Abdel,

Use a gas mixture of CF4 and H2.  The CF4:H2 ratio should be around 1:4.
Experiment with ratio to get the selectivity and etch rate you need.

Ad Hall
StarCryoelectronics
505-424-6454
ahall@starcryo.com


-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Abdel Moneim Marzouk
Sent: Wednesday, August 02, 2006 9:05 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Honeywell SOG 512B Etching Recipe with LPCVD
SiliconNitride Selectivity (Abdel Moneim Marzouk)

Hi,

I am currently working on developing a process that involves
Honeywell's Spin-on-Glass (SOG) 512B that is deposited on LPCVD
Silicon Nitride wafers. I am using a RIE dry etch to pattern the SOG,
and apparently my recipe etches the nitride faster than it does the
SOG. The recipe I am using includes CHF3 (40 sccm flow rate), Ar (70
sccm), and CF4 (7sccm).

This recipe etches SOG at a rate of 0.20 microns/min, and nitride at
0.5 microns/min. Since my main concern is etching SOG, and I need the
nitride for insulation puroposes, I was looking for an alternative RIE
etch that would be selective to LPCVD silicon nitride.