Dear Octavian,

a number of customers that use our porous silicon etching equipment
use LPCVD silicon nitride as etch mask for porosification in HF
mixtures. The etch rate of Si3N4 is not too high and, depending on the
thickness, porosification times of up to an hour are possible.

The etch rate of low-stress Si3N4 in conc. HF is around 5 nm/min,
although pin holes might give you problems earlier.

Best regards,

Jan Lichtenberg

--------------------------------

Dr. Jan Lichtenberg

AMMT Advanced Micromachining Tools GmbH
A.-Feuerbach-Str. 6
D-67227 Frankenthal
Deutschland/Germany

Tel.: +49-6233-4960014
Fax:  +49-6233-436214

eMail: mailto:[email protected]
WWW:   http://www.ammt.de