Try Nitto Denko Revalpha doublesided tape, we use 0.1mm thick 3195M
tape.

It has a good thermal conduction in the DRIE and the wafer is removed
by warming on a hotplate from 90C to 170C to release.

We etch clean through standard Si wafers without any problems

http://www.nittousa.com/products/electronic/revalpha.php

http://www.nitto.co.jp/company/bce/global.html

Andy Scholes