Abstract
The use of
SF
6
/
O
2
chemistry for polysilicon gate etching at a low temperature in an electron cyclotron resonance plasma etcher is considered. Sidewall angle, polysilicon etch rate, and selectivity to gate oxide and photoresist are reported as functions of temperature in the range
−125 °
C
to
25 °
C
.
The addition of oxygen to the plasma allows anisotropic etching to be obtained at higher temperatures than with pure
SF
6
.
0.3 μm long gates were formed at
−100 °
C
using an etch process with
≈3:1
selectivity to photoresist and
≈14:1
selectivity to oxide.