I have been using SU8 2050 and am finding it very difficult to achieve unifrom thickness across the wafer.
Also, the film thickness i get is very inconsistent for the same spin profile. The difference can be more than 10um on different attempts.
Has anyone encountered this problem of inconsistent thickness for the same spin profile and is there any solution to achieve more uniform thickness across the wafer?
P.S. I am using an old bottle of SU-8 that i found so i was wondering if the discrepancies could be due to this.