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