[labnetwork] Deep anisotropic etching of SiO2
Salzmann, Jeffrey
Jeffrey.Salzmann at integer.net
Thu Jan 19 08:20:18 EST 2023
If you can get access to it, I’ve had good success with vertical sidewalls on silica using a femtosecond laser.
Trumpf laser’s Top Cleave system and a sonicated KOH etch can easily do 500µm ‘drill’. The throughput is vastly faster than any traditional semiconductor approach. Note that you can’t do a partial depth so you might need to figure out a way to bond the silica onto a substrate.
From: labnetwork <labnetwork-bounces at mtl.mit.edu> On Behalf Of Robert Nidetz
Sent: Wednesday, January 18, 2023 8:34 PM
To: Howard Northfield <Howard.Northfield at uottawa.ca>
Cc: labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] Deep anisotropic etching of SiO2
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Could you mechanically remove most of the SiO2 using something like a dicing saw and then finish the removal using a wet etch? Maybe create a fin structure in the SiO2 you do not want and then let a wet etch remove the fins? Your undercut could be reduced in this manner.On Wed, J
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Could you mechanically remove most of the SiO2 using something like a dicing saw and then finish the removal using a wet etch? Maybe create a fin structure in the SiO2 you do not want and then let a wet etch remove the fins? Your undercut could be reduced in this manner.
On Wed, Jan 18, 2023 at 8:08 PM Howard Northfield <Howard.Northfield at uottawa.ca<mailto:Howard.Northfield at uottawa.ca>> wrote:
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
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From: labnetwork <labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu>> on behalf of Ningzhi Xie <nzxie at uw.edu<mailto:nzxie at uw.edu>>
Sent: Wednesday, January 18, 2023 4:23 PM
To: labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu> <labnetwork at mtl.mit.edu<mailto: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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