Power device termination structure and method of making the same

Abstract

The application provides a power device terminal structure and a method for manufacturing the same. The power device terminal structure comprises an N-type substrate, an N-type epitaxial layer arranged on one side of the N-type substrate, a plurality of grooves arranged in the N-type epitaxial layer in sequence and at intervals from a first side to a second side along the length direction of the N-type epitaxial layer, one end of each groove being arranged at intervals from the N-type substrate, the other end of each groove extending to the side of the N-type epitaxial layer away from the N-type substrate, and a plurality of P-type epitaxial layers arranged in sequence 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 part of each P-type epitaxial layer is located in at least one of the plurality of grooves. The doping concentration of the plurality of P-type epitaxial layers gradually decreases in the direction away from the N-type substrate, thereby solving the problem of low breakdown voltage of the SIC power device in the prior art.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to a power device termination structure and a method for fabricating it. Background Technology

[0002] Currently, with the development of microelectronic devices towards low power consumption, high voltage resistance, and high reliability, the requirements for semiconductor materials are also gradually increasing. Microelectronic devices are increasingly used in special environments such as high temperature, high radiation, high frequency, and high power. To meet the application requirements of microelectronic devices in areas such as high temperature resistance and radiation resistance, it is necessary to develop new semiconductor materials to maximize the performance of microelectronic devices. Traditional silicon and gallium arsenide devices limit the improvement of device and system performance. Third-generation semiconductor materials, represented by silicon carbide (SiC) and gallium nitride (GaN), have become ideal semiconductor materials for fabricating high-temperature, high-power, and radiation-resistant electronic devices due to their wide bandgap and high critical breakdown electric field.

[0003] Currently, the critical breakdown field strength of SiC-based devices (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. SiC's bandgap and thermal conductivity are both 3 times that of Si, and its intrinsic carrier concentration is only one-tenth that of silicon. These superior physical properties give SiC semiconductor power devices significant advantages in high-frequency, high-temperature, high-power, and high-irradiation environments. SiC can form different crystal structures under different environments; the three most commonly used crystal structures are 3C-SiC, 4H-SiC, and 6H-SiC. 4H-SiC, with its high bandgap, high hole mobility, and low intrinsic carrier concentration, has become the mainstream material for manufacturing semiconductor devices.

[0004] The most important performance characteristic of power devices is high voltage blocking. Devices are designed to withstand high voltage at the PN junction, metal-semiconductor contact, and depletion layer of the MOS interface. As the applied voltage increases, the electric field strength of the depletion layer also increases, eventually exceeding the material limit and causing avalanche breakdown. The increased curvature of the electric field in the depletion region at the device edge leads to a stronger electric field than inside the die. As the voltage rises, avalanche breakdown occurs earlier at the die edge than inside. To maximize device performance, a voltage divider structure needs to be designed at the device edge to reduce the curvature of the PN junction at the edge of the active region (cell region), extending the depletion layer laterally and enhancing the horizontal withstand voltage, allowing breakdown to occur simultaneously at the device edge and inside. The cutoff ring, located between the voltage divider structure and the dicing area, is distributed on the outermost edge of the chip and is indispensable for devices with high reliability requirements and modular packaging.

[0005] Field-limiting loop (FLL) technology is one of the most commonly used voltage divider structures in existing power devices. Its fabrication process is very simple; it can be formed together with the active region without additional processing steps. The spacing between the main junction and the FLL, the junction depth, the loop width, and the number of loops all affect the breakdown voltage. If the spacing is appropriately chosen so that the electric field strengths of both the main junction and the loop junction simultaneously reach the critical breakdown field strength, the highest breakdown voltage can be obtained. Generally, the breakdown voltage increases with the number of loops, but not linearly. More loops result in a larger chip area; therefore, the number of loops and the breakdown voltage should be considered during design.

[0006] The commonly used field limiting loop structure is shown in the figure 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 implantation region, and 4' represents the N-type implantation region. 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 and resulting in a lower breakdown voltage of the SiC power device. Summary of the Invention

[0007] The main objective of this invention is to provide a power device termination structure and a method for fabricating it, so as to solve the problem of low breakdown voltage of SiC power devices in the prior art.

[0008] To achieve the above objectives, according to one aspect of the present invention, a power device termination structure is provided, comprising: an N-type substrate; an N-type epitaxial layer disposed on one side of the N-type substrate; a plurality of trenches, the plurality of trenches being sequentially and spaced apart from a first side to a second side along the length direction of the N-type epitaxial layer, one end of each trench being spaced apart from the N-type substrate, and the other end of each trench extending 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 being sequentially disposed on the side of the N-type epitaxial layer away from the N-type substrate along a direction away from the N-type substrate, and a portion of each P-type epitaxial layer being located within at least one of the plurality of trenches; wherein the doping concentration of the plurality of P-type epitaxial layers gradually decreases along the 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 provided in a one-to-one correspondence with multiple trenches. 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. The layered epitaxial portion of each P-type epitaxial layer has the same thickness.

[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 epitaxial portions; where K is any integer from 1 to A; the Hth trench is provided with H trench epitaxial portions of P-type epitaxial layers; where H is any integer from 1 to A.

[0012] Furthermore, the plurality of trenches include a first trench, a second trench, a third trench, and a fourth trench, which are sequentially spaced from a first side to a 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 along a direction away from the N-type substrate; wherein the depths of the first trench, the second trench, the third trench, and the fourth trench are equal, and the widths of the first trench, the second trench, the third trench, and the fourth trench increase sequentially.

[0013] Furthermore, the first P-type epitaxial layer includes a first layered epitaxial portion and four first trench epitaxial portions connected together. The first first trench epitaxial portion is located within a first trench, the second first trench epitaxial portion is located within a second trench, the third first trench epitaxial portion is located within a third trench, and the fourth first trench epitaxial portion is located within a fourth trench. The second, third, and fourth first trench epitaxial portions 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 together. The first second trench epitaxial portion is located within a first opening groove in the second trench, and the second second trench epitaxial portion is located within a third trench. The third P-type epitaxial layer includes a third layered epitaxial portion and two third trench epitaxial portions connected to each other. The first third trench epitaxial portion is located in the second opening groove within the third trench, and the second third trench epitaxial portion is located in the second opening groove within the fourth trench. The second third trench epitaxial portion forms a third opening groove. The fourth P-type epitaxial layer includes a fourth layered epitaxial portion and a fourth trench epitaxial portion connected to each other. The fourth trench epitaxial portion is located in the third opening groove within the fourth trench.

[0014] Furthermore, the power device termination structure also includes: a cutoff ring groove, which is disposed at the N-type epitaxial layer and multiple P-type epitaxial layers. The cutoff ring groove is located on the first side of the length direction of the N-type epitaxial layer and is spaced apart from the second side of the length direction of the N-type epitaxial layer. One end of the cutoff ring groove is spaced apart from the N-type substrate, and the other end of the cutoff ring groove extends to the side of the N-type epitaxial layer away from the N-type substrate; an N-type epitaxial region, which is filled in the cutoff 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 cutoff ring groove coincides with a portion of the multiple trenches.

[0015] Furthermore, the stop ring groove includes a first groove segment and a second groove segment connected sequentially from the first side to the second side along the length direction of the N-type epitaxial layer, wherein the depth of the first groove segment is greater than the depth of the second groove segment.

[0016] According to another aspect of the present invention, a method for fabricating a power device termination structure is provided, applicable to the aforementioned power device termination structure. The method for fabricating the power device termination structure includes: setting an N-type substrate; setting an N-type epitaxial layer on the N-type substrate; forming a plurality of trenches on the N-type epitaxial layer by dry etching; and sequentially fabricating a plurality of P-type epitaxial layers on the N-type epitaxial layer.

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

[0018] Furthermore, the method for fabricating the power device termination structure includes: forming a cutoff ring groove on an N-type epitaxial layer and multiple P-type epitaxial layers by dry etching; and fabricating an N-type epitaxial region within the cutoff ring groove.

[0019] According to 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 disposed on one side of the N-type substrate; a plurality of trenches, which are sequentially and spaced apart from a first side to a second side along the length direction of the N-type epitaxial layer, with one end of each trench spaced apart from the N-type substrate and the other end of each trench extending to the side of the N-type epitaxial layer away from the N-type substrate; a plurality of P-type epitaxial layers, which are sequentially disposed on the side of the N-type epitaxial layer away from the N-type substrate along the direction away from the N-type substrate, with a portion of each P-type epitaxial layer located within at least one of the plurality of trenches; wherein the doping concentration of the plurality of P-type epitaxial layers gradually decreases along the direction away from the N-type substrate. Thus, the power device termination structure of this invention, by setting multiple trenches on an N-type epitaxial layer and sequentially fabricating multiple P-type epitaxial layers, with the doping concentration of the P-type epitaxial layers gradually decreasing away from the N-type substrate, effectively improves the electric field distribution of the power device, reduces the breakdown voltage, and enhances the breakdown voltage performance of the power device. The stacking of P-type epitaxial layers with different doping concentrations allows for precise control of the doping concentration and thickness of each P-type epitaxial layer, ensuring that the doping concentration at the bottom of the trench is greater than that at the surface of the trench. This significantly reduces the leakage current of the power device, enhances the breakdown voltage capability of the power device termination structure, solves the problem of low breakdown voltage in existing SiC power devices, and reduces the production cost of the power device termination structure. Furthermore, the multiple P-type epitaxial layers are fabricated using a multi-stage epitaxial process, eliminating the need for high-temperature ion implantation, simplifying the fabrication process, reducing manufacturing costs, avoiding SiC structure damage caused by implantation operations, and improving the yield of the power device termination structure product. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

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

[0022] Figure 2 It shows Figure 1 A cross-sectional view of the power device terminal structure shown;

[0023] Figure 3 A schematic diagram of the first state during the fabrication process of an embodiment of the power device termination structure according to the present invention is shown;

[0024] Figure 4 It shows Figure 3 The diagram shows the second state of the power device terminal structure during the fabrication process.

[0025] Figure 5It shows Figure 4 The diagram shows the third state of the power device terminal structure during the fabrication process.

[0026] Figure 6 It shows Figure 5 The diagram shows the fourth state of the power device terminal structure during the fabrication process.

[0027] Figure 7 It shows Figure 6 The diagram shows the fifth state of the power device terminal structure during the fabrication process.

[0028] Figure 8 It shows Figure 7 The diagram shows the sixth state of the power device terminal structure during the fabrication process.

[0029] Figure 9 It shows Figure 8 The diagram shows the final state of the power device terminal structure during the fabrication process.

[0030] Figure 10 A flowchart illustrating an embodiment of a method for fabricating a power device terminal structure according to the present invention is shown.

[0031] The above figures 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. Trench; 31. First trench; 32. Second trench; 33. Third trench; 34. Fourth trench;

[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. Stop ring groove; 51. First groove section; 52. Second groove section;

[0038] 6. N-type extensional region. Detailed Implementation

[0039] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0040] like Figures 3 to 9 As shown, the present invention provides a power device termination structure, comprising: an N-type substrate 1; an N-type epitaxial layer 2 disposed on one side of the N-type substrate 1; a plurality of trenches 3, which are sequentially and spaced apart from a first side to a second side along the length direction of the N-type epitaxial layer 2, with one end of each trench 3 spaced apart from the N-type substrate 1 and the other end of each trench 3 extending to the side of the N-type epitaxial layer 2 away from the N-type substrate 1; and a plurality of P-type epitaxial layers 4, which are sequentially disposed on the side of the N-type epitaxial layer 2 away from the N-type substrate 1 along the direction away from the N-type substrate 1, with a portion of each P-type epitaxial layer 4 located within at least one of the plurality of trenches 3; wherein the doping concentration of the plurality of P-type epitaxial layers 4 gradually decreases along the direction away from the N-type substrate 1.

[0041] The power device termination structure of this invention, by setting multiple trenches on an N-type epitaxial layer and sequentially fabricating multiple P-type epitaxial layers, with the doping concentration of the P-type epitaxial layers gradually decreasing away from the N-type substrate, effectively improves the electric field distribution of the power device, reduces the breakdown voltage, and enhances the breakdown voltage performance of the power device. The stacking of P-type epitaxial layers 4 with different doping concentrations allows for precise control of the doping concentration and thickness of each P-type epitaxial layer 4, ensuring that the doping concentration at the bottom of the trench 3 is greater than that at the surface of the trench 3. This significantly reduces the leakage current of the power device, enhances the breakdown voltage capability of the power device termination structure, solves the problem of low breakdown voltage in existing SiC power devices, and reduces the production cost of the power device termination structure. Furthermore, the multiple P-type epitaxial layers 4 are fabricated using a multi-epitaxy process, eliminating the need for high-temperature ion implantation, simplifying the fabrication process, reducing manufacturing costs, avoiding SiC structure damage caused by implantation operations, and improving the yield of the power device termination structure product.

[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 trench 3 increases sequentially from the first side to the second side along the length of the N-type epitaxial layer 2, and the depth of each trench 3 is equal. This design ensures that each P-type epitaxial layer 4 is uniformly distributed in the trenches, avoiding breakdown caused by excessive local electric field, improving the withstand voltage performance of power devices, improving the efficiency and stability of power devices, reducing energy loss, and improving the overall performance of the equipment. For power conversion systems that need to operate stably in high-voltage environments, such as high-voltage frequency converters and high-power motor drives, this structural design is key to improving their reliability and efficiency.

[0044] like Figure 4 As shown, multiple P-type epitaxial layers 4 are correspondingly arranged with multiple trenches 3. Each P-type epitaxial layer 4 includes a connected layered epitaxial portion 401 and a trench epitaxial portion 402. 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 trench epitaxial portion 402 is located within at least one of the multiple trenches 3. The layered epitaxial portion 401 of each P-type epitaxial layer 4 has the same thickness. By controlling the distribution of each P-type epitaxial layer 4 in different trenches 3, the electric field distribution of the power device can be finely adjusted, improving the voltage control capability of the power device. This is suitable for precision instruments and equipment requiring precise voltage control. It not only improves the voltage control accuracy of the power device but also enhances its adaptability and stability in complex environments. For applications requiring high-precision voltage control, it can provide a more stable power output, ensuring the normal operation of the equipment and improving 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 epitaxial portions 402; where K is any integer from 1 to A; the Hth trench 3 is provided with H trench epitaxial portions 402 of P-type epitaxial layers 4; where H is any integer from 1 to A.

[0046] like Figures 3 to 9 As shown, the multiple trenches 3 include a first trench 31, a second trench 32, a third trench 33, and a fourth trench 34 arranged sequentially from the first side to the second side along 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 arranged sequentially and spaced apart along the direction away from the N-type substrate 1. The first trench 31, the second trench 32, the third trench 33, and the fourth trench 34 have the same depth, and the widths of the first trench 31, the second trench 32, the third trench 33, and the fourth trench 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, and the fourth first trench epitaxial portion 412 is located in the fourth trench 34. The second, third, and fourth first trench epitaxial portions 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 within the second trench 32, and the second second trench epitaxial portion 422 is located in the first opening groove 413 within the third trench 33. Within an opening groove 413, a third second trench extension 422 is located within the first opening groove 413 within the fourth trench 34. Both the second and third second trench extensions 422 form second opening grooves 423. The third P-type epitaxial layer 43 includes a connected third layered epitaxial portion 431 and two third trench extensions 432. The first third trench extension 432 is located within the second opening groove 423 within the third trench 33, and the second third trench extension 432 is located within the second opening groove 423 within the fourth trench 34. The second third trench extension 432 forms a third opening groove 433. The fourth P-type epitaxial layer 44 includes a connected fourth layered epitaxial portion 441 and a fourth trench extension 442. The fourth trench extension 442 is located within the third opening groove 433 within the fourth trench 34.

[0048] Specifically, the thicknesses of the second first trench epitaxial portion 412, the third first trench epitaxial portion 412, the fourth first trench epitaxial portion 412, the second second trench epitaxial portion 422, the third second trench epitaxial portion 422, the second third trench epitaxial portion 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 Figure 9As shown, the power device termination structure also includes: a stop ring groove 5, which is disposed at the N-type epitaxial layer 2 and multiple P-type epitaxial layers 4. The stop ring groove 5 is located on the first side of the length direction of the N-type epitaxial layer 2 and is spaced apart from the second side of the length direction of the N-type epitaxial layer 2. One end of the stop ring groove 5 is spaced apart from the N-type substrate 1, and the other end of the stop 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 stop 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 stop ring groove 5 coincides with a portion of the multiple trenches 3. By setting a stepped N-type epitaxial region 6 with a high doping concentration, the reliability of the power device termination structure is significantly improved compared with the conventional N-type doped implantation region, effectively avoiding edge breakdown of the power device when operating under high voltage, improving the reliability of the device, and extending its service life. This design has a significant effect on power devices that need to operate in high voltage and high current environments. It not only improves the withstand voltage and current carrying capacity of power devices, but also optimizes the terminal structure of power devices, enabling them to remain stable under extreme operating conditions, reducing the failure rate and lowering equipment maintenance costs.

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

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

[0052] The method for fabricating power device termination structures according to the present invention not only improves the performance of power devices but also optimizes their production process. This enables low-cost, large-scale production of power devices while maintaining high performance, significantly promoting the development of power electronics technology and meeting the demands of modern industrial production for high-efficiency, high-reliability, and low-cost power devices. In particular, it has broad application prospects in new energy vehicles, industrial automation, and power systems, effectively improving equipment performance and efficiency, reducing energy consumption, and lowering maintenance costs, thus possessing significant social and economic value. With the continuous advancement of power electronics technology, its application scope will further expand, making an immeasurable contribution to promoting energy transformation and enhancing industrial intelligence.

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

[0054] like Figure 10 As shown, the method for fabricating the power device termination structure includes: forming a cutoff ring groove 5 by dry etching on an N-type epitaxial layer 2 and multiple P-type epitaxial layers 4; and fabricating an N-type epitaxial region 6 within the cutoff ring groove 5.

[0055] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0056] The power device termination structure of the present invention includes: an N-type substrate 1; an N-type epitaxial layer 2 disposed on one side of the N-type substrate 1; a plurality of trenches 3, which are sequentially and spaced apart from a first side to a second side along the length direction of the N-type epitaxial layer 2, with one end of each trench 3 spaced apart from the N-type substrate 1 and the other end of each trench 3 extending to the side of the N-type epitaxial layer 2 away from the N-type substrate 1; and a plurality of P-type epitaxial layers 4, which are sequentially disposed on the side of the N-type epitaxial layer 2 away from the N-type substrate 1 along the direction away from the N-type substrate 1, with a portion of each P-type epitaxial layer 4 located within at least one of the plurality of trenches 3; wherein the doping concentration of the plurality of P-type epitaxial layers 4 gradually decreases along the direction away from the N-type substrate 1. Thus, the power device termination structure of the present invention, by setting multiple trenches on an N-type epitaxial layer and sequentially fabricating multiple P-type epitaxial layers, and by gradually decreasing the doping concentration of the P-type epitaxial layers away from the N-type substrate, can effectively improve the electric field distribution of the power device, reduce the breakdown voltage, and improve the breakdown voltage performance of the power device. The stacking of P-type epitaxial layers 4 with different doping concentrations allows for precise control of the doping concentration and thickness of each P-type epitaxial layer 4, ensuring that the doping concentration at the bottom of the trench 3 is greater than that at the surface of the trench 3. This significantly reduces the leakage current of the power device, improves the breakdown voltage capability of the power device termination structure, solves the problem of low breakdown voltage in existing SiC power devices, and reduces the production cost of the power device termination structure. Furthermore, the multiple P-type epitaxial layers 4 are fabricated using a multi-epitaxy process, eliminating the need for high-temperature ion implantation, simplifying the fabrication process, reducing manufacturing costs, avoiding damage to the SiC structure caused by implantation operations, and improving the yield of the power device termination structure product.

[0057] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0058] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0059] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

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

[0061] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this application.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A power device termination structure, characterized by, Comprise: An N-type substrate (1); An N-type epitaxial layer (2) disposed on one side of the N-type substrate (1); A plurality of trenches (3) disposed in the N-type epitaxial layer (2) in sequence along a first side to a second side of a length direction of the N-type epitaxial layer (2), one end of each of the trenches (3) is disposed away from the N-type substrate (1), the other end of each of the trenches (3) extends to the side of the N-type epitaxial layer (2) away from the N-type substrate (1); An N-type substrate (1); A plurality of P-type epitaxial layers (4) disposed in sequence 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), part of each of the P-type epitaxial layers (4) is located in at least one of the plurality of trenches (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).

2. The power device termination structure of claim 1, wherein, The width of each of the trenches (3) increases in sequence along the first side to the second side of the length direction of the N-type epitaxial layer (2), and the depth of each of the trenches (3) is equal.

3. The power device termination structure of claim 1, wherein, The plurality of P-type epitaxial layers (4) are disposed in one-to-one correspondence with the plurality of trenches (3), each of the P-type epitaxial layers (4) comprises a layered epitaxial portion (401) and a trench epitaxial portion (402) connected in sequence, 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 trench epitaxial portion (402) is located in at least one of the plurality of trenches (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 termination structure according to claim 3, wherein: 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) comprises A-K+1 trench epitaxial portions (402); wherein K is any integer in 1 to A; H trench epitaxial portions (402) of the Hth P-type epitaxial layer (4) are disposed in the Hth trench (3); wherein H is any integer in 1 to A.

5. The power device termination structure of claim 3, wherein, The plurality of trenches (3) comprise a first trench (31), a second trench (32), a third trench (33) and a fourth trench (34) disposed in sequence along a first side to a second side of a length direction of the N-type epitaxial layer (2), and the P-type epitaxial layer (4) comprises 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) disposed in sequence away from the N-type substrate (1); wherein, the depths of the first trench (31), the second trench (32), the third trench (33) and the fourth trench (34) are equal, and the widths of the first trench (31), the second trench (32), the third trench (33) and the fourth trench (34) increase in sequence.

6. The power device termination structure according to claim 5, wherein the first P-type epitaxial layer (41) comprises a first layer-shaped epitaxial portion (411) and four first trench epitaxial portions (412) connected to each other, a first one of the first trench epitaxial portions (412) is located in the first trench (31), a second one of the first trench epitaxial portions (412) is located in the second trench (32), a third one of the first trench epitaxial portions (412) is located in the third trench (33), and a fourth one of the first trench epitaxial portions (412) is located in the fourth trench (34), the second one of the first trench epitaxial portions (412), the third one of the first trench epitaxial portions (412), and the fourth one of the first trench epitaxial portions (412) form a first open recess (413); the second P-type epitaxial layer (42) comprises a second layer-shaped epitaxial portion (421) and three second trench epitaxial portions (422) connected to each other, a first one of the second trench epitaxial portions (422) is located in the first open recess (413) in the second trench (32), a second one of the second trench epitaxial portions (422) is located in the first open recess (413) in the third trench (33), and a third one of the second trench epitaxial portions (422) is located in the first open recess (413) in the fourth trench (34), the second one of the second trench epitaxial portions (422) and the third one of the second trench epitaxial portions (422) form a second open recess (423); the third P-type epitaxial layer (43) comprises a third layer-shaped epitaxial portion (431) and two third trench epitaxial portions (432) connected to each other, a first one of the third trench epitaxial portions (432) is located in the second open recess (423) in the third trench (33), and a second one of the third trench epitaxial portions (432) is located in the second open recess (423) in the fourth trench (34), the second one of the third trench epitaxial portions (432) forms a third open recess (433); the fourth P-type epitaxial layer (44) comprises a fourth layer-shaped epitaxial portion (441) and a fourth trench epitaxial portion (442) connected to each other, the fourth trench epitaxial portion (442) is located in the third open recess (433) in the fourth trench (34). The power device termination structure further comprises:

7. The power device termination structure of claim 1, wherein, a cutoff ring groove (5) disposed at the N-type epitaxial layer (2) and the plurality of P-type epitaxial layers (4), the cutoff ring groove (5) is located at a first side of the length direction of the N-type epitaxial layer (2) and is spaced apart from a second side of the length direction of the N-type epitaxial layer (2), one end of the cutoff ring groove (5) is spaced apart from the N-type substrate (1), and the other end of the cutoff ring groove (5) extends to a side of the N-type epitaxial layer (2) away from the N-type substrate (1). ​ An N-type epitaxial region (6) is filled in the cutoff 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). The cutoff ring groove (5) coincides with a part of the plurality of trenches (3) in position.

8. The power device termination structure of claim 7, wherein, The cutoff ring groove (5) includes a first groove segment (51) and a second groove segment (52) connected in sequence from a first side to a second side along the length direction of the N-type epitaxial layer (2), and the depth of the first groove segment (51) is greater than the depth of the second groove segment (52). The method for preparing the power device terminal structure of any one of claims 1 to 8 comprises:

9. A method of preparing a termination structure for a power device, characterized by, providing an N-type substrate (1); providing an N-type epitaxial layer (2) on the N-type substrate (1); forming a plurality of trenches (3) on the N-type epitaxial layer (2) by dry etching; sequentially preparing a plurality of P-type epitaxial layers (4) on the N-type epitaxial layer (2). 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 the power device terminal structure comprises:

10. The method of preparing a termination structure for a power device according to claim 9, wherein, preparing a first P-type epitaxial layer (41) on the N-type epitaxial layer (2); preparing a second P-type epitaxial layer (42) on the 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 the side of the second P-type epitaxial layer (42) away from the N-type substrate (1); preparing a fourth P-type epitaxial layer (44) on the side of the third P-type epitaxial layer (43) away from the N-type substrate (1). The method for preparing the power device terminal structure comprises:

11. The method of preparing a termination structure for a power device according to claim 9, wherein forming a cutoff ring groove (5) on the N-type epitaxial layer (2) and the plurality of P-type epitaxial layers (4) by dry etching; preparing an N-type epitaxial region (6) in the cutoff ring groove (5). ​

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