A SiC deep etching method based on composite mask

Abstract

The application relates to a SiC deep etching method based on a composite mask, which comprises the following steps: depositing a first mask layer on a SiC substrate; sputtering a seed metal layer on the first mask layer; preparing a second mask layer on the seed metal layer; etching the second mask layer and the seed metal layer to form a plurality of interval-arranged preset grooves; removing the remaining photoresist, etching the first mask layer in the preset grooves to expose the upper surface of the SiC substrate; etching the SiC substrate in the preset grooves with a preset thickness by using a plasma etching mode to form a plurality of interval-arranged SiC initial grooves; removing the remaining second mask layer and the seed metal layer; etching the SiC initial grooves by using a gas to prepare SiC final grooves; and removing the remaining first mask layer to complete the etching of the SiC substrate grooves. The application can effectively avoid the micro mask phenomenon caused by the falling of the metal layer, reduce the roughness of the SiC groove sidewall, and reduce the vertical stripe of the sidewall by preparing a composite mask layer and twice etching processes.

Description

Technical Field

[0001] This invention relates to the field of semiconductor process technology, and more specifically to a deep etching method for SiC based on a composite mask. Background Technology

[0002] Current silicon carbide deep etching technology is still imperfect. During the etching process of trenches with large aspect ratios, there are micromasking effects similar to "growing grass" and bottom micro-trenches. The sidewall roughness of the etched area is high, and the bottom morphology of the trench is poor.

[0003] If microtrenches are formed, electric field spikes will form at the sharp corners of the bottom microtrench due to the electric field concentration effect, leading to reduced device reliability and premature avalanche breakdown, thereby reducing device performance. The presence of vertical stripes on the sidewalls and high surface roughness of the etched surface make the device prone to forming leakage channels, resulting in increased leakage current and affecting the device's current handling capability.

[0004] Conventional non-metallic mask etching has a low selectivity and is unsuitable for deep etching of silicon carbide under constant current, long duration, and high power conditions. The high edge roughness of a single metal mask pattern leads to rough sidewall morphology in the etching trenches. Furthermore, poor metal mask rigidity can cause detachment, resulting in a micro-mask effect at the bottom, creating a "grass-like" appearance. In addition, metal contamination from the metal mask can affect the performance of the substrate or epitaxial wafer. Existing processes require secondary treatments such as sacrificial oxygen etching after etching, which results in poor morphology optimization and reduced trench mesa height, affecting trench depth. These processes are also costly, inefficient, and time-consuming. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a deep etching method for SiC based on a composite mask. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] A deep etching method for SiC based on a composite mask, the SiC deep etching method comprising:

[0007] Step 1: Select a SiC substrate;

[0008] Step 2: Deposit a first mask layer on the SiC substrate. The first mask layer is a non-metallic mask layer.

[0009] Step 3: Sputter a seed metal layer onto the first mask layer;

[0010] Step 4: Electroplating or electroforming a second mask layer on the seed metal layer, wherein the second mask layer is a metal mask layer;

[0011] Step 5: Coat photoresist, etch the second mask layer and the seed metal layer to form a plurality of spaced pre-set trenches, the bottom of the pre-set trenches exposing the upper surface of the first mask layer;

[0012] Step 6: Remove the remaining photoresist and etch the first mask layer in the preset trench to expose the upper surface of the SiC substrate;

[0013] Step 7: Use plasma etching to etch the SiC substrate within the preset trench of a preset thickness to form a plurality of spaced-apart initial SiC trenches, wherein the preset thickness is less than the total thickness of the SiC substrate;

[0014] Step 8: Remove the remaining second mask layer and the seed metal layer;

[0015] Step 9: Use gas etching to create the initial SiC trench to prepare the final SiC trench;

[0016] Step 10: Remove the remaining first mask layer to complete the etching of the SiC substrate trench.

[0017] In one embodiment of the present invention, after step 4, the method further includes:

[0018] A preset layer is prepared on the second mask layer, wherein the preset layer is a metal layer or a metal oxide layer.

[0019] In one embodiment of the present invention, after step 4, the method further includes:

[0020] n sets of composite layers are prepared on the second mask layer. The composite layers include, from bottom to top, a seed metal layer and a second mask layer stacked together, wherein n≥1.

[0021] In one embodiment of the present invention, after step 4, the method further includes:

[0022] A third mask layer is prepared on the second mask layer, wherein the third mask layer is a non-metallic mask layer.

[0023] In one embodiment of the present invention, the first mask layer includes silicon dioxide or silicon nitride, the second mask layer includes a nickel layer, a copper layer, a gold layer or a chromium layer, and the seed metal layer includes, from bottom to top, a stacked metal adhesion layer and a metal conductive layer, wherein the thickness of the metal adhesion layer is less than the thickness of the metal conductive layer.

[0024] In one embodiment of the present invention, step 3 includes:

[0025] A seed metal layer is sputtered onto the first mask layer using DC magnetron sputtering, wherein the sputtering power is 20-200W, the atmosphere is Ar, and the sputtering pressure is 0.5-5mtorr.

[0026] In one embodiment of the present invention, etching the second mask layer and the seed metal layer to form a plurality of pre-set trenches arranged at intervals includes:

[0027] The second mask layer and the seed metal layer are etched using a wet etching method to form a number of pre-set trenches arranged at intervals.

[0028] In one embodiment of the present invention, the first mask layer within the preset trench is etched to expose the upper surface of the SiC substrate.

[0029] The first mask layer within the preset trench is etched using hydrofluoric acid until the upper surface of the SiC substrate is exposed.

[0030] In one embodiment of the present invention, step 7 includes:

[0031] In a mixed gas environment of SF6, O2, and Ar, and under constant current conditions, the SiC substrate within the preset trenches of a preset thickness is etched using plasma etching to form a plurality of initially spaced SiC trenches. The cavity pressure ranges from 20 to 50 mTorr, the ICP power ranges from 1000 to 1800 W, the RF power ranges from 150 to 250 W, the SF6 flow rate ranges from 50 to 500 sccm, the Ar flow rate ranges from 50 to 500 sccm, the O2 flow rate ranges from 100 to 200 sccm, and the substrate coolant temperature ranges from -15 to 10°C.

[0032] In one embodiment of the present invention, step 9 includes:

[0033] The initial SiC trenches are etched using hydrogen, chlorine, or hydrogen chloride gas to prepare the final SiC trenches. The reaction chamber temperature is 1000-1620℃, the pressure is 10-100mbar, the flow rate of hydrogen, chlorine, or hydrogen chloride gas is 20-80L / min, the protective gas is propane, acetylene, or silane, the flow rate of the protective gas is 10-50L / min, and the etching time is 5-20 minutes.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention proposes a deep etching method for SiC based on a composite mask. A first mask layer, a seed metal layer, and a second mask layer are sequentially stacked on a SiC substrate from bottom to top. These layers form a composite mask layer required for etching deep trenches in SiC. By fabricating the composite mask layer and performing a two-stage etching process on the SiC substrate, the micromask phenomenon caused by metal layer detachment can be effectively avoided. This reduces the roughness of the SiC trench sidewalls, minimizes vertical striations on the sidewalls, protects the SiC mesa from etching, and optimizes the trench morphology. Furthermore, the composite mask layer achieves a high etching selectivity, effectively preventing contamination of the silicon carbide etched sample by the metal mask. Therefore, this invention improves etching quality, reduces the time required for subsequent processes such as sacrificial oxidation repair, increases deep etching efficiency, and saves process costs.

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a deep SiC etching method based on a composite mask provided in an embodiment of the present invention;

[0038] Figures 2a-2h This is a schematic diagram of a deep SiC etching method based on a composite mask provided in an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the preparation of a preset layer on the second mask layer provided in an embodiment of the present invention;

[0040] Figure 4 This is a schematic diagram of the preparation of a composite layer on the second mask layer provided in an embodiment of the present invention;

[0041] Figure 5 This is a schematic diagram of the preparation of a third mask layer on a second mask layer provided in an embodiment of the present invention. Detailed Implementation

[0042] 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.

[0043] Example 1

[0044] Due to the high source and substrate power, long etching time, and high etching temperature of SiC deep trench etching, metal thin films with high etching selectivity are often used as etching mask layers. Using conventional metal mask layers can lead to sidewall striations, resulting in roughness on the etching trench sidewalls. Furthermore, the plasma required for ICP (Inductively Coupled Plasma) etching bombards the silicon carbide, causing parts of the metal mask to detach, resulting in a micromask effect resembling "growing grass" at the bottom of the trench, severely affecting the morphology of the etching trench.

[0045] Therefore, this invention provides a deep etching method for SiC based on a composite mask. Please refer to [link to relevant documentation]. Figure 1 , Figures 2a-2h , Figure 1 This is a schematic diagram of a SiC deep etching method based on a composite mask provided in an embodiment of the present invention. Figures 2a-2h This is a schematic diagram of a SiC deep etching method based on a composite mask provided in an embodiment of the present invention. The SiC deep etching method based on a composite mask provided in an embodiment of the present invention may include:

[0046] Step 1, please refer to Figure 2a SiC substrate 1 was selected.

[0047] Specifically, the SiC substrate 1 is cleaned using a standard silicon carbide cleaning process.

[0048] Optionally, the SiC substrate comprises, from bottom to top, stacked SiC substrate wafers and SiC epitaxial wafers.

[0049] Step 2, please continue reading Figure 2a A first mask layer 2 is deposited on the SiC substrate 1.

[0050] Specifically, the first mask layer 2 is deposited on the SiC substrate 1 using LPCVD (Low Pressure Chemical Vapor Deposition) or PECVD (Plasma Enhanced Chemical Vapor Deposition).

[0051] Optionally, the first mask layer 2 is a non-metallic mask layer.

[0052] There are two reasons why the first mask layer 2 is a non-metallic mask layer: 1. To reduce metal contamination and damage to the SiC substrate 1. Directly fabricating a metal mask on the SiC substrate 1 would result in metal contamination, damaging the performance of the SiC substrate 1. Fabricating a non-metallic mask first on the SiC substrate 1 prevents the metal mask from directly contacting the SiC substrate 1; 2. During subsequent high-temperature gas etching, the non-metallic mask protects the SiC mesa from excessive etching, reducing linewidth errors in the structural processing and preventing the introduction of metal impurities, thus reducing metal contamination.

[0053] Furthermore, the first mask layer 2 includes silicon dioxide (SiO2) or silicon nitride (Si3N4).

[0054] Optionally, the thickness of the first mask layer 2 is 8μm-10μm.

[0055] Step 3, please refer to Figure 2b Seed metal layer 3 is sputtered onto the first mask layer 2.

[0056] Specifically, a seed metal layer 3 is sputtered onto the first mask layer 2 using DC magnetron sputtering. The temperature is room temperature, the sputtering power is 20–200 W, the atmosphere is Ar, and the sputtering pressure is 0.5–5 mtorr. This is because the seed metal layer prepared by DC magnetron sputtering has good quality and dense grains. The prepared metal layer is not easily detached during etching, resulting in a high etching selectivity.

[0057] Optionally, the seed metal layer 3 includes, from bottom to top, a stacked metal adhesion layer and a metal conductive layer. The metal adhesion layer can reduce the stress difference between the metal mask layer and the non-metal mask layer, and avoid the metal mask layer from falling off due to high stress. A metal with low stress and good adsorption can be selected. The metal conductive layer has good metal conductivity, which makes it easy for the plated metal to adhere during electroplating, thereby improving the quality of the metal mask layer.

[0058] Preferably, the thickness of the metal adhesion layer is less than the thickness of the metal conductive layer. This is because the metal adhesion layer has a lower etching selectivity, making it more susceptible to etching and metal detachment than the metal conductive layer. Therefore, an excessively thick metal adhesion layer can lead to a "micromask effect" caused by etching and sputtering of the metal adhesion layer.

[0059] Furthermore, the material of the metal adhesion layer includes one of Ni, Cr, and Ti, and the material of the metal conductive layer includes one of Ni, Au, and Cu. Those skilled in the art can select and combine the required metal adhesion layer material and metal conductive layer material according to actual needs. For example, the metal adhesion layer material may be Ni and the metal conductive layer material may be Au, or the metal adhesion layer material may be Cr and the metal conductive layer material may be Au.

[0060] Furthermore, the thickness of the metal adhesion layer is 20-30 nm, the thickness of the metal conductive layer is 80-180 nm, and the total thickness of the seed metal layer 3 is 110 nm-200 nm.

[0061] For example, a Cr metal adhesion layer and a Cu metal conductive layer were prepared by DC magnetron sputtering at room temperature, sputtering powers of 50–200 W and 20–150 W, respectively, in an Ar atmosphere, with a sputtering pressure of 0.5–5 mtorr.

[0062] Step 4, please continue reading Figure 2b A second mask layer 4 is electroplated or electroformed on the seed metal layer 3.

[0063] Optionally, the second mask layer 4 is a metal mask layer. Compared with non-metallic masks, metal mask layers have a higher etching selectivity. Deep etching of silicon carbide has the characteristics of long etching time, high plasma density, and high power. Using a metal mask can effectively protect the silicon carbide mesa from etching and realize deep trench etching.

[0064] Furthermore, the second mask layer 4 includes a nickel layer, a copper layer, a gold layer, or a chromium layer.

[0065] Optionally, the thickness of the second mask layer 4 is 3μm-8μm.

[0066] In this embodiment, a first mask layer 2, a seed metal layer 3, and a second mask layer 4 are sequentially stacked on a SiC substrate 1 from bottom to top. Thus, the first mask layer 2, the seed metal layer 3, and the second mask layer 4 form a composite mask layer required for etching deep trenches in SiC. The first mask layer 2 effectively protects the seed metal layer 3 under plasma bombardment, preventing micromask phenomena caused by metal layer shedding. The second mask layer 4 of the composite mask layer ensures a high etching selectivity, thereby achieving the etching of deep trenches in SiC.

[0067] Step 5, please refer to Figure 2c Photoresist 5 is coated, and the second mask layer 4 and seed metal layer 3 are etched to form a number of pre-set trenches arranged at intervals, with the bottom of the pre-set trenches exposing the upper surface of the first mask layer 2.

[0068] Specifically, photoresist 5 is first coated on the second mask layer 4, then a pattern is formed by photolithography, and the second mask layer 4 and the seed metal layer 3 are etched by wet etching to form a number of pre-set trenches arranged at intervals.

[0069] Here, the metal layer mainly uses a solution containing sulfuric acid or nitric acid, which can etch the metal but cannot corrode the non-metallic mask layer (sulfuric acid or nitric acid does not easily react with SiO2 and Si3N4).

[0070] Step 6, please refer to Figure 2dRemove the remaining photoresist 5 and etch the first mask layer 2 in the preset trench to expose the upper surface of the SiC substrate 1.

[0071] Specifically, firstly, the remaining photoresist 5 on the second mask layer 4 is removed, and then the first mask layer 2 in the preset trench is etched with hydrofluoric acid to expose the upper surface of the SiC substrate 3.

[0072] Step 7, please refer to Figure 2e The SiC substrate 1 is etched in a preset trench of preset thickness using plasma etching to form a number of initially spaced SiC trenches, wherein the preset thickness is less than the total thickness of the SiC substrate 1.

[0073] Specifically, in a mixed gas environment of SF6, O2 and Ar (argon) and under constant current conditions, the SiC substrate 1 in a preset trench of a preset thickness is etched by plasma etching to form a number of initially spaced SiC trenches.

[0074] Optional plasma etching process parameters are as follows: cavity pressure range of 20–50 mTorr, ICP power range of 1000–1800 W, RF power range of 150–250 W, SF6 flow rate range of 50–500 sccm, Ar flow rate range of 50–500 sccm, O2 flow rate range of 100–200 sccm, and substrate coolant temperature range of -15–10℃.

[0075] Step 8, please refer to Figure 2f Remove the remaining second mask layer 4 and seed metal layer 3.

[0076] Specifically, the remaining second mask layer 4 and seed metal layer 3 above the first mask layer 2 are removed by wet etching.

[0077] For example, nickel can be etched using H₂O₂ (for oxidation) and hydrogen fluoride (for dissolving oxides). Nitric acid and hydrochloric acid can be used instead of hydrogen fluoride. A 30% aqueous solution of ferric chloride can also be used for etching. Copper can be etched using nitric acid or sulfuric acid and a saturated 30% ferric chloride solution. A mixture of NH₄OH and H₂O₂ can also be used to etch copper. Chromium can be etched using a solution prepared with cerium ammonium nitrate (molecular formula: (NH₄)₂Ce(NO₃)₅) and glacial acetic acid (molecular formula: CH₃COOH).

[0078] Step 9, please refer to Figure 2g The initial SiC trenches were etched using gas to prepare the final SiC trenches.

[0079] Specifically, the initial SiC trenches are etched using hydrogen (H2), chlorine (Cl2), or hydrogen chloride (HCl) gas to prepare the final SiC trenches. The reaction chamber temperature is 1000-1620℃, the pressure is 10-100 mbar, and the flow rate of hydrogen, chlorine, or hydrogen chloride gas is 20-80 L / min. The protective gas is propane (C3H8), acetylene (C2H2), or silane (SiH4), with a flow rate of 10-50 L / min. The etching time is 5-20 minutes. Because high-temperature gas etching is a slow method for etching SiC, the protective gas can protect the non-metallic mask from corrosion by hydrogen, chlorine, or hydrogen chloride gas, protecting the SiC mesa structure and achieving selective etching of the SiC trenches.

[0080] This embodiment utilizes hydrogen, chlorine, or hydrogen chloride gas to perform secondary etching on the initial SiC trenches. This optimizes the sidewall morphology of the initial SiC trenches, reduces sidewall roughness, and minimizes vertical stripes, resulting in final SiC trenches with optimized sidewall morphology. During the secondary etching of the initial SiC trenches, since the second mask layer 4 and seed metal layer 3 remain above the first mask layer 2 in step 8, and the first mask layer 2 is not removed, the trenches can be etched with high-temperature gas to reduce sidewall roughness. Furthermore, because the first mask layer 2 is not removed, the SiC mesa is protected from high-temperature gas etching during the trench etching process, thus optimizing the morphology of the etched trenches.

[0081] Step 10, please refer to Figure 2h Remove the remaining first mask layer 2 to complete the etching of the SiC substrate trench.

[0082] Specifically, the remaining first mask layer 2 on the upper surface of the SiC substrate 1 is removed to complete the etching of the SiC substrate trench.

[0083] For example, the remaining first mask layer 2 can be removed using a hydrofluoric acid solution (in the range of 0.5wt% to 5wt%).

[0084] This invention proposes a deep SiC etching method based on a composite mask. A first mask layer 2, a seed metal layer 3, and a second mask layer 4 are sequentially stacked on a SiC substrate 1 from bottom to top. These layers form a composite mask layer required for etching deep trenches in SiC. By preparing this composite mask layer, the roughness of the SiC trench sidewalls is reduced during subsequent fabrication processes by etching the SiC substrate twice. This is because the SiC substrate is etched using both plasma etching and high-temperature gas etching methods, which are performed on different equipment. If a single-layer metal mask is used instead of the composite mask layer of this invention, the metal mask would severely contaminate the reaction chamber if the SiC trench sidewalls are etched using high-temperature gas after plasma etching. Without a non-metal mask, the etching mesa would reduce the aspect ratio and affect the relative etching depth. Therefore, this invention, by fabricating a composite mask layer and employing plasma etching and high-temperature gas etching methods to etch SiC, effectively avoids the micromask phenomenon caused by metal layer detachment, reduces the roughness of the SiC trench sidewalls, decreases vertical striations on the sidewalls, protects the SiC mesa from etching, and optimizes the morphology of the etched trenches. Furthermore, the composite mask layer achieves a high etching selectivity, effectively preventing contamination of the silicon carbide etched sample by the metal mask.

[0085] This invention improves etching quality by reducing ICP etching damage on the trench surface after high-temperature gas etching (the SiC damaged by ICP etching is removed by the high-temperature gas etching, and the roughness of the remaining SiC is also reduced). This reduces the time required for subsequent processes such as sacrificial oxidation repair. Because this invention reduces etching damage through high-temperature gas etching, the etching rate can be increased more in the first etching step, rather than reducing power to decrease the etching rate in order to reduce etching damage. This improves deep etching efficiency and thus saves on process costs.

[0086] Example 2

[0087] Based on Example 1, this embodiment of the invention also provides another SiC deep etching method based on a composite mask. This SiC deep etching method, after step 4 of Example 1, performs the following steps:

[0088] Step a, please refer to Figure 3 A preset layer 6 is prepared on the second mask layer 4. The preset layer 6 includes a metal layer or a metal oxide layer. By preparing the preset layer, a thicker mask can be achieved, and deeper trenches can be etched. Furthermore, by combining metal thin films with different adhesion properties, the stress between different metal layers and between metal layers and non-metal layers can be reduced, the rigidity of the metal mask layer can be enhanced, and the etching selectivity can be improved.

[0089] After the preset layer 6 is prepared on the second mask layer 4, step 5 of Example 1 is performed. When performing step 5, photoresist needs to be coated on the preset layer 6, and then the preset layer 6, the second mask layer 4 and the seed metal layer 3 are etched to form a number of preset trenches arranged at intervals.

[0090] Optionally, the metal layer may include Cu, Au, or Ni.

[0091] Optionally, the metal oxide layer may include Al2O3.

[0092] Example 3

[0093] Based on Example 1, this invention also provides another SiC deep etching method based on a composite mask. This SiC deep etching method, after step 4 of Example 1, performs the following steps:

[0094] Step b, please refer to Figure 4 n composite layers are fabricated on the second mask layer. From bottom to top, each composite layer comprises a seed metal layer 3 and a second mask layer 4 stacked together, where n ≥ 1. By fabricating n composite layers, a thicker mask can be achieved, enabling deeper trench etching. Furthermore, by combining metal films with different adhesion properties, the stress between different metal layers and between metal and non-metal layers can be reduced, enhancing the rigidity of the metal mask layer and improving the etching selectivity.

[0095] After the n composite layers are prepared on the second mask layer 4, step 5 of Example 1 is performed. When performing step 5, photoresist needs to be coated on the n composite layers, and then the n composite layers, the bottom second mask layer 4 and the seed metal layer 3 are etched to form a number of pre-set trenches arranged at intervals.

[0096] Example 4

[0097] Based on Example 1, this invention also provides another SiC deep etching method based on a composite mask. This SiC deep etching method, after step 4 of Example 1, performs the following steps:

[0098] Step c, please refer to Figure 5 A third mask layer 7 is fabricated on the second mask layer 4. The third mask layer 7 is a non-metallic mask layer. Wafer-level fabrication of metal masks can result in edge warping or detachment due to metal oxidation. Therefore, adding a non-metallic mask layer can prevent the metal mask from being exposed to air, thus avoiding affecting the rigidity and density of the metal mask.

[0099] After the third mask layer 7 is prepared on the second mask layer 4, step 5 of Example 1 is performed. When performing step 5, photoresist needs to be coated on the third mask layer 7, and then the third mask layer 7, the second mask layer 4 and the seed metal layer 3 are etched to form a number of pre-set trenches arranged at intervals.

[0100] Furthermore, the third mask layer 7 includes silicon dioxide (SiO2) or silicon nitride (Si3N4).

[0101] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0102] 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, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0103] 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, disclosure, and appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0104] 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, any modifications made without departing from the inventive concept should be considered within the scope of protection of the present invention.

Claims

1. A deep etching method for SiC based on a composite mask, characterized in that, The SiC deep etching method includes: Step 1: Select a SiC substrate; Step 2: Deposit a first mask layer on the SiC substrate. The first mask layer is a non-metallic mask layer. Step 3: Sputter a seed metal layer onto the first mask layer; Step 4: Electroplating or electroforming a second mask layer on the seed metal layer, wherein the second mask layer is a metal mask layer; Step 5: Coat photoresist, etch the second mask layer and the seed metal layer to form a plurality of spaced pre-set trenches, the bottom of the pre-set trenches exposing the upper surface of the first mask layer; Step 6: Remove the remaining photoresist and etch the first mask layer in the preset trench to expose the upper surface of the SiC substrate; Step 7: Use plasma etching to etch the SiC substrate within the preset trench of a preset thickness to form a plurality of spaced-apart initial SiC trenches, wherein the preset thickness is less than the total thickness of the SiC substrate; Step 8: Remove the remaining second mask layer and the seed metal layer; Step 9: Use gas etching to create the initial SiC trench to prepare the final SiC trench; Step 10: Remove the remaining first mask layer to complete the etching of the SiC substrate trench.

2. The SiC deep etching method according to claim 1, characterized in that, Following step 4, the following is also included: A preset layer is prepared on the second mask layer, the preset layer comprising a metal layer or a metal oxide layer.

3. The SiC deep etching method according to claim 1, characterized in that, Following step 4, the following is also included: n sets of composite layers are prepared on the second mask layer. The composite layers include, from bottom to top, a seed metal layer and a second mask layer stacked together, wherein n≥1.

4. The SiC deep etching method according to claim 1, characterized in that, Following step 4, the following is also included: A third mask layer is prepared on the second mask layer, wherein the third mask layer is a non-metallic mask layer.

5. The SiC deep etching method according to claim 1, characterized in that, The first mask layer includes silicon dioxide or silicon nitride, the second mask layer includes a nickel layer, a copper layer, a gold layer or a chromium layer, and the seed metal layer includes, from bottom to top, a stacked metal adhesion layer and a metal conductive layer, wherein the thickness of the metal adhesion layer is less than the thickness of the metal conductive layer.

6. The SiC deep etching method according to claim 1, characterized in that, Step 3 includes: A seed metal layer is sputtered onto the first mask layer using DC magnetron sputtering, wherein the sputtering power is 20-200W, the atmosphere is Ar, and the sputtering pressure is 0.5-5mtorr.

7. The SiC deep etching method according to claim 1, characterized in that, Etching the second mask layer and the seed metal layer to form a plurality of pre-arranged trenches, including: The second mask layer and the seed metal layer are etched using a wet etching method to form a number of pre-set trenches arranged at intervals.

8. The SiC deep etching method according to claim 1, characterized in that, The first mask layer within the preset trench is etched until the upper surface of the SiC substrate is exposed. The first mask layer within the preset trench is etched using hydrofluoric acid until the upper surface of the SiC substrate is exposed.

9. The SiC deep etching method according to claim 1, characterized in that, Step 7 includes: In a mixed gas environment of SF6, O2, and Ar, and under constant current conditions, the SiC substrate within the preset trenches of a preset thickness is etched using plasma etching to form a plurality of initially spaced SiC trenches. The cavity pressure ranges from 20 to 50 mTorr, the ICP power ranges from 1000 to 1800 W, the RF power ranges from 150 to 250 W, the SF6 flow rate ranges from 50 to 500 sccm, the Ar flow rate ranges from 50 to 500 sccm, the O2 flow rate ranges from 100 to 200 sccm, and the substrate coolant temperature ranges from -15 to 10°C.

10. The SiC deep etching method according to claim 1, characterized in that, Step 9 includes: The initial SiC trenches are etched using hydrogen, chlorine, or hydrogen chloride gas to prepare the final SiC trenches. The reaction chamber temperature is 1000-1620℃, the pressure is 10-100mbar, the flow rate of hydrogen, chlorine, or hydrogen chloride gas is 20-80L / min, the protective gas is propane, acetylene, or silane, the flow rate of the protective gas is 10-50 L / min, and the etching time is 5-20 minutes.

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