Hi,
I think, It is due to the undercut etching by BOE solution. Use dry etching
to etch oxide. Recipe 15 sccm CF4:1.5O2, power 300 W, 0.3 um etching should
take about 5 min.

Pradeep


On 9/9/06, Shankar Dutta  wrote:
>
> 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.