TOPDOWN TECHNIQUES LITHOGRAPHY FOR MAKING QUANTUM WIRES Lingyun

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

Outline Introduction n Background n Technology n Future Work n

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

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

Outline Introduction n Background n Technology n Future Work n

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

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

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

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

Lithography Needs to Beat Its Limit To describe a lithography imaging system: ? Lithography == Photolithography Resolution (RES) = k 1 λ / NA Depth of focus (DOF) = k 2 λ / (NA)^2 k 1 and k 2 are process-related factors, normally ≥ 0. 6 According to Rayleigh criteria, theoretical values of k 1 and k 2 are equal to 0. 5 Use shorter wavelength To increase resolution Increase NA Continuous advancement of photolithography In the past decades’ struggle… Proposal and development of other techniques Electron beam lithography, nanoimprint lithography, interferometric lithography, X-ray lithography, extreme ultraviolet lithography, scanning probe lithography…

Outline Introduction n Background n Technology n n Engineering Tricks with Photolithography n Future Work

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

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

Double-exposure Patterning Shift reticle develop http: //www. imec. be/wwwinter/ mediacenter/en/SR 2005/html/ 142319. html or 2 nd reticle • Use reduced exposure dose (60 -80%) • Stepper movement must be controlled precisely (nm) -> piezoelectric element

Immersion Lithography Results 65 nm line-and-space pattern Ar. F laser with a 1. 07 NA imaged these 45 -nm features http: //www. nikon. co. jp/main/eng/portfolio/about/technology/nikon_technology/immersion_e/index. htm http: //oemagazine. com/Fromthe. Magazine/jul 04/underwater. html

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

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

Outline Introduction n Background n Technology n n Nanoimprint Lithography (NIL) n Future Work

Nanoimprint Lithography Thermoplastic Nanoimprint lithography Photo Nanoimprint Lithography http: //www. semiconductoronline. com/Content/Product. Showcase/ http: //www. nanonex. com/Picture/Resists 2. jpg

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

Scanning Probe Lithography Local oxidation (anodization process) 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 A. Notargiacomo et al. , Materials Science and Engineering C 19, 185 -188 (2002)

Outline Introduction n Background n Technology n n Summary of Different Lithography Techniques n Future Work

Summary of Different Lithography Techniques

Outline Introduction n Background n Technology n Future Work n

Future Work 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/p 14. 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