[labnetwork] Super / Ultra low stress LPCVD nitride deposition

[Aaron Mueller]

Dear all,

My group, among other activities, makes MEMS chips with nitride membranes.
Ideally, because I think it would be more economical, I am wondering if
anyone knows a facility that can deposit super or ultra low stress LPCVD
silicon nitride (180nm) on 300/400um thick 4"silicon wafers. Or perhaps
this is not a good idea as the achievable membrane performance may depend
on the bow/warp/etc. of the silicon wafers. Alternatively, I would like to
find a wafer vendor that can target such a low stress nitride coating at a
reasonable price.

I'm looking for something less than 50MPa tensile stress, maybe closer to
zero. I've used low stress ( nominally <250MPa) and now super low stress
(nominally <100MPa, paid about 100USD per wafer for 25 wafers, would be
willing to pay a bit more), but my nitride membranes are still breaking
more than is acceptable.

I am aware that our application is demanding, as the membranes are quite
large (440um x 440um), and we often make holes through them, either with
RIE (before the membranes are suspended) or FIB (after).

I would be very grateful for any suggestions. Thanks!

Best Regards,
Aaron

Aaron Mueller, PhD
Research Fellow
School of Materials Science and Engineering
Nanyang Technological University
Singapore
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