaxial layer 301 are N ^- type silicon carbide epitaxial layers, the thickness of the first epitaxial layer 201 is 4-20 μm, and the ion doping concentration is 5×10 ¹⁴ ˜1 ×10 ¹⁷ cm ^-3 , the thickness of the second epitaxial layer 301 is 5-20 μm, and the doping concentration is 5×10 ¹⁴ -1×10 ¹⁷ cm ^-3 .

Further, the shape of the P-type ion implantation region 203 is circular or square, and the implanted ions are aluminum, and the implantation concentration is 1×10 ¹⁷ -1×10 ¹⁹ cm ⁻³ .

Further, the width of the trench structure 302 is 1-4 μm, and the depth is 1-5 μm. The insulating dielectric layer 304 is made of SiO2, and the thickness of the insulating dielectric layer 304 is 50-500 μm. Except for the trench structure 302 in contact with the insulating dielectric isolation layer 401, the width of the rest of the trench structure 302 is the same as the width of the P-type ion implantation region 203, and the top view shape of the trench structure 302 is rectangular , a pentagon, a polygon with more than five sides, and a circle, and the groove structure is arranged in an equidistant arrangement, a dislocation arrangement or a mixture of the two arrangements.

Further, the insulating dielectric isolation layer 401 in the terminal area is made of SiO2, at least one trench structure 302 covered by the insulating dielectric isolation layer 401 in the terminal area, and the trench structure covered by the insulating dielectric isolation layer 401 in the terminal area The spacing and width between the trench structures 302 outside the coverage area and the spacing and width between the trench structures 302 are different.

Further, the Schottky metal layer 501 is made of Ti, Pt, Ni, Cr, W, Mo or Co.

A method for manufacturing a trench-type silicon carbide SBD device with a floating junction, the method comprising the steps of:

S1: Prepare N ⁺ type silicon carbide conductive substrate;

S2: growing the first epitaxial layer epitaxially on the surface of the N ⁺ type silicon carbide conductive substrate in S1, and setting several mask windows on the surface of the first epitaxial layer, and performing P-type ion implantation to form a P-type floating island structure;

S3: removing the mask in step S2, and epitaxially growing a second epitaxial layer on the surface of the first epitaxial layer;

S4: setting several mask windows on the surface of the second epitaxial layer and etching to form several grooves;

S5: removing the mask in step S4, setting a dielectric layer in the trench, and filling the trench with a conductive material;

S6: removing the dielectric layer on the surface of the second epitaxial layer in step S5, exposing the silicon carbide material, and growing an insulating dielectric layer on its surface;

S7: Remove the material in the middle region of the insulating dielectric layer until the silicon carbide on the surface of the second epitaxial layer is exposed, and retain the insulating dielectric layer at both ends of the device as a terminal area, set a Schottky metal layer on the surface of the second epitaxial layer, and set the front side electrode layer.

Further, the dielectric layer in the trench is SiO2, and the conductive material filled in the trench is highly doped polysilicon.

Further, in step S2, P-type ion implantation is performed to form a P-type floating island structure, wherein the implantation energy ranges from 200keV to 2MeV.

The beneficial effect of the present invention is that: the present invention introduces a P-type ion-doped floating junction structure inside the silicon carbide material, and combines the trench structure, and disperses the directional electric field of the device at the bottom of the trench by forming a SiO2 dielectric layer in the trench And the position of the floating junction improves the breakdown voltage of the device, and by filling the trench with polysilicon material, it forms a plate capacitor with the silicon carbide material on the other side of the SiO2 dielectric layer, which increases the soft recovery characteristics of the device. Therefore, the present invention has the advantage of maximally improving the reverse breakdown voltage of the existing Schottky barrier diode structure without affecting the conduction current of the device. The invention has simple structure and process steps, remarkable effect and broad application prospect.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings for illustration:

Fig. 1 is the structural representation of SBD device of the present invention;

Fig. 2～Fig. 5 is the schematic diagram of groove shape and arrangement mode in the structure of SBD device of the present invention;

6 to 14 are schematic diagrams of the process steps of the manufacturing method of the SBD device of the present invention;

The reference numerals are: 101 silicon carbide substrate, 201 first epitaxial layer, 202 barrier layer, 203 P-type ion implantation region, 301 second epitaxial layer, 302 trench structure, 303 mask layer, 304 insulating dielectric layer, 305 Conductive material, 401 terminal area insulating dielectric isolation layer, 501 Schottky metal layer, 502 metal electrode.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Figures 1 to 14 below show the structure and simple manufacturing method of a trench-type silicon carbide SBD device with a floating junction provided in this embodiment. It should be noted that the following figures are only schematic diagrams illustrating the basic idea of the present invention, and only components related to the present invention are shown in the figures, rather than drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the shape, size, quantity and ratio of each component can be changed at will according to the needs. Those who are familiar with this technology can complete all equivalent modifications or changes without departing from the spirit and technical ideas disclosed in the present invention. should still be covered by the claims of the present invention.

As shown in FIG. 1 , this embodiment provides a trench type silicon carbide SBD device with a floating junction. The silicon carbide SBD device includes: a silicon carbide substrate 101 , a first epitaxial layer 201 formed on the silicon carbide substrate 101 The surface of the barrier layer 202 is formed on the surface of the first epitaxial layer 201, and the P-type ion implantation region 203 forms a plurality of discontinuous P-type floating junction structures in the first epitaxial layer 201 through the barrier of the barrier layer 202; The second epitaxial layer 301 is formed on the surface of the first epitaxial layer 201; the mask layer 303 is formed on the surface of the second epitaxial layer 301; the trench structure 302 and the insulating dielectric layer 304 are formed on the surface of the second epitaxial layer 301 and The surface of the trench structure 302 ; the trench is filled with conductive material 305 and formed outside the insulating dielectric layer 304 ; the insulating dielectric isolation layer 401 in the termination area is formed in the termination regions on both sides of the surface of the second epitaxial layer 301 .

The Schottky metal layer 501 is formed on the surface of the second epitaxial layer 301 and the filled trench structure 302; the metal electrode 502 is formed on the terminal region insulating dielectric isolation layer 401 and the Schottky metal layer 501 surface.

In the embodiment of the present invention, the silicon carbide substrate 101 is an N ⁺ -type silicon carbide substrate with a doping concentration of 1×10 ¹⁹ to 1×10 ²⁰ cm ^-3 , and the first epitaxial layer 201 is a silicon carbide N ^- type, which is N-type lightly doped; specifically, the first epitaxial layer 201 is formed by epitaxial growth on the surface of the silicon carbide substrate 101, and its doping concentration ranges from 5×10 ¹⁴ to 1×10 ¹⁷ cm ^-3 , The epitaxial growth thickness ranges from 4 to 20 μm.

The barrier layer 202 is a SiO2 barrier layer located on the first epitaxial layer 201 and formed by thermal oxidation or chemical vapor deposition (CVD) process. In this embodiment, the thickness of the barrier layer 202 can be adjusted accordingly according to the P-type ion implantation energy to ensure that there is no P-type ion implantation dose under the barrier layer 202 .

Furthermore, the depth of the P-type ion implantation region 203 needs to be adjusted according to the voltage requirements designed in actual operation. The depth of the P-type ion implantation region 203 ranges from 0.3 to 0.6 μm, and the doping concentration of the ion implantation is 1×10 ¹⁷ to 1× 10 ¹⁹ cm ^-3 , the implanted ions are aluminum.

The second epitaxial layer 301 is an N ^- type silicon carbide epitaxial layer. Specifically, the second epitaxial layer 301 is formed by epitaxial growth on the surface of the first epitaxial layer 201, and its doping concentration ranges from 5×10 ¹⁴ to 1×10 ¹⁷ cm ^{− 3.} The epitaxial growth thickness ranges from 4 to 20 μm; the upper surface of the second epitaxial layer 301 is etched by introducing a mask layer 303 to form a groove shape 302, and after removing the mask layer 303, the second epitaxial layer 301 is thermally oxidized An insulating dielectric layer 304 is formed on the surface and the surface of the trench structure 302. The insulating dielectric layer 304 is SiO2 with a thickness of 50-500nm; then the trench is filled with a conductive material 305, specifically, the conductive material 305 is a P-type doped polysilicon material.

The material of the insulating dielectric isolation layer 401 in the terminal area is SiO2, and the thickness of the material is 0.5-2 μm; specifically, the insulating dielectric layer 401 in the terminal area is located in the terminal area, and the specific width can be determined according to the design. The Schottky metal layer 501 is formed on the surface of the second epitaxial layer 301, and is a metal material that forms a Schottky barrier with the silicon carbide material, which can be Ti, Pt, Ni, Cr, W, Mo or Co, and the metal electrode 502, It is formed on the surface of the insulating dielectric isolation layer 401 and the Schottky metal layer 501 in the terminal area.

It should be noted that the shape of the above trench structure 302 is consistent with the structure of the P-type ion implantation region 203 in the first epitaxial layer 201 in the cell region, their dimensions are the same, and there are various arrangements. 2 to 5 are schematic diagrams showing the shape and arrangement of the trench structure 302; as an example, the top view shape of the trench structure 302 can be one or more of a rectangle, a pentagon, a polygon with more than five sides, and a circle. The arrangement of the groove structure can be equidistant arrangement, dislocation arrangement or a mixture of the above two arrangements.

As shown in Figures 6 to 14, this example also provides a method for manufacturing a trench-type silicon carbide SBD device with a floating junction, including steps:

As shown in FIG. 6 , a silicon carbide substrate 101 is first prepared, and a first epitaxial layer 201 of silicon carbide is formed on the surface of the silicon carbide substrate 101 . As an example, the doping type of the first epitaxial layer 201 is N ^- type doping, and the doping concentration ranges from 5×10 ¹⁴ to 1×10 ¹⁷ cm ^-3 . The concentration of the epitaxial layer needs to be selected according to actual needs. The growth process is a silicon carbide epitaxial growth process, the epitaxial temperature range is 1550-1600° C., and the epitaxial growth thickness is 4-20 μm.

As shown in FIG. 7 , a barrier layer 202 is grown on the surface of the first epitaxial layer 201 , and P-type ion implantation is performed after the barrier layer is opened to form a P-type ion implantation region 203 structure. As an example, the medium of the barrier layer 202 is SiO2, and SiO2 is deposited on the surface of the first epitaxial layer 201 using a CVD process, and the SiO2 is etched using a photolithography process, and then a P-type ion implantation process is performed, and the implantation energy ranges from 200keV to 2MeV. Then annealing is carried out in a nitrogen atmosphere, and the annealing temperature is 1050° C.

As shown in FIGS. 8 and 9 , a silicon carbide second epitaxial layer 301 is grown on the surface of the first epitaxial layer 201 , and a trench structure 302 is etched on the surface of the second epitaxial layer 301 . As an example, the doping type of the second epitaxial layer 201 is N ^- type doping, and the doping concentration ranges from 5×10 ¹⁴ to 1×10 ¹⁷ cm ^-3 . The concentration of the epitaxial layer is selected according to actual needs. The epitaxial layer The growth process is a silicon carbide epitaxial growth process, the epitaxial temperature range is 1550-1600 °C, and the epitaxial growth thickness is 5-20 μm; the trench structure is etched by etching process, and the specific steps are as follows:

Coat photoresist on the surface of the second epitaxial layer 301 and develop it, etch the length and width of the trench opening on the photoresist layer, the trench length and width are equal to the P-type ion implantation region except the terminal region and are located in the P-type Directly above the ion implantation area 203;

A dry etching process is used to etch the silicon carbide material without photoresist coverage to form grooves with a width of 1-4 μm and a depth of 1-5 μm, and then remove the photoresist.

As shown in FIGS. 10-12 , an insulating dielectric layer 304 is formed on the surface of the trench, and then filled with a conductive material 305 , and excess material on the surface of the second epitaxial layer 301 is removed to expose the silicon carbide material. As an example, the insulating dielectric layer 304 on the surface of the trench structure is made of SiO2 material, formed by silicon carbide thermal oxidation or chemical vapor deposition (CVD) process, the thickness of the SiO2 material is 50-500nm, and the conductive material 305 is P-type doped The polysilicon material is filled by CVD process; and then the SiO2 and polysilicon on the surface of the second epitaxial layer 301 are removed by etching or chemical mechanical planarization (CMP) to expose the silicon carbide material.

As shown in Figures 13 and 14, an insulating dielectric isolation layer 401 is formed on the surface of the second epitaxial layer 301, and the insulating dielectric layers on both sides are reserved as terminals, and then a Schottky metal layer 501 and a metal electrode 502 are deposited; as For example, the material of the insulating dielectric layer is SiO2, which is generated by thermal oxidation or CVD process; by coating photoresist on the surface of the insulating dielectric isolation layer 401 in the terminal area and etching away the middle part of SiO2, the silicon carbide material is exposed, and the remaining SiO2 is used as an insulating layer in the terminal region; then, a Schottky metal layer 501 is deposited on the silicon carbide surface of the second epitaxial layer by a metal sputtering process, and a Schottky metal layer 501 is reacted with the silicon carbide material by using a rapid thermal annealing process to form a Schottky metal layer. The Tertky barrier layer, wherein the material of the Schottky metal layer may contain at least one metal of Ti, Pt, Ni, Cr, W, Mo or Co. Further, a metal electrode 502 is formed on the surface of the Schottky barrier layer 501, and the metal electrode 502 is selectively etched by using a photolithography mask to form a front electrode.

As mentioned above, the present invention introduces the combination of the floating junction structure and the trench structure. The PN junction and the trench structure divide the electric field of the device into two parts. Without affecting the conduction current of the device, the maximum The method improves the reverse breakdown voltage of the existing Schottky barrier diode structure to a certain extent, and has extremely high application value.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the invention and not limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it may be possible in form and details. Various changes can be made to it without departing from the scope defined by the claims of the present invention.

Claims (10)

1. A trench type silicon carbide SBD device with a floating junction, characterized in that the device comprises a silicon carbide substrate (101), a first epitaxial layer (201), a P-type ion implantation region (203), a second epitaxial layer (301), trench structure (302), terminal area insulating dielectric isolation layer (401), Schottky metal layer (501) and metal electrode (502); The silicon carbide substrate (101), the first epitaxial layer (201), the second epitaxial layer (301) and the Schottky metal layer (501) are stacked sequentially from bottom to top, and the P-type ion implantation region ( 203) are embedded in the upper surface of the first epitaxial layer (201) at a certain interval, and the P-type ion implantation region (203) is flush with the upper surface of the first epitaxial layer (201) and connected to the second epitaxial layer ( 301) in contact with the lower surface; The outer surfaces on both sides of the second epitaxial layer (301) are flush with the outer surfaces on both sides of the silicon carbide substrate (101) and the first epitaxial layer (201), and the trench structures (302) are spaced at a certain interval The distance is embedded in the upper surface of the second epitaxial layer (301), and the position of the trench structure (302) corresponds to the position of the P-type ion implantation region (203); The inner wall of the trench structure (302) is provided with an insulating dielectric layer (304), the insulating dielectric layer (304) is filled with a conductive material (305), the trench structure (302), the insulating dielectric layer (304) and The upper surfaces of the conductive material (305) are all flush with the upper surface of the second epitaxial layer (301); The insulating dielectric isolation layer (401) of the terminal area is arranged on both sides of the upper surface of the second epitaxial layer (301), and the insulating dielectric isolation layer (401) of the terminal area on both sides is respectively connected with at least one of the trenches. The upper surface of the structure (302) is in contact, the metal electrode (502) is attached to the upper surface of the Schottky metal layer (501) and the terminal area insulating dielectric isolation layer (401), and the metal electrode (502 ) does not exceed the two side surfaces of the insulating dielectric isolation layer (401) in the termination area. 2. The trench type silicon carbide SBD device with a floating junction according to claim 1, characterized in that: the silicon carbide substrate (101) is an N ⁺ type silicon carbide conductive substrate, and its doping concentration is 1 ×10 ¹⁹ ~1×10 ²⁰ cm ^-3 . 3. The trench type silicon carbide SBD device with floating junction according to claim 1, characterized in that: the first epitaxial layer (201) and the second epitaxial layer (301) are both N ^- type silicon carbide epitaxy layer, the thickness of the first epitaxial layer (201) is 4 to 20 μm, the ion doping concentration is 5×10 ¹⁴ to 1×10 ¹⁷ cm ^-3 , and the thickness of the second epitaxial layer (301) is 5 to 20 μm. 20 μm, the doping concentration is 5×10 ¹⁴ to 1×10 ¹⁷ cm ^-3 . 4. The trench type silicon carbide SBD device with a floating junction according to claim 1, characterized in that: the shape of the P-type ion implantation region (203) is circular or square, and the implanted ions are aluminum, and the implanted ion The concentration is 1×10 ¹⁷ to 1×10 ¹⁹ cm ^-3 . 5. The trench silicon carbide SBD device with a floating junction according to claim 1, characterized in that: the trench structure (302) has a width of 1-4 μm and a depth of 1-5 μm, and the insulating medium The layer (304) is made of SiO2, the thickness of the insulating dielectric layer (304) is 50-500 μm, except for the trench structure (302) in contact with the insulating dielectric isolation layer (401) in the terminal area, the rest The width of the trench structure (302) is the same as the width of the P-type ion implantation region (203), and the top view shape of the trench structure (302) is a rectangle, a pentagon, a polygon with more than five sides, and One or more combinations of circles, the groove structures are arranged in an equidistant arrangement, a dislocation arrangement or a mixture of the two arrangements. 6. The trench type silicon carbide SBD device with floating junction according to claim 1, characterized in that: the insulating dielectric isolation layer (401) of the terminal area is made of SiO2, and the insulating dielectric isolation layer of the terminal area ( 401) covers at least one trench structure (302), and the spacing and width between the trench structures (302) covered by the insulating dielectric isolation layer (401) in the terminal area are the same as those of the trench structures (302) outside the coverage area. ) with different spacing and widths. 7. The trench type silicon carbide SBD device with floating junction according to claim 1, characterized in that: the Schottky metal layer (501) is made of Ti, Pt, Ni, Cr, W, Mo or Co to make. 8. A method for manufacturing a trench-type silicon carbide SBD device with a floating junction, characterized in that: the method comprises the following steps: S1: Prepare N ⁺ type silicon carbide conductive substrate; S2: growing the first epitaxial layer epitaxially on the surface of the N ⁺ type silicon carbide conductive substrate in S1, and setting several mask windows on the surface of the first epitaxial layer, and performing P-type ion implantation to form a P-type floating island structure; S3: removing the mask in step S2, and epitaxially growing a second epitaxial layer on the surface of the first epitaxial layer; S4: setting several mask windows on the surface of the second epitaxial layer and etching to form several grooves; S5: removing the mask in step S4, setting a dielectric layer in the trench, and filling the trench with a conductive material; S6: removing the dielectric layer on the surface of the second epitaxial layer in step S5, exposing the silicon carbide material, and growing an insulating dielectric layer on its surface; S7: Remove the material in the middle region of the insulating dielectric layer until the silicon carbide on the surface of the second epitaxial layer is exposed, and retain the insulating dielectric layer at both ends of the device as a terminal area, set a Schottky metal layer on the surface of the second epitaxial layer, and set the front side electrode layer. 9. The manufacturing method of a trench-type silicon carbide SBD device with a floating junction according to claim 8, characterized in that: the dielectric layer in the trench is SiO2, and the conductive material filled in the trench is highly doped polysilicon . 10. The manufacturing method of a trench-type silicon carbide SBD device with a floating junction according to claim 8, characterized in that in step S2, P-type ion implantation is performed to form a P-type floating island structure, wherein the implantation energy ranges from 200keV to 2MeV.