Qingwei,
        Yes on the electroplating. The way you put down the metal is a vital
part of the lift off.  Evaporation is line of sight and as such will not
deposit on the side walls of the resist.  These side walls need to be open and
the reverse angle of image reversal helps keep the metal of the side walls.
With the side walls open an Acetone wash preferably with ultrasonic agitation
will lift off the resist and the metal that is deposited on top of the resist.
The opening size should have no effect on the lift off.  Bill Moffat

-----Original Message-----
From: Qingwei Mo [mailto:[email protected]]
Sent: Thursday, April 18, 2002 11:31 AM
To: [email protected]
Subject: RE: [mems-talk] pattern thick silver layer?


Hi, Bill,
   Thank you so much for the information. When you say "plate up", do you
mean "electroplating"? Will it make much difference to the results of lift
off by the way I put down the Metal?
    My another concern is that my pattern is a 20X30 rectangular opening,
not a meas or ridge. Is it gonna be a problem?

   Thank you again.
    Qingwei
**********************************************************
Mo, Qingwei                                              *
Phone:(512)-476-4746 (H)                                 *
      (512)-471-7917 (O)                                 *
Fax:  (512)-471-8575 (O)                                 *
Email: [email protected], [email protected]              *
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-----Original Message-----ELECTROPLATING
From: [email protected] [mailto:[email protected]]On
Behalf Of Bill Moffat
Sent: Thursday, April 18, 2002 9:55 AM
To: [email protected]
Subject: RE: [mems-talk] pattern thick silver layer?


Qingwei,
        Lift off will work well on thick metal.  One of our customers is
using
image reversal and 3 micron thick resist to pattern 1 micron thick gold.
The
reversal process is more repeatable because you are not trying to swell
resist
to produce the overhang profile.  For image control that is more precise
than
you need.  There are good technical papers showing control to 80 Angstroms
in
10,000 Angstrom thick resist.  One other approach using reversal could be
plate up.  With reversal you can achieve any angle of resist profile easily.
One of our customers is using 30 micron thick resist to plate up 20 micron
copper connections.  Let me know if you need any more technical help.  Bill
Moffat

-----Original Message-----
From: Qingwei Mo [mailto:[email protected]]
Sent: Wednesday, April 17, 2002 5:31 PM
To: [email protected]
Subject: [mems-talk] pattern thick silver layer?


    I am trying to pattern a thick silver layer on GaAs. The thickness could
be 5000A to 1um . The pattern I try to make is a 30X20um rectanglular
openning. I once tried the silver etchant from Transene. It gave me huge
undercut and ugly etch front. Anyone has the similar problem before? I
deposit silver in CHA E-beam deposition system at about 3~5A/sec.
   Is it OK to lift off this pattern in suck a thick layer? As I know, it is
normally more difficult to lift off a small openning than a mesa or ridge.
   Anther question is, I am using AZ5214, and AZ4330 now. will the image
reversal give these PR a better profile for lift off? Will the Chlorobenzene
process or toluene work to them too?

  Thanks a lot for your help
   Qingwei

**********************************************************
Mo, Qingwei                                              *
Phone:(512)-476-4746 (H)                                 *
      (512)-471-7917 (O)                                 *
Fax:  (512)-471-8575 (O)                                 *
Email: [email protected], [email protected]              *
                                                         *
/------   \ | | /  ---------------------\                *
|          -----       | |Microelectronic Research Center*
|        [  @ @  ]      | Electrical and Computer Eng.   *
\--oOOO-----(_)----OO0o-| University of Texas at Austin  *
**********************************************************
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Visit us at http://www.mems-exchange.org/
_______________________________________________
[email protected] mailing list: to unsubscribe or change your list
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Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.mems-exchange.org/