I am guessing that you have PECVD nitride, which is etched by HF solutions
at a reasonable rate.
The exact rate depends on the deposition recipe and thermal history of the
film.

Use 5:1 or 10:1 BHF (buffered hydrofluoric acid, also known as buffered
oxide etch, BOE).
These more dilute solutions do not cause peeling nearly as much as 49% HF
does.

    --Kirt Williams

----- Original Message -----
From: "Zhiyan Liu" 
To: 
Sent: Tuesday, November 16, 2004 7:54 AM
Subject: [mems-talk] Etch SiN


> Dear friends,
>
> I want to etch 250nm of SiN without attack the GaAs substrate. I tried the
> wet etch using HF and photoresist as the etch mask. But the PR all peeled
> off during the etching even after hard baked. I am wondering if anyone has
> a suggestion on the etch of SiN.
>
> Thank you very much,
>
> Zhiyan
>
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