Silicon carbide power device of a concentration-graded epitaxial layer structure

Abstract

The application discloses a silicon carbide power device with a concentration-graded epitaxial layer structure, which comprises an N-type substrate for forming an active region and a terminal region, a Schottky contact anode layer, an ohmic contact cathode layer, an epitaxial layer, an oxide layer, a surface terminal layer and a P-type doped layer; the terminal region is located at the periphery of the active region; the ohmic contact cathode layer is arranged below the N-type substrate, and the epitaxial layer is arranged above the N-type substrate; the surface terminal layer is arranged at the inner top end of the epitaxial layer, the Schottky contact anode layer and the oxide layer are both arranged above the epitaxial layer, and the oxide layer is arranged on both sides of the Schottky contact anode layer; the P-type doped layer is arranged at the inner top end of the first epitaxial layer part corresponding to the active region; wherein the N-type concentration in the epitaxial layer gradually decreases from the first epitaxial layer part to the second epitaxial layer part corresponding to the terminal region. The application can improve the avalanche resistance of the device.

Description

Technical Field

[0001] This invention belongs to the field of microelectronics technology, specifically relating to a silicon carbide power device with a concentration-gradient epitaxial layer structure. Background Technology

[0002] To further improve the performance of 4H-SiC power devices, termination structures, represented by JTE and FLR, are applied in related power devices. Diodes typically consist of a large-area active region and an outer termination structure. A termination structure involves adding one or more P+ doped regions to the termination region of a traditional 4H-SiC power device. These P+ regions are distributed sequentially outward from the top of the epitaxial layer. When a reverse voltage is applied to the device, the depletion layer extends outward and downward due to the termination structure. The subsequent P+ regions suppress the peak electric field generated at the bottom of the previous regions, causing the depletion layer to continuously extend outward, thereby increasing the reverse breakdown voltage of the device.

[0003] Although 4H-SiC power devices inherently possess some avalanche resistance, selecting a more stable device structure remains crucial for better robustness under avalanche stress conditions. The inclusion of a termination structure in traditional device structures necessitates a comprehensive consideration of the impact of various factors, including the epitaxial layer structure, the termination region structure, and the ion implantation dose, on device performance during the design process, resulting in relative complexity. Therefore, structural optimization studies are required to ensure the optimal performance of the termination structure.

[0004] To address this, several design solutions already exist in related technologies. For example, one or more P+ doped regions are added to the termination region of a traditional 4H-SiC power device, arranged sequentially from the top of the epitaxial layer outwards, achieving P+ doping in both the active and termination regions simultaneously through ion implantation. However, in this approach, when the 4H-SiC power device experiences avalanche stress, a large amount of avalanche current is conducted through the termination region, resulting in a high peak electric field in the termination region and making it prone to premature avalanche breakdown. Summary of the Invention

[0005] To address the aforementioned problems in related technologies, this invention provides a silicon carbide power device with a concentration-gradient epitaxial layer structure. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] The present invention provides a silicon carbide power device with a concentration gradient epitaxial layer structure, comprising: an N-type substrate (1), a Schottky contact anode layer (2), an ohmic contact cathode layer (3), an epitaxial layer (4), an oxide layer (5), a surface termination layer (6), and a P-type doped layer (7);

[0007] The N-type substrate (1), the Schottky contact anode layer (2), the ohmic contact cathode layer (3), the epitaxial layer (4), the oxide layer (5), and the surface terminal layer (6) are used to form an active region and a terminal region, wherein the terminal region is located outside the active region;

[0008] The ohmic contact cathode layer (3) is disposed below the N-type substrate (1), and the epitaxial layer (4) is disposed above the N-type substrate (1);

[0009] The surface terminal layer (6) is disposed at the inner top of the epitaxial layer (4), the Schottky contact anode layer (2) and the oxide layer (5) are both disposed above the epitaxial layer (4), and the oxide layer (5) is disposed on both sides of the Schottky contact anode layer (2);

[0010] The P-type doped layer (7) is disposed at the top of the inner part of the first epitaxial layer portion (41) corresponding to the active region;

[0011] The N-type concentration in the epitaxial layer (3) gradually decreases from the first epitaxial layer portion (41) to the second epitaxial layer portion (42) corresponding to the terminal region.

[0012] The present invention has the following beneficial technical effects:

[0013] By placing the ohmic contact cathode layer below the N-type substrate, the epitaxial layer above the N-type substrate, the surface termination layer at the inner top of the epitaxial layer, the Schottky contact anode layer and the oxide layer both above the epitaxial layer with the oxide layer on both sides of the Schottky contact anode layer, and the P-type doped layer at the inner top of the first epitaxial layer portion corresponding to the active region; and by gradually decreasing the N-type concentration in the epitaxial layer from the first epitaxial layer portion to the second epitaxial layer portion corresponding to the termination region, the N-type concentration in the epitaxial layer portion corresponding to the active region can be increased, reducing the depletion layer range of the active region. This makes it easier for the electric field to concentrate in the active region, allowing some of the electric field in the termination region to transfer to the active region when the device experiences avalanche stress. This reduces the peak electric field in the termination region, making it less prone to breakdown and thus improving the avalanche energy of the device, ultimately enhancing its avalanche tolerance.

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view of a silicon carbide power device with an exemplary concentration-gradient epitaxial layer structure provided in an embodiment of the present invention. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0017] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0018] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0019] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, disclosure, and appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0020] Figure 1 This is a cross-sectional view of a silicon carbide power device with an exemplary concentration-gradient epitaxial layer structure provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the silicon carbide power device includes: an N-type substrate 1, a Schottky contact anode layer 2, an ohmic contact cathode layer 3, an epitaxial layer 4, a terminal region oxide layer 5, a surface terminal layer 6, and a P-type doped layer 7; and the N-type substrate 1, the Schottky contact anode layer 2, the ohmic contact cathode layer 3, the epitaxial layer 4, the terminal region oxide layer 5, the surface terminal layer 6, and the P-type doped layer 7 form an active region and a terminal region located around the active region.

[0021] like Figure 1As shown, the ohmic contact cathode layer 3 is disposed below the N-type substrate 1, and the epitaxial layer 4 is disposed above the N-type substrate 1; the surface termination layer 6 (also called the surface termination region) is disposed at the inner top of the epitaxial layer 4 (specifically disposed at the inner top of the second epitaxial layer portion (42)); the Schottky contact anode layer 2 and the oxide layer 5 are both disposed above the epitaxial layer 4, and the oxide layer 5 is disposed on both sides of the Schottky contact anode layer 2. The epitaxial layer portion corresponding to the active region is called the first epitaxial layer portion (41), and the epitaxial layer portion corresponding to the termination region is called the second epitaxial layer portion (42). The P-type doped layer 7 is embedded at the inner top of the first epitaxial layer portion (41); and, as Figure 1 As shown, the N-type concentration in epitaxial layer 4 gradually decreases from the first epitaxial layer portion (41) to the second epitaxial layer portion (42).

[0022] In this embodiment of the invention, the above structure can increase the N-type concentration of the epitaxial layer corresponding to the active region, thereby reducing the width of the depletion layer in the active region and thus reducing the range of the depletion layer in the active region. As a result, the electric field is more easily concentrated in the active region, so that when the device experiences avalanche stress, part of the electric field in the terminal region can be transferred to the active region, thereby reducing the peak electric field in the terminal region and making the terminal region less prone to breakdown. This improves the avalanche energy of the device and ultimately improves the avalanche tolerance of the device.

[0023] Here, since the oxide layer is located within the terminal region, it can be called the terminal region oxide layer or the terminal region oxide region.

[0024] In some embodiments, the N-type concentration in the epitaxial layer 4 gradually and uniformly decreases from the first epitaxial layer portion (41) to the second epitaxial layer portion (42).

[0025] In some embodiments, the N-type concentration of the central portion of the first epitaxial layer portion (41) is 1 × 10⁻⁶. 15 / cm 3 ~5×10 16 / cm 3 In the second epitaxial layer portion (42), the N-type concentration in the outer portion farther from the first epitaxial layer portion (31) is 1×10⁻⁶. 14 / cm 3 ~1×10 16 / cm 3 .

[0026] Here, the central portion of the first epitaxial layer portion (41) can be the area around the center line in the vertical direction of the first epitaxial layer portion (41).

[0027] Here, in the second epitaxial layer portion (42), the outer portion away from the first epitaxial layer portion (41) can be the outer edge region of the second epitaxial layer portion (42).

[0028] In some embodiments, the terminal region may be P-type doped.

[0029] In some embodiments, the above-described epitaxial layer structure can be used in both the JTE and FLR terminal structures.

[0030] In this embodiment of the invention, the above structure allows for the formation of an epitaxial layer with decreasing concentration from the center of the active region to the edge of the terminal region, while simultaneously forming P-type doping in both the active and terminal regions.

[0031] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A silicon carbide power device with a concentration-gradient epitaxial layer structure, characterized in that, include: N-type substrate (1), Schottky contact anode layer (2), Ohmic contact cathode layer (3), epitaxial layer (4), oxide layer (5), surface terminal layer (6) and P-type doped layer (7); The N-type substrate (1), the Schottky contact anode layer (2), the ohmic contact cathode layer (3), the epitaxial layer (4), the oxide layer (5), and the surface terminal layer (6) are used to form an active region and a terminal region, wherein the terminal region is located outside the active region; The ohmic contact cathode layer (3) is disposed below the N-type substrate (1), and the epitaxial layer (4) is disposed above the N-type substrate (1); The surface terminal layer (6) is disposed at the inner top of the epitaxial layer (4), the Schottky contact anode layer (2) and the oxide layer (5) are both disposed above the epitaxial layer (4), and the oxide layer (5) is disposed on both sides of the Schottky contact anode layer (2); The P-type doped layer (7) is disposed at the top of the inner part of the first epitaxial layer portion (41) corresponding to the active region; The N-type concentration of the epitaxial layer (4) gradually decreases from the first epitaxial layer portion (41) to the second epitaxial layer portion (42) corresponding to the terminal region, and the N-type concentration of the central portion of the first epitaxial layer portion (41) is... / cm 3 ~ / cm 3 In the second epitaxial layer portion (42), the N-type concentration in the outer portion farther from the first epitaxial layer portion (41) is... / cm 3 ~ / cm 3 .

2. The silicon carbide power device with a concentration-gradient epitaxial layer structure according to claim 1, characterized in that, The terminal region is P-type doped.

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