Kevin -

Do you need the sloped walls of a crystallographic etch like KOH? If so, TMAH
will probably etch through a PECVD mask more slowly than KOH, as I think Joseph
Kung was suggesting to you in an earlier response.

If you don't need sloped walls - maybe you just need a deep trench or a via
through the wafer - and you don't mind shipping your wafers off to another
group, maybe we can help you. We can perform deep etches of silicon with
arbitrary patterns (e.g., straight or curved lines) and with "vertical" walls
on wafers that have aluminum on the wafer side that is being micromachined. Our
method is quick, does not involve any heroic processing effort or risks, does
not leave a residue, and should be CMOS compatible (we haven't proven this, but
expect this is the case).

If you are interested, please email or call me.

Perry Skeath
ITM, Inc.
[email protected]
(301) 577-1788