We also have made lithography on small samples (5mm x 5mm) and a big
issue for us was the photoresist accumulation on the edges.
Due to the high thickness this photoresist on the edges is not
sufficently exposed, so the effective area of the sample is considerable
reduced to 4mm x 4mm in our case. ¿Do you have ideas to reduce this effect?

Javier


Edward Sebesta escribió:
> I think you need to have the sample go onto a dummy wafer with travel
> stops. The travel stops could be silicon sections affixed to the edge of
> the wafer. That way the mask is physically prevented from getting too
> close to your small sample that you are exposing. Or you could have two
> fused wafers, one of which has a center section cut out, and  the rest
> of the remaining wafer acts as a travel stop or as a contact surface for
> the proximity check for some types of contact/proximity aligners.
>
> The critical thing would be that the wafer piece that acts as a travel
> stop be close to the same thickness as your sample, so you proximity
> settings for exposure acting on the wafer piece would work for your
> sample and not be out of the control range of the machine.
>
> If you have only a simple contact machine, the travel stop pieces should
> be thicker.
>
> Ed Sebesta

Dr. Javier Sesé
Investigador del programa Ramón y Cajal
INA - Instituto Universitario de Investigación en Nanociencia de Aragón
(Interfacultades II)
Universidad de Zaragoza
C/ Pedro Cerbuna 12
50009 Zaragoza, SPAIN
tel.: + 34 976 762783
fax: + 34 976 762776