Power device terminal structure and preparation method thereof

Abstract

The invention provides a power device terminal structure and a preparation method thereof. The power device terminal structure comprises an N-type substrate; the N-type epitaxial layer is arranged on one side of the N-type substrate; the grooves are sequentially arranged on the N-type epitaxial layer at intervals from the first side to the second side in the length direction of the N-type epitaxial layer, one end of each groove and the N-type substrate are arranged at intervals, and the other end of each groove extends to the side, away from the N-type substrate, of the N-type epitaxial layer; the multiple P-type epitaxial layers are sequentially arranged on the side, away from the N-type substrate, of the N-type epitaxial layer in the direction away from the N-type substrate, and a part of each P-type epitaxial layer is located in at least one of the multiple grooves; wherein the doping concentration of the plurality of P-type epitaxial layers is gradually reduced along the direction far away from the N-type substrate, so that the problem that the breakdown voltage of the SIC power device in the prior art is relatively low is solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a power device terminal structure and a method for preparing the same. Background Art

[0002] At present, with the development of microelectronic devices towards low power consumption, high voltage resistance and high reliability, the requirements for semiconductor materials are gradually increasing. Microelectronic devices are increasingly used in special environments such as high temperature, high radiation, high frequency and high power. In order to meet the application of microelectronic devices in the fields of high temperature resistance and radiation resistance, new semiconductor materials need to be developed to maximize the performance of microelectronic devices. Traditional silicon devices and gallium arsenide devices limit the improvement of device and system performance. The third-generation semiconductor materials represented by silicon carbide (SiC) and gallium nitride (GaN) have become ideal semiconductor materials for making high temperature resistant, high power and radiation resistant electronic devices due to the advantages of the wide bandgap and high critical breakdown electric field of the materials themselves.

[0003] The critical breakdown field strength of SiC materials used in the SiC-based devices currently under study (specifically including high-temperature and power SiC devices, microwave and high-frequency SiC devices, SiC optoelectronic devices, and radiation-resistant devices) is 10 times that of Si materials, the bandgap width and thermal conductivity of SiC are both 3 times that of Si materials, and the concentration of intrinsic carriers is only one-tenth of that of silicon materials. These excellent physical properties make semiconductor power devices made of SiC materials have great advantages in high-frequency, high-temperature, high-power and high-irradiation environments. SiC can form different crystal structures under different environments. The three commonly used crystal structures are 3C-SiC, 4H-SiC, and 6H-SiC. 4H-SiC material has become the mainstream material for manufacturing semiconductor devices due to its higher bandgap width and hole mobility and lower intrinsic carrier concentration.

[0004] The most important performance of power devices is to block high voltage. The devices are designed to withstand high voltage on the depletion layer of the PN junction, metal-semiconductor contact, and MOS interface. As the applied voltage increases, the electric field strength of the depletion layer will also increase, and eventually exceed the material limit to cause avalanche breakdown. The increase in the curvature of the electric field in the depletion region at the edge of the device will cause the electric field strength to be greater than that inside the die. During the process of voltage increase, avalanche breakdown will occur earlier at the edge of the die than inside the die. In order to maximize the performance of the device, it is necessary to design a voltage divider structure at the edge of the device to reduce the curvature of the PN junction at the edge of the active area (cell area), extend the depletion layer laterally, enhance the horizontal voltage resistance, and cause the device to break down at the edge and inside at the same time. The cutoff ring is distributed at the outermost edge of the chip between the voltage divider structure and the scribe groove area, and is indispensable for devices with high reliability requirements and module packaging.

[0005] Field limiting ring technology is one of the most commonly used voltage divider structures in power devices in the prior art. Its process is very simple and can be formed by diffusion with the active area without adding process steps. The spacing between the main junction and the field limiting ring, the junction depth, the width of the ring and the number of rings will affect the size of the breakdown voltage. If the spacing is selected appropriately so that the electric field strength of the main junction and the ring junction reaches the critical breakdown field strength at the same time, the highest breakdown voltage can be obtained. In general, the breakdown voltage increases with the increase in the number of rings, but it does not increase linearly. The more rings there are, the larger the chip area occupied. The number of rings and the size of the breakdown voltage should be considered during design.

[0006] The commonly used field limiting ring structure is shown below: Figure 1 and Figure 2 As shown: 1' represents the SIC wafer, 2' represents the N-type epitaxial layer, 3' represents the P-type injection area, and 4' represents the N-type injection area. The disadvantage of this structure is that the interface charge of the surface oxide layer will have a great influence on the surface potential of the device, affecting the voltage division effect, resulting in a lower breakdown voltage of the SIC power device. Summary of the invention

[0007] The main purpose of the present invention is to provide a power device terminal structure and a method for preparing the same, so as to solve the problem of low breakdown voltage of SIC power devices in the prior art.

[0008] To achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided a power device terminal structure, comprising: an N-type substrate; an N-type epitaxial layer, the N-type epitaxial layer being arranged on one side of the N-type substrate; a plurality of grooves, the plurality of grooves being arranged in sequence from the first side to the second side in the length direction of the N-type epitaxial layer, one end of each groove being arranged in sequence from the N-type substrate, and the other end of each groove extending to a side of the N-type epitaxial layer away from the N-type substrate; a plurality of P-type epitaxial layers, the plurality of P-type epitaxial layers being arranged in sequence on a side of the N-type epitaxial layer away from the N-type substrate in a direction away from the N-type substrate, and a portion of each P-type epitaxial layer being located in at least one of the plurality of grooves; wherein the doping concentration of the plurality of P-type epitaxial layers gradually decreases in a direction away from the N-type substrate.

[0009] Furthermore, the width of each trench increases sequentially from the first side to the second side along the length direction of the N-type epitaxial layer, and the depth of each trench is equal.

[0010] Furthermore, multiple P-type epitaxial layers are arranged in one-to-one correspondence with multiple grooves, and each P-type epitaxial layer includes a connected layered epitaxial portion and a trench epitaxial portion, the layered epitaxial portion is located on the side of the N-type epitaxial layer away from the N-type substrate, and the trench epitaxial portion is located in at least one of the multiple trenches; wherein the thickness of the layered epitaxial portion of each P-type epitaxial layer is equal.

[0011] Furthermore, the number of trenches is A, and the number of P-type epitaxial layers is also A; the Kth P-type epitaxial layer includes A-K+1 trench extension parts; wherein K is any integer from 1 to A; the Hth trench is provided with trench extension parts of H P-type epitaxial layers; wherein H is any integer from 1 to A.

[0012] Further, the plurality of grooves include a first groove, a second groove, a third groove and a fourth groove which are sequentially spaced apart from the first side to the second side along the length direction of the N-type epitaxial layer, and the P-type epitaxial layer includes a first P-type epitaxial layer, a second P-type epitaxial layer, a third P-type epitaxial layer and a fourth P-type epitaxial layer which are sequentially spaced apart in a direction away from the N-type substrate; wherein the depths of the first groove, the second groove, the third groove and the fourth groove are equal, and the widths of the first groove, the second groove, the third groove and the fourth groove increase sequentially.

[0013] Further, the first P-type epitaxial layer includes a first layered epitaxial portion and four first trench epitaxial portions connected to each other, the first first trench epitaxial portion is located in the first trench, the second first trench epitaxial portion is located in the second trench, the third first trench epitaxial portion is located in the third trench, the fourth first trench epitaxial portion is located in the fourth trench, the second first trench epitaxial portion, the third first trench epitaxial portion and the fourth first trench epitaxial portion all form a first opening groove; the second P-type epitaxial layer includes a second layered epitaxial portion and three second trench epitaxial portions connected to each other, the first second trench epitaxial portion is located in the first opening groove in the second trench, the second second trench epitaxial portion is located in the third trench The third second trench extension is located in the first opening groove in the fourth trench, and the second second trench extension and the third second trench extension both form a second opening groove; the third P-type epitaxial layer includes a third layered extension and two third trench extensions connected to each other, the first third trench extension is located in the second opening groove in the third trench, the second third trench extension is located in the second opening groove in the fourth trench, and the second third trench extension forms a third opening groove; the fourth P-type epitaxial layer includes a fourth layered extension and a fourth trench extension, and the fourth trench extension is located in the third opening groove in the fourth trench.

[0014] Furthermore, the power device terminal structure also includes: a cut-off ring groove, which is arranged at the N-type epitaxial layer and multiple P-type epitaxial layers, the cut-off ring groove is located on the first side of the length direction of the N-type epitaxial layer and is spaced from the second side of the length direction of the N-type epitaxial layer, one end of the cut-off ring groove is spaced from the N-type substrate, and the other end of the cut-off ring groove extends to a side of the N-type epitaxial layer away from the N-type substrate; an N-type epitaxial region, the N-type epitaxial region is filled in the cut-off ring groove, and the doping concentration of the N-type epitaxial region is greater than the doping concentration of the N-type epitaxial layer; wherein the cut-off ring groove overlaps with a portion of the multiple grooves.

[0015] Further, the cut-off ring groove includes a first groove section and a second groove section sequentially connected from the first side to the second side along the length direction of the N-type epitaxial layer, and the depth of the first groove section is greater than the depth of the second groove section.

[0016] According to another aspect of the present invention, a method for preparing a power device terminal structure is provided, which is applicable to the above-mentioned power device terminal structure. The method for preparing the power device terminal structure includes: providing an N-type substrate; providing an N-type epitaxial layer on the N-type substrate; forming a plurality of grooves on the N-type epitaxial layer by dry etching; and sequentially preparing a plurality of P-type epitaxial layers on the N-type epitaxial layer.

[0017] Furthermore, in the step of sequentially forming a plurality of N-type epitaxial layers on the N-type epitaxial layer, the method for preparing a power device terminal structure includes: preparing a first P-type epitaxial layer on the N-type epitaxial layer; preparing a second P-type epitaxial layer on a side of the first P-type epitaxial layer away from the N-type substrate; preparing a third P-type epitaxial layer on a side of the second P-type epitaxial layer away from the N-type substrate; and preparing a fourth P-type epitaxial layer on a side of the third P-type epitaxial layer away from the N-type substrate.

[0018] Furthermore, the method for preparing the power device terminal structure includes: forming a cut-off ring groove on an N-type epitaxial layer and a plurality of P-type epitaxial layers by dry etching; and preparing an N-type epitaxial region in the cut-off ring groove.

[0019] By applying the technical solution of the present invention, the power device terminal structure of the present invention includes: an N-type substrate; an N-type epitaxial layer, the N-type epitaxial layer is arranged on one side of the N-type substrate; a plurality of grooves, the plurality of grooves are sequentially arranged in intervals on the N-type epitaxial layer from the first side to the second side in the length direction of the N-type epitaxial layer, one end of each groove is spaced from the N-type substrate, and the other end of each groove extends to the side of the N-type epitaxial layer away from the N-type substrate; a plurality of P-type epitaxial layers, the plurality of P-type epitaxial layers are sequentially arranged on the side of the N-type epitaxial layer away from the N-type substrate in a direction away from the N-type substrate, and a portion of each P-type epitaxial layer is located in at least one of the plurality of grooves; wherein the doping concentration of the plurality of P-type epitaxial layers gradually decreases in a direction away from the N-type substrate. In this way, the power device terminal structure of the present invention can effectively improve the electric field distribution of the power device, reduce the breakdown voltage, and improve the withstand voltage performance of the power device by setting multiple grooves on the N-type epitaxial layer and preparing multiple P-type epitaxial layers in sequence, and gradually reducing the doping concentration of the P-type epitaxial layer in the direction away from the N-type substrate. The superposition of P-type epitaxial layers with different doping concentrations can accurately control the doping concentration and thickness of each P-type epitaxial layer, so that the doping concentration at the bottom of the groove is greater than the doping concentration on the surface of the groove, greatly reducing the leakage current of the power device, improving the withstand voltage capability of the power device terminal structure, solving the problem of low breakdown voltage of SIC power devices in the prior art, and reducing the production cost of the power device terminal structure. In addition, multiple P-type epitaxial layers adopt a multiple epitaxial process, and do not need high-temperature ion implantation, which simplifies the production process, reduces the production cost, avoids the damage of the SIC structure caused by the implantation operation, and improves the product yield of the power device terminal structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0021] Figure 1 A top view of a power device terminal structure in the prior art is shown;

[0022] Figure 2 Shows Figure 1 A cross-sectional view of a power device terminal structure shown;

[0023] Figure 3 A schematic diagram showing a first state of an embodiment of a power device terminal structure according to the present invention during preparation;

[0024] Figure 4 Shows Figure 3 A schematic diagram of a second state of a power device terminal structure during the preparation process shown;

[0025] Figure 5Shows Figure 4 A schematic diagram of a third state of a power device terminal structure during the preparation process is shown;

[0026] Figure 6 Shows Figure 5 A schematic diagram of a fourth state of a power device terminal structure during preparation is shown;

[0027] Figure 7 Shows Figure 6 A schematic diagram of a fifth state of a power device terminal structure during the preparation process is shown;

[0028] Figure 8 Shows Figure 7 A schematic diagram of a sixth state of the power device terminal structure during the preparation process shown;

[0029] Fig. 9 Shows Figure 8 The final state schematic diagram of the power device terminal structure during the preparation process is shown;

[0030] Fig.10 A flow chart of an embodiment of a method for preparing a power device terminal structure according to the present invention is shown.

[0031] The above drawings include the following reference numerals:

[0032] 1', SIC wafer; 2', N-type epitaxial layer; 3', P-type implantation region; 4', N-type implantation region;

[0033] 1. N-type substrate;

[0034] 2. N-type epitaxial layer;

[0035] 3. Groove; 31. First groove; 32. Second groove; 33. Third groove; 34. Fourth groove;

[0036] 4, P-type epitaxial layer; 401, layered epitaxial portion; 402, trench epitaxial portion; 41, first P-type epitaxial layer; 411, first layered epitaxial portion; 412, first trench epitaxial portion; 413, first opening groove; 42, second P-type epitaxial layer; 421, second layered epitaxial portion; 422, second trench epitaxial portion; 423, second opening groove; 43, third P-type epitaxial layer; 431, third layered epitaxial portion; 432, third trench epitaxial portion; 433, third opening groove; 44, fourth P-type epitaxial layer; 441, fourth layered epitaxial portion; 442, fourth trench epitaxial portion;

[0037] 5. Cut-off ring groove; 51. First groove section; 52. Second groove section;

[0038] 6. N-type epitaxial region. DETAILED DESCRIPTION

[0039] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0040] like Figures 3 to 9 As shown, the present invention provides a power device terminal structure, including: an N-type substrate 1; an N-type epitaxial layer 2, the N-type epitaxial layer 2 is arranged on one side of the N-type substrate 1; a plurality of grooves 3, the plurality of grooves 3 are sequentially arranged in the N-type epitaxial layer 2 from the first side to the second side in the length direction of the N-type epitaxial layer 2, one end of each groove 3 is spaced from the N-type substrate 1, and the other end of each groove 3 extends to the side of the N-type epitaxial layer 2 away from the N-type substrate 1; a plurality of P-type epitaxial layers 4, the plurality of P-type epitaxial layers 4 are sequentially arranged on the side of the N-type epitaxial layer 2 away from the N-type substrate 1 in a direction away from the N-type substrate 1, and a portion of each P-type epitaxial layer 4 is located in at least one of the plurality of grooves 3; wherein the doping concentration of the plurality of P-type epitaxial layers 4 gradually decreases in the direction away from the N-type substrate 1.

[0041] The power device terminal structure of the present invention is provided with multiple grooves on the N-type epitaxial layer, and multiple P-type epitaxial layers are prepared in sequence, and the doping concentration of the P-type epitaxial layer is gradually reduced in the direction away from the N-type substrate, which can effectively improve the electric field distribution of the power device, reduce the breakdown voltage, and improve the withstand voltage performance of the power device. The superposition of the P-type epitaxial layer 4 with different doping concentrations can accurately control the doping concentration and thickness of each P-type epitaxial layer 4, so that the doping concentration at the bottom of the groove 3 is greater than the doping concentration on the surface of the groove 3, greatly reducing the leakage current of the power device, improving the withstand voltage capability of the power device terminal structure, solving the problem of low breakdown voltage of the SIC power device in the prior art, and reducing the production cost of the power device terminal structure. In addition, the multiple P-type epitaxial layers 4 adopt a multiple epitaxial process, and do not need to perform high-temperature ion implantation, which simplifies the production process, reduces the production cost, avoids the damage of the SIC structure caused by the implantation operation, and improves the product yield of the power device terminal structure.

[0042] Specifically, the N-type substrate 1 is an N-type silicon carbide substrate, and the N-type epitaxial layer 2 is an N-type silicon carbide epitaxial layer.

[0043] like Figure 3As shown, the width of each groove 3 increases from the first side to the second side along the length direction of the N-type epitaxial layer 2, and the depth of each groove 3 is equal. This design can ensure that each P-type epitaxial layer 4 is evenly distributed in the groove, avoid breakdown caused by excessive local electric field, improve the withstand voltage performance of power devices, improve the efficiency and stability of power devices, reduce energy loss, and improve the overall performance of the equipment. For power conversion systems that need to work stably in a high voltage environment, such as high-voltage inverters, high-power motor drives, etc., this structural design is the key to improving their reliability and efficiency.

[0044] like Figure 4 As shown, multiple P-type epitaxial layers 4 are arranged in one-to-one correspondence with multiple grooves 3, and each P-type epitaxial layer 4 includes a layered epitaxial portion 401 and a groove epitaxial portion 402 connected to each other, the layered epitaxial portion 401 is located on the side of the N-type epitaxial layer 2 away from the N-type substrate 1, and the groove epitaxial portion 402 is located in at least one of the multiple grooves 3; wherein, the layered epitaxial portion 401 of each P-type epitaxial layer 4 has an equal thickness. By controlling the distribution of each P-type epitaxial layer 4 in different grooves 3, the fine adjustment of the electric field distribution of the power device can be achieved, and the voltage control capability of the power device can be improved. It is suitable for precision instruments and equipment that require precise voltage control, which not only improves the voltage control accuracy of the power device, but also enhances its adaptability and stability in complex environments. For occasions that require high-precision voltage control, it can provide more stable power output, ensure the normal operation of the equipment, and improve safety and reliability.

[0045] Specifically, the number of trenches 3 is A, and the number of P-type epitaxial layers 4 is also A; the Kth P-type epitaxial layer 4 includes A-K+1 trench extension portions 402; wherein K is any integer from 1 to A; the Hth trench 3 is provided with H trench extension portions 402 of the P-type epitaxial layer 4; wherein H is any integer from 1 to A.

[0046] like Figures 3 to 9 As shown, the plurality of grooves 3 include a first groove 31, a second groove 32, a third groove 33 and a fourth groove 34 which are sequentially spaced from the first side to the second side in the length direction of the N-type epitaxial layer 2, and the P-type epitaxial layer 4 includes a first P-type epitaxial layer 41, a second P-type epitaxial layer 42, a third P-type epitaxial layer 43 and a fourth P-type epitaxial layer 44 which are sequentially spaced in the direction away from the N-type substrate 1; wherein the depths of the first groove 31, the second groove 32, the third groove 33 and the fourth groove 34 are equal, and the widths of the first groove 31, the second groove 32, the third groove 33 and the fourth groove 34 increase sequentially.

[0047] like Figures 3 to 9As shown, the first P-type epitaxial layer 41 includes a first layered epitaxial portion 411 and four first trench epitaxial portions 412 connected to each other, the first first trench epitaxial portion 412 is located in the first trench 31, the second first trench epitaxial portion 412 is located in the second trench 32, the third first trench epitaxial portion 412 is located in the third trench 33, the fourth first trench epitaxial portion 412 is located in the fourth trench 34, the second first trench epitaxial portion 412, the third first trench epitaxial portion 412 and the fourth first trench epitaxial portion 412 all form a first opening groove 413; the second P-type epitaxial layer 42 includes a second layered epitaxial portion 421 and three second trench epitaxial portions 422 connected to each other, the first second trench epitaxial portion 422 is located in the first opening groove 413 in the second trench 32, the second second trench epitaxial portion 422 is located in the third opening groove 413 in the third trench 33, In an opening groove 413, the third second trench extension portion 422 is located in the first opening groove 413 in the fourth groove 34, and the second second trench extension portion 422 and the third second trench extension portion 422 both form a second opening groove 423; the third P-type epitaxial layer 43 includes a third layered extension portion 431 and two third trench extension portions 432 connected to each other, the first third trench extension portion 432 is located in the second opening groove 423 in the third groove 33, the second third trench extension portion 432 is located in the second opening groove 423 in the fourth groove 34, and the second third trench extension portion 432 forms a third opening groove 433; the fourth P-type epitaxial layer 44 includes a fourth layered extension portion 441 and a fourth trench extension portion 442 connected to each other, and the fourth trench extension portion 442 is located in the third opening groove 433 in the fourth groove 34.

[0048] Specifically, the thicknesses of the second first trench extension 412, the third first trench extension 412, the fourth first trench extension 412, the second second trench extension 422, the third second trench extension 422, the second third trench extension 432, the first layered epitaxial portion 411, the second layered epitaxial portion 421, the third layered epitaxial portion 431 and the fourth P-type epitaxial layer 44 are all equal.

[0049] like Figure 8 and Fig. 9As shown, the terminal structure of the power device also includes: a cut-off ring groove 5, which is arranged at the N-type epitaxial layer 2 and the plurality of P-type epitaxial layers 4, and the cut-off ring groove 5 is located at the first side of the length direction of the N-type epitaxial layer 2 and is spaced from the second side of the length direction of the N-type epitaxial layer 2, one end of the cut-off ring groove 5 is spaced from the N-type substrate 1, and the other end of the cut-off ring groove 5 extends to the side of the N-type epitaxial layer 2 away from the N-type substrate 1; an N-type epitaxial region 6, which is filled in the cut-off ring groove 5, and the doping concentration of the N-type epitaxial region 6 is greater than the doping concentration of the N-type epitaxial layer 2; wherein the cut-off ring groove 5 overlaps with a portion of the plurality of grooves 3. In this way, by setting the stepped N-type epitaxial region 6 with a high doping concentration, the reliability of the terminal structure of the power device is significantly improved compared with the conventional N-type doping injection region, and the edge breakdown of the power device when working under high voltage is effectively avoided, the reliability of the device is improved, and its service life is extended. This design has a significant implementation effect on power devices that need to work in high voltage and high current environments. It not only improves the voltage resistance and current carrying capacity of the power devices, but also optimizes the terminal structure of the power devices, allowing the power devices to remain stable under extreme working conditions, reducing the failure rate and reducing equipment maintenance costs.

[0050] like Figure 8 As shown, the cut-off ring groove 5 includes a first groove section 51 and a second groove section 52 sequentially connected from the first side to the second side along the length direction of the N-type epitaxial layer 2 , and the depth of the first groove section 51 is greater than the depth of the second groove section 52 .

[0051] like Fig.10 As shown, the present invention also provides a method for preparing a power device terminal structure, which is applicable to the above-mentioned power device terminal structure. The method for preparing a power device terminal structure includes: providing an N-type substrate 1; providing an N-type epitaxial layer 2 on the N-type substrate 1; forming a plurality of grooves 3 on the N-type epitaxial layer 2 by dry etching; and sequentially preparing a plurality of P-type epitaxial layers 4 on the N-type epitaxial layer 2.

[0052] The power device terminal structure prepared by the method for preparing the power device terminal structure of the present invention not only improves the performance of the power device, but also optimizes its production process, so that the power device can achieve low-cost and large-scale production while ensuring high performance, which greatly promotes the development of power electronics technology and meets the needs of modern industrial production for high-efficiency, high-reliability, and low-cost power devices. In particular, it has broad application prospects in the fields of new energy vehicles, industrial automation, power systems, etc., can effectively improve the performance and efficiency of equipment, reduce energy consumption, and reduce maintenance costs, and has important social and economic value. With the continuous advancement of power electronics technology, its scope of application will be further expanded, which will make an immeasurable contribution to promoting energy transformation and improving the level of industrial intelligence.

[0053] Specifically, in the step of sequentially forming a plurality of N-type epitaxial layers 2 on the N-type epitaxial layer 2, the method for preparing a power device terminal structure includes: preparing a first P-type epitaxial layer 41 on the N-type epitaxial layer 2; preparing a second P-type epitaxial layer 42 on a side of the first P-type epitaxial layer 41 away from the N-type substrate 1; preparing a third P-type epitaxial layer 43 on a side of the second P-type epitaxial layer 42 away from the N-type substrate 1; and preparing a fourth P-type epitaxial layer 44 on a side of the third P-type epitaxial layer 43 away from the N-type substrate 1.

[0054] like Fig.10 As shown, the method for preparing the terminal structure of a power device includes: forming a cut-off ring groove 5 on an N-type epitaxial layer 2 and a plurality of P-type epitaxial layers 4 by dry etching; and preparing an N-type epitaxial region 6 in the cut-off ring groove 5 .

[0055] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0056] The power device terminal structure of the present invention comprises: an N-type substrate 1; an N-type epitaxial layer 2, which is arranged on one side of the N-type substrate 1; a plurality of grooves 3, which are sequentially arranged in the N-type epitaxial layer 2 from the first side to the second side in the length direction of the N-type epitaxial layer 2, one end of each groove 3 is spaced from the N-type substrate 1, and the other end of each groove 3 extends to the side of the N-type epitaxial layer 2 away from the N-type substrate 1; a plurality of P-type epitaxial layers 4, which are sequentially arranged on the side of the N-type epitaxial layer 2 away from the N-type substrate 1 in a direction away from the N-type substrate 1, and a portion of each P-type epitaxial layer 4 is located in at least one of the plurality of grooves 3; wherein the doping concentration of the plurality of P-type epitaxial layers 4 gradually decreases in the direction away from the N-type substrate 1. In this way, the power device terminal structure of the present invention can effectively improve the electric field distribution of the power device, reduce the breakdown voltage, and improve the withstand voltage performance of the power device by setting multiple grooves on the N-type epitaxial layer and preparing multiple P-type epitaxial layers in sequence, and gradually reducing the doping concentration of the P-type epitaxial layer in the direction away from the N-type substrate. The superposition of P-type epitaxial layers 4 with different doping concentrations can accurately control the doping concentration and thickness of each P-type epitaxial layer 4, so that the doping concentration at the bottom of the groove 3 is greater than the doping concentration on the surface of the groove 3, greatly reducing the leakage current of the power device, improving the withstand voltage capability of the power device terminal structure, solving the problem of low breakdown voltage of SIC power devices in the prior art, and reducing the production cost of the power device terminal structure. In addition, multiple P-type epitaxial layers 4 adopt a multiple epitaxial process, do not need high-temperature ion implantation, simplify the production process, reduce the production cost, avoid the SIC structure damage caused by the implantation operation, and improve the product yield of the power device terminal structure.

[0057] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0058] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0059] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0060] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0061] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A power device terminal structure, characterized in that: include: N-type substrate (1); An N-type epitaxial layer (2), the N-type epitaxial layer (2) being arranged on one side of the N-type substrate (1); A plurality of grooves (3), wherein the plurality of grooves (3) are sequentially arranged in intervals on the N-type epitaxial layer (2) from a first side to a second side in a length direction of the N-type epitaxial layer (2), one end of each of the grooves (3) is arranged in intervals with the N-type substrate (1), and the other end of each of the grooves (3) extends to a portion of the N-type epitaxial layer (2) away from the N-type substrate (1). One side of an N-type substrate (1); a plurality of P-type epitaxial layers (4), the plurality of P-type epitaxial layers (4) being sequentially arranged on a side of the N-type epitaxial layer (2) away from the N-type substrate (1) in a direction away from the N-type substrate (1), and a portion of each of the P-type epitaxial layers (4) being located in at least one of the plurality of grooves (3); The doping concentration of the plurality of P-type epitaxial layers (4) gradually decreases in a direction away from the N-type substrate (1).

2. The power device terminal structure according to claim 1, characterized in that: The width of each of the grooves (3) increases sequentially from the first side to the second side along the length direction of the N-type epitaxial layer (2), and the depth of each of the grooves (3) is equal.

3. The power device terminal structure according to claim 1, characterized in that: The plurality of P-type epitaxial layers (4) are arranged in one-to-one correspondence with the plurality of grooves (3), and each of the P-type epitaxial layers (4) comprises a layered epitaxial portion (401) and a groove epitaxial portion (402) connected to each other, the layered epitaxial portion (401) being located on a side of the N-type epitaxial layer (2) away from the N-type substrate (1), and the groove epitaxial portion (402) being located in at least one of the plurality of grooves (3); wherein the thickness of the layered epitaxial portion (401) of each of the P-type epitaxial layers (4) is equal.

4. The power device terminal structure according to claim 3, characterized in that: The number of the trenches (3) is A, and the number of the P-type epitaxial layers (4) is also A; The Kth P-type epitaxial layer (4) includes A-K+1 trench epitaxial parts (402); wherein K is any integer from 1 to A; The Hth trench (3) is provided with H trench extension parts (402) of the P-type epitaxial layer (4); wherein H is any integer from 1 to A.

5. The power device terminal structure according to claim 3, characterized in that: The plurality of grooves (3) include a first groove (31), a second groove (32), a third groove (33) and a fourth groove (34) which are sequentially arranged from the first side to the second side in the length direction of the N-type epitaxial layer (2); the P-type epitaxial layer (4) includes a first P-type epitaxial layer (41), a second P-type epitaxial layer (42), a third P-type epitaxial layer (43) and a fourth P-type epitaxial layer (44) which are sequentially arranged in a direction away from the N-type substrate (1); wherein the depths of the first groove (31), the second groove (32), the third groove (33) and the fourth groove (34) are equal, and the widths of the first groove (31), the second groove (32), the third groove (33) and the fourth groove (34) increase sequentially.

6. The power device terminal structure according to claim 5, characterized in that: The first P-type epitaxial layer (41) comprises a first layered epitaxial portion (411) and four first trench epitaxial portions (412) connected to each other, the first first trench epitaxial portion (412) being located in the first trench (31), the second first trench epitaxial portion (412) being located in the second trench (32), the third first trench epitaxial portion (412) being located in the third trench (33), the fourth first trench epitaxial portion (412) being located in the fourth trench (34), and the second first trench epitaxial portion (412), the third first trench epitaxial portion (412) and the fourth first trench epitaxial portion (412) all forming a first opening groove (413); The second P-type epitaxial layer (42) comprises a second layered epitaxial portion (421) and three second trench epitaxial portions (422) connected to each other, wherein the first second trench epitaxial portion (422) is located in the first opening groove (413) in the second trench (32), the second second trench epitaxial portion (422) is located in the first opening groove (413) in the third trench (33), the third second trench epitaxial portion (422) is located in the first opening groove (413) in the fourth trench (34), and the second second trench epitaxial portion (422) and the third second trench epitaxial portion (422) both form a second opening groove (423); The third P-type epitaxial layer (43) comprises a third layered epitaxial portion (431) and two third trench epitaxial portions (432) connected to each other, the first third trench epitaxial portion (432) being located in the second opening groove (423) in the third trench (33), the second third trench epitaxial portion (432) being located in the second opening groove (423) in the fourth trench (34), and the second third trench epitaxial portion (432) forming a third opening groove (433); The fourth P-type epitaxial layer (44) comprises a fourth layered epitaxial portion (441) and a fourth trench epitaxial portion (442) connected to each other, and the fourth trench epitaxial portion (442) is located in the third opening groove (433) in the fourth trench (34).

7. The power device terminal structure according to claim 1, characterized in that: The power device terminal structure also includes: a cut-off ring groove (5), the cut-off ring groove (5) being arranged at the N-type epitaxial layer (2) and the plurality of P-type epitaxial layers (4), the cut-off ring groove (5) being located at a first side in the length direction of the N-type epitaxial layer (2) and being spaced apart from a second side in the length direction of the N-type epitaxial layer (2), one end of the cut-off ring groove (5) being spaced apart from the N-type substrate (1), and the other end of the cut-off ring groove (5) extending to a side of the N-type epitaxial layer (2) away from the N-type substrate (1); An N-type epitaxial region (6), the N-type epitaxial region (6) being filled in the cut-off ring groove (5), and the doping concentration of the N-type epitaxial region (6) being greater than the doping concentration of the N-type epitaxial layer (2); Wherein, the stop ring groove (5) overlaps with a portion of the plurality of grooves (3).

8. The power device terminal structure according to claim 7, characterized in that: The cut-off ring groove (5) includes a A first slot segment (51) and a second slot segment (52) are sequentially connected from the first side to the second side in the length direction of the N-type epitaxial layer (2), wherein the depth of the first slot segment (51) is greater than the depth of the second slot segment (52).

9. A method for preparing a power device terminal structure, characterized in that: The power device terminal structure according to any one of claims 1 to 8, wherein the method for preparing the power device terminal structure comprises: Providing an N-type substrate (1); Providing an N-type epitaxial layer (2) on the N-type substrate (1); Forming a plurality of grooves (3) on the N-type epitaxial layer (2) by dry etching; A plurality of P-type epitaxial layers (4) are sequentially prepared on the N-type epitaxial layer (2).

10. The method for preparing a power device terminal structure according to claim 9, characterized in that: In the step of sequentially forming a plurality of N-type epitaxial layers (2) on the N-type epitaxial layer (2), the method for preparing a power device terminal structure comprises: Preparing a first P-type epitaxial layer (41) on the N-type epitaxial layer (2); Preparing a second P-type epitaxial layer (42) on a side of the first P-type epitaxial layer (41) away from the N-type substrate (1); Preparing a third P-type epitaxial layer (43) on a side of the second P-type epitaxial layer (42) away from the N-type substrate (1); A fourth P-type epitaxial layer (44) is prepared on a side of the third P-type epitaxial layer (43) away from the N-type substrate (1).

11. The method for preparing a power device terminal structure according to claim 9, characterized in that: The method for preparing a power device terminal structure comprises: Forming a cut-off ring groove (5) on the N-type epitaxial layer (2) and the plurality of P-type epitaxial layers (4) by dry etching; An N-type epitaxial region (6) is prepared in the cut-off ring groove (5).

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