Silicon Carbide Device and Its Preparation Method

Abstract

The present invention provides a silicon carbide device and a method for manufacturing the same. The method for manufacturing the silicon carbide device includes: providing a substrate structure; forming a patterned first mask structure on the substrate structure by means of a photolithography process; forming a first ion implantation layer of a first conductivity type and a second ion implantation layer of the first conductivity type in the substrate structure by using the patterned first mask structure; forming a patterned second mask structure on the substrate structure by means of a photolithography process; forming a first trench and an ion implantation layer of a second conductivity type in the substrate structure by using the patterned second mask structure; forming an isolation layer on the sidewalls of the first trench; forming a second trench in the substrate structure by using the isolation layer; and forming a gate structure in the second trench. The method for manufacturing the silicon carbide device provided by the present invention can reduce the process time and cost required in the manufacturing process of the silicon carbide device.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a silicon carbide device and a preparation method thereof. Background Art

[0002] A Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET for short) is a field-effect transistor that can be widely used in analog circuits and digital circuits. Among them, a metal-oxide-semiconductor field-effect transistor made of silicon carbide material (referred to as silicon carbide MOSFET for short) has characteristics such as a high critical electric field, high thermal conductivity, and high saturation drift rate, and has great application advantages in fields such as high-voltage frequency conversion, new energy vehicles, and rail transit. And technicians have found that compared with a planar gate MOSFET, a trench gate MOSFET can greatly reduce the cell size, and thus greatly improve the current density. Therefore, the trench gate silicon carbide MOSFET has attracted much attention.

[0003] In the prior art, there are two preparation methods for a trench gate silicon carbide MOSFET. The first method is: after trench etching, deposit a dielectric and perform photolithography, and after forming a pattern, perform dry etching, and complete the ion implantation of each doped semiconductor region by repeating this process multiple times. The second solution is: perform ion implantation of each doped semiconductor region by depositing-photolithographing-etching the dielectric multiple times, and then perform trench etching. Both of the above two methods will use multiple sets of photomasks and multiple deposition-etching processes, and the process time is long and the cost is high.

[0004] Therefore, it is necessary to provide a silicon carbide device and a preparation method thereof to reduce the process time and cost required for the preparation of the silicon carbide device. Summary of the Invention

[0005] The purpose of the present invention is to provide a silicon carbide device and a preparation method thereof to reduce the process time and cost required for the preparation process.

[0006] To achieve the above purpose and other related purposes, the present invention provides a preparation method of a silicon carbide device, including the following steps:

[0007] Provide a substrate structure;

[0008] Use a photolithography process to form a patterned first mask structure on the substrate structure;

[0009] Use the patterned first mask structure to form a first ion implantation layer of a first conductivity type and a second ion implantation layer of the first conductivity type in the substrate structure, and the second ion implantation layer of the first conductivity type is located above the first ion implantation layer of the first conductivity type;

[0010] Form a patterned second mask structure on the substrate structure by means of a photolithography process, exposing a part of the second ion implantation layer of the first conductivity type;

[0011] Form a first trench in the substrate structure by means of the patterned second mask structure and form an ion implantation layer of the second conductivity type at the bottom of the first trench, the first trench extending from the surface of the second ion implantation layer of the first conductivity type into the first ion implantation layer of the first conductivity type;

[0012] Form an isolation layer on the sidewall of the first trench;

[0013] Form a second trench in the substrate structure by means of the isolation layer, the second trench communicating with the first trench;

[0014] Form a gate structure in the second trench;

[0015] Wherein, the conductivity types of the first conductivity type and the second conductivity type are opposite.

[0016] Optionally, in the method for manufacturing a silicon carbide device, the forming of the first ion implantation layer of the first conductivity type and the second ion implantation layer of the first conductivity type in the substrate structure by means of the patterned first mask structure includes: using the patterned first mask structure as a mask, performing multiple ion implantation processes on the substrate structure to form the first ion implantation layer of the first conductivity type and the second ion implantation layer of the first conductivity type.

[0017] Optionally, in the method for manufacturing a silicon carbide device, the forming of the first trench in the substrate structure by means of the patterned second mask structure and the forming of the ion implantation layer of the second conductivity type at the bottom of the first trench includes:

[0018] Using the patterned second mask structure as a mask, performing an etching process on the substrate structure to form the first trench;

[0019] Using the patterned second mask structure as a mask, performing an ion implantation process on the bottom of the first trench to form the ion implantation layer of the second conductivity type.

[0020] Optionally, in the method for manufacturing a silicon carbide device, before forming the ion implantation layer of the second conductivity type, the method for manufacturing a silicon carbide device further includes: forming a protective layer on the bottom of the first trench.

[0021] Optionally, in the method for manufacturing a silicon carbide device, the thickness of the protective layer is less than

[0022] Optionally, in the method for manufacturing a silicon carbide device, forming an isolation layer on the sidewalls of the first trench includes:

[0023] Forming an isolation structure on the patterned second mask structure and the ion implantation layer of the second conductivity type;

[0024] Etching the isolation structure to form an isolation layer on the sidewalls of the first trench.

[0025] Optionally, in the method for manufacturing a silicon carbide device, the material of the isolation layer includes silicon oxide.

[0026] Optionally, in the method for manufacturing a silicon carbide device, forming a gate structure in the second trench includes:

[0027] Forming a dielectric layer that covers the bottom and sidewalls of the second trench;

[0028] Filling polysilicon in the second trench to form a gate structure.

[0029] Optionally, in the method for manufacturing a silicon carbide device, the substrate structure includes a silicon carbide substrate and a silicon carbide epitaxial layer located on the silicon carbide substrate.

[0030] To achieve the above and other related objectives, the present invention also provides a silicon carbide device formed by using the method for manufacturing a silicon carbide device described above.

[0031] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0032] In the method for manufacturing a silicon carbide device of the present invention, during the process of forming the secondary trench, only two photolithography processes are required. Specifically, a first ion implantation layer of the first conductivity type and a second ion implantation layer of the first conductivity type are formed through one photolithography process, the first trench is formed through another photolithography process, and then the second trench is formed through a self-alignment process. That is, the present invention combines a small number of photolithography processes with self-alignment technology, which can reduce the number of photolithography processes, avoid the risk of layer-to-layer misalignment caused by multiple photolithography processes, and reduce the process time and cost required during the manufacturing process of the silicon carbide device. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of the product structure after performing step S03 in a method for manufacturing a silicon carbide device;

[0034] Figure 2 is a schematic diagram of the product structure after performing step S05 in a method for manufacturing a silicon carbide device;

[0035] Figure 3 It is a schematic diagram of the product structure after performing step S07 in a method for preparing a silicon carbide device;

[0036] Figure 4 It is a schematic diagram of the product structure after performing step S09 in a method for preparing a silicon carbide device;

[0037] Figure 5 It is a schematic diagram of the product structure after removing the patterned fourth mask structure and the patterned third mask structure in a method for preparing a silicon carbide device;

[0038] Figure 6 It is a schematic diagram of the product structure after performing step S010 in a method for preparing a silicon carbide device;

[0039] Figure 7 It is a flowchart of a method for preparing a silicon carbide device according to an embodiment of the present invention;

[0040] Figure 8 It is a schematic diagram of the product structure after performing step S3 in a method for preparing a silicon carbide device according to an embodiment of the present invention;

[0041] Figure 9 It is a schematic diagram of the product structure after forming the first trench in a method for preparing a silicon carbide device according to an embodiment of the present invention;

[0042] Figure 10 It is a schematic diagram of the product structure after performing step S5 in a method for preparing a silicon carbide device according to an embodiment of the present invention;

[0043] Figure 11 It is a schematic diagram of the product structure after performing step S61 in a method for preparing a silicon carbide device according to an embodiment of the present invention;

[0044] Figure 12 It is a schematic diagram of the product structure after performing step S62 in a method for preparing a silicon carbide device according to an embodiment of the present invention;

[0045] Figure 13 It is a schematic diagram of the product structure after performing step S7 in a method for preparing a silicon carbide device according to an embodiment of the present invention;

[0046] Figure 14 It is a schematic diagram of the product structure after removing the isolation layer and the patterned second mask structure in a method for preparing a silicon carbide device according to an embodiment of the present invention;

[0047] Figure 15 It is a schematic diagram of the product structure after performing step S8 in a method for preparing a silicon carbide device according to an embodiment of the present invention;

[0048] Figures 1 to 6 wherein:

[0049] 101 - Silicon carbide epitaxial layer, 102 - P-type well layer, 103 - P-type ion implantation layer, 104 - N-type ion implantation layer, 11 - Patterned first mask structure, 12 - Patterned second mask structure, 13 - Patterned third mask structure, 14 - Patterned fourth mask structure, 15 - Trench, 16 - Interlayer dielectric layer, 17 - Dielectric layer, 18 - Gate structure;

[0050] Figures 7 to 15 In:

[0051] 201 - Silicon carbide epitaxial layer, 202 - First ion implantation layer of the first conductivity type, 203 - Second ion implantation layer of the first conductivity type, 204 - Ion implantation layer of the second conductivity type, 21 - Patterned first mask structure, 22 - Patterned second mask structure, 23 - First trench, 24 - Isolation layer, 25 - Second trench, 26 - Interlayer dielectric layer, 27 - Dielectric layer, 28 - Gate structure, 29 - Metal layer. Detailed implementation mode

[0052] The following further elaborates on the silicon carbide device and its manufacturing method proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise scales, only for the purpose of conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0053] Refer to Figures 1~6 , a manufacturing method of a silicon carbide device includes the following steps:

[0054] Step S01: Provide a substrate structure;

[0055] Step S02: Form a patterned first mask structure 11 on the substrate structure by using a lithography process;

[0056] Step S03: Form a P-type well layer 102 in the substrate structure by using the patterned first mask structure 11;

[0057] Step S04: Form a patterned second mask structure 12 on the substrate structure by using a lithography process;

[0058] Step S05: Form a P-type ion implantation layer 103 in the P-type well layer 102 by using the patterned second mask structure 12;

[0059] Step S06: Form a patterned third mask structure 13 on the substrate structure by using a lithography process;

[0060] Step S07: Form an N-type ion implantation layer 104 in the substrate structure by using the patterned third mask structure 13, where the N-type ion implantation layer 104 is adjacent to the P-type ion implantation layer 103;

[0061] Step S08: Form a patterned fourth mask structure 14 on the sidewalls of the patterned third mask structure 13;

[0062] Step S09: Form a trench 15 in the substrate by using the patterned fourth mask structure 14, and the trench 15 extends from the surface of the N-type ion implantation layer 104 into the substrate structure below the P-type well layer 102;

[0063] Step S010: Form a gate structure 18 in the trench 15.

[0064] Refer to Figure 1 , perform step S01 to provide a substrate structure, which may include: a silicon carbide substrate (not shown in the figure) and a silicon carbide epitaxial layer 101 located on the silicon carbide substrate.

[0065] Please continue to refer to Figure 1 , perform step S02 to form a patterned first mask structure 11 on the substrate structure by using photolithography. Specifically, it includes: forming a first mask structure on the substrate structure and patterning the first mask structure by using photolithography and etching processes. The patterned first mask structure 11 is a hard mask layer, which may specifically be made of silicon oxide. A first photomask is used in the process of forming the patterned first mask structure 11, and the patterned first mask structure 11 exposes part of the silicon carbide epitaxial layer 101.

[0066] Please continue to refer to Figure 1 , perform step S03 to form a P-type well layer 102 in the substrate structure by using the patterned first mask structure 11. Specifically, with the patterned first mask structure 11 as a mask, perform P-type ion L 11 implantation on the substrate structure to obtain the P-type well layer 102.

[0067] Refer to Figure 2 , perform step S04 to form a patterned second mask structure 12 on the substrate structure by using photolithography. Specifically, it includes: forming a second mask structure on the substrate structure and patterning the second mask structure by using photolithography and etching processes. The patterned second mask structure 12 is a hard mask layer, which may specifically be made of silicon oxide. A second photomask is used in the process of forming the patterned second mask structure 12, and the patterned second mask structure 12 exposes part of the P-type well layer 102.

[0068] Please continue to refer to Figure 2 and perform step S05 to form a P-type ion implantation layer 103 in the P-type well layer 102 by using the patterned second mask structure 12. Specifically, using the patterned second mask structure 12 as a mask, perform P-type ion L 12 implantation on the P-type well layer 102 to obtain the P-type ion implantation layer 103.

[0069] Refer to Figure 3 and perform step S06 to form a patterned third mask structure 13 on the substrate structure by using a photolithography process. Specifically, it includes: forming a third mask structure on the substrate structure and patterning the third mask structure by using photolithography and etching processes. The patterned third mask structure 13 is a hard mask layer, which can specifically be made of silicon oxide material. During the process of forming the patterned third mask structure 13, a third photomask will be used, and the patterned third mask structure 13 will expose the P-type well layer 102 between the P-type ion implantation layers 103.

[0070] Please continue to refer to Figure 3 and perform step S07 to form an N-type ion implantation layer 104 in the substrate structure by using the patterned third mask structure 13. Specifically, using the patterned third mask structure 13 as a mask, perform N-type ion L 13 implantation on the substrate structure to obtain the N-type ion implantation layer 104. The N-type ion implantation layer 104 is adjacent to the P-type ion implantation layer 103.

[0071] Refer to Figure 4 and perform step S08 to form a patterned fourth mask structure 14 on the sidewalls of the patterned third mask structure 13. The patterned fourth mask structure 14 can be formed by depositing, photolithographing, and etching the fourth mask structure, or can be formed by a self-alignment process. The patterned fourth mask structure 14 is a hard mask layer, which can specifically be made of silicon oxide material. The patterned fourth mask structure 14 will expose a part of the N-type ion implantation layer 104.

[0072] Please continue to refer to Figure 4 and perform step S09 to form a trench 15 on the substrate by using the patterned fourth mask structure 14. The trench 15 will sequentially penetrate through the N-type ion implantation layer 104 and the P-type well layer 102 and extend into the silicon carbide epitaxial layer 101 below the P-type well layer 102.

[0073] Refer to Figure 5, after forming the trench 15, the method for manufacturing the silicon carbide device further includes: removing the patterned fourth mask structure 14 and the patterned third mask structure 13.

[0074] Refer to Figure 6 , perform step S010 to form a gate structure 18 in the trench 15. Specifically, it includes: forming a dielectric layer 17 that covers the bottom and sidewalls of the trench 15; then, filling polysilicon in the trench 15 to form the gate structure 18.

[0075] Please continue to refer to Figure 6 , after forming the gate structure 18, the method for manufacturing the silicon carbide device further includes: forming an interlayer dielectric layer 16 on the gate structure 18, and the interlayer dielectric layer 16 also covers the surfaces of the N-type ion implantation layer 104 and the P-type ion implantation layer 103. In addition, a top dielectric layer can be formed between the interlayer dielectric layer 16 and the gate structure 18, and it has the same material as the dielectric layer 17.

[0076] The above method for manufacturing a silicon carbide device uses at least three photolithography processes, that is, multiple sets of photomasks and multiple deposition-etching processes are used, and the process time is long and the cost is high. In order to reduce the number of photolithography processes and reduce the process time and cost required in the manufacturing process of the silicon carbide device, the present invention provides a new method for manufacturing a silicon carbide device.

[0077] Refer to Figure 7 , the new method for manufacturing the silicon carbide device includes the following steps:

[0078] Step S1: Provide a substrate structure;

[0079] Step S2: Use photolithography to form a patterned first mask structure on the substrate structure;

[0080] Step S3: Use the patterned first mask structure to form a first ion implantation layer of a first conductivity type and a second ion implantation layer of the first conductivity type in the substrate structure, and the second ion implantation layer of the first conductivity type is located above the first ion implantation layer of the first conductivity type;

[0081] Step S4: Use photolithography to form a patterned second mask structure on the substrate structure, exposing part of the second ion implantation layer of the first conductivity type;

[0082] Step S5: Form a first trench in the substrate structure by using the patterned second mask structure and form an ion implantation layer of a second conductivity type at the bottom of the first trench, where the first trench extends from the surface of the second ion implantation layer of the first conductivity type into the first ion implantation layer of the first conductivity type;

[0083] Step S6: Form an isolation layer on the sidewalls of the first trench;

[0084] Step S7: Form a second trench in the substrate structure by using the isolation layer, where the second trench communicates with the first trench;

[0085] Step S8: Form a gate structure in the second trench;

[0086] Wherein, the first conductivity type and the second conductivity type are of opposite conductivity types.

[0087] Refer to Figure 8 , perform Step S1 to provide a substrate structure. The substrate structure may include: a silicon carbide substrate (not shown in the figure) and a silicon carbide epitaxial layer 201 located on the silicon carbide substrate. In an embodiment of the present application, specifically, a silicon carbide substrate (not shown in the figure) may be provided first; then, an epitaxial process is performed on the silicon carbide substrate to form the silicon carbide epitaxial layer 201.

[0088] Please continue to refer to Figure 8, perform step S2, and form a patterned first mask structure 21 on the substrate structure by using a photolithography process. Specifically, it includes: forming a first mask structure on the substrate structure, and patterning the first mask structure by using photolithography and etching processes. The patterned first mask structure 21 is a hard mask layer, and specifically may be made of silicon oxide, but is not limited thereto. The specific process of patterning the first mask structure may be: first deposit a first mask structure on the silicon carbide epitaxial layer 201; secondly, deposit a first photoresist layer on the first mask structure; then, perform photolithography on the first photoresist layer by using a first photomask to form a patterned first photoresist layer; then, etch the first mask structure by using the patterned first photoresist layer as a mask to form a patterned first mask structure 21. In this embodiment, the formation process of the first mask structure may be low-pressure chemical vapor deposition (LPCVD), metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), plasma-assisted chemical vapor deposition (PECVD), laser sputtering, etc., but is not limited thereto. Further, the formation process of the first mask structure is preferably the LPCVD process. The etching of the first mask structure may be wet etching or dry etching. Since the opening size formed during the patterning of the first mask structure is large, in this embodiment, wet etching process is preferably used to etch the first mask structure to improve the etching efficiency. The patterned first mask structure 21 will expose a part of the silicon carbide epitaxial layer 201.

[0089] Please continue to refer to Figure 8 , perform step S3, and form a first ion implantation layer 202 of a first conductivity type and a second ion implantation layer 203 of a first conductivity type in the substrate structure by using the patterned first mask structure 21. In this embodiment, taking the patterned first mask structure 21 as a mask, multiple ion implantation processes are performed on the substrate structure to form a first ion implantation layer 202 of a first conductivity type and a second ion implantation layer 203 of a first conductivity type. Specifically, it may include the following steps:

[0090] Step S31: Taking the patterned first mask structure 21 as a mask, perform an ion implantation process on the substrate structure to form a first ion implantation layer 202 of a first conductivity type;

[0091] Step S32: Taking the patterned first mask structure 21 as a mask, perform an ion implantation process on the first ion implantation layer 202 of a first conductivity type to form a second ion implantation layer 203 of a first conductivity type.

[0092] In this embodiment, the conductivity types of the first conductivity type and the second conductivity type are opposite. Further, the conductivity type of the first conductivity type is preferably P-type, and correspondingly, the conductivity type of the second conductivity type is preferably N-type.

[0093] In step S31, using the patterned first mask structure 21 as a mask, the substrate structure is subjected to implantation of ions of the first conductivity type (not shown in the figure) to obtain the first ion implantation layer 202 of the first conductivity type. For example, the substrate structure is implanted with Al ions to obtain a P-type first ion implantation layer. The first ion implantation layer 202 of the first conductivity type is a lightly doped structural layer.

[0094] In step S32, continuing to use the patterned first mask structure 21 as a mask, the first ion implantation layer 202 of the first conductivity type is subjected to implantation of ions L 21 to obtain the second ion implantation layer 203 of the first conductivity type. The second ion implantation layer 203 of the first conductivity type is a heavily doped structural layer. In this embodiment, the heavy doping and light doping of the structural layer can be achieved by adjusting the energy and dose of the ion implantation process.

[0095] In this embodiment, the second ion implantation layer 203 of the first conductivity type and the first ion implantation layer 202 of the first conductivity type use the same mask layer. Therefore, the formation of the second ion implantation layer 203 of the first conductivity type and the first ion implantation layer 202 of the first conductivity type can be achieved by one photolithography process, that is, using one photomask can achieve the formation of the second ion implantation layer 203 of the first conductivity type and the first ion implantation layer 202 of the first conductivity type.

[0096] Before the step of forming the first ion implantation layer 202 of the first conductivity type, the method for preparing the silicon carbide device further includes: removing the patterned first photoresist layer. In this embodiment, it is preferably to use an ashing process to remove the patterned first photoresist layer.

[0097] In other embodiments, the step of removing the patterned first photoresist layer may also be arranged after the step of forming the second ion implantation layer 203 of the first conductivity type.

[0098] After the step of forming the second ion implantation layer 203 of the first conductivity type, the method for preparing the silicon carbide device further includes: removing the patterned first mask structure 21. In this embodiment, it is preferably to use an etching process to remove the patterned first mask structure 21.

[0099] Refer to Figure 9, perform step S4 to form a patterned second mask structure 22 on the substrate structure by means of a photolithography process. Specifically, it includes: forming a second mask structure on the substrate structure and patterning the second mask structure by using photolithography and etching processes. The patterned second mask structure 22 is a hard mask layer, which can specifically be made of silicon oxide, but is not limited thereto. The specific process of patterning the second mask structure can be as follows: first, deposit a second mask structure on the silicon carbide epitaxial layer 201; secondly, deposit a second photoresist layer (not shown in the figure) on the second mask structure; then, perform photolithography on the second photoresist layer by using a second photomask to form a patterned second photoresist layer; and then, etch the second mask structure by using the patterned second photoresist layer as a mask to form a patterned second mask structure 22. In this embodiment, the formation process of the second mask structure can be LPCVD, MOCVD, MBE, PECVD or laser sputtering, etc., but is not limited thereto. Further, the formation process of the second mask structure is preferably the LPCVD process. Since the graphic accuracy requirements for forming the second mask structure during patterning are high, a dry etching process is preferably used to etch the second mask structure in this embodiment. The patterned second mask structure 22 will expose a part of the second ion implantation layer 203 of the first conductivity type.

[0100] After the step of forming the patterned second mask structure 22, the method for manufacturing the silicon carbide device further includes: removing the patterned second photoresist layer. In this embodiment, the patterned second photoresist layer is preferably removed by an ashing process.

[0101] Refer to Figure 9 and Figure 10 , perform step S5 to form a first trench 23 in the substrate structure by using the patterned second mask structure 22 and form a second ion implantation layer 204 of the second conductivity type at the bottom of the first trench 23. This embodiment adopts a process flow combining front-side ion implantation and first trench etching, which can play a role in reducing the number of photolithography times. Specifically, it includes the following steps:

[0102] Step S51: Use the patterned second mask structure 22 as a mask to etch the substrate structure to form a first trench 23;

[0103] Step S52: Use the patterned second mask structure 22 as a mask to perform an ion implantation process on the bottom of the first trench 23 to form a second ion implantation layer 204 of the second conductivity type.

[0104] Refer to Figure 9, in step S51, a dry etching process is used to etch the substrate structure to form the first trench 23. The first trench 23 extends from the surface of the second ion implantation layer 203 of the first conductivity type into the first ion implantation layer 202 of the first conductivity type.

[0105] Refer to Figure 10 , in step S52, using the patterned second mask structure 22 as a mask, ions L of the second conductivity type are implanted into the bottom of the first trench 23 22 to obtain the second ion implantation layer 204 of the second conductivity type. The second ion implantation layer 204 of the second conductivity type is a heavily doped structural layer, and the second ion implantation layer 204 of the second conductivity type is located in the first ion implantation layer 202 of the first conductivity type.

[0106] Before step S52, that is, before forming the second ion implantation layer 204 of the second conductivity type, the method for manufacturing the silicon carbide device may further include: forming a protective layer (not shown in the figure) on the bottom of the first trench 23. The protective layer can protect the substrate structure from being damaged during the implantation of ions L of the second conductivity type into the bottom of the first trench 23. Preferably, the thickness of the protective layer is less than 22 Refer to

[0107] Refer to Figure 11 and Figure 12 , perform step S6 to form an isolation layer 24 on the sidewalls of the first trench 23. The isolation layer 24 is a hard mask structure, specifically, it can be made of silicon oxide, but is not limited thereto. The forming of the isolation layer 24 on the sidewalls of the first trench 23 may specifically include:

[0108] Step S61: Form an isolation structure on the patterned second mask structure 22 and the second ion implantation layer 204 of the second conductivity type;

[0109] Step S62: Etch the isolation structure to form the isolation layer 24 on the sidewalls of the first trench 23, and the isolation layer 24 will expose a part of the second ion implantation layer 204 of the second conductivity type.

[0110] Refer to Figure 11 , in step S61, the forming process of the isolation structure can be LPCVD, MOCVD, MBE, PECVD, laser sputtering, etc., but is not limited thereto. Further, the forming process of the isolation structure is preferably the LPCVD process.

[0111] Refer to Figure 12, in step S62, the etching process of the isolation structure is preferably dry etching. In this embodiment, the self-alignment technology is adopted to form the isolation layer 24, which can reduce the number of photolithography steps.

[0112] Refer to Figure 13 , perform step S7 to form a second trench 25 in the substrate structure by using the isolation layer 24. Specifically, with the isolation layer 24 as a mask, dry etching is performed on the substrate structure to form the second trench 25. The second trench 25 extends from the surface of the second-conductive-type ion implantation layer 204 to the substrate structure below the first ion implantation layer 202 of the first-conductive type. In this embodiment, the second trench 25 communicates with the first trench 23.

[0113] Refer to Figure 14 , after the step of forming the second trench 25, the method for manufacturing the silicon carbide device further includes: removing the isolation layer 24 and the patterned second mask structure 22. In this embodiment, it is preferably to use an etching process to remove the isolation layer 24 and the patterned second mask structure 22.

[0114] Refer to Figure 15 , perform step S8 to form a gate structure 28 in the second trench 25. Specifically, it includes: forming a dielectric layer 27 that covers the bottom and sidewalls of the second trench 25; then, filling polysilicon in the second trench 25 to form the gate structure 28. The dielectric layer 27 is preferably made of silicon oxide, but is not limited thereto.

[0115] Please continue to refer to Figure 15 , after forming the gate structure 28, the method for manufacturing the silicon carbide device further includes: forming an interlayer dielectric layer 26 on the gate structure 28, and the interlayer dielectric layer 26 also covers a part of the surface of the second-conductive-type ion implantation layer 204.

[0116] In addition, a top dielectric layer can be formed between the interlayer dielectric layer 26 and the gate structure 28. The top dielectric layer can be formed by deposition and etching processes, or by oxidation processes. For example, after forming the gate structure 28, an oxidation process is performed to form an oxide layer, that is, the top dielectric layer, on the exposed surface of the gate structure 28. The material of the top dielectric layer is the same as that of the dielectric layer 27.

[0117] Please continue to refer to Figure 15, after the step of forming the interlayer dielectric layer 26, the method for manufacturing the silicon carbide device further includes forming a metal layer 29 that covers the surface of the interlayer dielectric layer 26, the exposed ion implantation layer 204 of the second conductivity type, and the exposed second ion implantation layer 203 of the first conductivity type. The material of the metal layer 29 is preferably Cu or Al, but is not limited thereto.

[0118] The method for manufacturing the silicon carbide device of this embodiment can reduce the process time and cost required for the formation of trenches during the manufacturing process of the silicon carbide device by combining a small number of photolithography processes with self-alignment technology. The manufacturing method of this embodiment only uses two photolithography processes, which can reduce the number of photolithography, avoid the risk of interlayer misalignment caused by multiple photolithographies, and shorten the process cycle.

[0119] The present invention also provides a silicon carbide device formed by using the method for manufacturing the silicon carbide device described above. The silicon carbide device may include: a substrate structure; a first ion implantation layer of the first conductivity type and a second ion implantation layer of the first conductivity type formed in the substrate structure, and the second ion implantation layer of the first conductivity type is located on the first ion implantation layer of the first conductivity type; a first trench formed in the substrate structure, and the first trench extends from the surface of the second ion implantation layer of the first conductivity type to the first ion implantation layer of the first conductivity type; an ion implantation layer of the second conductivity type formed at the bottom of the first trench; a second trench formed in the substrate structure, and the second trench communicates with the first trench; and a gate structure formed in the second trench.

[0120] Since the method for manufacturing the silicon carbide device provided by the present invention can reduce the number of photolithographies, avoid the risk of interlayer misalignment caused by multiple photolithographies, and shorten the process cycle, the silicon carbide device prepared by this method has a high yield, high production capacity, and low cost.

[0121] In addition, it can be understood that although the present invention has been disclosed above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any person skilled in the art, without departing from the scope of the technical solution of the present invention, many possible changes and modifications can be made to the technical solution of the present invention by using the technical content disclosed above, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the protection of the technical solution of the present invention.

[0122] It should also be understood that the present invention is not limited to the specific methods, compounds, materials, manufacturing techniques, uses, and applications described herein, and they can vary. It should also be understood that the terms described herein are only used to describe specific embodiments and not to limit the scope of the present invention. It must be noted that the singular forms "a", "an", and "the" used herein and in the appended claims include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a step" means reference to one or more steps and may include sub-steps. The terms "first", "second", and the like used herein and in the appended claims do not denote any order, quantity, or importance, but are only used to distinguish different components. The terms such as "comprising" or "including" are intended to mean that the elements or items appearing before "comprising" or "including" encompass the elements or items listed after "comprising" or "including" and their equivalents, and do not exclude other elements or items. All conjunctions used should be understood in their broadest sense. Thus, the word "or" should be understood to have the definition of logical "or", rather than the definition of logical "exclusive or", unless the context clearly dictates otherwise. The structures described herein will be understood to also refer to functional equivalents of such structures. Language that may be construed as approximate should be so understood unless the context clearly dictates otherwise.

Claims

1. A method for preparing a silicon carbide device, characterized in that, Including the following steps: Providing a substrate structure; Forming a patterned first mask structure on the substrate structure by using a photolithography process; Forming a first ion implantation layer of a first conductivity type and a second ion implantation layer of the first conductivity type in the substrate structure by using the patterned first mask structure, where the second ion implantation layer of the first conductivity type is located above the first ion implantation layer of the first conductivity type; Forming a patterned second mask structure on the substrate structure by using a photolithography process, exposing a part of the second ion implantation layer of the first conductivity type; Forming a first trench in the substrate structure and forming an ion implantation layer of a second conductivity type at the bottom of the first trench by using the patterned second mask structure, where the first trench extends from the surface of the second ion implantation layer of the first conductivity type into the first ion implantation layer of the first conductivity type; Forming an isolation layer on the sidewall of the first trench; Forming a second trench in the substrate structure by using the isolation layer, where the second trench communicates with the first trench; Forming a gate structure in the second trench; Wherein, the conductivity types of the first conductivity type and the second conductivity type are opposite.

2. The manufacturing method of the silicon carbide device according to claim 1, wherein, The forming of the first ion implantation layer of the first conductivity type and the second ion implantation layer of the first conductivity type in the substrate structure by using the patterned first mask structure includes: using the patterned first mask structure as a mask, performing multiple ion implantation processes on the substrate structure to form the first ion implantation layer of the first conductivity type and the second ion implantation layer of the first conductivity type.

3. The manufacturing method of the silicon carbide device according to claim 1, characterized in that, The forming of the first trench in the substrate structure and the forming of the ion implantation layer of the second conductivity type at the bottom of the first trench by using the patterned second mask structure includes: Using the patterned second mask structure as a mask, performing an etching process on the substrate structure to form the first trench; Using the patterned second mask structure as a mask, performing an ion implantation process on the bottom of the first trench to form the ion implantation layer of the second conductivity type.

4. The method for preparing a silicon carbide device according to claim 3, characterized in that, Before forming the ion implantation layer of the second conductivity type, the method for manufacturing a silicon carbide device further includes: forming a protection layer at the bottom of the first trench.

5. The manufacturing method of the silicon carbide device according to claim 4, characterized in that, The thickness of the protective layer is less than 6. The manufacturing method of the silicon carbide device according to claim 1, characterized in that, The forming of the isolation layer on the sidewall of the first trench includes: Forming an isolation structure on the patterned second mask structure and the ion implantation layer of the second conductivity type; Etching the isolation structure to form the isolation layer on the sidewall of the first trench.

7. The manufacturing method of the silicon carbide device according to claim 1, characterized in that, The material of the isolation layer includes silicon oxide.

8. The manufacturing method of the silicon carbide device according to claim 1, characterized in that, The forming of the gate structure in the second trench includes: Forming a dielectric layer that covers the bottom and sidewall of the second trench; Filling polysilicon in the second trench to form a gate structure.

9. The method for preparing a silicon carbide device according to claim 1, characterized in that, The substrate structure includes a silicon carbide substrate and a silicon carbide epitaxial layer located on the silicon carbide substrate.

10. A silicon carbide device, characterized in that, Formed by using the method for manufacturing a silicon carbide device according to any one of claims 1 to 9.

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