Permission Request

Vishal Singhal vishal at
Fri Sep 29 13:41:31 PDT 2006

Dear SpecMat Committee Members,

I need to do processing on a non-standard substrate and need your permission
to do that.

The substrate is 0.5 mm thick, 4" PMMA wafers.  In this form, PMMA is also
known as Acrylic Glass and is used to make DVDs, contact lenses and
bulletproof vests among other things.  I am getting these wafers from Astra
Products of Baldwin, NY (  The
wafers are in typical silicon wafer shape with a flat.  They will be laser
cut in that shape from large sheets.  The wafers are covered on both sides
with a protective plastic sheet, which will be removed before processing
wafers.  The residual glue on PMMA wafers from the protective plastic sheets
will be removed by a soak in TMAH.

Aluminum will be evaporated on these wafers and then features will be
photolithographed in it using S1813 photoresist and MF CD-26 developer.
Following that, the PMMA wafers will be etched using PGMEA ( Propylene
glycol monomethyl ether acetate).

Let me know if additional information is required.


Vishal Singhal
Thorrn Micro Technologies, Inc.
vishal at
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