Hi Lu,

You can use HF:H2O2:DI with a ratio of 1:1:20. We do not know the
exact etch rate but we guess the solution can etch more than 1um per
minute. Therefore you may dilute the solution as 1:1:100 if it goes
too fast..

Mehmet Unlu
Research Assistant
Ph. D. student
MEMS-VLSI Group
Electrical-Electronics Eng. Dept.
Middle East Technical University
Ankara, Turkey

Tel:  90 312 210 44 09 or 17
Fax: 90 312 210 12 61