Yu,

With regard to your sputtering parameters, they seem in line with what
we derived for our system. Exact optimal parameters
will be system specific. I recommend, if you have time, to do a study on
test wafers to find the optimum, as we did. You should focus on Ar/N2
ratio, pressure, and power. Also, be sure you are able to obtain a good
base pressure and that your system is not leaking, as oxygen will reduce
the etch resistance greatly.

With regard to photoresist, you have many choices. for example, you can
etch through 1 um of wet-thermal oxide using AZ1512.

Thank,

Rob MacDonald
Shearwater Scientific
robm@shearwaterscientific.com


Rob,

Thank you for your kind reply. Sorry that I didn't go into enough
details of my
complicate design. Actually, the Si3N4 pattern I want to protect is a
bilayer of
sputtered Si3N4 (~0.3um) and LPCVD (~1.3um). The sputtered Si3N4 is
temporarily
inevitable in my process design. Here are my sputtering conditions:

Tool: AJA UHV magnetron supttering system
RF power: 150W
Target: Si3N4
Substrate: complicate patterned basically covered by LPCVD Si3N4 (~1.3um)
Substrate temperature: ~15C
Pressure: 2.8 mTorr
Working gases Ar=30sccm, N2=5sccm.
Time: ~200minutes

Also, I want to pattern a layer of BHF/BOE-resistant photoresist on my Si3N4
pattern to be protected. Do you think it will work as I hope? If yes,
what PR
would you suggest?

Best regards,

Yu