SiC etching method and SiC device

Abstract

The invention provides a SiC etching method and a SiC device. The method comprises the following steps: S1, preparing a mask layer on a SiC substrate and performing patterning; s2, inductively coupled plasma is adopted to etch the SiC substrate, etching comprises first etching and second etching which are circularly carried out for multiple times, the flow of O2 in etching gas adopted by the second etching is larger than that of O2 in etching gas adopted by the first etching, and the included angle between the side wall and the bottom of the etched groove is kept to be a right angle all the time. According to the SiC etching method, cyclic etching of etching gases in different proportions is adopted, the concentration of F plasma in the whole chamber can be changed in time, the electric field distribution condition can be changed, the etching rate can be adjusted, the transverse etching rate can be effectively controlled, micro-grooves are prevented from being generated in the SiC etching process, and the etching efficiency is improved. And therefore, the included angle between the side wall and the bottom of the groove after the SiC device is etched is always a right angle.

Description

Technical Field

[0001] The present invention relates to the field of etching technology, and in particular to a SiC etching method and a SiC device. Background Art

[0002] SiC is a third-generation wide-bandgap semiconductor with many unique electrical, mechanical, and chemical properties, including a large bandgap, high electron and hole mobility, extreme hardness, high wear resistance, high quality factor (Q), high thermal conductivity, and high chemical resistance. SiC is widely used in power electronics, microwave monolithic integrated circuits (MMICs), MEMS for extreme conditions, and high-temperature electronics.

[0003] Etching technology is a key support technology in the development of SiC devices. During the SiC device fabrication process, etching accuracy, etching damage, and etched surface residues all have a critical impact on the development and performance of SiC devices. Currently, SiC materials are mostly etched using dry etching. Among them, inductively coupled plasma (ICP) etching is a low-pressure, high-density etching method that has been widely used due to its advantages such as high etching rate, minimal device damage, and simple operation.

[0004] In SiC deep trench etching, the etching morphology often has some unfavorable conditions, such as the generation of micro-grooves, which are V-shaped grooves formed at the bottom near the sidewall (such as Figure 1 The presence of microgrooves can affect the performance and reliability of SiC devices. For example, microgrooves can impact the etch-stop layer, leading to void formation during the subsequent fill process. In pressure sensors, microgrooves can significantly weaken the diaphragm by concentrating stress. In high-voltage switching devices, microgrooves can easily cause localized electric field concentration, leading to premature device breakdown and failure to achieve high withstand voltage performance.

[0005] Although the etching method used in patent application 202311450648.4 can correct the uneven morphology in the middle of the micro-groove and ultimately complete etching without micro-grooves, the correction process makes it difficult to ensure that the angle between the side wall and the bottom of the groove is always a right angle.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The object of the present invention is to provide a SiC etching method and a SiC device, wherein the SiC etching method can avoid the generation of micro grooves during SiC etching, thereby ensuring that the angle between the sidewall and the bottom of the groove of the SiC device after etching is always a right angle.

[0008] A first aspect of the present invention provides a SiC etching method, comprising the following steps:

[0009] S1. Preparing a mask layer on a SiC substrate and performing patterning;

[0010] S2. Etch the SiC substrate using inductively coupled plasma, wherein the etching includes a first etching and a second etching performed in multiple cycles, wherein the O2 flow rate in the etching gas used in the second etching is greater than the O2 flow rate in the etching gas used in the first etching, and the angle between the side wall and the bottom of the groove after etching is always kept at a right angle.

[0011] Preferably, in step S2, when the first etching is performed until micro grooves are about to appear, the second etching is performed, and when the second etching is performed until micro grooves are about to appear, the first etching is performed again, and the etching cycle is repeated multiple times until the designed groove depth is reached.

[0012] When the micro-grooves are about to (start to) appear, it indicates that the F plasma content at this location has accumulated, resulting in an accelerated etching rate. The addition of O2 quickly changes the concentration of F plasma in the entire chamber, and the electric field distribution here is also forced to change. At the same time, the addition of a large amount of O2 can effectively control the anisotropy, and a SiOxFy passivation layer is generated when the Si surface appears in SiC, which effectively controls the lateral etching rate.

[0013] The timing when micro grooves will (begin to) appear varies depending on different experimental equipment. For example, if micro grooves appear when etching to about 1 μm, the second etching is performed before the first etching reaches a groove depth of 1 μm.

[0014] In the SiC etching method of the present invention, multiple cycles of etching can be performed according to the trench depth required by the SiC device. The duration of the first etching and the second etching can be the same or different, but both are within 5 minutes. The specific duration is set according to actual conditions.

[0015] For example, the second etching is performed when the first etching is performed for 2 minutes, and the first etching is performed again when the second etching is performed for 2 minutes, and the etching cycle is repeated multiple times until the designed groove depth is reached.

[0016] Preferably, the etching gases used in the first etching include: SF6 and Ar, and the gas flow ratio between SF6 and Ar is 1:(1-2), for example: 1:1, 1:1.5, 1:2, etc.

[0017] Preferably, the etching gas used in the second etching includes: SF6, O2 and Ar, and the gas flow ratio between SF6, O2 and Ar is 1:(2-3.5):(1-3), for example: 1:2:1.5, 1:2.3:3, 1:3:1, 1:3:2, 1:3:3, 1:3.5:3, etc. During the second etching process, it is necessary to control the etching gas in an appropriate ratio to ensure that the etching process does not generate micro grooves. When the increased O2 flow rate is too small, the etching process will still generate micro grooves. When the increased O2 flow rate is too large, the etching rate will be greatly reduced. Therefore, during the second etching process, controlling the etching gas in an appropriate ratio can ensure that the etching process does not generate micro grooves, keep the angle between the side wall and the bottom of the groove after etching always at a right angle, and ensure a certain etching rate.

[0018] In a specific embodiment, the gas flow ratio between SF6 and Ar in the etching gas used in the first etching is 1:1, and the gas flow ratio between SF6, O2 and Ar in the etching gas used in the second etching is 1:3:3.

[0019] Preferably, the etching conditions of the first etching and the second etching include: ICP power of 750 to 800 W, RF bias of -250 to -150 V, and chamber pressure of 2 to 2.5 Pa.

[0020] In a specific embodiment, the etching conditions of the first etching and the second etching include: ICP power of 750W, RF bias of -200V, and chamber pressure of 2.5Pa.

[0021] Preferably, step S1 includes:

[0022] sequentially preparing a first mask layer and a second mask layer on a SiC substrate;

[0023] patterning the second mask layer;

[0024] Using the second mask layer as a mask, etching the first mask layer to transfer the pattern on the second mask layer to the first mask layer;

[0025] The remaining second mask layer is removed and the SiC substrate is cleaned.

[0026] Preferably, the method further comprises the following steps:

[0027] S3. Post-processing the etched SiC substrate.

[0028] Preferably, the post-processing process is not strictly limited and can be reasonably set according to actual needs. The post-processing process includes but is not limited to sacrificial oxidation, implantation, annealing (preferably the annealing temperature is greater than 1000 degrees), etc.

[0029] A second aspect of the present invention provides a SiC device, which is prepared according to the above-mentioned SiC etching method.

[0030] Preferably, the angle between the sidewall and the bottom of the SiC device trench is a right angle.

[0031] In the present invention, the etching depth and width of the trench can be adjusted as needed according to the thickness of the mask. In a specific embodiment, the etching depth is greater than 5 μm, and the etching width is greater than 1 μm.

[0032] The present invention has the following beneficial effects:

[0033] The SiC etching method of the present invention adopts cyclic etching with etching gases of different proportions, which can timely change the concentration of F plasma in the entire chamber, change the electric field distribution, adjust the etching rate, and effectively control the lateral etching rate, thereby avoiding the generation of micro-grooves during the SiC etching process, thereby ensuring that the angle between the sidewall and the bottom of the groove after the SiC device is etched is always a right angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a morphology diagram of the existing V-groove.

[0036] Figure 2 This is a process flow chart of the SiC etching method of the present invention.

[0037] Figure 3 This is a morphology diagram of the SiC device prepared in Example 1 of the present invention.

[0038] Figure 4 This is a morphology diagram of the SiC device prepared in Comparative Example 1 of the present invention.

[0039] Figure 5 This is a morphology diagram of the SiC device prepared in Comparative Example 2 of the present invention.

[0040] Figure 6-10 This is a morphology diagram of the SiC device prepared in Comparative Example 3 of the present invention.

[0041] Description of reference numerals:

[0042] 1. SiC substrate; 2. First mask layer; 3. Second mask layer; 4. Pattern; 5. Groove after first etching; 6. Groove after second etching. DETAILED DESCRIPTION

[0043] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0044] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular also includes the plural. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0045] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Example 1

[0047] like Figure 2 As shown, this embodiment provides a SiC etching method, comprising the following steps:

[0048] S1. Preparing a mask layer on a SiC substrate and performing patterning;

[0049] Specifically, step S1 includes:

[0050] S11, sequentially preparing a first mask layer 2 and a second mask layer 3 on a SiC substrate 1;

[0051] S12, patterning the second mask layer 3 to form a pattern 4 on the second mask layer 3;

[0052] S13, etching the first mask layer 2 using the second mask layer 3 as a mask to transfer the pattern 4 on the second mask layer 3 to the first mask layer 2;

[0053] S14 , then removing the remaining second mask layer 2 and cleaning the SiC substrate 1 .

[0054] S2. Etch the SiC substrate using inductively coupled plasma. The etching includes a first etching and a second etching performed in multiple cycles. The O2 flow rate in the etching gas used in the second etching is greater than the O2 flow rate in the etching gas used in the first etching, and the angle between the side wall and the bottom of the groove after etching is always kept at a right angle.

[0055] According to the thickness of the mask, in this embodiment, the etching depth is expected to be >5μm, the etching width is expected to be >1μm, the first etching time is 4 minutes, the second etching time is 4 minutes, the average etching rate is expected to be 0.23μm / min, and the etching cycle is performed 3 times, totaling 24 minutes.

[0056] Specifically, step S2 includes:

[0057] S21, performing a first etching on the SiC substrate using an inductively coupled plasma, wherein the etching conditions for the first etching are as follows: an ICP power of 750 W, an RF bias of -200 V, and a chamber pressure of 2.5 Pa; etching gases used in the first etching are SF6 and Ar, and the gas flow ratio between SF6 and Ar is 1:1;

[0058] S22. When the first etching is performed until micro grooves are about to appear, a second etching is performed. The etching conditions of the second etching are as follows: ICP power is 750 W, RF bias is -200 V, and chamber pressure is 2.5 Pa. The etching gases used in the second etching are SF6, O2, and Ar, and the gas flow ratio between SF6, O2, and Ar is 1:3:3.

[0059] S23, performing the first etching and the second etching for three cycles, keeping the angle between the sidewall and the bottom of the trench after etching always at a right angle, until the designed trench depth is reached.

[0060] S3. Perform high-temperature annealing on the etched SiC substrate, where the annealing temperature is greater than 1000 degrees.

[0061] This embodiment also provides a SiC device, which is prepared according to the above-mentioned SiC etching method, and its morphology is as follows Figure 3 As shown, the angle between the sidewall and the bottom of the SiC device trench is a right angle.

[0062] Example 2

[0063] This embodiment is basically the same as the embodiment 1, except that the gas flow ratio between SF6 and Ar in the etching gas during the first etching is 1:2.

[0064] The SiC device prepared in this embodiment is basically the same as that prepared in Example 1.

[0065] Example 3

[0066] This embodiment is basically the same as the embodiment 1, except that the gas flow ratio of SF6, O2 and Ar in the etching gas during the second etching is 1:3:1.

[0067] The SiC device prepared in this embodiment is basically the same as that prepared in Example 1.

[0068] Example 4

[0069] This embodiment is basically the same as the embodiment 1, except that the gas flow ratio of SF6, O2 and Ar in the etching gas during the second etching is 1:3:2.

[0070] The SiC device prepared in this embodiment is basically the same as that prepared in Example 1.

[0071] Example 5

[0072] This embodiment is basically the same as the embodiment 1, except that the etching conditions include: ICP power of 800W, RF bias of -250V, and chamber pressure of 2Pa.

[0073] The SiC device prepared in this embodiment is basically the same as that prepared in Example 1.

[0074] Example 6

[0075] This embodiment is basically the same as the embodiment 1, except that the etching conditions include: ICP power of 780W, RF bias of -150V, and chamber pressure of 2.3Pa.

[0076] The SiC device prepared in this embodiment is basically the same as that prepared in Example 1.

[0077] Comparative Example 1

[0078] This comparative example is basically the same as Example 1, except that in step S2, only the first etching is used, and the second etching is not performed.

[0079] The morphology of the SiC device prepared in this comparative example is as follows Figure 4 As shown: only the first etching is performed without the second etching, resulting in a micro-groove. It cannot be guaranteed that the angle between the sidewall and the bottom of the groove after etching is always a right angle.

[0080] Comparative Example 2

[0081] This comparative example is basically the same as Example 1, except that in step S2, only the second etching is used, and the first etching is not performed.

[0082] The morphology of the SiC device prepared in this comparative example is as follows Figure 5 As shown: only the second etching is performed without the first etching, resulting in a micro-groove. It cannot be guaranteed that the angle between the sidewall and the bottom of the groove after etching is always a right angle.

[0083] Comparative Example 3

[0084] This comparative example is basically the same as comparative example 2, except that: in this comparative example, the etching is performed by controlling different O2 flow rates (3sccm, 10sccm, 15sccm, 20sccm, 35sccm), the SF6 flow rate is 15sccm, and the Ar flow rate is 45sccm. The SiC devices obtained are as follows: Figure 6-10 As shown in the figure: if the O2 flow rate is too small, micro grooves will be generated during the etching process. Controlling the appropriate proportion of etching gas can change the time and morphology of micro groove generation, while keeping the angle between the side wall and the bottom of the groove after etching always at a right angle.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A SiC etching method, characterized in that: The steps include: S1. Preparing a mask layer on a SiC substrate and performing patterning; S2. Etch the SiC substrate using inductively coupled plasma, wherein the etching includes a first etching and a second etching performed in multiple cycles, wherein the O2 flow rate in the etching gas used in the second etching is greater than the O2 flow rate in the etching gas used in the first etching, and the angle between the side wall and the bottom of the groove after etching is always kept at a right angle.

2. The SiC etching method according to claim 1, wherein: In step S2, when the first etching is performed until micro grooves are about to appear, the second etching is performed, and when the second etching is performed until micro grooves are about to appear, the first etching is performed again.

3. The SiC etching method according to claim 1, wherein: The etching gases used in the first etching include: SF6 and Ar, and the gas flow ratio between SF6 and Ar is 1:(1~2); the etching gases used in the second etching include: SF6, O2 and Ar, and the gas flow ratio between SF6, O2 and Ar is 1:(2~3.5):(1~3).

4. The SiC etching method according to claim 3, wherein: The gas flow ratio between SF6 and Ar in the etching gas used in the first etching is 1:1, and the gas flow ratio between SF6, O2 and Ar in the etching gas used in the second etching is 1:3:

3.

5. The SiC etching method according to claim 1, wherein: The etching conditions of the first etching and the second etching include: ICP power of 750 to 800 W, RF bias of -250 to -150 V, and chamber pressure of 2 to 2.5 Pa.

6. The SiC etching method according to claim 5, characterized in that: The etching conditions of the first etching and the second etching include: ICP power of 750W, RF bias of -200V, and chamber pressure of 2.5Pa.

7. The SiC etching method according to claim 1, wherein: Step S1 includes: sequentially preparing a first mask layer and a second mask layer on a SiC substrate; patterning the second mask layer; Using the second mask layer as a mask, etching the first mask layer to transfer the pattern on the second mask layer to the first mask layer; The remaining second mask layer is removed and the SiC substrate is cleaned.

8. The SiC etching method according to claim 1, wherein: The following steps are also included: S3. Post-processing the etched SiC substrate.

9. A SiC device, characterized in that: The SiC etching method is prepared according to any one of claims 1 to 8.

10. The SiC device according to claim 9, characterized in that The angle between the sidewall and the bottom of the SiC device trench is a right angle.

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