Etchants came up a few days on the discussion list.  and a comprehensive
list of references was posted on the maillist.

0.5% HF will etch Ti easily (depends on the thickness).  Thiourea and
iodites will etch gold.
Check the CRC handbook of metal etchants for detailed references and
compostions

You may also like to check the MEMS archives for information.

Shekhar bhansali

>To whomever it concerns,
>
>I am just getting into processing and wanted to obtain information on some
>things.  First I need to know what will etch Titanium, besides KOH?  What
>will etch gold?  Lastly, what metal can I pattern onto GaN, that will resist
>hot KOH? Thank you for your assistance
>
>Michael
>*****************************************
>*                                       *
>*       Michael Jackson                 *
>*                                       *
>*       Graduate Student Researcher     *
>*       UCLA                            *
>*       [email protected]            *
>*       Work:   (310) 206-3724          *
>*       Home    (310) 641-8133          *
>*       Fax:    (310) 206-4685          *
>*                                       *
>*****************************************
>
>

________________________________________________________________
Shekhar Bhansali Ph.D
Visiting Research Fellow (MEMS)
National Research Laboratory of Metrology
1-1-4 Umezono
Tsukuba, Ibaraki 305 JAPAN
Phone +81 298 54 4052       Fax:  =81 298 54 4135