mask for KOH etching
yyao at intpax.com
Mon Sep 24 20:42:09 PDT 2001
Recently, I always met problems when I conducted the KOH through wafer
etching. Film stack is: Nitride (4000A)/PolySi(3000A)/Nitride(4000A).
Backside has the same stack. I opened the backside for KOH etching.
Front side is covered by Nitride (no KOH openings). After two hours KOH
etching, the front side had a lot of blisters. It seems Nitride was
broken therefore the underlying PolySi was etched rapidly and worsened
the situation. More interesting thing was when I didn't open the
backside, just threw a wafer with film stack in KOH, after two hours,
the front side was good. No blisters were observed.
I tried different Nitride recipe: LONH378 and NITRIDE2. Both had the
problem. I changed to TMAH solution, problem was still there. Any
suggestion? Thank you in advance.
Yahong Yao, Ph. D.
Phone: (408) 252-6410 x. 407
Fax: (408) 252-6430
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