Hi Colleaques,

        I appreaciates all the information which is summarized as
follows.

later,
Andrew

[1]
Date: Sun, 6 Jun 1999 18:25:36 -0700 (PDT)
From: Xing Yang 
To: [email protected]
Subject: Re: isotropic etch recipe for silicon dioxide without attacking

aluminum

You can buy some chemicals named "Pad Etch". They are made for etching
contact windows in SiO2 layer on top of Al layer.

Hope this helps.

Xing Yang
ACLARA BioSciences

[2]
Date: Mon, 7 Jun 1999 08:55:17 +0100
From: Matthias Heschel 
To: 'Jer-Liang Yeh' 
Subject: RE: isotropic etch recipe for silicon dioxide without attacking
a
luminum

I know of a dry etch technique I used several times: reactive ion
etching in a CF4 plasma. If you need good selectivity to silicon you
should add CHF3. Aluminum is not attacked at all.
Good luck,

Matthias

________________________________________________________________________

Matthias Heschel
Microelectronics Center
Technical University of Denmark, Bldg. 345 east
DK-2800 Lyngby
phone (direct): +45 45256308
phone (switchboard): +45 45934610
fax: +45 45887762
http://www.dtu.dk/mic

[3]
Date: Mon, 7 Jun 1999 11:20:12 EDT
From: [email protected]
To: [email protected]
Subject: Re: isotropic etch recipe for silicon dioxide without attacking

aluminum

Try buffered oxide etch at maybe 10:1 ratio. Di water and ammonium
fluoride.
Bob

[4]
Date: Tue, 8 Jun 1999 15:21:49 -0400
From: Marisa Ahmad 
To: 'Jer-Liang Yeh' 
Subject: RE: isotropic etch recipe for silicon dioxide without attacking
a
luminum

You can use a buffered HF etch that will not etch Al (like BOE or
Transene).
This will be isotropic of course (wet etches) but will work if you
aren't
trying to look deep.   If you want to see several layers simulataneously
you
will have to use an anisotropic etch

If you have access to an RIE, you can use any fluorine chemistry (SF6,
CHF3,
CF4)to etch silicon dioxide anisotropically (dry etches).   None of them

will touch aluminum (although sputtering will occur eventually).  For
maximun etch rates use a mixture with 10% O2 added.  If you are looking
very
deep (more than two layers) you will need a deep etching ICP-RIE.

Good luck,

Marisa