Hi all,

i need to realize silicon membranes having thickness 14um and lateral size
5x5 mm in 4'' silicon wafers, starting thickness is 300um.
I can not use any stop layer or SOI wafers.

I already realized some membranes using KOH etch, but thickness is not so
uniform (thickness variation is about 4-5um).
I tried to use magnetic agitation, but it did not helped much.

Any suggestion on how to improve thickness uniformity ? I tried also
ultrasonic agitation, but membranes went broken along the (100) planes.

Best regards,
Andrea