Silicon carbide power device and manufacturing method thereof

Abstract

The invention relates to the technical field of semiconductor devices, and discloses a silicon carbide power device and a manufacturing method thereof.The terminal structure of the silicon carbide power device comprises a silicon carbide substrate layer which is provided with a first surface and a second surface, and the first surface and the second surface are opposite in the thickness direction of the silicon carbide substrate layer; the epitaxial layer is arranged on the first surface of the silicon carbide substrate layer; the terminal part is arranged on the surface, deviating from the silicon carbide substrate layer, of the epitaxial layer; the terminal part is annular and is provided with an inner hole and an outer edge; the terminal part is provided with at least two sub-parts, all the sub-parts in the at least two sub-parts are arranged in the direction that the inner hole points to the outer edge, and the thicknesses of every two adjacent sub-parts are different. According to the scheme, the electric field of the silicon carbide power device is uniformly distributed, and the peak problem is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a silicon carbide power device and a manufacturing method thereof. Background Art

[0002] Silicon carbide (SiC) has been widely used in photovoltaics, charging stations, new energy vehicles, aerospace, and other fields due to its excellent material properties, including a wide bandgap, high breakdown field strength, high thermal conductivity, and high mobility similar to silicon. However, the vertical structure of most SiC power devices makes it prone to electric field concentration or increased current density in the device's pore area, forming so-called "spikes." These spikes can cause localized overheating and reduced breakdown voltage. Summary of the Invention

[0003] The present invention provides a silicon carbide power device and a manufacturing method thereof, which is conducive to uniformly distributing the electric field of the silicon carbide power device and improving the spike problem.

[0004] To achieve the above object, the present invention provides the following technical solutions: A silicon carbide power device includes an active area and a terminal area, wherein the terminal area surrounds the active area and is provided with a terminal structure; the terminal structure includes: a silicon carbide substrate layer having a first surface and a second surface, the first surface and the second surface being opposite to each other in a thickness direction of the silicon carbide substrate layer; an epitaxial layer, disposed on the first surface of the silicon carbide substrate layer; a terminal portion, disposed on a surface of the epitaxial layer away from the silicon carbide substrate layer; the terminal portion is annular and has an inner hole and an outer edge; The terminal portion has at least two sub-portions, and each of the at least two sub-portions is arranged along the direction from the inner hole to the outer edge; the thicknesses of two adjacent sub-portions are different, or the thickness of the terminal portion gradually decreases along the direction from the inner hole to the outer edge.

[0005] Optionally, the thicknesses of two adjacent sub-portions are different; the terminal portion includes an annular stepped structure, and the annular stepped structure includes the at least two sub-portions.

[0006] Optionally, the thicknesses of two adjacent sub-parts are different; the terminal part includes a main body part, the main body part is annular and has at least one annular groove; On the main body, the portion where the annular groove is located and the portions on both sides of the annular groove and connected to the annular groove each constitute a sub-portion.

[0007] Optionally, the distance between the inner hole and the outer edge is greater than the sum of the thicknesses of the epitaxial layer and the terminal portion.

[0008] Optionally, the doping concentration of the epitaxial layer is lower than the doping concentration of the silicon carbide substrate layer.

[0009] Optionally, the conductivity type of the terminal portion is opposite to the conductivity type of the epitaxial layer; Optionally, the conductivity type of the epitaxial layer and the conductivity type of the silicon carbide substrate layer are both n-type.

[0010] Optionally, the terminal portion is a continuous annular structure or an annular structure with discontinuous portions.

[0011] The present invention also provides a method for manufacturing a silicon carbide power device, which comprises the following steps: Providing a silicon carbide substrate layer; wherein the silicon carbide substrate layer has a first surface and a second surface, the first surface and the second surface being opposite to each other in a thickness direction of the silicon carbide substrate layer; providing an initial epitaxial layer on a first surface of the silicon carbide substrate layer; preparing a terminal portion on a surface of the initial epitaxial layer away from the silicon carbide substrate layer; Among them, the epitaxial layer of the silicon carbide power device is located between the terminal portion and the silicon carbide substrate layer; the terminal portion is annular and has an inner hole and an outer edge; the terminal portion has at least two sub-portions, and each of the at least two sub-portions is arranged along the direction from the inner hole to the outer edge; the thicknesses of two adjacent sub-portions are different, or the thickness of the terminal portion gradually decreases along the direction from the inner hole to the outer edge.

[0012] In this solution, the thickness of the terminal part is different in the direction from the inner hole of the terminal part to the outer edge, which can effectively regulate the electric field distribution and reduce the electric field concentration phenomenon, thereby reducing the possibility of peak formation and improving the structural reliability of the silicon carbide power device.

[0013] In addition, when this solution is adopted, the process is simple and the linear decrease of the charge dose can be accurately controlled, which has a high area efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1a A top view of a silicon carbide power device provided by an embodiment of the present invention; Figure 1b A top view of another silicon carbide power device provided by an embodiment of the present invention; Figure 2 for Figure 1a The AA cross-sectional view of the silicon carbide power device is shown with the active area omitted; Figure 3a A flowchart of a method for manufacturing a silicon carbide power device provided in an embodiment of the present invention; Figure 3b A schematic diagram of the steps of a method for manufacturing a silicon carbide power device provided by an embodiment of the present invention; Figure 3c A schematic diagram of the steps of a method for manufacturing a silicon carbide power device provided by an embodiment of the present invention; Figure 3d A schematic diagram of the steps of a method for manufacturing a silicon carbide power device provided by an embodiment of the present invention; Figure 4 A cross-sectional view of the structure of another silicon carbide power device provided by an embodiment of the present invention, omitting the active region; Figure 5 A cross-sectional view of another silicon carbide power device provided by an embodiment of the present invention with the active region omitted; Icons: 10 - silicon carbide substrate layer; 20 - epitaxial layer; 30 - terminal portion; 301 - inner hole; 302 - outer edge; 31 - first sub-portion; 32 - second sub-portion; 33 - third sub-portion; 40 - metal layer; 50 - passivation layer. DETAILED DESCRIPTION

[0015] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0016] Figure 1a A top view of a silicon carbide power device provided in an embodiment of the present application is shown. Figure 2 for Figure 1a The AA cross-section of the silicon carbide power device is shown in FIG. Figure 1a and Figure 2 As shown, the silicon carbide power device includes an active area Y and a terminal area. The terminal area surrounds the active area Y and is provided with a terminal structure. The terminal structure includes a silicon carbide substrate layer 10, an epitaxial layer 20 and a terminal portion 30, wherein: The silicon carbide substrate layer 10 has a first surface and a second surface, the first surface and the second surface opposing each other in the thickness direction of the silicon carbide substrate layer 10. The epitaxial layer 20 is disposed on the first surface of the silicon carbide substrate layer 10. The terminal portion 30 is disposed on the surface of the epitaxial layer 20 facing away from the silicon carbide substrate layer 10. The terminal portion 30 is annular and has an inner hole 301 and an outer edge 302. The terminal portion 30 has at least two sub-portions, each of which is arranged in a direction from the inner hole 301 to the outer edge 302. Adjacent sub-portions have different thicknesses, or the thickness of the terminal portion 30 gradually decreases along the direction from the inner hole 301 to the outer edge 302. In this solution, the thickness of the terminal portion 30 varies along the direction from the inner hole 301 to the outer edge 302, thereby effectively regulating the electric field distribution and reducing electric field concentration, thereby reducing the possibility of spike formation and improving the structural reliability of the silicon carbide power device.

[0017] In addition, when this solution is adopted, the process is simple and the linear decrease of the charge dose can be accurately controlled, which has a high area efficiency.

[0018] In some embodiments, as Figure 1a As shown, the terminal portion is a continuous ring structure; the continuous ring structure can more evenly disperse the force and improve the stability and strength of the overall structure. Figure 1b As shown, the terminal portion is a ring-shaped structure with a discontinuous portion. The discontinuous ring structure can effectively interrupt the continuous distribution path of the electric field, reduce the local electric field intensity, and thus improve the breakdown voltage and reliability of the device.

[0019] like Figure 1a As shown, in a specific implementation, the cross-sections of the inner holes and outer edges of the silicon carbide substrate layer 10 , the epitaxial layer 20 and the terminal portion 30 may all be rectangular, and each vertex of the rectangle may be rounded.

[0020] For example, Figure 2 As shown, the terminal portion includes a first sub-portion 31 , a second sub-portion 32 and a third sub-portion 33 arranged in a direction from the outer edge 302 to the inner hole 301 .

[0021] like Figure 3a As shown, a method for manufacturing a silicon carbide power device provided in an embodiment of the present application may include the following steps: Step S11, providing a silicon carbide substrate layer 10; The silicon carbide substrate layer 10 has a first surface and a second surface, and the first surface and the second surface are opposite to each other in the thickness direction of the silicon carbide substrate layer 10; Step S12: providing an initial epitaxial layer on the first surface of the silicon carbide substrate layer 10; For example, a process such as chemical vapor deposition (CVD) may be used to grow the silicon carbide epitaxial layer 20 on the first surface of the silicon carbide substrate layer 10 .

[0022] Step S13: Figure 3b 、 Figure 3c and Figure 3d As shown, a terminal portion 30 is prepared on the surface of the initial epitaxial layer away from the silicon carbide substrate layer 10; Among them, the epitaxial layer 20 of the silicon carbide power device is located between the terminal portion 30 and the silicon carbide substrate layer 10; the terminal portion 30 is annular and has an inner hole 301 and an outer edge 302; the terminal portion 30 has at least two sub-portions, and each of the at least two sub-portions is arranged along the direction from the inner hole 301 to the outer edge 302; the thickness of two adjacent sub-portions is different, or the thickness of the terminal portion 30 gradually decreases along the direction from the inner hole 301 to the outer edge 302.

[0023] For example, ion implantation is performed at one end of the initial epitaxial layer away from the silicon carbide substrate to form a termination region having a conductivity type opposite to that of the initial epitaxial layer. The termination region is then etched using an etching process, such as reactive ion etching (RIE), to form the termination portion 30. In specific implementations, parameters such as the energy, dose, and type of ion implantation can be precisely controlled based on actual needs.

[0024] In a specific implementation, step S13, preparing the terminal portion 30 on the surface of the initial epitaxial layer away from the silicon carbide substrate layer 10, includes: Step 1: Ion implantation is performed at one end of the initial epitaxial layer away from the silicon carbide substrate layer 10 to form a terminal region having a conductivity type opposite to that of the initial epitaxial layer; Step 2: Laying a first photoresist layer on top of the terminal area; Step 3: photolithographically shaping the first photoresist layer to form a first preset pattern; Step 4: Etch away the material of the preset depth outside the first preset pattern on the upper surface of the initial epitaxial layer to form a first sub-portion 31, that is, a sub-portion close to the outer edge 302; Figure 3b shown.

[0025] Step 5: removing the first photoresist layer; Step 6: Laying a second photoresist layer on top of the terminal region, wherein, in the direction from the inner hole 301 to the outer edge 302, the length of the second photoresist layer is less than the length of the terminal region; Step 7: Photolithography the second photoresist layer to form a second layer of preset pattern; Step 8: Etching away the material of the second layer to a preset depth outside the preset pattern on the upper surface of the initial epitaxial layer to form a second sub-portion 32; removing the second layer of photoresist; Repeat steps 2 to 5 until the terminal unit 30 is completed.

[0026] In some embodiments, the method for manufacturing a silicon carbide power device may further include depositing a metal layer 40 on the second surface of the silicon carbide substrate layer 10. For example, a deposition method such as physical vapor deposition (PVD) may be used to uniformly deposit metal on the second surface of the silicon carbide substrate layer 10 to form the metal layer 40. The metal layer 40 may be used for functions such as electrical connection of the device.

[0027] In some embodiments, the method for manufacturing a silicon carbide power device may further include depositing a dielectric layer on a surface of the terminal portion 30 that faces away from the silicon carbide substrate layer 10 to form a passivation layer 50. For example, a dielectric material (e.g., silicon dioxide) is deposited on a surface of the terminal portion 30 that faces away from the silicon carbide substrate layer 10 using methods such as chemical vapor deposition to form the passivation layer 50. The passivation layer 50 can protect the device surface and prevent the external environment from affecting device performance.

[0028] In some embodiments, epitaxial layer 20 may be a silicon carbide layer; the conductivity type of epitaxial layer 20 is opposite to the conductivity type of terminal portion 30. In other words, one of epitaxial layer 20 and terminal portion 30 is doped with n-type impurities, and the other is doped with p-type impurities. For example, epitaxial layer 20 is doped with n-type impurities, and terminal portion 30 is doped with p-type impurities.

[0029] In some embodiments, the conductivity type of the epitaxial layer 20 and the conductivity type of the silicon carbide substrate layer 10 are both n-type. In other words, both the epitaxial layer 20 and the silicon carbide substrate layer 10 are doped with n-type impurities. In a specific embodiment, the doping concentration of the n-type impurities in the epitaxial layer 20 is lower than the doping concentration of the n-type impurities in the silicon carbide substrate layer 10. Exemplarily, the epitaxial layer 20 is a lightly n-type (n-) silicon carbide layer, and the silicon carbide substrate layer 10 is a heavily n-type (n+) silicon carbide layer.

[0030] Please continue to refer to Figure 1a and Figure 2 In some embodiments, in the direction from the inner hole 301 to the outer edge 302, the thicknesses of the two adjacent sub-portions are different. The terminal portion 30 includes an annular stepped structure, and the annular stepped structure includes at least the above-mentioned two sub-portions. The terminal portion 30 of the annular stepped structure can effectively regulate the electric field distribution and reduce the electric field concentration phenomenon, thereby reducing the possibility of spike formation and improving the structural reliability of the silicon carbide power device. Exemplarily, the inner ring of the annular stepped structure and the inner ring of the epitaxial layer 20 and the inner ring of the silicon carbide substrate layer 10 are located in the same rectangular cylindrical surface. It is not difficult to understand that the corners between two adjacent faces of the rectangular cylindrical surface can be rounded.

[0031] For example, Figure 2As shown, the thickness of each subsection decreases sequentially along the direction from the inner hole 301 of the terminal portion 30 toward the outer edge 302. For example, the at least two subsections include a third subsection 33, a second subsection 32, and a first subsection 31, arranged along the direction from the inner hole 301 of the terminal portion 30 toward the outer edge 302. The thickness of the third subsection 33 is greater than that of the second subsection 32, and the thickness of the second subsection 32 is greater than that of the first subsection 31. It will be appreciated that in specific embodiments, the number of subsections in the terminal portion 30 can be adjusted based on actual needs, for example, there can be two, four, or more subsections.

[0032] Additionally, in some embodiments, the thickness difference between any two adjacent sub-sections can be the same. Of course, in other embodiments, the thickness difference between any two adjacent sub-sections can also be different. Along the direction from the inner hole 301 of the terminal portion 30 toward the outer edge 302, the thickness of each sub-section can increase sequentially or vary randomly.

[0033] For example, in the direction from the inner hole 301 of the terminal portion 30 to the outer edge 302 , the difference in length between two adjacent sub-portions may be 10 nanometers to 5 micrometers.

[0034] Figure 4 The manufacturing method of the silicon carbide power device shown is Figure 3a The difference is: Step S12, providing an initial epitaxial layer on the first surface of the silicon carbide substrate layer 10, may include the following steps: Step 1: Prepare a first initial epitaxial layer of the same conductivity type on the first surface of the silicon carbide substrate layer 10. For example, chemical vapor deposition (CVD) is used with precisely controlled process parameters, including temperature, pressure, and gas flow, to grow a first initial epitaxial layer of the same conductivity type as the silicon carbide substrate layer 10 on the first surface of the silicon carbide substrate layer 10, thereby forming a foundation layer for the subsequent device structure.

[0035] Step 2: Epitaxially grow a second initial epitaxial layer of opposite conductivity type on the surface of the first initial epitaxial layer facing away from the silicon carbide substrate layer 10. For example, after the first initial epitaxial layer is grown, by adjusting the type and flow rate of the impurity source during the epitaxial growth process, a second initial epitaxial layer of opposite conductivity type to the first initial epitaxial layer is grown on the surface of the first initial epitaxial layer facing away from the silicon carbide substrate layer 10.

[0036] The initial epitaxial layer includes a first initial epitaxial layer and a second initial epitaxial layer.

[0037] Step S13, preparing a terminal portion 30 on a surface of the initial epitaxial layer away from the silicon carbide substrate layer 10, may include: A termination portion 30 is formed on a surface of the second initial epitaxial layer facing away from the silicon carbide substrate layer 10 .

[0038] In some embodiments, the fabrication method may further include depositing a metal layer 40 on the second surface of the silicon carbide substrate layer 10. For example, a deposition method such as physical vapor deposition (PVD) may be used to evaporate a metal material under a vacuum environment and deposit it on the second surface of the silicon carbide substrate layer 10 to form the metal layer 40. The metal layer 40 may be used for functions such as electrical connection of the device.

[0039] In some embodiments, the manufacturing method may further include depositing a dielectric layer on a surface of the terminal portion 30 that faces away from the silicon carbide substrate layer 10 to form a passivation layer 50. For example, a dielectric material (e.g., silicon dioxide) is deposited on a surface of the terminal portion 30 that faces away from the silicon carbide substrate layer 10 using a method such as chemical vapor deposition to form the passivation layer 50. The passivation layer 50 can protect the device surface and prevent the external environment from affecting device performance.

[0040] Figure 5 This is a cross-sectional view of another silicon carbide power device provided in an embodiment of the present application. Figure 5 As shown, in other embodiments, the thicknesses of two adjacent sub-sections in the direction from the inner hole 301 to the outer edge 302 are different. Specifically, the terminal portion 30 includes a main body portion, which is annular and has at least one annular groove. The portion of the main body portion where the annular groove is located and the portions on both sides of the annular groove that are connected to the annular groove each constitute a sub-section. For example, the portion of the main body portion where the annular groove a is located, the portion b located on the side of the annular groove a near the inner hole 301 and connected to the annular groove a, and the portion c located on the side of the annular groove a near the outer edge 302 and connected to the annular groove a each constitute a sub-section.

[0041] Illustratively, the aspect ratios of the annular grooves may be the same or different.

[0042] In some embodiments, the distance between the inner hole 301 and the outer edge 302 is greater than the sum of the thicknesses of the epitaxial layer 20 and the terminal portion 30 , so as to effectively improve the edge electric field distribution and prevent edge breakdown, thereby improving the reliability and stability of the device.

[0043] In some embodiments, the doping concentration of the termination region is 1E15 / cm 3 to 1E19 / cm 3 .

[0044] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A silicon carbide power device, comprising an active area and a terminal area, wherein the terminal area surrounds the active area and is provided with a terminal structure; characterized in that: The terminal structure includes: a silicon carbide substrate layer having a first surface and a second surface, the first surface and the second surface being opposite to each other in a thickness direction of the silicon carbide substrate layer; an epitaxial layer, disposed on the first surface of the silicon carbide substrate layer; a terminal portion, disposed on a surface of the epitaxial layer away from the silicon carbide substrate layer; the terminal portion is annular and has an inner hole and an outer edge; The terminal portion has at least two sub-portions, and each of the at least two sub-portions is arranged along the direction from the inner hole to the outer edge; the thicknesses of two adjacent sub-portions are different, or the thickness of the terminal portion gradually decreases along the direction from the inner hole to the outer edge.

2. The silicon carbide power device according to claim 1, characterized in that The thicknesses of two adjacent sub-portions are different; the terminal portion includes an annular stepped structure, and the annular stepped structure includes the at least two sub-portions.

3. The silicon carbide power device according to claim 1, characterized in that: The thickness of two adjacent sub-parts is different; the terminal part includes a main body part, the main body part is annular and has at least one annular groove; On the main body, the portion where the annular groove is located and the portions on both sides of the annular groove and connected to the annular groove each constitute a sub-portion.

4. The silicon carbide power device according to any one of claims 1 to 3, characterized in that: The distance between the inner hole and the outer edge is greater than the sum of the thicknesses of the epitaxial layer and the terminal portion.

5. The silicon carbide power device according to any one of claims 1 to 3, characterized in that: The doping concentration of the epitaxial layer is lower than the doping concentration of the silicon carbide substrate layer.

6. The silicon carbide power device according to any one of claims 1 to 3, characterized in that: The conductivity type of the terminal portion is opposite to the conductivity type of the epitaxial layer.

7. The silicon carbide power device according to any one of claims 1 to 3, characterized in that: The conductivity type of the epitaxial layer and the conductivity type of the silicon carbide substrate layer are both n-type.

8. The silicon carbide power device according to any one of claims 1 to 3, characterized in that: The terminal portion is a continuous annular structure or an annular structure with discontinuous portions.

9. A method for manufacturing a silicon carbide power device, characterized in that: The steps include: Providing a silicon carbide substrate layer; wherein the silicon carbide substrate layer has a first surface and a second surface, the first surface and the second surface being opposite to each other in a thickness direction of the silicon carbide substrate layer; providing an initial epitaxial layer on a first surface of the silicon carbide substrate layer; preparing a terminal portion on a surface of the initial epitaxial layer away from the silicon carbide substrate layer; Among them, the epitaxial layer of the silicon carbide power device is located between the terminal portion and the silicon carbide substrate layer; the terminal portion is annular and has an inner hole and an outer edge; the terminal portion has at least two sub-portions, and each of the at least two sub-portions is arranged along the direction from the inner hole to the outer edge; the thicknesses of two adjacent sub-portions are different, or the thickness of the terminal portion gradually decreases along the direction from the inner hole to the outer edge.

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