Hi all,

I'm looking for a RIE recipe for silicon etching using PMMA mask. The PMMA
mask is about 20nm thick and spin-coated on silicon substrate. The etching
depth into silicon is expected to be 20nm~30nm. I tried different recipes
but didn't get decent results.

The recipes I tried include
1) SF6 15sccm + O2 7.5sccm, 40W, 30mTorr -- mask degraded making silicon
surface very rough.
2) SF6 15sccm, 40W, 30mTorr for 2min -- etching rate for this one is very
high, the features expanded and I got an etching depth of 70nm. Degraded
mask and rough surface. Selectivity is not yet measured.
3) CH4 25sccm, 90W, 50mTorr -- selectivity PMMA/Si is around 6:1, the mask
film barely survived.

Does anyone have suggestions for my situation? Thanks!

Li

--
Li. Zhang
---------
Graduate Research Assistant
Edward P. Fitts Department of Industrial and Systems Engineering
North Carolina State University
416, 111 Lampe Dr., Daniels Hall
Raleigh, NC 27695-7906
USA
TEL: (919) 413-5459
Email: lzhang13@ncsu.edu
Web:  http://www.ise.ncsu.edu
          http://www.nnf.ncsu.edu