A floating junction thickness graded silicon carbide power device

Abstract

The present application relates to a kind of silicon carbide power devices of floating junction thickness gradually changes, comprising: N+ silicon carbide substrate layer;N- silicon carbide epitaxial layer is located on N+ silicon carbide substrate layer;A layer P-type silicon carbide floating junction layer is arranged in the N- silicon carbide epitaxial layer in vertical direction, each P-type silicon carbide floating junction layer includes B P-type silicon carbide floating junction structure, P-type silicon carbide floating junction structure is symmetrical along central axis and is the structure of thickness gradually changes;Back electrode is located in the lower surface of N+ silicon carbide substrate layer;Front electrode is located on N- silicon carbide epitaxial layer.The present application makes the thickness of floating junction gradually increase from the center of floating junction to the edge of floating junction, thereby reducing the electric field peak value of corresponding electrode position higher at the center of floating junction when device is in reverse working state, while the epitaxial layer drift region between floating junction is more sufficient, makes the electric field peak value of floating junction interval center and edge position be lifted.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to a silicon carbide power device with a gradually varying floating junction thickness. Background Technology

[0002] To further improve the performance of silicon carbide power devices, "superjunction" structures, represented by floating junctions, have been applied in related fields. A floating junction structure involves adding one or more discontinuous P+ structures to the drift region of the N-type epitaxial layer in a traditional device, approximating the formation of a PN junction structure within the drift region. When the device operates in reverse, the addition of the floating junction structure transforms the original triangular or trapezoidal longitudinal electric field distribution within the drift region into two independent triangular or trapezoidal longitudinal electric field distributions centered on the floating junction structure. This increases the reverse breakdown voltage of the device without changing the doping concentration and thickness of the drift region.

[0003] However, the overall thickness parameter value of conventional floating junction structures remains the same. Under normal circumstances, the conventional floating junction structure layout will cause the electric field value at the center of the floating junction structure to be larger than the electric field value at the edge of the floating junction and the epitaxial drift region between the two floating junctions when the device is operating in the reverse state. This results in uneven electric field distribution at the floating junction structure and electrode positions, and poor depletion of the epitaxial drift region between the floating junctions. To a certain extent, this weakens the effect of the floating junction structure on improving the breakdown voltage of silicon carbide power devices. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a silicon carbide power device with a gradually varying floating junction thickness. The technical problem to be solved by this invention is achieved through the following technical solution:

[0005] One embodiment of the present invention provides a silicon carbide power device with a floating junction thickness gradient, the silicon carbide power device comprising:

[0006] N+ silicon carbide substrate layer;

[0007] An N-silicon carbide epitaxial layer, wherein the N-silicon carbide epitaxial region is located above the N+ silicon carbide substrate layer;

[0008] A layer of P-type silicon carbide floating junction layer, wherein the A layer of P-type silicon carbide floating junction layer is disposed vertically within the N-silicon carbide epitaxial layer, each layer of the P-type silicon carbide floating junction layer includes B P-type silicon carbide floating junction structures, wherein the P-type silicon carbide floating junction structures are symmetrical along the central axis and have a gradually changing thickness, wherein A and B are both integers greater than or equal to 1;

[0009] A back electrode is located on the lower surface of the N+ silicon carbide substrate layer, and the back electrode is in ohmic contact with the N+ silicon carbide substrate layer.

[0010] The front electrode is located on the N-silicon carbide epitaxial layer, and the region of the front electrode on the N-silicon carbide epitaxial layer is a Schottky contact.

[0011] In one embodiment of the present invention, the thickness of the P-type silicon carbide floating junction structure gradually increases from the center to the edge.

[0012] In one embodiment of the present invention, the P-type silicon carbide floating junction structure includes a first floating junction structure and a second floating junction structure. The first floating junction structure and the second floating junction structure are symmetrical along a central axis, and the thickness of the first floating junction structure and the second floating junction structure gradually decreases from the edge to the center. The upper surfaces of the first floating junction structure and the second floating junction structure are parallel to the horizontal plane, and the acute angle between the lower surfaces of the first floating junction structure and the horizontal plane is greater than 0 degrees and less than 90 degrees. Alternatively, the acute angle between the upper surfaces of the first floating junction structure and the second floating junction structure and the horizontal plane is greater than 0 degrees and less than 90 degrees, and the lower surfaces of the first floating junction structure and the second floating junction structure are parallel to the horizontal plane. Alternatively, both the acute angle between the upper surfaces of the first floating junction structure and the second floating junction structure and the horizontal plane, and the acute angle between the lower surfaces of the first floating junction structure and the horizontal plane, are greater than 0 degrees and less than 90 degrees.

[0013] In one embodiment of the present invention, the thickness of the P-type silicon carbide floating junction structure satisfies the formula:

[0014]

[0015] Among them, T max T is the thickness at the edge of the p-type silicon carbide floating junction structure. min W is the thickness at the center of the P-type silicon carbide floating junction structure, W is the width of the P-type silicon carbide floating junction structure, and S is the distance between two adjacent P-type silicon carbide floating junction structures in the same layer.

[0016] In one embodiment of the present invention, the distance S between two adjacent P-type silicon carbide floating junction structures in the same layer ranges from 1 to 5 μm.

[0017] In one embodiment of the present invention, the thickness of the P-type silicon carbide floating junction structure ranges from 0.3 to 3 μm.

[0018] In one embodiment of the present invention, the doping concentration of the p-type silicon carbide floating junction structure is 1×10⁻⁶. 16 ~1×10 19 cm -3 .

[0019] In one embodiment of the present invention, the material of the back electrode 1 includes Ni, and the material of the front electrode includes Ti.

[0020] In one embodiment of the present invention, the silicon carbide power device further includes:

[0021] A P+ silicon carbide surface layer is disposed within the N-silicon carbide epitaxial layer. The P+ silicon carbide surface layer is located above the A-layer P-type silicon carbide floating junction layer. The upper surface of the P+ silicon carbide surface layer and the upper surface of the N-silicon carbide epitaxial layer are located on the same plane. The P+ silicon carbide surface layer includes B P-type silicon carbide surface regions. The b-th P-type silicon carbide surface region and the b-th silicon carbide floating junction structure of each layer are in the same column in the vertical direction, where 1≤b≤B.

[0022] The front electrode is located on the N-silicon carbide epitaxial layer and the P+ silicon carbide surface layer, and the area of ​​the front electrode on the P+ silicon carbide surface layer is an ohmic contact.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention modifies the geometry of the floating junction, gradually increasing its thickness from the center to the edge. This reduces the high electric field peak at the electrode position corresponding to the center of the floating junction when the device is in reverse operation. Simultaneously, the epitaxial drift region between the floating junctions is more fully depleted, thereby increasing the lower electric field peak in the epitaxial drift region between the floating junctions. This results in a more uniform electric field distribution across the entire device, further optimizing the effect of the floating junction structure and improving the breakdown voltage of the floating junction silicon carbide power device. Attached Figure Description

[0025] Figure 1 A schematic diagram of the structure of a silicon carbide power device with a gradually varying floating junction thickness provided by the present invention;

[0026] Figure 2 A schematic diagram of another silicon carbide power device with gradually varying floating junction thickness provided by the present invention;

[0027] Figure 3 A schematic diagram of the structure of another silicon carbide power device with gradually varying floating junction thickness provided by the present invention;

[0028] Figure 4A schematic diagram of the structure of another silicon carbide power device with gradually varying floating junction thickness provided by the present invention;

[0029] Figure 5 The present invention provides a structural diagram of a silicon carbide power device with gradually varying thickness of a floating junction and a P-type silicon carbide floating junction structure with gradually varying thickness.

[0030] Figure 6 A schematic diagram of the electric field distribution cutoff position provided by the present invention;

[0031] Figure 7 A schematic diagram of the electric field distribution at the center of the floating junction of a conventional P-type floating junction region and the P-type floating junction structure of the present invention.

[0032] Figure 8 A schematic diagram of the electric field distribution at the edge of the floating junction of the conventional P-type floating junction region and the P-type silicon carbide floating junction structure of the present invention.

[0033] Figure 9 This is a schematic diagram of the electric field distribution at the center of the epitaxial layer drift region between conventional floating junctions and at the center of the epitaxial layer drift region between floating junctions of the present invention. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0035] It should be noted that, in this embodiment, "up," "down," "left," and "right" refer to the positional relationship of the silicon carbide power device when it is in the illustrated state, "width" refers to the lateral dimension of the silicon carbide power device when it is in the illustrated state, and "thickness" refers to the longitudinal dimension of the silicon carbide power device when it is in the illustrated state.

[0036] Please see Figure 1 , Figure 1 This invention provides a schematic diagram of a silicon carbide power device with a gradually varying floating junction thickness. The embodiment of this invention provides a silicon carbide power device with a gradually varying floating junction thickness, comprising:

[0037] N+ silicon carbide substrate layer 2;

[0038] N-silicon carbide epitaxial layer 3, which is located on N+silicon carbide substrate layer 2;

[0039] A-layer P-type silicon carbide floating junction layer is vertically disposed within the N-silicon carbide epitaxial layer 3. Each P-type silicon carbide floating junction layer includes B P-type silicon carbide floating junction structures 4. The P-type silicon carbide floating junction structures 4 are symmetrical along the central axis and have a gradually changing thickness. Here, A and B are both integers greater than or equal to 1. That is, a single layer or multiple layers of P-type silicon carbide floating junction layers can be disposed vertically within the N-silicon carbide epitaxial layer 3. Each P-type silicon carbide floating junction layer may include one or more P-type silicon carbide floating junction structures 4. Figure 1 The vertical direction in the diagram is the same as the vertical direction. Figure 1 The dashed line in the diagram represents the central axis.

[0040] Back electrode 1 is located on the lower surface of N+ silicon carbide substrate 2, and the back electrode 1 and N+ silicon carbide substrate 2 are in ohmic contact.

[0041] The front electrode 6 is located on the N-silicon carbide epitaxial layer 3, and the area of ​​the front electrode 6 on the N-silicon carbide epitaxial layer 3 is a Schottky contact.

[0042] Additionally, please see Figure 2 The silicon carbide power device may further include a P+ silicon carbide surface layer, which is disposed within the N-silicon carbide epitaxial layer 3. The P+ silicon carbide surface layer is located above the A-layer P-type silicon carbide floating junction layer. The upper surface of the P+ silicon carbide surface layer is on the same plane as the upper surface of the N-silicon carbide epitaxial layer 3. The P+ silicon carbide surface layer includes B P-type silicon carbide surface regions 5. The b-th P-type silicon carbide surface region 5 and the b-th silicon carbide floating junction structure 4 of each layer are in the same column in the vertical direction, that is, the central axis of the b-th P-type silicon carbide surface region 5 and the b-th silicon carbide floating junction structure 4 of each layer are on the same straight line. The P-type silicon carbide surface region 5 is a symmetrical structure, where 1≤b≤B. The front electrode 6 is located above the N-silicon carbide epitaxial layer 3 and the P+ silicon carbide surface layer. The area of ​​the front electrode 6 on the P+ silicon carbide surface layer is an ohmic contact.

[0043] Optionally, the thickness of the P-type silicon carbide floating junction structure 4 gradually increases from the center to the edge.

[0044] Furthermore, the P-type silicon carbide floating junction structure 4 includes a first floating junction structure 7 and a second floating junction structure 8. The first floating junction structure 7 and the second floating junction structure 8 are symmetrical along the central axis, and the thickness of the first floating junction structure 7 and the second floating junction structure 8 gradually decreases from the edge to the center. The first floating junction structure 7 and the second floating junction structure 8 can be, for example, as shown in the figure below. Figures 2 to 4 Three forms, the first form is as follows: Figure 2As shown, the upper surfaces of the first floating structure 7 and the second floating structure 8 are parallel to the horizontal plane, and the acute angle between the lower surfaces of the first floating structure 7 and the second floating structure 8 and the horizontal plane is greater than 0 degrees and less than 90 degrees. Alternatively, the second form is as follows: Figure 3 As shown, the acute angle between the upper surfaces of the first floating structure 7 and the second floating structure 8 and the horizontal plane is greater than 0 degrees and less than 90 degrees; the lower surfaces of the first floating structure 7 and the second floating structure 8 are parallel to the horizontal plane; or, in a third form as shown... Figure 4 As shown, the acute angle between the upper surface of the first part floating structure 7 and the second part floating structure 8 and the horizontal plane, and the acute angle between the lower surface of the first part floating structure 7 and the second part floating structure 8 and the horizontal plane are both greater than 0 degrees and less than 90 degrees.

[0045] Wherein, N+ represents the heavily doped N-type region, N- represents the lightly doped N-type region, P+ represents the heavily doped P-type region, and P- represents the lightly doped P-type region.

[0046] This invention modifies the geometry of the P-type silicon carbide floating junction structure, making it symmetrical along the central axis. Simultaneously, the thickness of the P-type silicon carbide floating junction structure gradually increases from the center to the edge. This reduces the high electric field peak at the center of the floating junction when the power device is in reverse operation. At the same time, the epitaxial layer drift region between the floating junctions is more fully depleted, further improving the lower electric field peak in the drift region. This results in a more uniform electric field distribution across the entire P-type silicon carbide floating junction power device, further optimizing the floating junction structure and increasing the breakdown voltage of the floating junction silicon carbide power device.

[0047] Optionally, the thickness of the P-type silicon carbide floating junction structure satisfies the formula:

[0048]

[0049] Among them, such as Figure 5 As shown, T max T represents the thickness at the edge of the P-type silicon carbide floating junction structure 4. min Let W be the thickness at the center of the P-type silicon carbide floating junction structure, W be the width of the P-type silicon carbide floating junction structure, and S be the distance between two adjacent P-type silicon carbide floating junction structures in the same layer. The above formula is based on charge balance.

[0050] This invention, by gradually increasing the thickness of a region from the center to the edge of a P-type silicon carbide floating junction structure, and combining this with the constraints on the center and edge thicknesses of the P-type silicon carbide floating junction structure based on the charge balance principle, adjusts the charge distribution at different locations of the floating junction structure. This allows for more holes at the edge of the P-type silicon carbide floating junction structure during reverse operation, leading to more complete electron depletion in the epitaxial drift region between the floating junctions. Consequently, the peak electric field in the epitaxial drift region between the floating junctions is increased to some extent. Furthermore, it reduces the peak electric field at the center of the floating junction to some extent, resulting in a more uniform longitudinal electric field distribution throughout the device.

[0051] Optionally, the width W of the P-type silicon carbide floating junction structure ranges from 1 to 5 μm.

[0052] Optionally, the distance S between two adjacent P-type silicon carbide floating junction structures in the same layer can range from 1 to 5 μm.

[0053] Optionally, the thickness of the P-type silicon carbide floating junction structure ranges from 0.3 to 3 μm.

[0054] Optionally, the doping concentration of the p-type silicon carbide floating junction structure is 1×10⁻⁶. 16 ~1×10 19 cm -3 .

[0055] Optionally, the material of the back electrode 1 is Ni, and the material of the front electrode is Ti.

[0056] Please see Figure 6 Based on the above embodiments, a specific silicon carbide power device with a gradually varying floating junction thickness is also provided. The silicon carbide power device includes a back electrode 1, an N+ silicon carbide substrate layer 2, an N- silicon carbide epitaxial layer 3, a P-type silicon carbide floating junction layer, a P+ silicon carbide surface layer, and a front electrode 6.

[0057] The N-silicon carbide epitaxial layer 3 is located on the N+ silicon carbide substrate layer 2. A single-layer P-type silicon carbide floating junction layer is formed in the vertical direction within the N-silicon carbide epitaxial layer 3. The P-type silicon carbide floating junction layer includes two P-type silicon carbide floating junction structures 4. The P+ silicon carbide surface layer is located on the topmost layer of the N-silicon carbide epitaxial layer 3. Each P-type silicon carbide surface region 5 of the P+ silicon carbide surface layer is directly opposite a P-type silicon carbide floating junction structure 4. The back electrode 1 is on the lower surface of the N+ silicon carbide substrate layer 2, and the front electrode 6 is on the N-silicon carbide epitaxial layer 3 and the P+ silicon carbide surface layer.

[0058] Among them, the P-type silicon carbide floating junction structure 4 is a symmetrical trapezoid, and the thickness of the P-type silicon carbide floating junction structure 4 gradually increases from the center to the edge; the back electrode 1 is an ohmic contact, the front electrode 6 is an ohmic contact in the region on the P-type silicon carbide surface region 5, and a Schottky contact in the region on the N-silicon carbide epitaxial layer 3; the metals used for the back electrode 1 and the front electrode 6 include Ni and Ti, respectively.

[0059] Furthermore, the N+ silicon carbide substrate layer 2 is an N-type SiC material with a thickness of 350 μm and a doping concentration of 5 × 10⁻⁶. 18 cm -3 The N-silicon carbide epitaxial layer 3 is made of N-type SiC material, with a thickness of 30 μm and a doping concentration of 7 × 10⁻⁶. 15 cm -3 The p-type silicon carbide floating junction structure 4 is made of p-type SiC material, with a width W of 3 μm, a spacing S of 3 μm, and a doping concentration of 1.5 × 10⁻⁶. 17 cm -3 The thickness T at the center of the P-type silicon carbide floating junction structure 4 min The thickness is 0.7 μm, which, combined with the formula satisfied by the thickness of the P-type silicon carbide floating junction structure, is... The thickness T at the edge position max The doping concentration is set to 1.4 μm; the P-type silicon carbide surface region 5 is made of P-type SiC material with a doping concentration of 1 × 10⁻⁶. 19 cm -3 .

[0060] To demonstrate the beneficial effects of the silicon carbide power device with gradually varying floating junction thickness provided by this invention, this invention compares the specific silicon carbide power device with gradually varying floating junction thickness provided above with a conventional silicon carbide power device. Specifically, the device structure is simulated using SILVACO Atlas software, wherein the simulated device structure parameters are set with reference to the parameters of the specific silicon carbide power device with gradually varying floating junction thickness provided above.

[0061] Specifically, with other device parameters remaining unchanged, the thickness of the traditional P-type floating junction region is set to 1.05 μm to achieve the effect that the total charge of the P-type floating junction region of the P-type silicon carbide floating junction structure 4 provided by the present invention is equal to that of the traditional silicon carbide floating junction structure.

[0062] Based on the simulation results of reverse IV characteristics, and using the location of the current inflection point as the breakdown criterion, the power device provided by this invention breaks down near 3598V, while the traditional floating junction structure device breaks down near 3339V. The electric field distribution cutoff location is as follows: Figure 6 As shown, when the comparator device breaks down, the electric field distribution at the center of the floating junction is as follows: Figure 7 As shown, by Figure 7 As can be seen, because the thickness of the P-type floating junction gradually increases from the center to the edge, the peak electric field at the electrode position at the center of the floating junction is reduced, resulting in a more uniform longitudinal electric field distribution throughout the device. This reduces the probability of breakdown due to excessively high local electric fields and improves the stability of the device during reverse operation. The electric field distribution at the edge of the floating junction is shown in the figure. Figure 8 As shown, by Figure 8 It can be seen that because the thickness of the P-type floating junction gradually increases from the center to the edge, the P-type doping concentration at the edge is relatively higher than at the center, providing more opportunities for hole-electron combination. Therefore, the depletion of the epitaxial drift region at the edge of the floating junction is more complete, resulting in a higher peak electric field at the edge, which improves the device's breakdown voltage and optimizes its performance. The electric field distribution at the center of the epitaxial drift region between the floating junctions is shown in the figure. Figure 9 As shown, by Figure 9 It can be seen that because the thickness of the P-type floating junction gradually increases from the center to the edge, the P-type doping concentration at the edge is relatively higher than at the center. This provides more opportunities for holes and electrons to combine, resulting in more complete depletion of the epitaxial drift region between the floating junctions. This raises the peak electric field of the drift region, making the overall longitudinal electric field distribution of the device more uniform, improving the breakdown voltage, and optimizing the device performance. Figure 7 , Figure 8 and Figure 9 The horizontal axis represents the longitudinal length from the top of the N-drift region 3 (bottom of the front electrode 6) to the bottom (top of the N+ substrate region).

[0063] In summary, compared with traditional silicon carbide floating junction power devices, this invention changes the thickness of the P-type silicon carbide floating junction structure 4 from a uniform overall thickness to a gradually increasing thickness from the center to the edge of the floating junction. This allows for greater hole availability at the edge of the P-type silicon carbide floating junction structure 4 during reverse operation, resulting in more electron depletion between the holes and electrons in the epitaxial drift region between the floating junction and the floating junction.

[0064] Under the condition of equal total P-type charge as in traditional floating junction structures, this invention has the following advantages: 1. Since the thickness of the P-type silicon carbide floating junction structure 4 gradually increases from the center to the edge, the peak electric field at the corresponding electrode position at the center of the floating junction is reduced, making the longitudinal electric field distribution in the floating junction region of the device more uniform, reducing the probability of breakdown due to excessively high local electric fields, and improving the stability of the device during reverse operation. 2. Since the thickness of the P-type silicon carbide floating junction structure 4 gradually increases from the center to the edge, the P-type doping amount at the edge of the floating junction is relatively higher than that at the center, providing more holes and electrons for combination. Therefore, the depletion of the epitaxial layer drift region between floating junctions and at the edge of the floating junction is more complete, which raises the peak electric field of the epitaxial layer drift region between floating junctions, improves the breakdown voltage of the device, and optimizes the device performance indicators.

[0065] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or data point described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or data points described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0067] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A silicon carbide power device with a gradually varying floating junction thickness, characterized in that, The silicon carbide power device includes: N+ silicon carbide substrate layer; An N-silicon carbide epitaxial layer is located on top of the N+ silicon carbide substrate layer; A layer of P-type silicon carbide floating junction layer, wherein the A layer of P-type silicon carbide floating junction layer is disposed vertically within the N-silicon carbide epitaxial layer, each layer of the P-type silicon carbide floating junction layer includes B P-type silicon carbide floating junction structures, wherein the P-type silicon carbide floating junction structures are symmetrical along the central axis and have a gradually changing thickness, wherein A and B are both integers greater than or equal to 1; A back electrode is located on the lower surface of the N+ silicon carbide substrate layer, and the back electrode is in ohmic contact with the N+ silicon carbide substrate layer. A front electrode, wherein the front electrode is located on the N-silicon carbide epitaxial layer, and the region of the front electrode on the N-silicon carbide epitaxial layer is a Schottky contact; The thickness of the P-type silicon carbide floating junction structure gradually increases from the center to the edge.

2. The silicon carbide power device with gradually varying floating junction thickness according to claim 1, characterized in that, The P-type silicon carbide floating junction structure includes a first floating junction structure and a second floating junction structure. The first and second floating junction structures are symmetrical along a central axis, and their thickness gradually decreases from the edge to the center. The upper surfaces of the first and second floating junction structures are parallel to the horizontal plane, and the acute angle between the lower surfaces of the first and second floating junction structures and the horizontal plane is greater than 0 degrees and less than 90 degrees. Alternatively, the acute angle between the upper surfaces of the first and second floating junction structures and the horizontal plane is greater than 0 degrees and less than 90 degrees, and the lower surfaces of the first and second floating junction structures are parallel to the horizontal plane. Or, both the acute angle between the upper and lower surfaces of the first and second floating junction structures and the horizontal plane is greater than 0 degrees and less than 90 degrees.

3. The silicon carbide power device with gradually varying floating junction thickness according to claim 2, characterized in that, The thickness of the P-type silicon carbide floating junction structure satisfies the formula: in, T max The thickness at the edge of the P-type silicon carbide floating junction structure. T min The thickness at the center of the P-type silicon carbide floating junction structure is given. W The width of the P-type silicon carbide floating junction structure is given. S The distance between two adjacent P-type silicon carbide floating junction structures in the same layer.

4. The silicon carbide power device with gradually varying floating junction thickness according to claim 3, characterized in that, The width of the P-type silicon carbide floating junction structure W The range is 1–5 μm.

5. The silicon carbide power device with gradually varying floating junction thickness according to claim 4, characterized in that, The distance between two adjacent P-type silicon carbide floating junction structures in the same layer S The range is 1–5 μm.

6. The silicon carbide power device with gradually varying floating junction thickness according to claim 4, characterized in that, The thickness of the P-type silicon carbide floating junction structure ranges from 0.3 to 3 μm.

7. The silicon carbide power device with gradually varying floating junction thickness according to claim 1, characterized in that, The doping concentration of the P-type silicon carbide floating junction structure is 1×10⁻⁶. 16 ~1×10 19 cm 3 .

8. The silicon carbide power device with gradually varying floating junction thickness according to claim 1, characterized in that, The material of the back electrode includes Ni, and the material of the front electrode includes Ti.

9. The silicon carbide power device with gradually varying floating junction thickness according to claim 1, characterized in that, Also includes: A P+ silicon carbide surface layer is disposed within the N-silicon carbide epitaxial layer. The P+ silicon carbide surface layer is located above the A-layer P-type silicon carbide floating junction layer. The upper surface of the P+ silicon carbide surface layer and the upper surface of the N-silicon carbide epitaxial layer are located on the same plane. The P+ silicon carbide surface layer includes B P-type silicon carbide surface regions. The b-th P-type silicon carbide surface region and the b-th silicon carbide floating junction structure of each layer are in the same column in the vertical direction, where 1≤b≤B. The front electrode is located on the N-silicon carbide epitaxial layer and the P+ silicon carbide surface layer, and the area of ​​the front electrode on the P+ silicon carbide surface layer is an ohmic contact.

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