Dear all,

We had performed DRIE to etch the 20 um thick silicon layer on SOI wafer.
However, the silicon layer was not fully etched, so the silicon was remained
at the bottom (on top of buried oxide).

For the perfect etching of silicon, we had performed second DRIE process on
same layer. We realized that the many compliant beams were distorted (it
looks like distortion after releasing the residual stress between two
layers) after second DRIE process and became thin compared to the result of
first DRIE process.

We think that the high temperature during DRIE would be one of candidate for
distortion.

It will be highly appreciated if anybody knows or guesses the reasons and
possibilities of distortion after second DRIE process. The solution to avoid
the distortion of beams will be very helpful to us.

Regards,

Jungwook Choi