A method for preparing a multi-angle etching terminal of silicon carbide and a silicon carbide diode
By utilizing the combination of photoresist and hard mask layers in the fabrication method of silicon carbide multi-angle etching terminals, vertical and orthogonal etching morphologies of silicon carbide etching trenches are formed, solving the problems of process complexity and electrical performance in the prior art, and realizing the reduction of terminal area and cost savings.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHU RES INST OF XIAN UNIV OF ELECTRONIC SCI & TECH
- Filing Date
- 2024-12-23
- Publication Date
- 2026-05-19
AI Technical Summary
The existing silicon carbide multi-angle etching process increases the complexity of the process and affects the electrical performance of the device, making it difficult to meet the device breakdown voltage design requirements while reducing the terminal area.
The fabrication method of silicon carbide multi-angle etching terminal involves sequentially depositing a silicon carbide epitaxial layer and a hard mask layer on a substrate to form a mask etching trench. Photoresist is then spin-coated onto the terminal surface, followed by exposure, baking, development, and hard film treatment to form a slanted photoresist morphology. The silicon carbide epitaxial layer is then etched downwards along the mask etching trench to form vertical and angular etching morphologies of the silicon carbide etching trench.
It achieves a simplified process flow, reduces the terminal area, and lowers device manufacturing costs while maintaining good electrical performance.
Smart Images
Figure CN119767761B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor technology, specifically relating to a method for preparing a silicon carbide multi-angle etching terminal and a silicon carbide diode. Background Technology
[0002] Silicon carbide (SiC) power devices are a typical example of power devices, widely used in electric vehicles, aerospace, and power conversion. With the development of planar power devices, conventional planar terminations require larger termination areas to meet breakdown voltage design requirements. Single-angle etched terminations, due to the negative angle at the main junction, need to reduce the angle to meet breakdown voltage design requirements, also requiring a larger termination area. To reduce the termination area, multi-angle etched terminations have emerged in recent years. This type of termination adjusts the etching angle at the main junction to 90°, eliminating the negative angle and electric field concentration at the main junction. By increasing the etching angle on the upper side, the termination area is significantly reduced. However, this design increases process complexity. If an etching mask is re-fabricated and photolithography is performed between two etching operations, misalignment issues will affect the device's electrical performance. Summary of the Invention
[0003] To address the aforementioned problems in the prior art, this invention provides a method for fabricating a silicon carbide multi-angle etching terminal and a silicon carbide diode.
[0004] The technical problem to be solved by this invention is achieved through the following technical solution:
[0005] A method for fabricating a silicon carbide multi-angle etching terminal includes:
[0006] Step 1: Provide a substrate, and sequentially deposit a silicon carbide epitaxial layer and a hard mask layer on the substrate to form the initial terminal;
[0007] Step 2: Etch the hard mask layer to form mask etching trenches; the depth of the mask etching trenches is greater than or equal to the thickness of the hard mask layer;
[0008] Step 3: Spin-coat photoresist onto the terminal surface, such that the photoresist thickness within the mask etching trench is greater than the photoresist thickness on the terminal surface on both sides of the mask etching trench.
[0009] Step 4: Perform general exposure, baking, development and hardening treatment on the photoresist on the terminal in sequence, so that the sidewalls of the mask etching trench form a sloping photoresist morphology.
[0010] Step 5: Etch the silicon carbide epitaxial layer downwards along the mask etching trench until all photoresist is consumed and a silicon carbide etching trench is formed; wherein, the sidewalls of the silicon carbide etching trench have a vertical etching morphology, and a positive angle etching morphology is formed between the sidewalls and the bottom surface;
[0011] Step 6: Remove the remaining hard mask layer.
[0012] Optionally, in step three, the spin coating thickness of the photoresist is less than the depth of the etched trenches in the mask.
[0013] Optionally, in step four, the dose of generalized exposure is 20mJ to 100mJ.
[0014] Optionally, in step four, the baking temperature after exposure is 80℃~130℃, and the baking time is 1 minute.
[0015] Optionally, in step four, the development time is 60 to 180 seconds.
[0016] Optionally, in step four, the temperature for the hardening treatment is 90℃~130℃, and the treatment time is 1 minute.
[0017] Optionally, the hard mask layer is made of TiN, SiN, or SiO2.
[0018] Optionally, the substrate is a silicon carbide substrate.
[0019] The present invention also provides a silicon carbide diode having silicon carbide etched trenches, wherein the sidewalls of the silicon carbide etched trenches have a vertical etched morphology and a positive angle etched morphology is formed between the sidewalls and the bottom surface.
[0020] The present invention also provides a silicon carbide diode having silicon carbide etched trenches, wherein the silicon carbide etched trenches are prepared by any of the above-described methods for preparing silicon carbide multi-angle etched terminals.
[0021] The present invention provides a method for fabricating a silicon carbide multi-angle etching terminal. After sequentially depositing a silicon carbide epitaxial layer and a hard mask layer on a substrate, a mask etching trench is formed by etching the hard mask layer, creating a stepped structure on the terminal surface. Photoresist is spin-coated onto this stepped structure to achieve photoresist morphologies with different heights (thicknesses). Then, the photoresist on the terminal is sequentially subjected to generalized exposure, baking, development, and hardening treatment, resulting in a sloping photoresist morphology on the sidewalls of the mask etching trench. Next, the silicon carbide epitaxial layer is etched downwards along the mask etching trench to form a silicon carbide etching trench. Since the photoresist selectivity for silicon carbide is less than 1, a positive angle etching morphology can be formed between the sidewalls and the bottom surface of the silicon carbide etching trench after all the photoresist has been consumed. Furthermore, since the hard mask layer near the silicon carbide epitaxial layer has a silicon carbide etching selectivity greater than 1, a vertical etching morphology can be formed on the sidewalls of the silicon carbide etching trench. Therefore, by using a double-layer mask formed by a photoresist with a sloping morphology and a hard mask layer to etch silicon carbide, multi-angle etched silicon carbide trenches can be formed in one step. The process is simple and has little impact on the electrical performance of the device. At the same time, it effectively reduces the terminal area and saves device manufacturing costs while meeting the terminal design requirements of silicon carbide devices.
[0022] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description
[0023] Figure 1 This is a flowchart of a method for fabricating a silicon carbide multi-angle etching terminal according to an embodiment of the present invention;
[0024] Figure 2 yes Figure 1 A schematic diagram of the deposition of a silicon carbide epitaxial layer on the substrate in step one of the method shown;
[0025] Figure 3 yes Figure 1 A schematic diagram of the deposition of a hard mask layer on the silicon carbide epitaxial layer in step one of the method shown;
[0026] Figure 4 yes Figure 1 A schematic diagram of etching the hard mask layer to form mask etching trenches in step two of the method shown;
[0027] Figure 5 yes Figure 1 A schematic diagram of step three of the method shown, after spin coating of photoresist on the terminal surface;
[0028] Figure 6 yes Figure 1 A schematic diagram of the beveled photoresist morphology formed on the sidewall of the mask etching trench in step four of the method shown;
[0029] Figure 7This is a schematic diagram of the etching morphology formed after etching silicon carbide when there are beveled photoresist and hard mask on silicon carbide respectively;
[0030] Figure 8 yes Figure 1 A schematic diagram showing the formation of a positive angle etching morphology between the sidewalls and bottom surface of the silicon carbide etching trench during the etching of the silicon carbide epitaxial layer downward along the mask etching trench in step five of the method shown.
[0031] Figure 9 yes Figure 1 A schematic diagram showing the formation of a vertical etching morphology on the sidewall of the silicon carbide etching trench during step five of the method shown, when etching the silicon carbide epitaxial layer downward along the mask etching trench.
[0032] Figure 10 yes Figure 1 A schematic diagram of the terminal after removing the remaining hard mask layer in step six of the method shown;
[0033] Figure 11 It is to utilize Figure 1 The diagram shows a silicon carbide terminal prepared by the method shown, in which a vertical etching morphology is formed at the main junction and a positive angle etching is formed at the lower homogeneous junction. Detailed Implementation
[0034] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.
[0035] To achieve the fabrication of silicon carbide power devices with good electrical performance using a simple process, embodiments of the present invention provide a method for fabricating silicon carbide multi-angle etching terminals, such as... Figure 1 As shown, the method includes the following steps:
[0036] Step 1: Provide a substrate, and deposit a silicon carbide epitaxial layer and a hard mask layer sequentially on the substrate to form the initial terminal.
[0037] Specifically, a silicon carbide epitaxial layer 2 is grown on substrate 1 using an epitaxial growth process, such as... Figure 2 As shown; then, a hard mask layer 3 is deposited on the silicon carbide epitaxial layer 2 using a CVD (Chemical Vapor Deposition) process, as shown. Figure 3 As shown.
[0038] The substrate 1 is preferably a silicon carbide substrate, but is not limited thereto. The hard mask layer is an inorganic thin film material. For example, the material of the hard mask layer 3 can be TiN, SiN or SiO2, but is not limited thereto.
[0039] Step 2: Etch the hard mask layer to form a mask etching trench; the depth of the mask etching trench is greater than or equal to the thickness of the hard mask layer.
[0040] Specifically, an etching mask for the hard mask layer 3 is formed using photoresist photolithography. Then, based on this etching mask, the hard mask layer 3 is etched using dry etching to form mask etching trenches, such as... Figure 4 As shown.
[0041] Step 3: Spin-coat photoresist onto the terminal surface so that the photoresist thickness inside the mask etching trench is greater than the photoresist thickness on the terminal surface on both sides of the mask etching trench.
[0042] Specifically, due to the mask etching trenches, the terminal surface has a stepped structure. Photoresist 4 is spin-coated onto this stepped structure. Because of the steps, the spin-coated photoresist 4 naturally exhibits a morphology where its thickness within the mask etching trenches is greater than the photoresist thickness on the terminal surface on both sides of the trenches. Figure 5 As shown. In practice, the spin-coating thickness of photoresist 4 is preferably less than the depth of the mask etching trench, and usually does not exceed 1 μm.
[0043] Step 4: Perform general exposure, baking, development and hardening treatment on the photoresist on the terminal in sequence, so that the sidewalls of the mask etching trench form a sloping photoresist morphology.
[0044] Here, the photoresist 4 on the terminal is first subjected to generalized exposure, and then the photoresist 4 is processed using a subsequent photolithography process. The subsequent photolithography process includes baking, development, and hardening.
[0045] Preferably, the dose of generalized exposure is 20mJ to 100mJ.
[0046] Preferably, the baking temperature after exposure is 80℃~130℃, and the baking time is 1 minute.
[0047] Preferably, the development time is 60 to 180 seconds.
[0048] Preferably, the temperature for the hardening treatment is 90℃~130℃, and the treatment time is 1 minute.
[0049] Therefore, by utilizing the aforementioned generalized exposure and subsequent photolithography processes, a sloping photoresist morphology can be formed on the sidewalls of the mask etching trenches, such as... Figure 6 As shown, the photoresist 4 on the sidewall of the mask etching trench naturally presents a sloping shape that is smaller at the top and larger at the bottom.
[0050] Step 5: Etch the silicon carbide epitaxial layer downwards along the mask etching trench until all photoresist is consumed and a silicon carbide etching trench is formed; wherein, the sidewalls of the silicon carbide etching trench have a vertical etching morphology, and a positive angle etching morphology is formed between the sidewalls and the bottom surface.
[0051] See Figure 7 When there is a sloped photoresist 4 on silicon carbide, because the selectivity of the photoresist to silicon carbide is less than 1, the etching of silicon carbide will cause the angle θ2 between the sidewall of the etched trench and the plane to be smaller than the angle θ1 between the photoresist and the plane, i.e., θ2 < θ1. When there is a sloped hard mask on silicon carbide, because the etching selectivity of the hard mask to silicon carbide is greater than 1, the angle θ2 between the sidewall of the etched trench and the plane will be larger than the angle θ1 between the photoresist and the plane, i.e., θ2 > θ1.
[0052] Therefore, in Figure 6 In the terminal configuration shown, etching the silicon carbide epitaxial layer 2 downwards along the mask etching trench can form a positive angle etching morphology between the sidewalls and bottom surface of the silicon carbide etching trench 5, such as... Figure 8 As etching progresses, the sidewalls of the silicon carbide etching trench 5 tend to become vertical, forming a vertical etching morphology, such as... Figure 9 Therefore, by using a double-layer mask formed by a photoresist layer with a beveled morphology and a hard mask layer to etch silicon carbide, multi-angle etching of silicon carbide can be achieved in a single etching process, avoiding the misalignment problem caused by photolithography. This allows for the formation of multi-angle etched silicon carbide trenches 5 in a single etching process. The process is simple and has little impact on the electrical performance of the device. Furthermore, it effectively reduces the terminal area while meeting the terminal design requirements of silicon carbide devices, thus saving device manufacturing costs.
[0053] In step five, the silicon carbide epitaxial layer 2 is etched downwards along the mask etching trench by dry etching.
[0054] Step 6: Remove the remaining hard mask layer.
[0055] Specifically, such as Figure 10 As shown, the remaining hard mask layer 3 is removed by wet etching to obtain a silicon carbide terminal with multi-angle silicon carbide etched trenches 5. Figure 11 As shown, a vertical etching morphology is formed at the main junction, that is, the etching angle is 90°, and a positive angle etching is formed at the lower junction of the same type.
[0056] Based on the same inventive concept, this invention also provides a silicon carbide diode having silicon carbide etched trenches. These trenches are fabricated using the silicon carbide multi-angle etching terminal fabrication method shown in the above-described fabrication method embodiments. For the specific fabrication process, please refer to the above-described method embodiments; it will not be repeated here. Furthermore, regarding other structures included in the silicon carbide diode, such as the anode electrode and cathode electrode, the same applies to existing silicon carbide diodes, and this invention will not elaborate further.
[0057] This invention also provides a silicon carbide diode having silicon carbide etched trenches. The sidewalls of the silicon carbide etched trenches have a vertical etched morphology, and a positive angle etched morphology is formed between the sidewalls and the bottom surface, such as... Figure 10 and Figure 11 As shown. In practice, the silicon carbide etched trenches of this silicon carbide diode can be prepared using the silicon carbide multi-angle etching terminal preparation method shown in the above-described preparation method embodiments, which will not be elaborated upon in this embodiment. Furthermore, regarding other structures included in the silicon carbide diode, such as the anode electrode and cathode electrode, the same as in existing silicon carbide diodes, will not be elaborated upon in this embodiment.
[0058] It should be noted that the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention.
[0059] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.
[0060] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings and the disclosure in carrying out the claimed invention. In the description of the invention, the word "comprising" does not exclude other components or steps, "a" or "an" does not exclude a plurality, and "a plurality" means two or more, unless otherwise explicitly specified. Furthermore, while different embodiments may describe certain measures, this does not mean that these measures cannot be combined to produce good results.
[0061] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0062] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0063] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0064] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.
Claims
1. A method for fabricating a silicon carbide multi-angle etching terminal, characterized in that, include: Step 1: Provide a substrate, and sequentially deposit a silicon carbide epitaxial layer and a hard mask layer on the substrate to form the initial terminal; Step 2: Etch the hard mask layer to form mask etching trenches, so that the terminal surface has a stepped structure; the depth of the mask etching trenches is greater than or equal to the thickness of the hard mask layer; Step 3: Spin-coat photoresist onto the terminal surface. Due to the presence of the steps, the thickness of the photoresist in the mask etching trench is naturally greater than the thickness of the photoresist on the terminal surface on both sides of the mask etching trench. Step 4: The photoresist on the terminal is subjected to general exposure, baking, development and hard film treatment in sequence, so that the sidewalls of the mask etching trench form a sloping photoresist morphology with a smaller top and a larger bottom; wherein, the sloping photoresist and the hard mask layer form a soft and hard combined double mask. Step 5: Etch the silicon carbide epitaxial layer downwards along the mask etching trench until all photoresist is consumed and a silicon carbide etching trench is formed; wherein, the sidewalls of the silicon carbide etching trench have a vertical etching morphology, and a positive angle etching morphology is formed between the sidewalls and the bottom surface; Step 6: Remove the remaining hard mask layer.
2. The method for fabricating a silicon carbide multi-angle etching terminal according to claim 1, characterized in that, In step three, the spin coating thickness of the photoresist is less than the depth of the etched trenches in the mask.
3. The method for fabricating a silicon carbide multi-angle etching terminal according to claim 1, characterized in that, In step four, the dose of generalized exposure is 20mJ~100mJ.
4. The method for fabricating a silicon carbide multi-angle etching terminal according to claim 1, characterized in that, In step four, the baking temperature after overexposure is 80℃~130℃, and the baking time is 1 minute.
5. The method for fabricating a silicon carbide multi-angle etching terminal according to claim 1, characterized in that, In step four, the development time is 60 to 180 seconds.
6. The method for fabricating a silicon carbide multi-angle etching terminal according to claim 1, characterized in that, In step four, the temperature for the hardening treatment is 90℃~130℃, and the treatment time is 1 minute.
7. The method for fabricating a silicon carbide multi-angle etching terminal according to claim 1, characterized in that, The hard mask layer is made of TiN, SiN, or SiO2.
8. The method for fabricating a silicon carbide multi-angle etching terminal according to claim 1, characterized in that, The substrate is a silicon carbide substrate.
9. A silicon carbide diode, characterized in that, The silicon carbide diode has silicon carbide etched trenches, which are prepared by the method for preparing silicon carbide multi-angle etched terminals as described in any one of claims 1 to 8.