>From what I remember the only selective etches for Boron doping are KOH,
TMAH, EDP and Hydrazine mixtures, they are anisotropic etches. The
HF/Nitric is iso-tropic and non-selective. If you use electrical current
and do an electrochem etch then the NH/Nitric will be selective.

Rick Morrison



-----Original Message-----
From: mems-talk-bounces+rmorrison=draper.com@memsnet.org
[mailto:mems-talk-bounces+rmorrison=draper.com@memsnet.org] On Behalf Of
morad massalha
Sent: Tuesday, September 21, 2010 10:27 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Selective Poly etch for P+

Hello,

I'm using HNO, 1:3:8 volume, while HF is 49%, Nitric 70% acetic 99.7%.
I'm doing
this etch in a lab, not in machine. I'm just doing feasibility. To found
the etch
rate ratio.