Dear friends

I am trying micromaching of silicon <100> wafer, 525
micron thick and 7 micron EPI layer (Ar) using TMAH
25%.  After 8 hours, the etching becomes so slow that
it hardly etch the wafer  to the oxide layer grown on
silicon wafer.  If I try etching from EPI layer,
polished side, initially it etches with its actual
etch rate,i.e. 1 micron/minute  but when wafer
thickness remains about 15-20 microns, the etching
becomes almost negligible.  Now If I start etching
from the unpolished side of wafer, the same problems
occures on the other side i.e. it stops etching the
remaining 15-20 micron silicon layer.  I can not
understand what is happening.  Is it solution weekness
or something ? i don't know.  Can somebody help me
please.


M. Aslam

m_aslammalik@yahoo.com
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