Silicon carbide power device and method of making the same

Abstract

The application 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, a first surface and a second surface, the first surface and the second surface are opposite in the thickness direction of the silicon carbide substrate layer; an epitaxial layer is arranged on the first surface of the silicon carbide substrate layer; a terminal part is arranged on the surface of the epitaxial layer which is away from the silicon carbide substrate layer; the terminal part is annular and has an inner hole and an outer edge; the terminal part has at least two subparts, each of the at least two subparts is arranged in the direction from the inner hole to the outer edge, and the thicknesses of the adjacent two subparts are different. The scheme is favorable for uniformly distributing the electric field of the silicon carbide power device and improving the sharp peak problem.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a silicon carbide power device and its fabrication method. Background Technology

[0002] Silicon carbide (SiC) has been widely used in photovoltaics, charging piles, new energy vehicles, and aerospace due to its excellent material properties, such as wide bandgap, high breakdown field strength, high thermal conductivity, and high mobility similar to silicon. However, most SiC power devices have a vertical structure, which easily leads to electric field concentration or increased current density in the hole region of the device, forming so-called "spikes". These spikes can cause problems such as localized overheating and reduced breakdown voltage. Summary of the Invention

[0003] This invention provides a silicon carbide power device and its fabrication method, which is beneficial for achieving a uniform electric field distribution in the silicon carbide power device and improving the spike problem.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A silicon carbide power device includes an active region and a termination region, the termination region surrounding the active region, and a termination structure disposed thereon; the termination structure includes:

[0006] A silicon carbide substrate layer has a first surface and a second surface, the first surface and the second surface being opposite each other in the thickness direction of the silicon carbide substrate layer;

[0007] An epitaxial layer is disposed on the first surface of the silicon carbide substrate layer;

[0008] A terminal portion is disposed on the surface of the epitaxial layer opposite to the silicon carbide substrate layer; the terminal portion is annular and has an inner hole and an outer edge;

[0009] The terminal portion has at least two sub-portions, each of which is arranged along the inner hole toward the outer edge; the thickness of two adjacent sub-portions is different, or the thickness of the terminal portion gradually decreases along the inner hole toward the outer edge.

[0010] Optionally, the thicknesses of two adjacent sub-parts are different; the terminal part includes an annular stepped structure, the annular stepped structure including the at least two sub-parts.

[0011] Optionally, the thicknesses of two adjacent sub-parts are different; the terminal part includes a main body, which is annular and has at least one annular groove;

[0012] On the main body, the portion where the annular groove is located and the portions on both sides of the annular groove that are connected to the annular groove are each a sub-part.

[0013] 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.

[0014] Optionally, the doping concentration of the epitaxial layer is lower than the doping concentration of the silicon carbide substrate layer.

[0015] Optionally, the conductivity type of the terminal portion is opposite to that of the epitaxial layer;

[0016] Optionally, the conductivity type of the epitaxial layer and the conductivity type of the silicon carbide substrate layer are both n-type.

[0017] Optionally, the terminal portion is a continuous ring structure or a ring structure with discontinuous portions.

[0018] The present invention also provides a method for fabricating a silicon carbide power device, the method comprising the following steps:

[0019] A silicon carbide substrate layer is provided; 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 the thickness direction of the silicon carbide substrate layer;

[0020] An initial epitaxial layer is formed on the first surface of the silicon carbide substrate layer;

[0021] A terminal portion is prepared on the surface of the initial epitaxial layer opposite to the silicon carbide substrate layer;

[0022] The terminal portion and the silicon carbide substrate layer are the epitaxial layer of the silicon carbide power device; the terminal portion is annular and has an inner hole and an outer edge; the terminal portion has at least two sub-parts, and each of the at least two sub-parts is arranged along the direction from the inner hole to the outer edge; the thickness of two adjacent sub-parts is different, or the thickness of the terminal portion gradually decreases along the direction from the inner hole to the outer edge.

[0023] In this scheme, the thickness of the terminal part varies in the direction from the inner hole to the outer edge, which can effectively control the electric field distribution and reduce the electric field concentration phenomenon, thereby reducing the possibility of peak formation and improving the structural reliability of silicon carbide power devices.

[0024] In addition, this approach is simple to implement and allows for precise control of the linear decrease in charge dose, resulting in high area efficiency. Attached Figure Description

[0025] Figure 1aA top view of a silicon carbide power device provided in an embodiment of the present invention;

[0026] Figure 1b A top view of another silicon carbide power device provided in an embodiment of the present invention;

[0027] Figure 2 for Figure 1a The diagram shows a cross-sectional view of the silicon carbide power device with the active region omitted.

[0028] Figure 3a A flowchart illustrating a method for fabricating a silicon carbide power device according to an embodiment of the present invention;

[0029] Figure 3b A schematic diagram illustrating the steps of a method for fabricating a silicon carbide power device according to an embodiment of the present invention;

[0030] Figure 3c A schematic diagram illustrating the steps of a method for fabricating a silicon carbide power device according to an embodiment of the present invention;

[0031] Figure 3d A schematic diagram illustrating the steps of a method for fabricating a silicon carbide power device according to an embodiment of the present invention;

[0032] Figure 4 This is a cross-sectional view of the structure of another silicon carbide power device provided in an embodiment of the present invention, with the active region omitted.

[0033] Figure 5 A cross-sectional view of another silicon carbide power device provided in an embodiment of the present invention, with the active region omitted;

[0034] Icons: 10-Silicon carbide substrate; 20-Epipolar layer; 30-Terminal portion; 301-Inner hole; 302-Outer edge; 31-First sub-part; 32-Second sub-part; 33-Third sub-part; 40-Metal layer; 50-Passivation layer. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Figure 1a This is a top view of a silicon carbide power device provided in an embodiment of this application. Figure 2 for Figure 1a The diagram shows a cross-sectional view (AA) of the silicon carbide power device with the active region omitted. Figure 1a and Figure 2 As shown, the silicon carbide power device includes an active region Y and a termination region. The termination region surrounds the active region Y and has a termination structure. The termination structure includes a silicon carbide substrate layer 10, an epitaxial layer 20, and a termination portion 30, wherein:

[0037] The silicon carbide substrate 10 has a first surface and a second surface, which are opposite to each other in the thickness direction of the silicon carbide substrate 10. An epitaxial layer 20 is disposed on the first surface of the silicon carbide substrate 10. A terminal portion 30 is disposed on the surface of the epitaxial layer 20 facing away from the silicon carbide substrate 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 along the direction from the inner hole 301 to the outer edge 302. The thicknesses of adjacent sub-portions are different, 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 design, the thickness of the terminal portion 30 is different along the direction from the inner hole 301 to the outer edge 302, thereby effectively controlling the electric field distribution, reducing electric field concentration, and thus reducing the possibility of peak formation and improving the structural reliability of the silicon carbide power device.

[0038] In addition, this approach is simple to implement and allows for precise control of the linear decrease in charge dose, resulting in high area efficiency.

[0039] In some embodiments, such as Figure 1a As shown, the terminal portion is a continuous ring structure; the continuous ring structure can distribute the force more evenly, improving the stability and strength of the overall structure. In other embodiments, such as Figure 1b As shown, the terminal section is a ring structure with discontinuities. The discontinuous ring structure can effectively interrupt the continuous distribution path of the electric field, reduce the local electric field strength, and thus improve the breakdown voltage and reliability of the device.

[0040] like Figure 1a As shown, in a specific implementation, the cross-sections of the inner hole and outer edge of the silicon carbide substrate layer 10, the epitaxial layer 20 and the terminal portion 30 can all be rectangular, and each vertex of the rectangle can be rounded.

[0041] For example, such as Figure 2 As shown, the terminal portion includes a first sub-part 31, a second sub-part 32, and a third sub-part 33 arranged in the direction from the outer edge 302 to the inner hole 301.

[0042] like Figure 3a As shown in the embodiments of this application, a method for fabricating a silicon carbide power device may include the following steps:

[0043] Step S11: Provide a silicon carbide substrate layer 10;

[0044] The silicon carbide substrate 10 has a first surface and a second surface, which are opposite to each other in the thickness direction of the silicon carbide substrate 10.

[0045] Step S12: An initial epitaxial layer is formed on the first surface of the silicon carbide substrate 10;

[0046] For example, a silicon carbide epitaxial layer 20 may be grown on the first surface of the silicon carbide substrate 10 using a process such as chemical vapor deposition (CVD).

[0047] Step S13, as follows Figure 3b , Figure 3c and Figure 3d As shown, a terminal portion 30 is fabricated on the surface of the initial epitaxial layer away from the silicon carbide substrate layer 10;

[0048] The terminal portion 30 is located between the silicon carbide substrate layer 10 and the epitaxial layer 20 of the silicon carbide power device. 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-parts, and each of the at least two sub-parts is arranged along the direction from the inner hole 301 to the outer edge 302. The thickness of adjacent two sub-parts 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.

[0049] For example, at the end of the initial epitaxial layer furthest from the silicon carbide substrate, ion implantation forms a terminal region with a conductivity type opposite to that of the initial epitaxial layer. The terminal region is then etched using an etching process, such as reactive ion etching (RIE), to obtain the terminal portion 30. In specific implementations, parameters such as the energy, dose, and type of ion implantation can be precisely controlled according to actual needs.

[0050] In one specific implementation, step S13, fabricating a terminal portion 30 on the surface of the initial epitaxial layer away from the silicon carbide substrate layer 10, includes:

[0051] Step 1: At the end of the initial epitaxial layer furthest from the silicon carbide substrate 10, ion implantation is performed to form a terminal region with the opposite conductivity type to the initial epitaxial layer.

[0052] Step 2: Lay the first photoresist layer on top of the terminal area;

[0053] Step 3: Photolithography to form the first preset pattern from the shape of the first photoresist layer;

[0054] Step 4: Etch away the material at a predetermined depth outside the first predetermined pattern on the upper surface of the initial epitaxial layer to form the first sub-part 31, which is the sub-part near the outer edge 302; as shown Figure 3b As shown.

[0055] Step 5: Remove the first photoresist layer;

[0056] Step 6: Lay a second photoresist layer on top of the terminal area, wherein the length of the second photoresist layer is less than the length of the terminal area in the direction from the inner hole 301 to the outer edge 302.

[0057] Step 7: Photolithography to form the second preset pattern by shaping the second photoresist layer;

[0058] Step 8: Etch away the material at a predetermined depth outside the predetermined pattern of the second layer on the upper surface of the initial epitaxial layer to form the second sub-part 32;

[0059] Remove the second layer of photoresist;

[0060] Repeat steps two through five until the terminal part 30 is prepared.

[0061] In some embodiments, the method for fabricating a silicon carbide power device may further include depositing a metal layer 40 on the second surface of a silicon carbide substrate 10. For example, metal can be uniformly deposited on the second surface of the silicon carbide substrate 10 by a deposition method such as physical vapor deposition (PVD) to form the metal layer 40. The metal layer 40 can be used for functions such as electrical connections of the device.

[0062] In some embodiments, the method for fabricating a silicon carbide power device may further include: depositing a dielectric layer on the surface of the terminal portion 30 away from the silicon carbide substrate 10 to form a passivation layer 50. For example, a dielectric material (e.g., silicon dioxide) is deposited on the surface of the terminal portion 30 away from the silicon carbide substrate 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 the device performance.

[0063] In some embodiments, the epitaxial layer 20 may be a silicon carbide layer; the conductivity type of the epitaxial layer 20 is opposite to that of the terminal portion 30, in other words, one of the epitaxial layer 20 and the terminal portion 30 is doped with an n-type impurity, and the other is doped with a p-type impurity. For example, the epitaxial layer 20 is doped with an n-type impurity, and the terminal portion 30 is doped with a p-type impurity.

[0064] In some embodiments, the conductivity type of the epitaxial layer 20 and the silicon carbide substrate layer 10 are both n-type, meaning that both the epitaxial layer 20 and the silicon carbide substrate layer 10 are doped with n-type impurities. In one specific embodiment, the doping concentration of the n-type impurities in the epitaxial layer 20 is less than the doping concentration of the n-type impurities in the silicon carbide substrate layer 10. For example, the epitaxial layer 20 is a lightly doped (n-) n-type silicon carbide layer, and the silicon carbide substrate layer 10 is a heavily doped (n+) n-type silicon carbide layer.

[0065] Please continue to refer to Figure 1a and Figure 2In some embodiments, the thicknesses of two adjacent sub-parts are different in the direction from the inner hole 301 to the outer edge 302. The terminal portion 30 includes an annular stepped structure, which includes the aforementioned at least two sub-parts. The terminal portion 30 of the annular stepped structure can effectively regulate the electric field distribution and reduce electric field concentration, thereby reducing the possibility of peak formation and improving the structural reliability of silicon carbide power devices. Exemplarily, the inner ring of the annular stepped structure, the inner ring of the epitaxial layer 20, and the inner ring of the silicon carbide substrate layer 10 are located within the same cuboid cylindrical surface. It is easy to understand that the corners between adjacent faces of this cuboid cylindrical surface can be rounded.

[0066] For example, such as Figure 2 As shown, the thickness of each sub-part decreases sequentially along the direction from the inner hole 301 of the terminal portion 30 to the outer edge 302. For example, the aforementioned at least two sub-parts include a third sub-part 33, a second sub-part 32, and a first sub-part 31 arranged along the direction from the inner hole 301 of the terminal portion 30 to the outer edge 302. The thickness of the third sub-part 33 is greater than the thickness of the second sub-part 32, and the thickness of the second sub-part 32 is greater than the thickness of the first sub-part 31. It is easy to understand that, in specific embodiments, the number of sub-parts in the terminal portion 30 can be set according to actual needs; for example, there can be two, four, or more sub-parts.

[0067] Furthermore, in some embodiments, the thickness difference between any two adjacent sub-parts can be the same. Of course, in other embodiments, the thickness difference between any two adjacent sub-parts can also be different. Along the direction from the inner hole 301 of the terminal portion 30 to the outer edge 302, the thickness of each sub-part can increase sequentially or the thickness can vary irregularly.

[0068] 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-parts can be from 10 nanometers to 5 micrometers.

[0069] Figure 4 The fabrication method of the silicon carbide power device shown is similar to Figure 3a The difference is:

[0070] Step S12, forming an initial epitaxial layer on the first surface of the silicon carbide substrate 10, may include the following steps:

[0071] Step 1: Prepare a first initial epitaxial layer with the same conductivity type on the first surface of the silicon carbide substrate 10. For example, using chemical vapor deposition (CVD) technology, precisely control the process parameters, including temperature, pressure, gas flow rate, etc., to grow a first initial epitaxial layer with the same conductivity type as the silicon carbide substrate 10 on the first surface of the silicon carbide substrate 10, so as to build the base layer for subsequent device structures.

[0072] Step 2: Epitaxially grow a second initial epitaxial layer with the opposite conductivity type on the surface of the first initial epitaxial layer away from the silicon carbide substrate 10. For example, after the growth of the first initial epitaxial layer is completed, by adjusting the type and flow rate of the impurity source in the epitaxial process, a second initial epitaxial layer with the opposite conductivity type to the first initial epitaxial layer is grown on the surface of the first initial epitaxial layer away from the silicon carbide substrate 10.

[0073] The initial epitaxial layer includes a first initial epitaxial layer and a second initial epitaxial layer.

[0074] Step S13, fabricating a terminal portion 30 on the surface of the initial epitaxial layer away from the silicon carbide substrate layer 10, may include:

[0075] A terminal portion 30 is prepared on the surface of the second initial epitaxial layer away from the silicon carbide substrate layer 10.

[0076] In some embodiments, the fabrication method may further include depositing a metal layer 40 on the second surface of the silicon carbide substrate 10. For example, the metal layer 40 can be formed by evaporating and depositing a metal material on the second surface of the silicon carbide substrate 10 in a vacuum environment using a deposition method such as physical vapor deposition (PVD). The metal layer 40 can be used for functions such as electrical connections in the device.

[0077] In some embodiments, the fabrication method may further include depositing a dielectric layer on the surface of the terminal portion 30 away from the silicon carbide substrate 10 to form a passivation layer 50. For example, a dielectric material (e.g., silicon dioxide) is deposited on the surface of the terminal portion 30 away from the silicon carbide substrate 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 the device performance.

[0078] Figure 5 This is a cross-sectional view of another silicon carbide power device provided in an embodiment of this application. (See attached image.) Figure 5 As shown, in some embodiments, the thicknesses of two adjacent sub-parts are different in the direction from the inner hole 301 to the outer edge 302. Specifically, the terminal portion 30 includes a main body portion, which is annular and has at least one annular groove. On the main body portion, the portion where the annular groove is located and the portions on both sides of the annular groove that connect with the annular groove are each a sub-part. For example, the portion where the annular groove a is located on the main body portion, 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 are each one of the aforementioned sub-parts.

[0079] For example, the aspect ratios of the depths of the annular grooves may be the same or different.

[0080] 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, prevent edge breakdown, and thereby improve the reliability and stability of the device.

[0081] In some embodiments, the doping concentration of the terminal region is 1E15 / cm3 to 1E19 / cm3.

[0082] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

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

2. 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 an annular stepped structure, and the annular stepped structure includes the at least two sub-parts.

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, which 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 that are connected to the annular groove are each a sub-part.

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

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

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

7. The silicon carbide power device according to any one of claims 1-3, characterized in that, The terminal portion is a continuous ring structure or a ring structure with discontinuities.

8. A method for fabricating a silicon carbide power device, characterized in that, Includes the following steps: A silicon carbide substrate layer is provided; 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 the thickness direction of the silicon carbide substrate layer; An initial epitaxial layer is formed on the first surface of the silicon carbide substrate layer; A terminal portion is prepared on the surface of the initial epitaxial layer opposite to the silicon carbide substrate layer; Wherein, the terminal portion and the silicon carbide substrate layer are the epitaxial layer of the silicon carbide power device; the terminal portion is annular and has an inner hole and an outer edge; the terminal portion has at least two sub-parts, and each of the at least two sub-parts is arranged along the direction from the inner hole to the outer edge; the thickness of two adjacent sub-parts is different, or, along the direction from the inner hole to the outer edge, the thickness of the terminal portion gradually decreases; 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.

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