CN114105087A - Method for removing step silicon grass of MOEMS device - Google Patents
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- CN114105087A CN114105087A CN202111479941.4A CN202111479941A CN114105087A CN 114105087 A CN114105087 A CN 114105087A CN 202111479941 A CN202111479941 A CN 202111479941A CN 114105087 A CN114105087 A CN 114105087A
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- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00436—Shaping materials, i.e. techniques for structuring the substrate or the layers on the substrate
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- B81C1/00777—Preserve existing structures from alteration, e.g. temporary protection during manufacturing
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Abstract
The invention provides a method for removing step silicon grass of an MOEMS device, which comprises the following steps: s1, selecting an SOI wafer and etching to form a step; s2, cleaning the SOI wafer; s3, etching the top silicon layer and the steps to form a comb structure and silicon grass; s4, arranging a thick passivation layer on the comb tooth structure and the silicon grass; s5, removing the passivation layer on the horizontal plane by etching gas; s6, etching the step and the root of the silicon grass by etching gas; s7, removing the passivation layer on the surface of the silicon grass by etching gas; s8, etching the silicon grass poured on the step by etching gas; and S9, cleaning the residual passivation layer and the silicon grass. The invention has convenient operation and clean removal of silicon grass, effectively improves the use reliability of the device and prolongs the service life.
Description
The technical field is as follows:
the invention relates to the technical field of MOMES device manufacturing, in particular to a method for removing step silicon grass of an MOEMS device.
Background art:
when a MOMES device is manufactured, steps are usually formed firstly, then comb tooth structure etching is carried out, grass-shaped burrs (silicon grass) appear at the steps, the burrs are very similar to small grass under an electron microscope, so the burrs are called as silicon grass, the silicon grass is generally fragile, short circuit and damage to the comb tooth structure are easily caused under large electrostatic force, the working reliability of the device is reduced, and the service life is shortened. And removing the step silicon grass, generally adopting a method that after the comb tooth structure is etched, SF6 (sulfur hexafluoride) gas is introduced for a certain time to etch the silicon grass.
The problem of the removing method is that when silicon grass is etched, the side face of the comb tooth structure is exposed in etching gas and is also etched to cause damage; meanwhile, in order to reduce damage of the comb tooth structure, the flow, power and time of SF6 gas need to be strictly controlled, so that the step silicon grass is difficult to completely remove.
The invention content is as follows:
the invention provides a method for removing step silicon grass of an MOEMS device to overcome the defects in the prior art.
The application provides the following technical scheme:
a method for removing step silicon grass of a MOEMS device comprises the following steps: selecting an SOI wafer and etching to form a groove body; s2, cleaning the SOI wafer; s3, etching the top layer silicon to form a second groove body, and forming a comb structure and a silicon grass, wherein the second groove body is characterized in that: s4, forming a passivation layer on the comb tooth structure, the silicon grass and the second groove body by using C4F8 gas; s5, removing the passivation layer horizontally distributed on the second groove body, the comb tooth structure and the silicon grass by using SF6 gas; s6 and SF6 gas carry out transverse underetching on the comb tooth structure and the bottom of the silicon grass, so that the silicon grass collapses; s7, removing the passivation layer on the upper surface of the collapsed silicon grass by using SF6 gas; s8, etching off the silicon grass by using SF6 gas; and S9, cleaning the wafer, and cleaning all the residual passivation layer on the lower surface of the silicon grass and the residual fragments of the silicon grass in a small amount.
On the basis of the technical scheme, the following further technical scheme can be provided:
in the step of S4, the C4F8 gas is changed into plasma under the action of radio frequency power, the service time of the C4F8 gas is 8S-12S, the flow rate is 300sccm-350sccm, the source power is 2500W-3000W, and the pressure is 30mtorr-40 mtorr.
In the step S5, the SF6 gas is changed into plasma under the action of rf power, so as to generate SF5 with positively charged particles+Bombarding the steps, the comb-tooth structure and the passivation layer on the upper surface of the silicon grass under the pull-down power of the lower electrode plateau, the SF6 gasThe time is 3s-4s, the flow rate is 300sccm-350sccm, the source power is 2500W-3000W, the plateau power is 300W-400W, and the pressure is 20mtorr-30 mtorr.
In the step of S6, SF6 gas is changed into plasma under the action of radio frequency power to generate F radicals, the time of the SF6 gas is 10S-20S, the flow rate is 300sccm-350sccm, the source power is 2500W-3000W, the plain power is 30W-40W, and the pressure is 20mtorr-30 mtorr.
In the step S7, the SF6 gas is changed into plasma under the action of the radio frequency power, and the SF5 with positive charge particles is generated+Bombarding the passivation layer under the pull-down power of a lower electrode plasten, wherein the SF6 gas has the time of 3s-4s, the flow rate of 300sccm-350sccm, the source power of 2500W-3000W, the plasten power of 300W-400W and the pressure of 20mtorr-30 mtorr.
In the step S8, SF6 gas is changed into plasma under the action of radio frequency power to generate F radicals, the time of the SF6 gas is 5S-10S, the flow rate is 300sccm-500sccm, the source power is 2500W-3000W, the flux power is 30W-40W, and the pressure is 20mtorr-30 mtorr.
And an EKC solution is used for cleaning the wafer in the step S9, the cleaning time is more than 30min, and the temperature is 75-85 ℃.
The invention has the advantages that:
the invention has the advantages that after the steps and the comb tooth structure are formed, firstly, the side surface of the comb tooth structure is protected by adopting a thick passivation layer, and then, the positively charged particles SF5+Bombarding to remove the horizontal passivation layer, and then etching the step silicon grass root. Because the etching can be carried out for a longer time, the widest silicon grass roots can also be completely etched away. After the silages are poured on the steps, the side surfaces of the silages are provided with passivation layers, and the positively charged particles SF5 are adopted+And bombarding to remove the horizontal passivation layer, and then etching the silicon grass, so that the silicon grass at the step can be etched cleanly. And finally, the surfaces of the steps and the comb tooth structures are cleaned by using an organic solvent, so that the passivation layer and the silicon grass can be effectively and completely removed. Therefore, the reliability of the device is obviously improved, and the service life is prolonged.
Description of the drawings:
fig. 1 is a schematic structural view after step S1 is completed;
fig. 2 is a schematic structural view after step S3 is completed;
fig. 3 is a schematic structural view after step S4 is completed;
fig. 4 is a schematic structural view after step S5 is completed;
fig. 5 is a schematic structural view after step S6 is completed;
fig. 6 is a schematic structural view after step S7 is completed;
FIG. 7 is a schematic diagram of the structure after the silicon grass is etched away in step S8;
fig. 8 is a schematic structural view after step S8 is completed;
fig. 9 is a schematic structural diagram after step S9 is completed.
The specific implementation mode is as follows:
example 1:
as shown in fig. 1 to 9, a method for removing step silicon grass of a MOEMS device comprises the following steps: selecting an SOI wafer, wherein the wafer comprises a substrate 1, a buried oxide layer 2 and a top silicon 3, etching the upper surface of the top silicon 3 to form a patterned oxide layer 4 and a groove 31 with the bottom reaching the buried oxide layer 2. The height of the groove body 31 is 25 μm, and the height of the groove body 31 is defined as the height difference between the surface of the top silicon 3 and the surface of the oxygen buried layer 2.
S2, cleaning the SOI wafer by using EKC solution for more than 30min at 76 ℃. The step can clean the passivation layer remained when the step is formed by etching.
And S3, etching a second groove body 34 on the top silicon 3 by adopting a Bosch process, thereby forming comb teeth and silicon grass 32. Wherein the depth of the comb teeth is usually 20 μm, the width is usually 5 μm, and the width of the silicon grass 32 is less than 1 μm, so that the width of the comb tooth structure 33 is much larger than the width of the silicon grass 32.
S4, introducing C4F8 gas into the etching reaction chamber, wherein the C4F8 gas is changed into plasma under the action of radio frequency power, so that a passivation layer 5 with the thickness of more than 100nm is formed on the groove bottom surface, the horizontal plane and the side surface of the comb teeth, and the horizontal plane and the side surface of the silicon grass 32 of the second groove body 34 in a covering mode. The C4F8 gas was passed through for 9s at a flow rate of 310sccm, a source power of 2700W and a pressure of 32 mtorr.
S5, introducing SF6 gasIn the etching reaction chamber, the plasma is formed under the action of radio frequency power, so that the SF5 with positive charge particles is generated+And bombarding the passivation layer 5 distributed on the groove bottom surface of the second groove body 34, the horizontal plane of the comb teeth and the horizontal plane of the silicon grass 32 under the pull-down power of the lower electrode plateau, and removing the passivation layer cleanly. But the passivation layer 5 on the comb teeth and the side surfaces of the silicon grass 32 is remained, wherein the passivation layer 5 on the side surfaces of the comb teeth can block the etching gas SF6 and plays a role of protecting the side surfaces of the comb teeth. The introduction time of the SF6 gas is 3s, the flow rate is 310sccm, the source power is 2600W, the place power is 3200W, and the pressure is 22 mtorr.
And introducing the S6 and SF6 gases into the etching reaction chamber again, converting the gases into plasma under the action of radio frequency power, thereby generating F radicals, and performing transverse underetching 35 on the contact part of the bottoms of the comb teeth and the silicon grass 32 and the groove bottom surface of the second groove body 34, wherein at the moment, the passivation layers 5 on the side surfaces of the comb tooth structure 33 and the silicon grass 32 block the F radicals, so that the side surfaces of the comb tooth structure 33 and the silicon grass 32 are protected, and only the groove bodies at the underetching parts of the roots of the comb tooth structure 33 and the silicon grass 32 can be etched. Since the width of the silicon grass 32 is much smaller than the width of the comb tooth structure 33, the comb tooth structure 33 remains upright when the root of the silicon grass 32 is completely underetched and collapsed. The introduction time of the SF6 gas is 12s, the flow rate is 350sccm, the source power is 3000W, the place power is 30W, and the pressure is 20 mtorr.
S7, introducing SF6 gas into the etching reaction chamber again, wherein the SF6 gas is changed into plasma under the action of radio frequency power to generate the SF5 particles with positive charges+The passivation layer 5 on the surface of the silicon grass 32 is bombarded at the lower electrode platen pull-down power, removing it clean. The SF6 gas was passed for 3s at a flow rate of 300sccm, a source power of 2500W, a place power of 40W, and a pressure of 30 mtorr.
S8, introducing SF6 gas into the etching reaction chamber again, and changing into plasma under the action of rf power to generate F radicals, so as to etch away the silicon grass 32 and leave a very small amount of silicon grass 32 debris. The SF6 gas was passed for 5s at a flow rate of 500sccm, a source power of 2500W, a place power of 30W, and a pressure of 20 mtorr.
And S9, cleaning the wafer by using an EKC solution, and cleaning all the passivation layer 5 left on the other side of the silicon grass 32. The cleaning time is more than 30min, and the temperature is 75 ℃. During the cleaning process, the remaining minute silicon grass 32 chips are also completely cleaned.
Example 2:
as shown in fig. 1 to 9, a method for removing step silicon grass of a MOEMS device comprises the following steps: selecting an SOI wafer, wherein the wafer comprises a substrate 1, a buried oxide layer 2 and a top silicon 3, etching the upper surface of the top silicon 3 to form a patterned oxide layer 4 and a groove 31 with the bottom reaching the buried oxide layer 2. The height of the groove body 31 is 78 mu m, and the height of the groove body 31 is defined as the height difference between the surface of the top silicon 3 and the surface of the oxygen buried layer 2.
S2, cleaning the SOI wafer by using EKC solution for more than 30min at 84 ℃. The step can clean the passivation layer remained when the step is formed by etching.
And S3, etching a second groove body 34 on the top silicon 3 by adopting a Bosch process, thereby forming comb teeth and silicon grass 32. Wherein, the depth of the comb-teeth structure 33 is generally 48 μm, the width is generally 7.5 μm, and the width of the silicon grass 32 is less than 1 μm, so that the width of the comb-teeth structure 33 is much larger than the width of the silicon grass 32.
S4, introducing C4F8 gas into the etching reaction chamber, wherein the C4F8 gas is changed into plasma under the action of radio frequency power, so that a passivation layer 5 with the thickness of more than 100nm is formed on the groove bottom surface, the horizontal plane and the side surface of the comb teeth, and the horizontal plane and the side surface of the silicon grass 32 of the second groove body 34 in a covering mode. The C4F8 gas is introduced for 11s, the flow rate is 350sccm, the source power is 2900W, and the pressure is 38 mtorr.
S5, introducing SF6 gas into the etching reaction chamber, and converting the gas into plasma under the action of radio frequency power so as to generate the SF5 with positively charged particles+And bombarding the passivation layer 5 distributed on the groove bottom surface of the second groove body 34, the horizontal plane of the comb teeth and the horizontal plane of the silicon grass 32 under the pull-down power of the lower electrode plateau, and removing the passivation layer cleanly. But the passivation layer 5 on the comb teeth and the side surfaces of the silicon grass 32 is remained, wherein the passivation layer 5 on the side surfaces of the comb teeth can block the etching gas SF6 and plays a role of protecting the side surfaces of the comb teeth. The introduction time of the SF6 gas is 4s, the flow rate is 350sccm, source power 2900W, Platen power 3200W, pressure 29 mtorr.
And introducing the S6 and SF6 gases into the etching reaction chamber again, converting the gases into plasma under the action of radio frequency power, thereby generating F radicals, and performing transverse underetching 35 on the contact part of the bottoms of the comb teeth and the silicon grass 32 and the groove bottom surface of the second groove body 34, wherein at the moment, the passivation layers 5 on the side surfaces of the comb tooth structure 33 and the silicon grass 32 block the F radicals, so that the side surfaces of the comb tooth structure 33 and the silicon grass 32 are protected, and only the groove bodies at the underetching parts of the roots of the comb tooth structure 33 and the silicon grass 32 can be etched. Since the width of the silicon grass 32 is much smaller than the width of the comb tooth structure 33, the comb tooth structure (33) remains upright when the root of the silicon grass 32 is completely underetched and collapsed. The introduction time of the SF6 gas is 19s, the flow rate is 300sccm, the source power is 2500W, the place power is 40W, and the pressure is 30 mtorr.
S7, introducing SF6 gas into the etching reaction chamber again, wherein the SF6 gas is changed into plasma under the action of radio frequency power to generate the SF5 particles with positive charges+The passivation layer 5 on the surface of the silicon grass 32 is bombarded at the lower electrode platen pull-down power, removing it clean. The SF6 gas was passed for 4s at a flow rate of 500sccm, a source power of 3000W, a plane power of 30W, and a pressure of 20 mtorr.
S8, introducing SF6 gas into the etching reaction chamber again, and changing into plasma under the action of rf power to generate F radicals, so as to etch away the silicon grass 32 and leave a very small amount of silicon grass 32 debris. The SF6 gas was passed for 10s at a flow rate of 300sccm, a source power of 2900W, a place power of 39W, and a pressure of 30 mtorr.
And S9, cleaning the wafer by using an EKC solution, and cleaning all the passivation layer 5 left on the other side of the silicon grass 32. The cleaning time is more than 30min, and the temperature is 84 ℃. During the cleaning process, the remaining minute silicon grass 32 chips are also completely cleaned.
Claims (7)
1. A method for removing step silicon grass of a MOEMS device comprises the following steps: selecting an SOI wafer and etching to form a groove body (31); s2, cleaning the SOI wafer; s3, etching the top layer silicon to form a second groove body (34), and forming a comb structure (33) and a silicon grass (32), wherein the method is characterized in that: s4, forming a passivation layer (5) on the comb tooth structure (33), the silicon grass (32) and the second groove body (34) by using C4F8 gas; s5, removing the passivation layer (5) horizontally distributed on the second groove body (34), the comb tooth structure (33) and the silicon grass (32) by using SF6 gas; s6 and SF6 gas carry out transverse underetching (35) on the comb tooth structure (33) and the bottom of the silicon grass (32), so that the silicon grass (32) collapses; s7, removing the passivation layer (5) on the upper surface of the collapsed silicon grass (32) by using SF6 gas; s8, etching off the silicon grass (32) by using SF6 gas; and S9, cleaning the wafer, and cleaning all the residual passivation layer (5) on the lower surface of the silicon grass (32) and the residual fragments of the silicon grass (32) with a small amount.
2. The method of claim 1, wherein the step silicon of the MOEMS device is removed by: in the step of S4, the C4F8 gas is changed into plasma under the action of radio frequency power, the service time of the C4F8 gas is 8S-12S, the flow rate is 300sccm-350sccm, the source power is 2500W-3000W, and the pressure is 30mtorr-40 mtorr.
3. The method of claim 1, wherein the step silicon of the MOEMS device is removed by: in the step S5, the SF6 gas is changed into plasma under the action of rf power, so as to generate SF5 with positively charged particles+And bombarding the second groove body (34), the comb tooth structure (33) and the passivation layer (5) on the upper surface of the silicon grass (32) under the pull-down power of a lower electrode platene, wherein the time of SF6 gas is 3s-4s, the flow rate is 300sccm-350sccm, the source power is 2500W-3000W, the platene power is 300W-400W, and the pressure is 20mtorr-30 mtorr.
4. The method of claim 1, wherein the step silicon of the MOEMS device is removed by: in the step of S6, SF6 gas is changed into plasma under the action of radio frequency power to generate F radicals, the time of the SF6 gas is 10S-20S, the flow rate is 300sccm-350sccm, the source power is 2500W-3000W, the plain power is 30W-40W, and the pressure is 20mtorr-30 mtorr.
5. The method of claim 1, wherein the step silicon of the MOEMS device is removed by: in the step S7, the SF6 gas is changed into plasma under the action of the radio frequency power, and the SF5 with positive charge particles is generated+And bombarding the passivation layer (5) under the pull-down power of the lower electrode plateau, wherein the SF6 gas has the time of 3s-4s, the flow rate of 300sccm-350sccm, the source power of 2500W-3000W, the plateau power of 300W-400W and the pressure of 20mtorr-30 mtorr.
6. The method of claim 1, wherein the step silicon of the MOEMS device is removed by: in the step S8, SF6 gas is changed into plasma under the action of radio frequency power to generate F radicals, the time of the SF6 gas is 5S-10S, the flow rate is 300sccm-500sccm, the source power is 2500W-3000W, the flux power is 30W-40W, and the pressure is 20mtorr-30 mtorr.
7. The method of claim 1, wherein the step silicon of the MOEMS device is removed by: and an EKC solution is used for cleaning the wafer in the step S9, the cleaning time is more than 30min, and the temperature is 75-85 ℃.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115849298A (en) * | 2023-01-18 | 2023-03-28 | 胜科纳米(苏州)股份有限公司 | Comb tooth layer removing method with comb tooth structure chip |
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2021
- 2021-12-07 CN CN202111479941.4A patent/CN114105087A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115849298A (en) * | 2023-01-18 | 2023-03-28 | 胜科纳米(苏州)股份有限公司 | Comb tooth layer removing method with comb tooth structure chip |
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