I tried Ti in 33% KOH at 80 C.
It became soft. After ~30 min, the apparent etch rate was 62 nm/min.
Ti under Au may end up being OK, however.

You might use Cr instead.
For Cr, I measured a slow etch rate of 4.2 nm/min in the same solution.
100 nm Au with 10 nm Cr as an adhesion layer worked fine for ~1 hour of KOH
etching.

The other popular adhesion layer, 10Ti/90W, did not fare well, being etched
at > 300 nm/min.

    --Kirt Williams, Ph.D.   consultant

----- Original Message -----
From: Roger Shile 
To: MEMS Discussion Group 
Sent: Tuesday, March 25, 2003 12:51 PM
Subject: [mems-talk] Ti attack by KOH


> Can someone tell me if titnanium can be used as an adhesion layer for gold
when the metalization will be subjected to a long KOH etch?
> In my experience, chemistries that etch Si, such as HF and fluorine based
plasmas, will also etch Ti.  I therefore suspect that KOH will etch Ti, but
haven't found any published data.
>
> Roger Shile
> _______________________________________________
> [email protected] mailing list: to unsubscribe or change your list
> options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
> Hosted by the MEMS Exchange, providers of MEMS processing services.
> Visit us at http://www.memsnet.org/