Hello,

When I was at the Foxboro Company in the 1980's we used a mixture of HF and
Ammonium Fluoride at 80C to etch quartz tuning forks, we used a Cr/Au mask
and it took a couple of hours. The Ammonium Fluoride buffers the solution to
keep a constant etch rate.

I do not remember the ratios but try looking up papers from that era about
quartz tuning forks.

One caution the vapors are very nasty use a good hood. We used a stainless
steel beaker to heat water and put a Teflon container (covered into the hot
water to control the temperature.

Good Luck

Rick

-----Original Message-----
From: Oliver Horn
Subject: [mems-talk] How to etch single crystal quartz?

How to etch single crystal quartz? I tried HF (49%) at room temperture.
This had an etchrate of  only 3 um/h. I need to etch at least 40 um, and
I think my mask (Cr) will not withstand this long time. I also tried
ammonium fluoridel, this only etched 14 nm/h.