Hi,

I am doing a trilayer processing LOR Ge(40nm thick )  PMMA.
The e-beam pattern defined on PMMA is tranferred to Ge via SF6 RIE.
Usually this is the hardest part as the PMMA might not survive teh RIE
process. I found this works with 55 watts and 10 morr pressue of SF6 for
40 s in the RIE .

In the past I found O2 etch does not affect Ge (say 30-50 w and 10-30
mtorr pressure) and transfers the patern with an undercut to the resist
below in 3-5 mins etch time.

But the current RIE system I am using an Oxford Plasma lab 80 seems to
clean out the entire trilayer when I do the O2 etch (even in low powers as
low as 30W and pressure around 20-30 mtorr). If anyone has a suggestion
that will be great.

Thanks

Ananth