E-beam Process for ZEP – 520 to be used for Metal Liftoff and RIE.

Revision 2.2, March 12, 2002

James W. Conway - Stanford Nanofabrication Facility - Stanford University

ZEP-520 is very high resolution positive tone resist, that like PMMA is simple to use and gives reproducible results. Compared to PMMA, it has an advantage of being 3 times faster and has good dry etch resistance. It has the disadvantages of poor adhesion (requires HMDS prime layer) and normal exposure doses result in re-entrant pattern profiles. This inherent undercut is useful for metal liftoff deposition.

1. HMDS prime

2. Spin 3000 rpm for 30 seconds Thickness = ~.24 µm

3. Post Application Bake: Oven - 1 hr at 150°C OR hotplate - 2 minutes at 200°C

4. Exposure:
   Hitachi H-700 Dose:  70 - 200 µC at 30 KV  170 uC/cm² optimized Lines.
   Raith Dose: 40 uC /cm² @ 10 kV for Areas, 80 – 120 for Single Pixel Lines.

5. Develop in Xylenes 40 second with very gentle agitation

6. STOP1: Rinse in 1:3 MIBK:IPA mixture for 30 seconds (optional)

7. STOP2: Rinse in IPA for 30 seconds

8. Dry: N2 Blow dry.

9. Oxygen Plasma Descum: 30W. -- 15 Seconds  -- 0.200 mT O2 pressure.
   
   
10. Post Process:  Deposit Metal or RIE etching suitable to process result desired.

11. Metal Liftoff:

1.      5-20 min ACETONE SOAK

2.      3 - 5 MIN. ACETONE FLUSH WITH SQUEEZE BOTTLE.

3.      3 MIN ACETONE SOAK W/ ULTRASONIC.

4.      3 MIN. IPA W/ ULTRASONIC.

5.      Final Strip: NMP or PRS-1000, at 80 degrees C. or O2 ash.

12. Optical Microscope Inspection: 50 and 500 or 1000 X Magnification.
      SEM Inspection:  CD Measurements and dose determination.

E-beam Technology Group - Stanford Nanofabrication Facility - Stanford University