You can try image reversale using AZ5214 photoresist go give
the desired undercut profile for liftoff, or use one of the
LOR-series of resist from Microchem under the 1813S resist.
Basically, you need an undercut profile so that the metal to
remain is not connected (by metal) to the metal to be removed.
>On 7/8/05, ahajjiah  wrote:
>>
>> I am currently working on depositing (300A)Ti/1000A(Al)
metals on GaN. I am
>> using S1813 as my photoresist. i am spinning the
photoresist at 3000rpm for
>> 30s. My deposition rate on the e-beam is 7-10 A/s for both
metals.The vacuum
>> pressure inside the chamber of the e-beam is 9e-7 before
doing my deposition.
>> i use Acetone for the lift-off process. For some reason
when i stick the
>> sample in acetone without ultrasonic agitation, the lift-
off process does not
>> happen, basically the sample just sets there and nothing
happens. On the other
>> hand, when i use the ultrasonic agitation, all the metals
on my sample will
>> lift-off and the lift-off process fails!! it seems that
the metals are not
>> sticking very well to the sample for some reason??
>>
>> Keep in mind that i cleaned the GaN sample with (HCL:HNO3
3:1) for 15 min then
>> used Acetone and methanol and finally DI water and blow
dry with N before
>> doing lithography. I believe this is enough to clean the
sample.
>>
>> Any suggestions on how to deal with this problem???