If you are talking about HF glass etching for smooth walls then you have to play
with
the temperature of the HF. I think the lower the temperature the better the
smoothness but you have to try and see what works best.

I hope it helps.
Nimo

________________________________
From: Wenbin Du 
To: mems-talk@memsnet.org
Sent: Mon, August 16, 2010 8:19:09 PM
Subject: [mems-talk] Commercial glass for HF etching

Hi All,

It's the first time I post here :)

I'm doing glass etchign using HF/NH4F/HNO3 with depth up to 80 um. The
soda-lime glass I used is polished and coated with standard process,
ordered from Telic co. The problem I have is: I often got rough burry
etching edge even if I only etched 30 um.

The phenomena might caused by:

1) during polish, some sodium salt was deposit back on the glass
surface, and it was easily etched away in HF and form burry edge

2) polish causes stress in the surface of glass, and casues
non-isotropic etching, sometimes I can observe thorn like structure.

It seems to me that the problem can be solved by following methods:

1) annealing of glass at it's transition temperature

2) chemically stripping the glass after polish, before coating chrome
and photoresist.

Since I don't want to take these time consuming steps, I wonder if
anyone knows of a company which can offer glass with optical flatness +
annealing or stripping.

If anyone is also doing glass etching (especially Soda-lime and Crown
white glass) and can get smooth edge, Could you share your experience
or your source of order with me?

Thanks a lot.

Thanks all.
--
Best,
Wenbin Du