For through etching, I like to use sapphire wafers so I can inspect
the etch pattern from the back. We also use silicon with a micron or
2 of oxide. If I am doing acetone release, I use silicon backing
wafers that are deep etched slightly (50 microns?) with radial slots
and rings to make it easier for the acetone to get in from the edges.

On Jun 15, 2007, at 8:38 AM, Xiaoguang Liu wrote:

> Hi Jim
>
> What support wafer would you use? Is it silicon also? How would you
> prevent
> the support wafer from being etched?