Dear all,

I am now trying to make silicon nitride cantilevers with dimension of
about 200 um in length, 50 um in width and 1 um thick.

Firstly, a 1.5 um thermal oxide was grown on a 6 inch wafer, then I
deposited 1 um silicon nitride(LPCVD) on top of it, followed by RIE
pattern.  Then I patterned the backside oxide, and  did the TMAH
etching.  However, most of the cantilevers were broken during this
backside etching process.

I am wondering if there is some way to avoid that.  I did very
carefully when handling the wafer, but since the area of unsupported
oxide film on the frontside after the TMAH etching was so large that
it was very fragile to break, so the nitride cantilever was broken
with the oxide film.

The oxide film on the frontside was used as the mask to protect the
silicon from the TMAH etching  from the top.

I searched the literatures and found that most of the processes in
making nitride cantilevers used the same process as I did to release
the cantilevers.  But I failed in doing so.  Could someone give some
suggestion??

Thanks very much!!!!!!!!!!!!!!!!!

Duan