The selectivity looks real low (~2) for the Ashland Pad etch 4 !!!

Do you have any lab data on using one of the HF formulations (73% HF
(selectivity ~680 (literature)), 49% HF (~547), Buffered HF/Glycerol (~170))
or Dry etching.

thanks,
Sunil Kumar

MuSquared, Inc

----- Original Message -----
From: 
To: 
Sent: Wednesday, February 26, 2003 12:09 PM
Subject: [mems-talk] RE: [mems-talk] Wet etchant not attack Al and SiO2


> > -----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
>
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