> Who knows the temperature in DRIE when silicon is
> deep-etched, say 500microns?

In an STS system with 600 W of coil power,
the surface temperature in steady-state
should be less than about 70 C.
As the silicon etching is very exothermic,
more exposed area will give a higher temperature,
while a wafer with only photoresist or oxide exposed
has only a small temperature rise.

The wafer temperature can be lowered by about 15 C
by turning the temperature on the chiller from
20 C (the typical setpoint) down to 5 C (the
lower limit for water chillers).

If there is not good contact of the aluminum chuck
to the silicon wafer, the temperature can get much
higher, over 100 C, which results in loss of the
fluoropolymer sidewall coating, yielding more undercutting.

        --Kirt Williams Agilent Technologies