Preparation method of silicon carbide multi-angle etching terminal and silicon carbide diode

Abstract

The invention discloses a preparation method of a silicon carbide multi-angle etching terminal and a silicon carbide diode, and the preparation method comprises the steps: sequentially depositing a silicon carbide epitaxial layer and a hard mask layer on a substrate, and forming an initial terminal; etching the hard mask layer to form a mask etching groove; photoresist is spin-coated on the surface of the terminal, so that the thickness of the photoresist in the mask etching groove is greater than the thickness of the photoresist on the surface of the terminal on the two sides of the mask etching groove; the photoresist on the terminal is subjected to flooding exposure, baking, developing and hardening treatment in sequence, so that the side wall of the mask etching groove forms an inclined plane photoresist morphology; etching the silicon carbide epitaxial layer downwards along the mask etching groove until all the photoresist is consumed and a silicon carbide etching groove is formed; wherein the side wall of the silicon carbide etching groove is in a vertical etching shape, and a positive angle etching shape is formed between the side wall and the bottom surface; and removing the residual hard mask layer. According to the invention, the silicon carbide power device with relatively good electrical properties is prepared by a simple process.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and in particular relates to a method for preparing a silicon carbide multi-angle etching terminal and a silicon carbide diode. Background Art

[0002] Silicon carbide power devices are typical representatives of power devices and are widely used in electric vehicles, aerospace, power conversion and other fields. With the development of planar power devices, conventional planar terminals require a larger terminal area to meet the device breakdown voltage design requirements. Due to the existence of a negative angle at the main junction, the single-angle etched terminal needs to reduce the angle to meet the device breakdown voltage design requirements, and also requires a larger terminal area. In order to reduce the terminal area, a multi-angle etched terminal has emerged in recent years. This terminal adjusts the etching angle at the main junction on the basis of the conventional etched terminal to 90°. At this time, the main junction is no longer a negative angle terminal, and there is no electric field concentration. Since the etching angle on the upper side is increased, the area of ​​the terminal is greatly reduced. However, this design increases the complexity of the process. If the etching mask is re-prepared and photolithography is performed between two etchings, the electrical performance of the device will be affected due to the offset problem. Summary of the invention

[0003] In order to solve the above problems existing in the prior art, the present invention provides a method for preparing a silicon carbide multi-angle etching terminal and a silicon carbide diode.

[0004] The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0005] A method for preparing a silicon carbide multi-angle etching terminal, comprising:

[0006] Step 1: providing a substrate, and sequentially depositing a silicon carbide epitaxial layer and a hard mask layer on the substrate to form an initial terminal;

[0007] Step 2: etching the hard mask layer to form a mask etching groove; the depth of the mask etching groove is greater than or equal to the thickness of the hard mask layer;

[0008] Step 3, spin-coating photoresist on the terminal surface so that the thickness of the photoresist in the mask etching groove is greater than the thickness of the photoresist on the terminal surface on both sides of the mask etching groove;

[0009] Step 4: performing flood exposure, baking, development and hardening treatment on the photoresist on the terminal in sequence, so that the sidewalls of the mask-etched grooves form a bevel photoresist morphology;

[0010] Step 5, etching the silicon carbide epitaxial layer downward along the mask etching groove until all the photoresist is consumed and a silicon carbide etching groove is formed; wherein the sidewall of the silicon carbide etching groove presents a vertical etching morphology, and a positive angle etching morphology is formed between the sidewall and the bottom surface;

[0011] Step 6: Remove the remaining hard mask layer.

[0012] Optionally, in step three, the spin-coated thickness of the photoresist is smaller than the depth of the mask-etched grooves.

[0013] Optionally, in step 4, the dose of flood exposure is 20 mJ to 100 mJ.

[0014] Optionally, in step 4, the baking temperature after flood exposure is 80° C. to 130° C., and the baking time is 1 minute.

[0015] Optionally, in step 4, the developing time is 60 seconds to 180 seconds.

[0016] Optionally, in step 4, the temperature of the hardening treatment is 90° C. to 130° C., and the treatment time is 1 minute.

[0017] Optionally, the material of the hard mask layer is TiN, SiN or SiO 2 .

[0018] Optionally, the substrate is a silicon carbide substrate.

[0019] The present invention also provides a silicon carbide diode, which has a silicon carbide etching groove, the side wall of the silicon carbide etching groove presents a vertical etching morphology, and a positive angle etching morphology is formed between the side wall and the bottom surface.

[0020] The present invention also provides a silicon carbide diode having a silicon carbide etching groove, wherein the silicon carbide etching groove is prepared by using any of the above-mentioned methods for preparing a silicon carbide multi-angle etching terminal.

[0021] The method for preparing a silicon carbide multi-angle etching terminal provided by the present invention comprises the following steps: after a silicon carbide epitaxial layer and a hard mask layer are sequentially deposited on a substrate, a mask etching groove is formed by etching the hard mask layer, and a step-like structure is formed on the terminal surface. The step-like structure is spin-coated with photoresist to realize a photoresist morphology with different heights (thicknesses), and then the photoresist on the terminal is sequentially subjected to flood exposure, baking, development, and hardening treatment, so that the sidewall of the mask etching groove forms an inclined photoresist morphology. Then, the silicon carbide epitaxial layer is etched downward along the mask etching groove to form a silicon carbide etching groove. Among them, since the photoresist etching silicon carbide selectivity ratio is less than 1, a positive angle etching morphology can be formed between the sidewall and the bottom surface of the silicon carbide etching groove after all the photoresist is consumed. Since the hard mask layer close to the silicon carbide epitaxial layer has an etching selectivity ratio of greater than 1 to silicon carbide, a vertical etching morphology can be formed on the sidewall of the silicon carbide etching groove. Therefore, by etching silicon carbide using a double-layer mask combining soft and hard formed by a beveled photoresist and a hard mask layer, multi-angle etched silicon carbide etching grooves can be formed at one time. The process is simple and has little impact on the electrical properties of the device. It also effectively reduces the terminal area while meeting the terminal design requirements of the silicon carbide device, saving device manufacturing costs.

[0022] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of a method for preparing a silicon carbide multi-angle etching terminal provided by an embodiment of the present invention;

[0024] Figure 2 yes Figure 1 A schematic diagram of depositing a silicon carbide epitaxial layer on a substrate in step 1 of the method shown;

[0025] Figure 3 yes Figure 1 A schematic diagram of depositing a hard mask layer on a silicon carbide epitaxial layer in step 1 of the method shown;

[0026] Figure 4 yes Figure 1 A schematic diagram of etching the hard mask layer to form a mask etching groove in step 2 of the method shown;

[0027] Figure 5 yes Figure 1 A schematic diagram of the method shown in step 3 after spin coating photoresist on the terminal surface;

[0028] Figure 6 yes Figure 1 A schematic diagram of forming a sloped photoresist profile on the sidewall of a mask-etched trench in step 4 of the method;

[0029] Figure 7It is a schematic diagram of the etching morphology formed after etching silicon carbide when there are bevel-state photoresist and hard mask on silicon carbide respectively;

[0030] Figure 8 yes Figure 1 A schematic diagram of a positive-angle etching morphology formed between the sidewall and bottom surface of the silicon carbide etching groove when etching the silicon carbide epitaxial layer downward along the mask etching groove in step five of the method shown;

[0031] Fig. 9 yes Figure 1 A schematic diagram of a vertical etching morphology formed on the sidewall of the silicon carbide etching groove when etching the silicon carbide epitaxial layer downward along the mask etching groove in step five of the method shown;

[0032] Fig.10 yes Figure 1 A schematic diagram of the terminal after removing the remaining hard mask layer in step six of the method;

[0033] Fig.11 is to use Figure 1 A schematic diagram showing a vertical etching morphology formed at the main junction and a positive angle etching formed at the lower side isotype junction in the silicon carbide terminal prepared by the method shown. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0035] In order to realize the preparation of silicon carbide power devices with good electrical performance by simple process, an embodiment of the present invention provides a method for preparing silicon carbide multi-angle etching terminals, such as Figure 1 As shown, the method comprises the following steps:

[0036] Step 1: Provide a substrate, and sequentially deposit a silicon carbide epitaxial layer and a hard mask layer on the substrate to form an initial terminal.

[0037] Specifically, a silicon carbide epitaxial layer 2 is grown on a substrate 1 by an epitaxial growth process, such as Figure 2 Then, a hard mask layer 3 is deposited on the silicon carbide epitaxial layer 2 using a CVD (Chemical Vapor Deposition) process, as shown in FIG. Figure 3 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 SiO 2 , but is not limited to this.

[0039] Step 2: etching the hard mask layer to form a mask etching groove; the depth of the mask etching groove is greater than or equal to the thickness of the hard mask layer.

[0040] Specifically, an etching mask of the hard mask layer 3 is formed by photolithography using a photoresist, and then the hard mask layer 3 is etched by dry etching based on the etching mask to form a mask etching groove, such as Figure 4 shown.

[0041] Step 3: Spin-coat photoresist on the terminal surface so that the thickness of the photoresist in the mask etching groove is greater than the thickness of the photoresist on the terminal surfaces on both sides of the mask etching groove.

[0042] Specifically, the terminal surface has a step-like structure because of the mask etching groove. The photoresist 4 is spin-coated on the step-like structure. Due to the presence of the step, the spin-coated photoresist 4 can naturally present a morphology in which the thickness in the mask etching groove is thicker than the thickness of the photoresist on the terminal surfaces on both sides of the groove. Figure 5 In practice, the spin-coated thickness of the photoresist 4 is preferably smaller than the depth of the mask-etched trench, and is usually no more than 1 μm.

[0043] Step 4: perform flood exposure, baking, development and hardening treatment on the photoresist on the terminal in sequence, so that the sidewalls of the mask-etched grooves form a bevel photoresist morphology.

[0044] Here, the photoresist 4 on the terminal is firstly exposed, and then the photoresist 4 is processed by a back-end photolithography process, wherein the back-end photolithography process includes baking, developing and hardening.

[0045] Preferably, the dose of flood exposure is 20 mJ to 100 mJ.

[0046] Preferably, the baking temperature after flood exposure is 80° C. to 130° C., and the baking time is 1 minute.

[0047] Preferably, the development time is 60 seconds to 180 seconds.

[0048] Preferably, the temperature of the film hardening treatment is 90° C. to 130° C., and the treatment time is 1 minute.

[0049] Therefore, by using the above-mentioned flood exposure and back-end photolithography process, the sidewall of the mask-etched groove can be formed into a bevel photoresist morphology, such as Figure 6 As shown, the photoresist 4 on the sidewall of the mask-etched groove naturally presents a slope shape that is smaller at the top and larger at the bottom.

[0050] Step 5: Etch the silicon carbide epitaxial layer downward along the mask etching groove until all the photoresist is consumed and a silicon carbide etching groove is formed; wherein the sidewall of the silicon carbide etching groove presents a vertical etching morphology, and a positive angle etching morphology is formed between the sidewall and the bottom surface.

[0051] See also Figure 7 When there is a beveled photoresist 4 on silicon carbide, since the photoresist etching silicon carbide selectivity is less than 1, the etching of silicon carbide will make the angle θ between the etched groove sidewall and the plane 2 Smaller than the angle θ between the photoresist and the plane 1 , that is, θ 2 <θ 1 When there is a beveled hard mask on silicon carbide, the etching selectivity of the hard mask to silicon carbide is greater than 1, which will cause the angle θ between the etched trench sidewall and the plane to be 2 Greater than the angle θ between the photoresist and the plane 1 , that is, θ 2 >θ 1 .

[0052] Therefore, in Figure 6 In the terminal state shown, the silicon carbide epitaxial layer 2 is etched downward along the mask etching groove, and a positive angle etching morphology can be formed between the side wall and the bottom surface of the silicon carbide etching groove 5, such as Figure 8 As the etching progresses, the sidewalls of the silicon carbide etched trench 5 tend to be vertical, forming a vertical etching morphology, such as Fig. 9 Therefore, by etching silicon carbide using a double-layer mask combining soft and hard formed by a photoresist + hard mask layer with an inclined surface morphology, multi-angle etching of silicon carbide can be achieved in one etching of silicon carbide, avoiding the problem of offset caused by photolithography, so that multi-angle etched silicon carbide etching grooves 5 can be formed in one etching. The process is simple and has little impact on the electrical performance of the device. It can also effectively reduce the terminal area while meeting the terminal design requirements of the silicon carbide device, saving the device manufacturing cost.

[0053] In step five, etching the silicon carbide epitaxial layer 2 downward along the mask etching groove is achieved by dry etching.

[0054] Step 6: Remove the remaining hard mask layer.

[0055] Specifically, Fig.10 As shown, the remaining hard mask layer 3 is removed by wet etching to obtain a silicon carbide terminal having a multi-angle silicon carbide etched groove 5. Fig.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 isotype junction.

[0056] Based on the same inventive concept, an embodiment of the present invention further provides a silicon carbide diode having a silicon carbide etched groove, which is prepared by the method for preparing a silicon carbide multi-angle etched terminal shown in the above preparation method embodiment. For the specific preparation process, please refer to the above method embodiment, which will not be repeated here. In addition, other structures included in the silicon carbide diode, such as an anode electrode and a cathode electrode, are the same as those of the related existing silicon carbide diodes, and the embodiments of the present invention will not be repeated.

[0057] The embodiment of the present invention further provides a silicon carbide diode, which has a silicon carbide etched groove, the sidewall of the silicon carbide etched groove has a vertical etched morphology, and a positive angle etched morphology is formed between the sidewall and the bottom surface, such as Fig.10 and Fig.11 In practice, the silicon carbide etched groove of the silicon carbide diode can be prepared by the method for preparing the silicon carbide multi-angle etching terminal shown in the above-mentioned preparation method embodiment, which will not be described in detail in the present embodiment. In addition, other structures included in the silicon carbide diode, such as the anode electrode and the cathode electrode, are the same as those of the related existing silicon carbide diodes, and will not be described in detail in the present 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 the data used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order 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. Instead, they are merely examples of devices and methods consistent with some aspects of the present invention.

[0059] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0060] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art can understand and implement other changes to the disclosed embodiments by viewing the drawings and the disclosed content. In the description of the present invention, the term "comprising" does not exclude other components or steps, "one" or "an" does not exclude multiple situations, and "multiple" means two or more, unless otherwise clearly and specifically limited. In addition, certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0061] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0062] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0063] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0064] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing a silicon carbide multi-angle etching terminal, characterized in that: include: Step 1: providing a substrate, and sequentially depositing a silicon carbide epitaxial layer and a hard mask layer on the substrate to form an initial terminal; Step 2: etching the hard mask layer to form a mask etching groove; The depth of the mask etching groove is greater than or equal to the thickness of the hard mask layer; Step 3, spin-coating photoresist on the terminal surface so that the thickness of the photoresist in the mask etching groove is greater than the thickness of the photoresist on the terminal surface on both sides of the mask etching groove; Step 4: performing flood exposure, baking, development and hardening treatment on the photoresist on the terminal in sequence, so that the sidewalls of the mask-etched grooves form a bevel photoresist morphology; Step 5, etching the silicon carbide epitaxial layer downward along the mask etching groove until all the photoresist is consumed and a silicon carbide etching groove is formed; wherein the sidewall of the silicon carbide etching groove presents a vertical etching morphology, and a positive angle etching morphology is formed between the sidewall and the bottom surface; Step 6: Remove the remaining hard mask layer.

2. The method for preparing a silicon carbide multi-angle etching terminal according to claim 1, characterized in that: In step three, the spin-coated thickness of the photoresist is smaller than the depth of the mask-etched grooves.

3. The method for preparing a silicon carbide multi-angle etching terminal according to claim 1, characterized in that: In step 4, the dose of flood exposure is 20 mJ to 100 mJ.

4. The method for preparing a silicon carbide multi-angle etching terminal according to claim 1, characterized in that: In step 4, the baking temperature after flood exposure is 80° C. to 130° C., and the baking time is 1 minute.

5. The method for preparing a silicon carbide multi-angle etching terminal according to claim 1, characterized in that: In step 4, the developing time is 60 seconds to 180 seconds.

6. The method for preparing a silicon carbide multi-angle etching terminal according to claim 1, characterized in that: In step 4, the temperature of the hardening treatment is 90° C. to 130° C., and the treatment time is 1 minute.

7. The method for preparing a silicon carbide multi-angle etching terminal according to claim 1, characterized in that: The material of the hard mask layer is TiN, SiN or SiO2.

8. The method for preparing 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 a silicon carbide etching groove, the side wall of the silicon carbide etching groove presents a vertical etching morphology, and a positive angle etching morphology is formed between the side wall and the bottom surface.

10. A silicon carbide diode, characterized in that: The silicon carbide diode has a silicon carbide etching groove, and the silicon carbide etching groove is prepared by the method for preparing a silicon carbide multi-angle etching terminal according to any one of claims 1 to 8.

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