A silicon carbide etching method based on dynamic parameter etching and post-processing

Abstract

The present invention relates to a silicon carbide etching method based on dynamic parameter etching and post-processing, belonging to the field of microelectronics manufacturing technology. The method comprises depositing a silicon oxide layer on a silicon carbide substrate, performing a uniform development to form a photoresist barrier layer, dry etching to obtain a silicon oxide layer mask with a vertical morphology, and removing the surface photoresist barrier layer, performing a first vertical etching on the substrate, replacing the etching gas with a hydrogen-containing element to perform a second optimized etching process, fixing the hydrogen-containing etching gas flow rate, changing the ratio of the remaining gas species, and gradually reducing the bias power, performing a third and fourth optimized etching process, removing the remaining silicon oxide layer, forming a metal film on the back of the wafer, and annealing to obtain a high-quality etched surface and an arc-shaped groove morphology. The method is simple and easy to implement, has high etched surface quality, a small number of interface traps, and a good bottom groove morphology presenting an arc shape, thus avoiding electric field concentration and improving the electrical performance of the device.

Description

Technical Field

[0001] The invention relates to a silicon carbide etching method based on dynamic parameter etching and post-processing, and belongs to the technical field of microelectronics production. Background Art

[0002] As a core material for third-generation wide-bandgap semiconductors, silicon carbide (SiC) demonstrates significant application value in cutting-edge fields such as power semiconductors and radio frequency devices, leveraging its physical and chemical advantages, including superior thermal conductivity, high critical breakdown field strength, and excellent thermal stability. Compared to first-generation silicon-based materials, SiC devices have successfully surpassed their application limits in high-voltage, high-frequency, and extreme-temperature scenarios, and have now reached a market size in the tens of billions of yuan. Particularly with the rapid development of 5G networks and the new energy vehicle industry, the penetration rate of SiC power devices continues to rise, and related technologies are constantly being updated and iterated, accelerating the replacement of traditional silicon-based materials.

[0003] In the fabrication of silicon carbide devices, especially in advanced process technologies, the surface quality and topography of trench etching have a decisive impact on device performance. Currently, there are two main types of gases used for dry etching of silicon carbide: fluorine-based gases and chlorine-based gases. The former has a high etch rate but is prone to causing surface damage that is difficult to fully repair. The latter has less impact on the etched surface, but is toxic and prone to forming non-volatile etch products, which shortens machine maintenance cycles and increases production costs. Therefore, it is necessary to research the use of fluorine-based gases to achieve high etch rates, low damage, and low contamination.

[0004] Micro-grooves and sidewall comb morphologies are common adverse phenomena in silicon carbide etching and are also important causes of device failure and performance degradation. For micro-grooves optimization, additional passivation processes are usually introduced during the etching process, which increases the complexity of etching; in order to eliminate or improve the sidewall comb structure, high-temperature annealing treatment is often required.

[0005] This increases energy consumption and production time. Therefore, achieving a low-defect-density silicon carbide etched surface and a circular-arc transition bottom trench morphology without increasing process production costs is of great significance for improving device performance. To this end, the present invention is proposed. Summary of the Invention

[0006] To address the shortcomings of the existing technology, the present invention provides a simple and easy-to-operate silicon carbide etching method based on dynamic parameter etching and post-processing. Through dynamic parameter etching and the introduction of a hydrogen-containing etching gas, the silicon carbide etching rate is not significantly reduced, while the number of interface traps on the etched surface is reduced, thereby improving the quality of the silicon carbide etched surface. Combined with the traditional ohmic contact preparation process as a post-processing step, high-temperature annealing is performed to optimize the etched surface without increasing production costs. This method achieves an arc-shaped trench etch morphology, optimizes the comb effect of the trench sidewalls, reduces electric field concentration and switching losses, and thus improves the electrical performance of the device.

[0007] The technical solutions of the present invention are as follows:

[0008] A silicon carbide etching method based on dynamic parameter etching and post-processing, the steps are as follows:

[0009] S1: Depositing an oxide layer on a silicon carbide substrate using plasma chemical vapor deposition;

[0010] S2: Spin-coating photoresist on the oxide layer, and forming a photoresist barrier layer through exposure, development, and hard baking;

[0011] S3: dry-etching the oxide layer using an inductively coupled plasma etcher to form an oxide barrier layer;

[0012] S4: using pure oxygen plasma to dry-remove the remaining photoresist barrier layer on the oxide layer;

[0013] S5: etching silicon carbide using an inductively coupled plasma etcher with etching gas combination 1 to form an initial vertical silicon carbide groove morphology, with an etching depth of h1;

[0014] S6: Replace the mixed etching gas combination 2 containing hydrogen element, and perform the initial optimized etching on the silicon oxide-silicon carbide sample based on S5, with the etching depth = h2;

[0015] S7: Based on S6, the flow rate of hydrogen-containing etching gas is fixed, the etching bias power is reduced and the proportions of other gases are adjusted. The oxide layer-silicon carbide sample is subjected to the second and third optimized etchings in sequence, with etching depths of h3 and h4 respectively.

[0016] S8: removing the remaining oxide barrier layer by wet pickling;

[0017] S9: depositing a metal layer on the back side of the silicon carbide substrate by physical vapor deposition;

[0018] S10: subjecting the grooved silicon carbide-metal sample to a high-temperature rapid annealing treatment in a nitrogen-based atmosphere;

[0019] S11: The annealed sample is cleaned in concentrated sulfuric acid and hydrogen peroxide, hydrofluoric acid and deionized water in sequence.

[0020] Preferably, according to the present invention, in step S1, the oxide layer is a silicon oxide layer, and the thickness of the oxide layer is 1000-3000 nm; correspondingly, in step S3, the barrier layer is a silicon oxide barrier layer.

[0021] According to the preferred embodiment of the present invention, in step S2, the thickness of the photoresist barrier layer is 2000 to 4000 nm.

[0022] Preferably, according to the present invention, in step S3, there are three options for etching gas, namely CHF3 and Ar, or CF4 and Ar, or C4F6 and Ar, the flow ratio of CHF3 and Ar is 4:1, the flow ratio of CF4 and Ar is 4:1, and the flow ratio of C4F6 and Ar is 3:1.

[0023] Preferably, in step S4, oxygen plasma is used to remove the photoresist barrier layer at a temperature range of 50-200°C; or only wet stripping is used, with NMP as the stripping solution at a temperature of 30°C.

[0024] According to the preferred embodiment of the present invention, in step S5, there are two options for the etching gas combination 1, namely SF6 and Ar, or SF6, O2 and Ar, the flow ratio of SF6 to Ar is 1:5, and the flow ratio of SF6, O2 and Ar is 1:1:5.

[0025] Preferably, according to the present invention, in step S5, the inductively coupled plasma etcher is a conventional device, comprising an upper electrode and a lower electrode, the power of the upper electrode is 1500-2000W, and the power of the lower electrode is 300-500W.

[0026] According to the preferred embodiment of the present invention, in step S6, there are two options for the etching gas combination 2, namely SF6, CHF3 and O2, or SF6, CH2F2 and O2, the flow ratio of SF6, CHF3 and O2 is 4:2:1, and the flow ratio of SF6, CH2F2 and O2 is 4:2:1.

[0027] Preferably, according to the present invention, in step S6, the upper electrode power of the inductively coupled plasma etcher is 1000-1500W, and the lower electrode power is 300-500W.

[0028] Preferably, according to the present invention, in step S7, during the two optimized etchings, the flow rate of CHF3 or CH2F2 is fixed unchanged, the flow rate ratio of SF6 and O2 during the second optimized etching is 2:1, and the flow rate ratio of SF6 and O2 during the third optimized etching is 1:1.

[0029] Preferably, in step S7, before etching for the second and third time, overlay is increased, and overlay is for etching on the silicon carbide wafer of existing pattern, using different patterns to perform photoetching again, and photoresist covers horizontal surface and groove sidewall when leveling. It is intended to protect the etching sidewall and prevent the etching gas from causing excessive bending of the sidewall due to isotropy. Only the bottom area is exposed for subsequent optimized etching, and the groove morphology is further finely regulated to prevent sidewall corrosion or damage. By increasing overlay, the groove sidewall is protected, and accurate optimization only to the groove bottom and groove corner is achieved. When adjusting the parameters, the vertical bombardment effect of etching gradually weakens, isotropy is strengthened, and the groove curvature gradually becomes larger, and the transition is better.

[0030] Further preferably, in step S7, the exposure width of the photoresist pattern at the horizontal edge is shortened by 20-50 nm compared to the photoresist pattern in step S2.

[0031] Preferably, according to the present invention, in step S7, the power of the lower electrode during the second optimized etching is 150-300W, and the power of the lower electrode during the third optimized etching is 50-150W.

[0032] Preferably, in step S7, the total etching depth h = h1 + h2 + h3 + h4, and the depth ratios are h1:h2:h3:h4 = 8:1:0.6:0.4. Taking the total etching depth h = 1000nm as an example, the figure of merit for each depth etching is as follows: h1: 800nm, h2: 100nm, h3: 60nm, h4: 40nm.

[0033] Preferably, according to the present invention, in step S8, the acid solution is a hydrofluoric acid solution, and the volume ratio of hydrofluoric acid to water is 1:10.

[0034] According to a preferred embodiment of the present invention, in step S9, the metal layer is Ni, or Al, or Ti / Ni, and has a thickness of 50 to 100 nm.

[0035] According to the preferred embodiment of the present invention, in step S10, the annealing atmosphere is N2, or N2-H2, or NO atmosphere.

[0036] According to the preferred embodiment of the present invention, in step S10, the annealing temperature is 800-1200°C.

[0037] Preferably, in step S11 , the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 4:1, the heating temperature is 90-120° C., and the volume ratio of hydrofluoric acid to deionized water is 1:10-1:100.

[0038] According to the preferred embodiment of the present invention, the dry etching is specifically physical etching, chemical etching or physical-chemical etching.

[0039] Step 6 begins with changing the etching gas. Compared to SF6 / O2, SF6 / CHF3 / O2 enhances the lateral etching effect, resulting in an arc-shaped pattern observed in the experiment. Furthermore, the flow ratio and electrode power of the change are regular. We gradually increase the passivation effect and reduce the power of the lower electrode to improve the lateral etching effect of the etching ions. Further optimization is performed to expand the arc of the etched trench.

[0040] As the gas ratio changes, the etching effect on SiC decreases and the passivation effect increases, which makes the arc at h4 slightly larger than that at h3.

[0041] By dynamically adjusting the etching parameter ratio and the lower electrode power, arc-shaped grooves are obtained while ensuring the etched surface quality. The fillet radius can be measured to be 60-150nm.

[0042] By overlaying, the trench sidewalls are protected and only the trench bottom is optimized.

[0043] Through various steps, the etching surface quality is controlled and surface defects are passivated. At the same time, the bottom transition morphology of the non-vertical corner trench is obtained to avoid electric field concentration.

[0044] The beneficial effects of the present invention are:

[0045] The present invention provides a silicon carbide etching method based on dynamic parameter etching and post-processing. Compared with pure fluorine-based and chlorine-based gas etching, this method is safe and environmentally friendly. While ensuring a high silicon carbide etching rate, it reduces the number of etching interface traps, improves the etching surface quality, and improves the electrical performance and stability of the device.

[0046] Compared with traditional hydrogen passivation treatment methods, the introduction and fixation of a certain content of hydrogen-containing etching gas reduces the number of surface interface traps after etching through the optimization effect of hydrogen, effectively passivating silicon carbide during rapid etching, reducing residual carbon and fluorine contamination on the etched surface, and improving the etched surface quality. At the same time, by controlling its doping content, it is neither unable to play an optimization role due to a low content nor excessively high content, such as CHF3, which will cause excessive carbon deposition on the surface after etching and deteriorate the etched surface.

[0047] This shifts from the traditional device fabrication process of first preparing the ohmic contact and then etching. Instead, the front side is etched first, then the ohmic contact is annealed to optimize the front side etched surface. After pickling, the front side Schottky metal is deposited. This is because the nitrogen element can passivate residual carbon (C) from etching and repair etching damage at high temperatures. This allows for optimized front side etching while preparing the ohmic contact, improving final device quality and reducing costs.

[0048] Through the isotropic effect of CHF3 etching gas, like SF6 / CHF3 / O2, there will be a bowling effect after etching, which makes the sidewall of the etched groove appear arc-shaped, which can improve the etched surface quality and reduce the number of etching defects.

[0049] Using dynamic etching parameters, the SiC etched surface is minimally damaged. Combined with the isotropic nature of the mixed etching gas, a circular trench bottom morphology is achieved, reducing the combing effect on the trench sidewalls, avoiding electric field concentration, and further improving device reliability. This method is simple and easy to implement, combining the device's ohmic contact preparation process with passivation treatment, saving production costs while further optimizing the SiC etched surface in a nitrogen-based atmosphere. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a flow chart of the method of the present invention;

[0051] Figure 2 is a schematic diagram of the product of step S1 of the present invention;

[0052] Figure 3 is a schematic diagram of the product of step S2 of the present invention;

[0053] Figure 4 is a schematic diagram of the product of step S3 of the present invention;

[0054] Figure 5 is a schematic diagram of the product of step S4 of the present invention;

[0055] Figure 6 is a schematic diagram of the product of step S5 of the present invention;

[0056] Figure 7 is a schematic diagram of the product of step S6 of the present invention;

[0057] Figure 8 This is a schematic diagram of the product after the second optimized etching in step S7 of the present invention;

[0058] Figure 9 This is a schematic diagram of the product after the third optimized etching in step S7 of the present invention;

[0059] Figure 10 is a schematic diagram of the product of step S8 of the present invention;

[0060] Figure 11 is a schematic diagram of the product of step S9 of the present invention;

[0061] Figure 12 This is a schematic diagram of adding overlay in step S7 of the present invention;

[0062] Figure 13 This is a schematic diagram of the product after overlay etching is added in step S7 of the present invention;

[0063] Figure 14 is a groove topography image of step S5 in an embodiment of the present invention;

[0064] Figure 15is a groove topography image of step S6 in an embodiment of the present invention;

[0065] Figure 16 is a groove topography image of step S7 in an embodiment of the present invention;

[0066] Figure 17 This is a comparative diagram of the bottom micro-groove morphology in etching using the existing method;

[0067] Among them: 1. Silicon oxide layer; 2. Silicon carbide substrate; 3. Photoresist barrier layer. DETAILED DESCRIPTION

[0068] The present invention will be further described below with reference to embodiments and accompanying drawings, but is not limited thereto.

[0069] Example 1:

[0070] A silicon carbide etching method based on dynamic parameter etching and post-processing, such as Figure 1-11 As shown, the steps are as follows:

[0071] S1: On the silicon carbide substrate 2, a silicon oxide layer 1 is grown by plasma chemical vapor deposition, with a thickness of 1000 to 3000 nm.

[0072] Table 1 Silicon oxide deposition parameters

[0073] Pressure (mT) <![CDATA[ SiH4(sccm)]]> <![CDATA[ N2O(sccm)]]> <![CDATA[ N2(sccm)]]> Power (W) Time (min) 50--200 50--300 100--400 500--1500 100--300 5--15

[0074] S2: After deposition and observation, photoresist is spin-coated on the silicon oxide layer with a thickness of 2000 to 4000 nm. Exposure, development, and hard baking are performed according to the required layout to form a photoresist blocking layer 3.

[0075] S3: The silicon oxide layer 1 is dry-etched using an inductively coupled plasma etcher until the silicon carbide substrate is exposed, thereby forming an oxide barrier layer; the etching gases are CHF3 and Ar, and the flow ratio of CHF3 to Ar is 4:1.

[0076] Table 2: CHF3 and Ar etching parameters

[0077] Pressure (mT) <![CDATA[CHF3(sccm)]]> Ar (sccm) Power supply power (W) Platform power (W) Time(s) 2--12 20--80 5--20 500--1000 50--300 100--300

[0078] S4: After dry etching, the remaining photoresist barrier layer on the oxide layer is removed by oxygen plasma dry method at a temperature of 150°C.

[0079] S5: Using the silicon oxide layer as a mask, etching gas combination 1 is used to etch silicon carbide using an inductively coupled plasma etcher to form an initial vertical silicon carbide groove morphology, and the etching depth = h1; the inductively coupled plasma etcher is a conventional device, including an upper electrode and a lower electrode, the upper electrode power is 1500~2000W, and the lower electrode power is 300~500W.

[0080] The etching gases are SF6, O2 and Ar, and the flow ratio of SF6, O2 and Ar is 1:1:5. A mixed gas of SF6, O2 and Ar is used. Ar plasma enhances the vertical directionality of physical bombardment. F ions and O ions chemically react with silicon atoms and carbon atoms to generate volatile compounds, which are promptly pumped out with the molecular pump.

[0081] Table 3: SF6, O2 and Ar etching parameters

[0082] Pressure (mT) <![CDATA[SF6(sccm)]]> <![CDATA[O2(sccm)]]> Ar(sccm) Power supply power (W) Platform power (W) Time(s) 8--24 20--50 20--50 100--200 1500--2000 300--500 50--150

[0083] The groove morphology obtained in step S5 is as follows: Figure 14 shown.

[0084] S6: Replace the mixed etching gas combination 2 containing hydrogen element, and perform the initial optimized etching on the silicon oxide-silicon carbide sample based on S5, with the etching depth = h2.

[0085] The etching gas was changed to SF6, CHF3 and O2, and other etching parameters remained unchanged. The flow ratio of SF6, CHF3 and O2 was 4:2:1. The H in CHF3 reduced the deposition of fluorocarbon film on the etched surface, and the isotropic etching characteristics passivated the bottom and sidewall morphology of the groove. The upper electrode power of the inductively coupled plasma etcher was 1000-1500W, and the lower electrode power was 300-500W. The groove morphology obtained in step S6 is as follows: Figure 15 shown.

[0086] S7: Based on S6, the flow rate of hydrogen-containing etching gas is fixed, the etching bias power is reduced and the proportions of other gases are adjusted. The oxide layer-silicon carbide sample is subjected to the second and third optimized etching in sequence, with etching depths of h3 and h4 respectively.

[0087] The CHF3 gas flow rate was fixed at 20 sccm. During the two optimized etching cycles, the SF6 and O2 gas flow ratios were changed to 2:1 and 1:1, respectively. The platform power was reduced to 150W and 50W, respectively. Excess CHF3 may leave carbon residue on the surface, and O2 promotes CHF3 ionization, further enhancing the passivation effect. The lower electrode power during the second optimized etch was 150-300W, and the lower electrode power during the third optimized etch was 50-150W.

[0088] Table 4: Dynamic etching parameters of SF6, CHF3 and O2

[0089] step Pressure (mT) <![CDATA[SF6(sccm)]]> <![CDATA[CHF3(sccm)]]> <![CDATA[O2(sccm)]]> Power supply power (W) Platform power (W) Time(s) S6 8--24 80--200 20--100 20--50 1500--2000 300--500 10--30 S7 8--24 70--100 20--100 30--100 1000--1500 150--300 10--30 S7 8--24 40--80 20--100 40--150 1000--1500 50--150 30--60

[0090] The total etching depth h = h1 + h2 + h3 + h4, and the ratio of each depth is h1:h2:h3:h4 = 8:1:0.6:0.4. Taking the total etching depth h = 1000nm as an example, the figure of merit of each depth etching is as follows: h1: 800nm, h2: 100nm, h3: 60nm, h4: 40nm. The groove morphology obtained in step S7 is as follows Figure 16 shown.

[0091] S8: removing the remaining oxide barrier layer by wet pickling; preparing a hydrofluoric acid solution to etch and remove the remaining silicon oxide layer, with a volume ratio of hydrofluoric acid to water of 1:10.

[0092] S9: After cleaning and drying with nitrogen, a Ni metal layer with a thickness of 100 nm is formed on the back of the silicon carbide substrate by PVD (Physical Vapor Deposition).

[0093] S10: The grooved silicon carbide-metal sample was rapidly annealed at 900°C for 3 min in a N2 atmosphere with a heating rate of 15°C / s.

[0094] S11: The annealed samples were sequentially soaked and cleaned in concentrated sulfuric acid and hydrogen peroxide, hydrofluoric acid, and deionized water, with a volume ratio of concentrated sulfuric acid to hydrogen peroxide of 4:1, a heating temperature of 90°C, and a time of 15 minutes; they were then cleaned in a hydrofluoric acid solution with a volume ratio of hydrofluoric acid to water of 1:100 for 5 minutes; finally, the samples were ultrasonically cleaned with deionized water.

[0095] The dry etching specifically adopts physical etching, chemical etching or physical-chemical etching.

[0096] Example 2

[0097] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S3, the etching gases are CF4 and Ar, and the flow ratio of CF4 to Ar is 4:1.

[0098] Example 3

[0099] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S3, the etching gases are C4F6 and Ar, and the flow ratio of C4F6 to Ar is 3:1.

[0100] Example 4

[0101] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S4, wet stripping is adopted, NMP is used as the stripping solution, and the temperature is 30°C.

[0102] Example 5

[0103] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S4, oxygen plasma is used to remove the photoresist barrier layer at a temperature of 50°C.

[0104] Example 6

[0105] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S4, oxygen plasma is used to remove the photoresist barrier layer at a temperature of 200°C.

[0106] Example 7

[0107] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S5, the etching gas combination 1 is SF6 and Ar, and the flow ratio of SF6 to Ar is 1:5.

[0108] Example 8

[0109] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S6, the etching gas combination 2 is SF6, CH2F2 and O2, and the flow ratio of SF6, CH2F2 and O2 is 4:2:1.

[0110] Example 9

[0111] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S7, before the second and third etchings, overlay is added. Overlay is to perform photolithography again on the silicon carbide wafer with the existing pattern using a different pattern. When the photoresist is spread, it covers the horizontal surface and the sidewall of the groove. Figure 12 、 Figure 13 As shown. It aims to protect the etching sidewalls and prevent the etching gas from causing excessive bending of the sidewalls due to isotropy. Only the bottom area is exposed for subsequent optimized etching to further fine-tune the groove morphology and prevent sidewall corrosion or damage. By increasing overlay and protecting the groove sidewalls, precise optimization of only the groove bottom and groove corners is achieved. When the parameters are adjusted, the vertical bombardment effect of etching gradually weakens, the isotropy is strengthened, the curvature of the groove gradually increases, and the transition is better. Compared with the photolithography pattern in step S2, the exposure width of the photolithography pattern at the horizontal edge is shortened by 20-50nm.

[0112] Example 10

[0113] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S9, the metal layer is Al and has a thickness of 50 nm.

[0114] Example 11

[0115] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S9, the metal layer is Ti / Ni.

[0116] Example 12

[0117] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S10, the annealing atmosphere is an N2-H2 atmosphere and the annealing temperature is 800°C.

[0118] Example 13

[0119] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S10, the annealing atmosphere is an NO atmosphere and the annealing temperature is 1200°C.

[0120] Example 14

[0121] A silicon carbide etching method based on dynamic parameter etching and post-processing, wherein the steps are as described in Example 1, except that in step S11, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 4:1, the heating temperature is 120° C., and the volume ratio of hydrofluoric acid to deionized water is 1:10.

[0122] Comparative Example:

[0123] The comparative example provides an etching method without dynamic parameter adjustment and hydrogen-containing etching gas introduction. Compared with Example 1, the difference is that step S5 is etched with SF6 and O2 and then step S8 is directly performed. The product is as follows: Figure 17 As shown, micro grooves appear at the bottom of the groove after etching.

[0124] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto in form or substance. It should be noted that those skilled in the art may make various improvements and supplements without departing from the basic principles of the present invention, and such improvements and supplements should also be considered within the scope of protection of the claims of the present invention.

Claims

1. A silicon carbide etching method based on dynamic parameter etching and post-processing, characterized in that: Here are the steps: S1: Depositing an oxide layer on a silicon carbide substrate using plasma chemical vapor deposition; S2: Spin-coating photoresist on the oxide layer, and forming a photoresist barrier layer through exposure, development, and hard baking; S3: dry-etching the oxide layer to form an oxide barrier layer; S4: Oxygen plasma dry removal of the remaining photoresist barrier layer on the oxide layer; S5: etching silicon carbide using an inductively coupled plasma etcher with etching gas combination 1 to form an initial vertical silicon carbide groove morphology, with an etching depth of h1; S6: Replace the mixed etching gas combination 2 containing hydrogen element, and perform the initial optimized etching on the silicon oxide-silicon carbide sample based on S5, with the etching depth = h2; S7: Based on S6, the flow rate of hydrogen-containing etching gas is fixed, the etching bias power is reduced and the proportions of other gases are adjusted. The oxide layer-silicon carbide sample is subjected to the second and third optimized etchings in sequence, with etching depths of h3 and h4 respectively. S8: removing the remaining oxide barrier layer by wet pickling; S9: depositing a metal layer on the back side of the silicon carbide substrate by physical vapor deposition; S10: annealing the grooved silicon carbide-metal sample at high temperature in a nitrogen-based atmosphere; S11: The annealed sample is cleaned in concentrated sulfuric acid and hydrogen peroxide, hydrofluoric acid and deionized water in sequence.

2. The silicon carbide etching method based on dynamic parameter etching and post-processing according to claim 1, characterized in that: Methods include one or more of the following: I. In step S1, the oxide layer is a silicon oxide layer, and the thickness of the oxide layer is 1000 to 3000 nm; correspondingly, in step S3, the barrier layer is a silicon oxide barrier layer; II. In step S2, the thickness of the photoresist barrier layer is 2000 to 4000 nm; III. In step S4, oxygen plasma is used to remove the photoresist barrier layer at a temperature range of 50 to 200° C.; or only wet stripping is used, with NMP as the stripping solution at a temperature of 30° C.; IV. In step S8, the acid solution is a hydrofluoric acid solution, and the volume ratio of hydrofluoric acid to water is 1:10; V. In step S9, the metal layer is Ni, Al, or Ti / Ni, and has a thickness of 50 to 100 nm; VI. In step S10, the annealing atmosphere is N2, or N2-H2, or NO atmosphere; VII. In step S10, the annealing temperature is 800-1200° C.; VIII. In step S11, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 4:1, and the heating temperature is 90-120° C.; the volume ratio of hydrofluoric acid to deionized water is 1:10-1:

100.

3. The silicon carbide etching method based on dynamic parameter etching and post-processing according to claim 1, characterized in that: In step S3, there are three options for etching gas, namely CHF3 and Ar, or CF4 and Ar, or C4F6 and Ar, the flow ratio of CHF3 and Ar is 4:1, the flow ratio of CF4 and Ar is 4:1, and the flow ratio of C4F6 and Ar is 3:

1.

4. The silicon carbide etching method based on dynamic parameter etching and post-processing according to claim 1, characterized in that: In step S5, there are two options for etching gas combination 1, namely SF6 and Ar, or SF6, O2 and Ar, the flow ratio of SF6 to Ar is 1:5, and the flow ratio of SF6, O2 and Ar is 1:1:

5.

5. The silicon carbide etching method based on dynamic parameter etching and post-processing according to claim 1, characterized in that: In step S5, the inductively coupled plasma etcher includes an upper electrode and a lower electrode, the upper electrode power is 1500~2000W, and the lower electrode power is 300~500W; in step S6, the upper electrode power of the inductively coupled plasma etcher is 1000~1500W, and the lower electrode power is 300~500W; in step S7, the lower electrode power of the second optimized etching is 150~300W, and the lower electrode power of the third optimized etching is 50~150W.

6. The silicon carbide etching method based on dynamic parameter etching and post-processing according to claim 1, characterized in that: In step S6, there are two options for etching gas combination 2, namely SF6, CHF3 and O2, or SF6, CH2F2 and O2, the flow ratio of SF6, CHF3 and O2 is 4:2:1, and the flow ratio of SF6, CH2F2 and O2 is 4:2:

1.

7. The silicon carbide etching method based on dynamic parameter etching and post-processing according to claim 1, characterized in that: In step S7, during the two optimized etchings, the flow rate of CHF3 or CH2F2 is fixed unchanged, the flow rate ratio of SF6 and O2 is 2:1 during the second optimized etching, and the flow rate ratio of SF6 and O2 is 1:1 during the third optimized etching.

8. The silicon carbide etching method based on dynamic parameter etching and post-processing according to claim 1, characterized in that: In step S7, before the second and third etchings, overlay is added. Overlay is to perform photolithography again using a different pattern on the silicon carbide wafer with the existing pattern. The photoresist covers the horizontal surface and the sidewalls of the trench during the spread.

9. The silicon carbide etching method based on dynamic parameter etching and post-processing according to claim 8, characterized in that: In step S7 , the exposure width of the photoresist pattern at the edge in the horizontal direction is shortened by 20-50 nm compared to the photoresist pattern in step S2 .

10. The silicon carbide etching method based on dynamic parameter etching and post-processing according to claim 1, characterized in that: In step S7 , the total etching depth h=h1+h2+h3+h4, and the depth ratios are h1:h2:h3:h4=8:1:0.6:0.4.

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