This is a tricky one. What you're describing may be difficult to get from
polyimide.

But not from photoresist. There is a trick that people have used with some
types of photoresists. They want to eventually make dome shaped features in
underlying silicon dioxide. Actually, they want to make lenses. So what they
do is for patterned photoresist patches that have a cylindrical shape. Then
they melt the photoresist so that it forms a dome. Finally (and this part is
not important to you) they etch the exposed oxide and photoresist at the
same etch rate. When they're done, the dome shaped photoresist pattern is
transferred into the silicon dioxide.

For your purposes, you could make concentric annuli (annuluses) in
photoresist and then melt to achieve the desired profile. If you really need
to use polyimide, you could try developing a process similar to the
photoresist/silicon dioxide, except you'd replace silicon dioxide with
polymide. And you'd have to figure out an appropriate etch that will etch
photoresist and polyimide at the same rate.

Good luck.

Bill Eaton, Ph.D.
Materials & Analysis Manager
NP Photonics
mailto://[email protected]




> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of A H M Habib Ahsan
> Sent: Wednesday, June 04, 2003 12:40 PM
> To: [email protected]
> Subject: [mems-talk] Changing the surface of a cured polyimide thin
> layer
>
>
>
> Dear all:
>
> A flat surface of polyimide layer is found after spun some
> liquid polyimide
> over a substrate.
> Can anyone suggest me atleast a way that can help me make a
> change in that
> surface, so that it would no longer be flat, rather something
> like a lot of
> ripplings with a desired dimension. Each ripple should have
> dome-shaped pick,
> and the joint of two ripples should be down very near to the
> bottom surface
> of 2mu thin polyimide layer.
> I would be help.
>
> Thanks
> Habib
> Alberta, Canada
>
>
> _______________________________________________
> [email protected] mailing list: to unsubscribe or change your list
> options, visit
http://mail.mems-exchange.org/mailman/listinfo/mems-talk
Hosted by the MEMS Exchange, providers of MEMS processing services.
Visit us at http://www.memsnet.org/