Generally when you get an etch factor that is ten times worse than expected
the problem is poor adhesion of the resist.  Copper is easily oxidized.
I suggest you try a light clean before you coat the resist.  Try applying
a very dilute sulfuric acid followed by DI water rinse and then spin on the
resist.
You also want to make sure the resist is not over-developed and is fully
cured
before etching.  Adding a short bake wouldn't hurt etch performance but
might cause extended stripping time.


> -----Original Message-----
> From: Jeffrey A. Gregus [SMTP:[log in to unmask]]
> Sent: Wednesday, February 03, 1999 7:13 PM
> To:   [log in to unmask]
> 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
>
> ################################################################
> TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
> ################################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in the body:
> To subscribe:   SUBSCRIBE TechNet <your full name>
> To unsubscribe:   SIGNOFF TechNet
> ################################################################
> Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
> section for additional information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or
> 847-509-9700 ext.312
> ################################################################

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################