Photoresist will only last briefly in hot phosphoric acid.
I have deposited LPCVD LTO on top of low-stress nitride, used photoresist to
mask the LTO, then used the LTO to mask the nitride, finally stripping off
the LTO mask.
    --Kirt Williams

----- Original Message -----
From: "PRAMOD GUPTA" 
To: "General MEMS discussion" 
Sent: Thursday, April 12, 2007 11:07 PM
Subject: Re: [mems-talk] Re: silicon rich nitride wet etch


> Try Phosphoric acid @ 155C used for etching of LPCVD, i.e. silicon rich
> SiN film in Semiconductor/MEMS industry. For process details, open the
> Stanford Nano Fabrication (SNF) Process link as follows;
>
>  http://www-snf.stanford.edu/Equipment/wbgeneral/NitrideEtchWBGen.html
>
>
> Ciro Chiappini  wrote:
>
> I have to etch a 2000A thick silicon rich nitride film under a
> photoresist (AZ5209) mask. I need to get a nitride mask since the next
> step is electrochemical etching in EToH:HF 3:7. I am currently RIE
> etching it, but the process is very time consuming.
>
> I tried wet etch both HF:H2O 1:10 AND HF:HCL 1:1 but the resist gets
> peeled off in few minutes.
>
> Do you have any alternative recipe to suggest?