I am currently working on a project involving the LIGA Technology.

The problems I' m working on regards the spinning of PMMA on 4" Si/Ti/TiOx
substrates.

Until now I' ve spinned PMMA in different concentration (from 15 to 25 % of
PMMA in diluted chlorobenzen and MMA). The result of the spinning give a 20m
layer up to 60m (spinning twice) and more. With the spinning speed of 200rpm
for 15s and then up to 2000rpm for 15s, I obtain a good layer distribution and
uniformity.

My problems are the prebake conditions and moreover the develop step. After
these phases several cracks are present on my wafers (also in the un-exposed
areas). The develop procedure I' ve used is our standard that means GG/BDG/H2O
with the typical time 15/20/10 minutes.

As regards the prebake I' ve tried these 2 types:

1. up to 60 C; for 30 min; up to 85C; for 60 min; up to 105C; for 60 min; up to
185C; for 60 min; down to room temp with up = 15 C/h; down = 10 C/h ;

2. up to 150C; for 30 min; down at room temp with up and down = 40C/h;

But I do not see any difference in the final results.

Before to try different condition I would like to ask you some information
about your experience in these problems.

Thank you in advance.

Francesco De Carlo
decarlo@imtmv2.kfk.de
Forschungszentrum IMT
Karlsruhe, Germany