> -----Original Message-----
> From: HE,Han+AFw-(Johnny+AFw-) [mailto:[email protected]]
> Sent: Tuesday, February 25, 2003 3:26 PM
> To: [email protected]
> Subject: [mems-talk] Wet etchant not attack Al and SiO2
> Hi,
> Just wondering if there is any special wet etchant recipe
> (Such as TMAH+Si powder+NH4S2O8) will not attack Al and SiO2
> respectively.
> Thanks.
> Johnny

To etch aluminum without etching silicon dioxide,
use Transene Aluminum Etchant Type A (containing H3PO4, HNO3, CH3COOH,
and H2O) at 50 deg C. It can be patterned with photoresist.
My data: Al ER = 660 nm/min; SiO2 ER = 0 nm/min.

Etching SiO2 without etching Al is trickier.
Perhaps the best wet solution, which can be patterned with photoresist,
is Ashland Pad Etch 4 (containing NH4F, CH3COOH, H2O, propylene glycol, and
and a surfactant).
Our data: SiO2 ER = 31 nm/min; Al ER < 15 nm/min (the surface was roughend).

        --Kirt Williams Agilent Technologies