Jan M. Yarrison-Rice Physics Dept. Miami University/University of Cincinnati

1. A Novice’s View of E-Beam Lithography Jan M. Yarrison-RicePhysics Dept.Miami University/University of Cincinnati Raith 150 User Meeting Stanford University September 29 & 30, 2003 w/ Sebastian Mackowski & Scott Masturzo -- UC

2. Brief History of Raith 150 at University Of Cincinnati • NSF MRI Grant funded August 2002 • Instrument installed July 2003 • Initial training sessions July 7-11 • Small groups (2-3) begin design & exposure July to present 2 micron squares exposed on silicon w/ 100 nm PMMA

3. Research Interests • Surface Enhanced Microscopies, e.g. SERS • Pickup Coils for Magnetic Field Sensing • Electrochemical Sensing • Photonic Bandgap (PBG) Structures Exposure Schedule for Dimers

4. 50 to 200 nm feature sizes Inter-feature spacing as small as 50 nm Pattern on ITO glass, silicon, or silicon nitride/dioxide Lithographic Requirements

5. Prepared Silicon Wafer Exposed Resist a) b) PMMA Silicon Dioxide Silicon Developed Resist Etched Silicon Dioxide c) d) Evaporated Metal Completed Co-planar Electrodes e) f) Exposure and Processing

6. E-beam Source

7. Source Properties

8. Block Diagram of E-beam

9. E-Beam Column

10. Charging on Sample

11. Exposure Matrices

12. Proximity Effect

13. Evidence of Proximity

14. Methods around Proximity

15. Other Methods

16. Surface Enhanced Spectroscopy

17. Surface Enhanced Microscopies • Dimers – sharp edged doublets • Ag or Au - on glass for optical access • Size determined by plasmon frequency of nonlinear system Challenges.. • Sharp corners • Closely spaced nanoparticles 100 nm square dimers separated by 50 nm

18. Pick-Up Coils • Contact Pads (~200 mm) • Coil lines (300 - 400 nm) • Challenges: • Sharp corners • Proximity effect of multiple lines • Overlap of write-fields Pick-up coil from a Distance

19. Pick-Up Coil – Close Up

20. Electro-Chemical Sensors • Interdigitated Arrays • Long 100 to 500 nm thick fingers w/ ~50 nm separation • Large contact Pads separated by mm • Au or Ag on glass Top: 500 nm digits, Bottom: 200 nm digits

21. Interdigitated Array #1 • 200 nm digits • Separation 200 nm • 495 PMMA A12 on Silicon ~100 nm thick Challenges - • Strong proximity effect • Write field overlap • Very different sized structures combined

22. Interdigitated Array #2 • 150 nm digits • Separated by 400 nm • ITO on Glass • 495 PMMA A12 to 100 nm thick

23. Oxide cover layer (75nm) 260 nm 450 nm Nitride core (250 nm) 225 nm Oxide buffer (1.8 mm) x 260 nm Substrate y PBG Structures • 2D arrays of etched pores • Particular Structures of Interest include: • De-multiplexer • Polarization Switching • Microcavity for Sensing

24. 2D Triangular arrays of 150 nm etched holes Pitch ~ 250 nm Silicon nitride/silicon dioxide planar waveguide substrate Challenges - Large field patterning – write field overlap & registration Two-step etching process PBG Structure Requirements

25. Lithography Challenge • Best practices to make small, closely spaced features • Design of structure • Dosage choices • Aperture choice • Resist • What we have tried to date • Dosage schedules within feature for proximity • Lines around area features to sharpen edges • Dots and their use to sharpen corners

26. EVERYTHING else!! - from making contacts, to metallic coatings, to liftoff All advice is welcome! Other Challenges..