Hi Ed, Thank you for your suggestion. Is the surface etched using "BOE" still smooth enough? I will put Au electrode on the surface. Regards, Yoshi -----Original Message----- Wet etch is isotropic when the substrate to be etched is largely or completely isotropic in nature, such as glass. Some type of flouride solution should do well. Depending on the type of resist you might want to use a buffered oxide etch solution which comes either 13:2 or 6:1 from vendors and is known as "BOE". Ed