TOP-DOWN TECHNIQUES (LITHOGRAPHY)

FOR MAKING QUANTUM WIRES

Lingyun Miao, Limin Ji

ECE Dept.

University of Rochester

Outline

Introduction Background Technology Future Work

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]

Introduction

Why nanotehcnology? Restrict of the current

technology. Wide application area. Fantastic characteristic.

How far has it gone? Beginning of 3rd generation.

Fig. 2. Four generations of nanotechnology. [1]

Outline

Introduction Background Technology Future Work

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.html

Fig. 4. A carbon nanotube between two electrodes from http://www.mb.tn.tudelft.nl

Background

Top-down & Bottom-up

Fig. 5 Two approaches to control matter at the nanoscale. [6]

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]

Outline

Introduction Background Technology Lithography Needs to Beat Its Limit

Future Work

Lithography Needs to Beat Its Limit

Lithography == Photolithography?To describe a lithography imaging system:

Resolution (RES) = k1 λ / NA

Depth of focus (DOF) = k2 λ / (NA)^2

k1 and k2 are process-related factors, normally ≥ 0.6According to Rayleigh criteria, theoretical values of k1 and k2 are equal to 0.5

To increase resolutionUse shorter wavelength

Increase NA

In the past decades’ struggle…Continuous advancement of photolithography

Proposal and development of other techniquesElectron beam lithography, nanoimprint lithography, interferometric lithography, X-ray lithography, extremeultraviolet lithography, scanning probe lithography…

Outline

Introduction Background Technology Engineering Tricks with Photolithography

Future Work

Engineering Tricks with Photolithography

“Dear old” photolithography technique MUST be saved !

V-groove Heterostructure Patterning Double-exposure Patterning Immersion Lithography

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

Double-exposure Patterning

Shift reticle

or 2nd 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

Immersion Lithography

http://www.nikon.co.jp/main/eng/portfolio/about/technology/nikon_technology/immersion_e/index.htmhttp://oemagazine.com/FromtheMagazine/jul04/underwater.html

Immersion Lithography Results65nm line-and-space pattern

ArF laser with a 1.07 NA imaged these 45-nm features

Outline

Introduction Background Technology Electron Beam Lithography (EBL)

Future Work

Electron Beam LithographyUse 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.htmhttp://www.ee.pdx.edu/~jeske/litho/electronbeamlitho.html

Masaya Notomi and Toshiaki Tamamura

Outline

Introduction Background Technology Nanoimprint Lithography (NIL)

Future Work

Nanoimprint Lithography

Thermoplastic Nanoimprint lithography Photo Nanoimprint Lithography

http://www.semiconductoronline.com/Content/ProductShowcase/http://www.nanonex.com/Picture/Resists2.jpg

Outline

Introduction Background Technology Scanning Probe Lithography (SPL)

Future Work

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)

Outline

Introduction Background Technology Summary of Different Lithography Techniques

Future Work

Summary of Different Lithography Techniques

Outline

Introduction Background Technology Future Work

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/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