Wenyu,
   I'm no longer using that recipe and have turned to lift-off for all Pt
patterning.  I do use aqua regia for Au patterning. Here's our new recipe:

3 HCl: 1 HNO3 at room temp., about 60sec to go through 173nm Au
For 2 wafers used 100ml HCL and 33ml Nitric in 1000ml beaker use larger beaker

Note: that I would suggest that you use an adhesion promoter for your resist to
keep undecutting to a minimum.  Also, the properties of the etchant change
drastically over time.  You must use the Aqua Regia within about 5 min.. of
mixing.  Otherwise the etch rate goes up and it becomes harder on the
photoresist.

-Michael Martin
 U. of Louisville


>>> "Song Wenyu"  7/19/2007 10:43 AM >>>
Hi,Mike

I found the following information on MEMSTALK. It was published in 2002, I know
many things may change or some of your memory

may not that fresh. But still, I want to try to bother you, if you could offer
some information related to the etching Pt with

any mask. The etching solution and etching rate.