Hi
I would like to remove a metal mask of 300 nm Al on top of 10 nm Ti by wet etching. The requirement is that LPCVD-silicon nitride and silicon should not be etched by a significant degree
Do you have any suggestions on what wet etch to use?
Hello Madeleine Nilsen ,
Have a look at the attached article, 'Etch Rates for Micromachining Processing Part II'.
Al etchant: 80% H3PO4 / 5% HNO3 / 5% HAc / 10% H2O at 50 oC
Si rates are very slow.
SiNx rates are very slow
Ti rate is zero
You need to check the values for your exact Si/SiNx type. I used the same etch processes in my thesis:
Thesis Micro- and nanogap based biosensors.
Also, the website of 'BYU cleanroom' was very useful during my PhD, see the information under Etching Resoruces > Chemical Etching:
https://cleanroom.byu.edu/processes#Microfab_Etch
Hope it helps.
I would imagine NaOH will strip the metal very efficiently without effecting the Silicon / Silicon nitride.
I would incline toward J. L. Hammond's suggestion.
High pH (Phil Denby's suggestion) may work but not plain strong base, which will etch too much silicon. Keeping the pH around 12 may allow decent selectivity between Al and Si.
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