1. TOP-DOWN TECHNIQUES (LITHOGRAPHY) FOR MAKING QUANTUM WIRES Lingyun Miao, Limin Ji ECE Dept. University of Rochester

2. Outline Introduction Background Technology Future Work

3. Introduction What is Nanotechnology? “A field of applied science and technology covering a broad range of topics.” -from Wikipedia What does it do? Control of matter on a scale smaller than 100nm. Fig. 1 A parallel-shaft speed reducer gear which is one of the largest nanomechanical devices ever modeled in atomic detail. [1]

4. Introduction Why nanotehcnology?  Restrict of the current technology.  Wide application area.  Fantastic characteristic. How far has it gone? Beginning of 3 rd generation. Fig. 2. Four generations of nanotechnology. [1]

5. Outline Introduction Background Technology Future Work

6. Background What is Quantum Wire? “A strip of conducting material about 10nm or less in width and thickness that displays quantum mechanical effects.” - from Science and Technology Dictionary Essential Difference? Not copying quantum info, but transported-destroy at source then recreating at destination. Fig. 3. Illustration of carbon nanotube from www.spacedaily.com/news/nanotech-05zn.htmlwww.spacedaily.com/news/nanotech-05zn.html Fig. 4. A carbon nanotube between two electrodes from http://www.mb.tn.tudelft.nlhttp://www.mb.tn.tudelft.nl

7. Background Top-down & Bottom-up Fig. 5 Two approaches to control matter at the nanoscale. [6]

8. Background Top-down Techniques:  Bulk-/film-machining  Surface-machining  Mold-machining Fig. 6 Bulk-/film-machining [7] Fig. 7 Surface-machining [7] Fig. 8 Mold-machining with soft lithography [7]

9. Outline Introduction Background Technology Lithography Needs to Beat Its Limit Future Work

10. Lithography Needs to Beat Its Limit Lithography == Photolithography ? To describe a lithography imaging system: Resolution (RES) = k 1 λ / NA Depth of focus (DOF) = k 2 λ / (NA)^2 k1 and k2 are process-related factors, normally ≥ 0.6 According to Rayleigh criteria, theoretical values of k 1 and k 2 are equal to 0.5 To increase resolution Use shorter wavelength Increase NA In the past decades’ struggle… Continuous advancement of photolithography Proposal and development of other techniques Electron beam lithography, nanoimprint lithography, interferometric lithography, X-ray lithography, extreme ultraviolet lithography, scanning probe lithography…

11. Outline Introduction Background Technology Engineering Tricks with Photolithography Future Work

12. Engineering Tricks with Photolithography “Dear old” photolithography technique MUST be saved ! V-groove Heterostructure Patterning Double-exposure Patterning Immersion Lithography

13. V-groove Heterostructure Patterning C. Percival et al. IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 47, NO. 9, 2000 E. Kapon et al. Appl. Phys. Lett. 55, 2715 (1989) K. F. Karlsson et al. Appl. Phys. Lett. 90, 101108 2007

14. Double-exposure Patterning Shift reticle or 2 nd reticle develop Use reduced exposure dose (60-80%) Stepper movement must be controlled precisely (nm) -> piezoelectric element http://www.imec.be/wwwinter/ mediacenter/en/SR2005/html/ 142319.html

15. Immersion Lithography http://www.nikon.co.jp/main/eng/portfolio/about/technology/nikon_technology/immersion_e/index.htm http://oemagazine.com/FromtheMagazine/jul04/underwater.html Immersion Lithography Results 65nm line-and-space pattern ArF laser with a 1.07 NA imaged these 45-nm features

16. Outline Introduction Background Technology Electron Beam Lithography (EBL) Future Work

17. Electron Beam Lithography Use high voltage electrons (1 kV – 100 kV) to transfer nano-patterns into resist (ex. PMMA) on the substrate by directly writing. Define pattern on spin coated E-beam resist Resist development RIE etching Cladding deposition http://people.ece.cornell.edu/lipson/nature/fabrication.htm http://www.ee.pdx.edu/~jeske/litho/electronbeamlitho.html Masaya Notomi and Toshiaki Tamamura

18. Outline Introduction Background Technology Nanoimprint Lithography (NIL) Future Work

19. Nanoimprint Lithography Thermoplastic Nanoimprint lithography Photo Nanoimprint Lithography http://www.semiconductoronline.com/Content/ProductShowcase/ http://www.nanonex.com/Picture/Resists2.jpg

20. Outline Introduction Background Technology Scanning Probe Lithography (SPL) Future Work

21. Scanning Probe Lithography mask fabrication and etching to produce quantum wires (a) Starting from a patterned aluminium film (b) “positive” mask (d) “negative” mask (c, e) Reactive ion etching Local oxidation (anodization process) A. Notargiacomo et al., Materials Science and Engineering C 19, 185-188 (2002)

22. Outline Introduction Background Technology Summary of Different Lithography Techniques Future Work

23. Summary of Different Lithography Techniques

24. Outline Introduction Background Technology Future Work

25. Figure 1. Two quantum dots connected by a wire behave somewhat like atoms in a molecule, with different energy levels, a property that might be useful as a switch in a quantum computer. ( Arizona State University) from www.aip.org/tip/INPHFA/vol-9/iss- 1/p14.htmlwww.aip.org/tip/INPHFA/vol-9/iss- 1/p14.html Figure 2. Nano robots From http://www.witn.psu.edu/articles/article.phtml? article_id=41&show_id=7 Figure 3. 1 Organic Light Emitting Diodes (OLEDs) for displays 2 Photovoltaic film that converts light into electricity 3 Scratch-proof coated windows that clean themselves with UV 4 Fabrics coated to resist stains and control temperature 5 Intelligent clothing measures pulse and respiration 6 Bucky-tubeframe is light but very strong 7 Hipjoint made from biocompatible materials 8 Nano-particle paint to prevent corrosion 9 Thermo-chromic glass to regulate light 10 Magnetic layers for compact data memory 11 Carbon nanotube fuel cells to power electronics and vehicles 12 Nano-engineered cochlear implant