Hi James, have you considered HF vapour etching? I know it is pretty useful for
SiO2 etching though I am unsure how your resist will react to the HF vapour.
There are a couple of companies that I know of that deal with this.. One based
at Livingston and also within Edinburgh University at their SMC building is
MEMSSTAR who do this kind of work. As I say, I am unsure of the reaction that
the vapour would have with the HF but its a possibility i guess.

Good luck!

Mr Daniel Drysdale
BEng Hons, MSc Eng D
Research Engineer
School of Engineering and Physical Sciences
Earl Mountbatten Building
Room EM 3.32
Heriot-Watt University Edinburgh, EH14 4AS
Tel: 0131 451 8316
Fax: 0131 451 4155
Email: dd71@hw.ac.uk