H2O is a required component of the chemical reaction that takes place
during exposure. When you soft bake you also dehydrate the resist. So, you
have to let it redhydrate from ambient moisture before doing the exposure.
Thicker films will need longer time. A certain level of ambient moisture is
needed, typically 45%.
Hi Andrew,
Thanks for your reply. Could you please clarify a little bit more? I would
really appreciate that.
What do you mean by longer "relaxation"? When do you recommend to do
"relaxation"? Before exposure, or after exposure?

Regards,

Mehmet

On Tue, Sep 29, 2015 at 7:04 PM, Andrew Sarangan 
wrote:

> I have seen this before, and I think it may have to do with inadequate
> rehydration of the photoresist. You need to let the resist relax for 30
> minutes or more depending on the thickness and ambient humidity. Thicker
> films and lower ambient humidity will need longer relaxation times. If it
> is not rehydrated properly, the bottom parts of the resist will not
develop
> regardless of the dose.
>
> On the other hand, I don't know why this is happening only when you use
> HMDS. One possibility could be that the untreated surface is holding on to
> some surface moisture which is helping to rehydrate the resist.
>
>
>
> On Mon, Sep 21, 2015 at 5:24 AM, Mehmet Yilmaz 
> wrote:
>
> > Dear mems-talk community,
> > If I use HMDS as adhesion layer, I am having a problem with the
> development
> > of a photoresist called AZ4562 (about 10 micron thickness). In addition,
> I
> > am having the same development problem with AZ5214E (about 1.4 micron
> > thickness).
> >
> > If I do not use HMDS, the development time is usually about 60 seconds,
> or
> > even less. However, if I use HMDS, the development time goes up to 45
> > minutes (not seconds...) and still the development is not successful,
but
> > the resist is completely removed from some parts of the patterned areas
> on
> > the wafer.
> >
> > Also, I have seen this problem with different substrates such as
Silicon,
> > Quartz, and Pyrex.
> >
> > I am wondering what would be the reason for that? Is it possible that
> HMDS
> > is old, and out of date? Could that explain the problem? Or, do you have
> > any other comments based on your own experience? Could you please
> comment?
> >
> > I am looking forward to your replies.
> >
> > Thanks in advance,
> >
> > Mehmet
> >
> > Mechanical Engineer
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