How much silicon are you actually etching. From you question you could be

1. removing all of a thin sacrificial layer of silicon or poly below a membrane
or
2. taking off 500um off the back of a wafer.

If TMAH is not working there may be two possibilities both using xenon
difluoride. Xenon difluoride has selectivity to oxide over silicon of better
than 1000:1. So you can use reasonable thicknesses of oxide.

In case 1 XeF2 is usually the perfect way to remove a sacrificial layer for
micromachining a membrane with a silicon release layer.

In case 2 XeF2 will be quite slow, it will work find on chips or small pieces
but on a full wafer you would want to ugrind down the back, use TMAH or some
other method to remove most of Silicon before using the XeF2 to remove the last
of the silicon while protecting the membrane.

If you have any questions or would like to try using XeF2 please feel free to
contact me directly. XACTIX is the overwhelming market leader in supplying
equipment to etch silicon using XeF2.

David Springer
XACTIX, Inc.
412 381 3195
[email protected]
www.xactix.com




If


>>  Dear community

 >>  I'd like to use SiO2 as an wet etch mask in TMAH, but TMAH does etch SiO2.
 >>  What I want to do is etch whole Si except membrane which is spun on Si.
 >>  So, much thick SiO2 is needed.

 >>  1) How much %wt TMAH is preferred? Only TMAH or mix with other chemicals?

 >>  2) How much thickness of SiO2 is needed to persist in TMAH during Si
 >>  etching?

 >>  3) Etch time and temperature of TMAH which is corresponding to 2)?



 >>  Sincerely,

 >>  ---------------------------------------------------------
 >>  Byunghoon Bae

 >>  Visiting scholar
 >>  Mechanical & Industrial Engineering
 >>  Univesity of Illinois at Urbana-Champaign
 >>  26 MEB MC-244
 >>  1206 W. Green St. Urbana, IL 61801
 >>  Tel: 1-217-244-7301, Fax: 1-217-244-6534
 >>  E-mail: [email protected]

 >>  Ph. D. candidate
 >>  Dept. of Mechatronics
 >>  Kwangju Inst. of Science and Technology(K-JIST)

 >>  ¸¶À½¼ö·Ãȸ ȸ¿ø
 >>  Member of mind(maum) meditation center

 >>  -¸¶À½Àº Çϳª, ¸¶À½Àº ¸ðµç °Í
 >>  Âü³ª¸¦ ã¾Æ, ¼ø¸®ÀÇ ˜®À»-
 >>  -Mind is one, mind is everything
 >>  Taking the path toward the truthful life-

 >>  Mind meditation center:
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 >>  English: http://211.47.66.148/eng/
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