Hi Fabiano,

Though not 100% sure, you might want to try PDMS (Polydimethylsiloxane).

welcome!

You can find the answer of your question in the paper

Polymeric mask protection for alternative KOH silicon wet etching at the link: http://iopscience.iop.org/article/10.1088/0960-1317/17/7/022/meta

Best wishes

Hi, Santana

It depends upon how much Silicon you want to etch. If you would like to etch more than 50 Micron i suggest you to use ONO (Oxide Nitride Oxide). If you want to etch oxide you should deposit equal amount of oxide extra.

Good Luck

I would directly think about silicon nitride but you asked about a metallic mask. Apparently, your best candidates will be Ni, Mo or Pt.

There is list of metals (Al, Cu, Mo, Ni, Pt and Ti) and their HF etch rate in table 3 (page 24):

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.507.7610&rep=rep1&type=pdf

KOH solution is used as etchant of Al, Cu and Ti:

https://en.wikibooks.org/wiki/Microtechnology/Etching_Processes

Hi!

PDMS is a chemically very resistant material but it has been figured out how to use it in lithograpy as a resist material.

If you would like to use PDMS as a resist material you can look into these two papers in which PDMS is selectively etched by KOH (positive resist case) and concentrated sulphuric acid (negative resist case).

S.Z. Szilasi, C. Cserháti, Selective etching of PDMS: Etching technique for application as a positive tone resist, Applied Surface Science 457 (2018) 662–669

S.Z. Szilasi, L. Juhasz, Selective etching of PDMS: Etching as a negative tone resist, Applied Surface Science 447 (2018) 697–703

Best regards

I suggest to use thermally grown oxide (about 1 um) as a mask material and TMAH (tetramethylammonium hydroxide) solution instead of KOH. This solution is very selective and doesn't attack to the oxide layer. You can also use Aluminium as a mask in this solution if you want to etch up to 5-10 um.

Better use a polymeric coating to mask the top side.But you need to see about the thickness pf the mask,it will depend upon the thickness of Silicon you want to etch.

Using Si3N4, specially LPCVD grown Si3N4, is a standard mask using in KOH process. Specially, because you are removing your oxide using HF, you do not need to be concerned for selectivity.

I want to etch 195 um of Silicon using KOH wet etching. Which masking material should i use?

Abhishek Kumar For 195um, use LPCVD Nitride.