Hi,

If you are using PECVD for the deposition of your silicon nitride then
you might use buffered HF. The etch rate would depend on de H content of
your layers, but it will be generally slow. On the other hand, if you
are not using this deposition technique, buffered HF would be useless.
For calibration curves of etch rate see:

W. A. Lanford and M. J. Rand, J. Appl. Phys. 49(1978) p. 2473
R. Chow et al. J. Appl. Phys. 53(1982) p. 5630

Best regards,
E. Sillero

avinash balakrishnan wrote:

>Hi all,
>
>    I am interested in chemical etching silicon nitride. I read somewhere in
the forum that 85 % phosphoric acid at 160 C is helpful. Can any one tell me how
long should i etch to get a decent microstructure. References or paper links can
be very helpful.