> -----Original Message-----
> From: abhay [mailto:abhayporwal@yahoo.com]
> Sent: Sunday, January 26, 2003 7:34 PM
> To: mems-talk@memsnet.org
> Subject: [mems-talk] Polysilicon Etching

> hi all,
>   We are looking for etching a 4000 A polysilicon
> layer. We want the etching do be completed in less
> then 2min as there after our photoresist tend to etch
> away. So what solution shd we try and what proportion.
>          Thanks
> Regards
> Abhay Porwal

Use an HF-nitric solution. A good one is
126 HNO3 : 60 H2O : 5 NH4F.
Let it sit for > 8 hours after mixing!
In my measurements (yours will probably be a little different),
undoped poly etched at 1000 A/min and
 doped  poly etched at 3100 A/min.
Two types of positive photoresist did not etch.

        --Kirt Williams Agilent Technologies