Microchem advise to thermally process each layer as an individual layer
(i.e. do not extend bake times on subsequent layers). The exposure will need
to extended for the 2nd mask.

I.e.:
Spin, softbake, expose, PEB as for a 30um layer
Spin, softbake, (expose as for 45um) and PEB as for a 15um layer
Develop 45um combined layer

As always, some tweaking may be required for but generally this is how it
should be done.

As mentioned, I have only ever done multiple layers using the standard
series which uses GBL as a solvent. I am really not sure what will happen
with an SU-8 3000 layer on top of SU-8 2000. As far as I know they use
different solvents which may cause problems during the baking steps but I
really couldn't say for sure.

Gareth

On Tue, Oct 26, 2010 at 21:26, Abhishek Jain
wrote:

> Hi Gareth
>
> I intend to use a different mask for the 15um layer. Do you mean I
> should spin, pre-bake, expose, PEB as per spec for the 1st 30um  layer
> and then spin, pre-bake, expose, PEB 15um 2nd layer as per spec before
> developing the 45um thick 2 layers?
>
> thanks a lot
>
> -AJ