A method for preparing lower comb teeth of MOEMS device
Through multiple etching steps, the lower comb tooth structure is gradually formed, which solves the problem of low verticality of the lower comb tooth in the prior art, achieves high perpendicularity and rectangular section shape, and improves the working performance of MOEMS devices.
Patent Information
- Application Number
- CN202211341930.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-31
- Publication Date
- 2025-06-06
- Estimated Expiration
- 2042-10-31
AI Technical Summary
In the prior art, when making the upper and lower comb tooth structure of MOEMS devices, the verticality of the lower comb tooth during the etching process is low, and the cross-sectional shape becomes "special shape", resulting in the larger spacing of the upper and lower comb tooth, reducing the working performance of the MOEMS device.
The lower comb tooth structure is gradually formed by multiple etching steps. By preparing shallow cavity and isolation groove on the first SOI wafer, and forming an oxide layer on its surface, multiple etchings are carried out in conjunction with the Bosch process to gradually form a lower comb tooth structure with high perpendicularity.
The high perpendicularity and rectangular section shape of the lower comb teeth are achieved, ensuring high accuracy of the spacing between the upper and lower comb teeth and the high performance of the MOEMS devices.
Smart Images
Figure CN115626606B_ABST
Abstract
Description
Technical field:
[0002] The invention relates to the technical field of MOEMS device manufacturing, and in particular to a method for manufacturing lower comb teeth of a MOEMS device. Background technology:
[0004] A common structure in MOEMS devices is the upper and lower comb teeth structure. The process method is usually to make the lower comb teeth first, then wafer bonding, and finally make the upper comb teeth. The problem is that when making the lower comb teeth, the cross-sectional shape is rectangular and the verticality is very high; but when making the upper comb teeth by etching process, the lower comb teeth will be etched again, which will cause the cross-sectional shape of the lower comb teeth to become "irregular" with small top and large bottom, and the verticality becomes very low. After the verticality is reduced, the spacing between the upper and lower comb teeth becomes larger, which ultimately reduces the working performance of the MOEMS device. Summary of the invention:
[0006] The present invention aims to overcome the deficiencies in the prior art and provides a method for preparing the lower comb teeth of a MOEMS device.
[0007] This application provides the following technical solutions:
[0008] The present application aims to overcome the deficiencies in the prior art and to provide a method for preparing the lower comb teeth of a MOEMS device.
[0009] This application provides the following technical solutions:
[0010] A method for preparing lower comb teeth of a MOEMS device, characterized in that it comprises the following steps: S1, taking a first SOI wafer, preparing a shallow cavity and an isolation groove on it, preparing a first oxide layer in the shallow cavity, and preparing a second oxide layer on the patterned oxide layer and on the first SOI wafer; S2, etching the lower comb teeth for the first time to form the first part of the lower comb teeth; S3, etching the lower comb teeth for the second time to form the second part of the lower comb teeth; S4, taking a second SOI wafer, and then bonding the first and second SOI wafers; S5, etching the upper comb teeth and etching the lower comb teeth for the third time at the same time, finally forming a lower comb tooth structure with high verticality.
[0011] On the basis of the above technical solutions, there are also the following further technical solutions:
[0012] The first SOI wafer is composed of a substrate, a buried oxide layer, and a top silicon layer.
[0013] The first oxide layer is thermal silicon oxide, and the second oxide layer is PE silicon oxide.
[0014] In step S2, Bosch etching process is adopted, the passivation gas is C4F8, the pre-etching gas is SF6, the etching gas is SF6, the etching cycle number is 40-45 times, and the cross-sectional shape of the first part of the lower comb teeth formed by etching is an inverted trapezoid.
[0015] In the S3, Bosch etching process is adopted, the passivation gas is C4F8, the pre-etching gas is SF6, the etching gas is SF6, the etching cycle number is 135-140 times, and the cross-sectional shape of the second part of the lower comb teeth formed by etching is rectangular.
[0016] In step S5, Bosch etching process is adopted, C4F8 is used as the passivation gas, SF6 is used as the etching gas, the number of etching cycles is 160-165 times, and both sides of the first part of the lower comb teeth are etched so that the cross-sectional shape is a rectangle.
[0017] Advantages of the invention:
[0018] The process of the invention is simple and easy to operate, and solves the problem that the lower comb teeth made by conventional process methods have low verticality and "irregular" cross-sectional shape; it ensures high precision of the upper and lower comb teeth spacing and high performance of the MOEMS device. Description of the drawings:
[0020] Figure 1 is a flow chart of the present invention;
[0021] Figure 2 It is a schematic diagram of the structure after the present invention completes step S1;
[0022] Figure 3 It is a schematic diagram of the structure after the present invention completes step S2;
[0023] Figure 4 It is a schematic diagram of the structure after the present invention completes step S3;
[0024] Figure 5 It is a schematic diagram of the structure after the present invention completes step S4;
[0025] Figure 6 It is a schematic diagram of the structure after the present invention completes step S5. Specific implementation method:
[0027] like Figure 1-6 As shown, a method for preparing the lower comb teeth of a MOEMS device includes the following steps: S1, taking a first SOI wafer, wherein the first SOI wafer is composed of a substrate 1, a buried oxide layer 2, and a top silicon layer 3. A shallow cavity 31 is prepared on the top silicon layer 3, and an isolation groove 32 having one end reaching the buried oxide layer 2 is prepared on the top silicon layer 3 on one side of the shallow cavity 31. The width of the shallow cavity 31 is greater than the width of the isolation groove 32, and the depth is less than the depth of the isolation groove 32.
[0028] A patterned first oxide layer 4 is prepared in the shallow cavity, and a second oxide layer 5 is prepared on the upper surface of the first oxide layer 4 and on the surface of the first SOI wafer. The first oxide layer 4 is thermal silicon oxide, and the second oxide layer 5 is PE silicon oxide. The first oxide layer and the second oxide layer 5 are etching masks of the lower comb teeth 33, and the width is 4.5 μm.
[0029] S2, etching the lower comb teeth for the first time, using the Bosch process to form the first part 331 of the lower comb teeth on the top silicon 3 below the first oxide layer 4. The etching depth is 9 μm, so that the cross-sectional shape of the first part 331 is an inverted trapezoid, the top width of the inverted trapezoid is 4.5 μm, and the bottom width of the inverted trapezoid is 4.2 μm.
[0030] The passivation gas used in the etching is C4F8, the time is 1.2s, the flow rate is 330sccm, the source power is 2500W, the platen power is 0W, and the pressure is 50mtorr. The pre-etching gas used in the etching is SF6, the time is 0.8s, the flow rate is 220sccm, the source power is 2500W, the platen power is 160W, and the pressure is 18mtorr. The etching gas used in the etching is SF6, the time is 2.0s, the flow rate is 330sccm, the source power is 2500W, the platen power is 30W, and the pressure is 35mtorr. The number of etching cycles is 42 times.
[0031] In the first etching, the comb teeth will also etch the isolation groove 32 to increase its width to form a wide portion a. The etching depth is the same as that of the first portion 331.
[0032] S3, etching the lower comb teeth for the second time, using the Bosch process to etch the top silicon 3 below the first part 331 to form the second part 332 of the lower comb teeth. The etching depth is 35 μm, the cross-sectional shape is rectangular, and the width is 4.1 μm. Thus, the lower comb teeth 33 consisting of the first part 331 and the second part 332 of the lower comb teeth are formed, and the total depth is 40 μm-50 μm.
[0033] The passivation gas used in the etching is C4F8, the time is 1.2s, the flow rate is 330sccm, the source power is 2500W, the platen power is 0W, and the pressure is 50mtorr. The pre-etching gas used in the etching is SF6, the time is 0.8s, the flow rate is 220sccm, the source power is 2500W, the platen power is 160W, and the pressure is 18mtorr. The etching gas used in the etching is SF6, the time is 1.9s, the flow rate is 330sccm, the source power is 2500WW, the platen power is 22W, and the pressure is 35mtorr. The number of etching cycles is 137 times.
[0034] In the second etching, the comb teeth will further etch the wide portion a to increase its depth. The etching depth is the same as that of the second portion 332.
[0035] S4. Take the second SOI wafer, and after removing the second oxide layer 5 by the BOE process, bond the top silicon 3 of the first SOI wafer and the top silicon 6 of the second SOI wafer, and remove the substrate silicon and buried oxide layer of the second SOI wafer, leaving the top silicon 6 of the second SOI wafer with a thickness of 30 μm-40 μm.
[0036] S5, etching the upper comb teeth 61 on the top silicon 6 of the second SOI wafer using the Bosch process, while etching the lower comb teeth 33 for the third time. Finally, the top width of the lower comb teeth 33 is 4.0 μm, the bottom width is 4.0 μm, the depth is 45 μm-55 μm, the steepness is 90 degrees, and the overall cross-sectional shape of the lower comb teeth 33 is a rectangle.
[0037] The passivation gas used in the etching is C4F8, the time is 1.0s, the flow rate is 350sccm, the source power is 2500W, the platen power is 0W, and the pressure is 40mtorr. The etching gas used in the etching is SF6, the time is 2.0s, the flow rate is 350sccm, the source power is 2700W, the platen power is 33W, and the pressure is 30mtorr. The number of etching cycles is 163 times.
Claims
1. A method for preparing the lower comb teeth of a MOEMS device, Features: The following steps are involved: S1, take a first SOI wafer, prepare a shallow cavity and an isolation groove on it, prepare a first oxide layer (4) in the shallow cavity, and prepare a second oxide layer (5) on the first SOI wafer on the oxide layer (4); S2, etch the lower comb teeth for the first time to form a first part (331) of the lower comb teeth; S3, etch the lower comb teeth for the second time to form a second part (332) of the lower comb teeth; S4, take a second SOI wafer, and then bond the first and second SOI wafers; S5, etching the upper comb teeth and etching the lower comb teeth for the third time at the same time, finally forming a high verticality lower comb tooth structure; in the step S2, Bosch process is used for etching, the passivation gas is C4F8, the pre-etching gas is SF6, the etching gas is SF6, the etching cycle number is 40-45 times, and the cross-sectional shape of the first part (331) of the lower comb teeth formed by etching is an inverted trapezoid; in the step S3, Bosch process is used for etching, the passivation gas is C4F8, the pre-etching gas is SF6, the etching gas is SF6, the etching cycle number is 135-140 times, and the cross-sectional shape of the second part (332) of the lower comb teeth formed by etching is a rectangle.
2. According to the method for preparing the lower comb teeth of a MOEMS device as described in claim 1, Features: The first SOI wafer consists of a substrate (1), a buried oxide layer (2), and a top silicon layer (3).
3. According to the method for preparing the lower comb teeth of a MOEMS device as described in claim 1, Features: The first oxide layer (4) is thermal silicon oxide, and the second oxide layer (5) is PE silicon oxide.
4. According to the method for preparing the lower comb teeth of a MOEMS device as described in claim 1, Features: In step S5, Bosch etching process is adopted, the passivation gas is C4F8, the etching gas is SF6, the etching cycle number is 160-165 times, and both sides of the first part (331) of the lower comb teeth are etched.
Citation Information
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