we are trying to do a DRIE etching (~15-20 micron deep) for comb like structure.
the masking layer is 0.3micron oxide layer. we patterned the oxide layer by BOE
etchant. after that we performed the DRIE experiment. but surprisingly we find
some scalopes in etched area, as if it does some isotropic etching. is this
problem related to paterning of oxide layer with BOE.