Jing Kong Process No. 1:  Bi-layer PMMA Ebeam Resist for Liftoff.
Revision 1.4 Dated March 1, 2003.
James W. Conway

This Bi-layer resist recipe utilizes both 950K PMMA and 495K PMMA. This recipe was intended for metal liftoff and pattern has an undercut to aid in release.

1.      Singe Bake 150°C for 30 minutes.

2.      Layer 1:  Spin 5% 495K PMMA in chlorobenzene   6000rpm, 40 sec.

3.      Bake on hotplate 180C, 30 minutes.

4.      Layer 2:  Spin 2% 950K PMMA in chlorobenzene   5000rpm 40 sec.

5.      Bake on hotplate, 180C, 30 minutes.

6.      Expose:  Dose: 650 - 800 uC/cm² @ 30 KV dependent on feature size on H-700.

7.      Develop: MIBK:IPA=1:3 (volume) for 2 min
Develop time can vary from 30 sec to 2 min.  Temperature 20 – 21 C.

8.      Microscope Inspection:  Is pattern developed out and pattern cleared?

9.      Post Process:  Deposit Metal for liftoff, thickness as desired.