Dear Yilei,

You can use DRIE process to get constant tapered profile
(negative/positive). You will have to optimize certain parameters like
Oxygen flow rate, SF6 flow rate and etch/passivation cycle time ratio.
however its a bit difficult to control.

Thanks,
Pradeep

On 2/25/06, yilei zhang  wrote:
>
> Dear colleagues,
> Is there a way to get high aspect ratio of silica structures? Like DRIE
> for
> silicon? Thanks.
>
> Regards,
> Yilei Zhang