Hello Kris

Exactly what are you trying to accomplish with your etch. Are you using it as a
quasi isotropic etch to undercut your device? Is the shape of the hole
important? If you are looking to undercut a device or could live with an
isotropic etch pattern then you might want to try another process like xenon
difluoride which will not attack your aluminum at all. If this would work for
you feel free to give me call or send email and we can run some samples to try
it out.

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




 >>  Dear all,

 >>  I was performing TMAH etching of silicon on one of my
 >>  devices that has Al on it.I was following the process
 >>  given in "An Improved TMAH si-etching solution without
 >>  attacking exposed Aluminum",Guizhen Yan
 >>  et,al,Proceedings of the IEEE Micro Electro Mechanical
 >>  Systems (MEMS), 2000, p 562-567.


 >>  This paper explains that with the addition of adequate
 >>  amounts of silicon(1.6%) and Ammonium peroxy
 >>  disulphate(APODS)[0.5%] in 5%TMAH solution can give
 >>  good protection on Al and good surface smoothness.

 >>  After i performed the process given in the paper,i
 >>  could get good protection from Al.But after sometime
 >>  the surface roughness increased drastically and
 >>  resulted in slow etch rate of silicon.I presume that
 >>  this roughness is due to depletion of APODS in the
 >>  solution for which extra APODS is needed to be added
 >>  to make up for the lost amount of APODS in the
 >>  solution.

 >>  This paper did not explain about addition of some
 >>  quantity of APODS to be added at regular intervals of
 >>  time.

 >>  If someone is familiar of the TMAH process,please
 >>  guide me in this aspect.

 >>  I would appreciate your help.

 >>  Thanks
 >>  Kris

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