Did the addition of helium result in smoother etched surfaces?  Adding O2 to
SF6 will result in a more anisotropic etch, but tends to result in rougher
surfaces.  I wonder if adding helium will result in smoother surfaces, while
maintaining an anisotropic etch profile.

Roger Shile

>>> yaopeng@UDel.Edu 03/28/02 12:47PM >>>
Hi all,
I am using SF6+He to etch silicon. I thought He will be helpful to get a
smother surface. I fixed all the other parameters like pressure, power,
etching time... and only change the flow rate of SF6 and He. The strange
thing is that the etching speed of SF6:He=10:20 was larger than that of
SF6:He=20:20. (They were etched in same machine and at same day, one
after the other) And also I found that if I fix the gas flow of SF6 and
only change the persentage of He, the etching rate will increase with
increasing the persentage of He. All these seem to indicate that He can
not only cool the photoresist, but also will help the etching. Does anyone
else has similar experience.
And I am not sure what kind effect of He to side wall, will it make the
process more isotropic or more anisotropic?
Thanks a lot!

Peng Yao
DOEs lab
Electrical Engineering Dept.
Univeristy of delaware
Newark D.E 19716
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