[labnetwork] Deep anisotropic etching of SiO2

[Howard Northfield]

That's a very deep etch.

Regarding dry etching:
I have recently done etch tests on PEVCD SiO2 with a SAMCO 10NR RIE:

- 50W, 80sccm CF4, 16sccm O2, 3.0Pa: ~21nm/min

- 25W, 25sccm SF6, 10sccm O2, 3.0Pa: ~7nm/min
- 50W, 25sccm SF6, 10sccm O2, 3.0Pa: ~19nm/min

... yes for 500um that would be around a 417 hour etch .... not feasible/realistic.
So you can probably rule out these etch recipes.

Regarding wet etching, generally I find it very hard to control and mask under-cut is significant.

Howard Northfield
Research Associate
Advanced Research Complex (ARC)
University of Ottawa

________________________________
From: labnetwork <labnetwork-bounces at mtl.mit.edu> on behalf of Ningzhi Xie <nzxie at uw.edu>
Sent: Wednesday, January 18, 2023 4:23 PM
To: labnetwork at mtl.mit.edu <labnetwork at mtl.mit.edu>
Subject: [labnetwork] Deep anisotropic etching of SiO2

Attention : courriel externe | external email
 Dear college,

We want to perform a highly anisotropic, very deep (~500um) etching of SiO2 with a vertical side wall. On top of the SiO2 is nanostructures protected by photoresist. The etch depth needs to be controlled with a precision of 20% (we are thinking of using another  material as the substrate underneath the SiO2 layer, which acts as an etch-stopper). The structure and dimensions are shown in the attached image. It would be very helpful if anyone has any idea of this kind of etching (either dry and wet chemical etch is fine).

Thank you very much.

Best regards,
Ningzhi Xie
Department of Electrical and Computer Engineering
University of Washington
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