Dear All,
             I am trying to get the CTLM pattern by the Lift-off process on
p-GaN...and the minimum feature size is 30micron...but i am unable to get
it...my procedure steps includes...

1) Cleaning of the wafer...acetone,methanol ultrasonically for 5 min and then
HCl:H20::1:5 for 3 min then DI water rinsing.
2)Prebaking for 30 min at 200C
3)Coating of positive photoresist (AZ-300MIF) at 4000 rpm for 15sec.
4)Post baking for 20min at 65C.
5)Soaking in Chlorobenzene for 35min.
6)Exposure
7)Leave it for 18 hours.
8)Developing in 2.38%TMAH developer.
but during the development the central part of the 1/1cm sample developed OK but
the edge part does not...
Can anybody suggest me where is the problem...

Regards
Hare Krishna
M.Tech Student
IIT Kanpur
India.