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February 1999

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Subject:
From:
Yongheng Zhu <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 3 Feb 1999 23:22:08 -0600
Content-Type:
text/plain
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text/plain (75 lines)
Jeff:

I don't have any experience in IC industry, since I work in PCB world. Just
some old memory from school.
Could you use dry etch instead?. As you know wet etching is an isotropic
etching, which naturally producing undercutting in the pattern edge profile.
Doesn't matter acid, base or oxidizing etching system. As far as adhesion of
resist, promoter like HMDS may be used to help. In PCB world, Situation is a
lot worse. I think some people do use H2SO4/HO2 for like flash etching on
SBU to achieve fine line. But again you talking 25 micron vs 1 micron. They
are in complete different world.

-----Original Message-----
From: Jeffrey A. Gregus <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Wednesday, February 03, 1999 6:28 PM
Subject: [TN] photoresists for copper etching


>Group,
>I am interested in wet etching sputtered copper on a semiconductor
>wafer.
>I realize that I'm not talking boards here, but I'm hoping that someone
>can
>give me some insight to the problems that I'm facing.
>Using traditional positive photoresists for semiconductor manufacturing,
>I
>am getting a very large undercut of my copper features.  Features are
>4-8
>mils in x,y and anywhere from a few thousand angstroms to 1 um thick.
>Unfortunately, the amount of undercut is 10-20 times the feature
>thickness.
> (I would expect 1x the feature thickness)  I believe the problem is the
>interface between the copper and the resist.  When I use a metal mask
>(say
>Al), no appreciable undercut is observed.  Also, the undercut seems to
>be
>independent of etch solution.  Right now I am using a dilute
>sulfuric/peroxide mixture.
>In the pcb world, I assume copper is etched with photoresist masks.  The
>question is, is the photoresist a different chemistry to improve the
>adhesion/interface between the polymer and the copper?  If so, what
>photoresists exist out there?  And finally, is there a version that can
>be
>applied by SPIN coating (i.e. semiconductor process)?
>Any insight would be greatly appreciated!
>Jeff
>
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