I am not an expert, but I remember that I had the same problem once.
Analytically:



The appearance of air bubbles or particles in the coated resist film is
very similar to each other (Figure above). Particles often stem from an
*insufficient substrate cleaning*, or an *expired resist*. Air bubbles
in the resist are often caused by transport, refilling or dispensing of
the resist. N2-bubbles originate from the gradual decomposition of the
photo active compound in the liquid resist. If, after storage for a
certain time, the resist bottle is opened, the N2 dissolved in the
resist may form bubbles. In case of either air or N2 bubbles, a delay
before dispensing of  (depends on the resist viscosity) a few hours will
help for out-gassing the bubbles.

Regards


Le 1/8/2015 4:17 PM, Orozaliev Ajymurat Nurdinovich a écrit :
> Hi All,
>
> Anyone knows a good recipe for AZ 40XT positive resist?
> My target thickness is 50 um.
>
> I am doing following process but always getting bubbles during post
> exposure bake and sometimes bubbles appear during soft baking step.
>
> Sometimes foam would form on the middle of the subsrate.
>
> 1.HMDS priming in an YES oven.
>
> 2.Spin coating
>   -1000 rpm - 20 sec,100 rpm/s ramp
>   -2500 rpm - 2 sec,1000 rpm/s ramp (to remove the edge bead)
>
> 3.  Soft baking on a contact hotplate
>   - 40 - 100 C, gradually increasing
>   - 115 C,for 3 mins (second hotplate)
>
> 4. Exposure (No rehydration performed, since the datasheet says so)
>    - Exposure for 60 seconds on a SUSS MA8 contact aligner tool,lamp
> intensity 10mW/cm2.
>
> 5. Post exposure bake on a hotplate
>     -60-90 C, gradually increase the T.\
>     - 105 C for 100 sec.
>
> 6. Develop
>      AZ726 MIF for 8-10 um.
>
> Any expert can comment on this?
>
> thanks in advance,
> Ajy
> _______________________________________________
> Hosted by the MEMS and Nanotechnology Exchange, the country's leading
> provider of MEMS and Nanotechnology design and fabrication services.
> Visit us at http://www.mems-exchange.org
>
> Want to advertise to this community?  See http://www.memsnet.org
>
> To unsubscribe:
> http://mail.mems-exchange.org/mailman/listinfo/mems-talk

_______________________________________________
Hosted by the MEMS and Nanotechnology Exchange, the country's leading
provider of MEMS and Nanotechnology design and fabrication services.
Visit us at http://www.mems-exchange.org

Want to advertise to this community?  See http://www.memsnet.org

To unsubscribe:
http://mail.mems-exchange.org/mailman/listinfo/mems-talk