Just ideas, never tried to test it ...

1. Cut the wafer  into pieces _after_  applying photoresist, as the layer
is already spin-coated and partially soft-baked, then continue soft baking
so that the photoresist layer relaxes.

2. Break the wafer into pieces and stick them together as strictly
as possible matching the edges precisely, e.g. on a sheet of
scotch tape. Then process such a sandwich as the wholeness
and disassemble not until it is developed. By the way, with this
method you can make several pieces at once - the only crux
is the exact sticking of the puzzle pieces; stick them together
on a flat substrate upside down, then cover with a piece of
scotch tape and reverse - IMO, it should work.

2008/2/8, Javier Sesé :
> 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?