1. Jan M. Yarrison-Rice Physics Dept. Miami University/University of Cincinnati Raith 150 User Meeting Stanford University September 29 & 30, 2003 A Novice’s View of E-Beam Lithography 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. Lithographic Requirements 50 to 200 nm feature sizes Inter-feature spacing as small as 50 nm Pattern on ITO glass, silicon, or silicon nitride/dioxide

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

6. E-beam Source

7. Source Properties source typebrightness (A/cm 2 /sr) source sizeenergy spread (eV) vacuum requirement (Torr) tungsten thermionic ~10 5 25 um2-310 -6 LaB 6 ~10 6 10 um2-310 -8 thermal (Schottky) field emitter ~10 8 20 nm0.910 -9 cold field emitter ~10 9 5 nm0.2210 -10

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 systemChallenges.. –Sharp corners –Closely spaced nanoparticles 100 nm square dimers separated by 50 nm

18. Pick-Up Coils Contact Pads (~200  m) 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. PBG Structures 2D arrays of etched pores Particular Structures of Interest include: –De-multiplexer –Polarization Switching –Microcavity for Sensing Oxide cover layer (75nm) Nitride core (250 nm) Oxide buffer (1.8  m  ) Substrate  nm  nm  nm   nm y x

24. PBG Structure Requirements 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

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