We have tried liftoff processes using two layers of
photoresist for ceating undercut profile. The first
layer is AZ1518 and the top layer is AZ4400. Using
AZ351 developer (diluted to 1/3.5) will undercut
AZ1518. We have been sucessful lifting off 2000A of
metal using this method. The other more complicate
way is to use metal layer (like Al) for undercut
profile. After depositing Al layer, say 3-4 um,
spin and pattern photoresist, then etch Al for
longer time to creat undercut.

Tseng-Yang Hsu
Integrated Micromachines
yang@micromachines.com


On Tue, 25 Aug 1998, Han Park wrote:

> I am trying to obtain a good undercut profile of the photoresist to get
> a good liftoff.
>
> The thickness of the photoresist needs to be about 6~7microns.
> The deposited material is about 3microns thick.
>
> Soaking in chlorobenzene for 30 minutes was not enough to give a good
> enough undercut profile for a good liftoff.
>
> Is there anyone who can help me with this?  Is there an alternative to
> this process?
>
>