Krishna,

You may want to check out Transene's etch type "N"  for etching Si3N4 on
GaAs.  I dry etch it in my RIE using SF6.

Brent

> Some questions on Si3N4 wet etch
> - H3PO4 :H20, what is a good ratio and temp (160?).
> - would static immersion of wafer in a quartz container with H3PO4 work or
> do we need a special circulating tank.
> - would it still work for GaAs substrates.
> - does H3PO4 attack PR's (AZ 5214).