Yeah, I used a DRIE process -- etched 1/2 on one side of wafer, and 1/2 on
the other.  Diminishes your aspect ratio, but you need to ensure good
alignment (obviously).  Probably it would work directly on one side, but I
had to be sure with my particular devices.

Brian.

At 06:06 AM 5/22/2005, you wrote:

>Has any one achieved 15-20 microns "through holes" in 400-450 thick
>wafer. Aspect ratio > 20 ?
>
>Please let me know if any one has got success in it.