DRIE etching using Bosch ICP or Cryo ICP will do the trick. aspect ratio
of up to 10 is feasible. The choice depends on availability and mask
design and -material.
greetings Carel

Jeff chen wrote:

>Hi,
>
>I am working on a project which needs to etch a hole through the
>silicon wafer (525 micron thick). The hole diameter is around 50
>micron.
>Does anyone have experience to do that?
>Is there any way to do that? Etching? Laser excimer? or grounding
>technology?