Dear MEMS-Experts,

When I'm developing a 28micron thick AZ9260 photoresist with the AZ400K
developer in 1:4 dilution (Developer:H2O)on silicon, I can see a selective
developing rate between thin lines and square areas that have a much bigger
diameter.
Since I have such a selectivity, my lines are flaking off when I use longer
developing times in order to develop the squares as well!

Can someone tell me what's going on here?

Overview of procedures

Spin 28microns on Si-sample
Softbake 10 min at 50 degree C
Softbake 30 min at 90-95 degree C
Exposure 40 min at 10 mW / cm cubic
Development in 1:4 dilution (Developer:H2O)