18-200

Introduction to Nanotechnology & Nanoelectronics

Yi Luo ECE 18-200 Nov 10, 2005

11/10/05 1 Some facts: Nanoscience and nanotechnology are “hot”. It is one of the most-talked about topics among scientific and engineering communities. Government agencies and industry are investing ~ $2 billion per year directly on nanotechnology.

What is “Nanotechnology” ? Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications. Encompassing nanoscale science, engineering and technology, nanotechnology involves imaging, measuring, modeling, fabricating, synthesizing and manipulating matter at this length scale.

Which area is it involved ? Many scientific disciplines, e.g. physics, chemistry, biology, medicine, and materials etc., and almost all engineering fields. It expands over many industrial areas such as electronic, health care, chemical, so on and so forth.

Can you name any nanotechnology or anything made with nanotechnology ?

11/10/05 2 Transistor (2005)

Switching molecule

O O MeS S N SS N SS N N N O O 4 nm O H O O 2 S

O O ~0.2nm O

O O O O O OMeO MeO MeO . . .

nucleus of hydrogen (proton) 1 fm = 10-15 m ~ 0.000001 nm Source: National Nanotechnology Initiative 11/10/05 3 Is “nano” special in nature? Probably not. … kilo-, meter, milli-, micro-, nano-, pico-, femto-, atto-…

Why nanotechnology is getting popular now? 1. now we are able to image, make, and manipulate materials on this scale;

2. there are needs and applications in the real world (justified by the costs).

11/10/05 4 Two major distinct approaches build to nanoscale systems :

1. the more traditional approach: “top-down” – starting from bulk materials to fabricate nanostructures via patterning, etching, and deposition, etc.; more physical flavored. Best represented by CMOS technology.

2. the novel approach: “bottom up” – starting from basic elements to synthesize and assemble more complicated nanostructures; more chemical flavored. Nanocrystal, carbon nanotube, supramolecule, etc.

For the rest of the lecture, we are discuss nanotechnology based on these two approaches.

11/10/05 5 Top-down Approach (best represented by CMOS fabrication)

11/10/05 6 A close look of FET (field effect transistor) Source: Intel

The challenge is to make a billion of them on a chip. 11/10/05 7 There are over 200 processing steps in CMOS IC fabrications.

To name a few: patterning etching metalization implantation deposition cleaning CMP annealing wafer bonding packaging Source: intel . . .

This time we will only talk about how to make small things. 11/10/05 8 Optical Lithography -sub micron technology

UV light radiation

Develop with solvent SUSS MA6 Mask Si wafer Photo-resist

Advantage – very mature, fast, parallel processing.

Limits – relatively large feature sizes, mask can be very expansive. SUSS MA200/300PLUS

11/10/05 9 EUV Lithography EUV system at ALS in LBL -Deep sub-micron technology -10’s to ~100 eV incident light

How it works: The scanning mirror directs focused EUV light from the Kirkpatrick-Baez mirrors into the converted interferometer with the desired degree of spatial coherence and illumination pattern. Installed inside the interferometer tank, the Set-2 optic images the EUV light reflected from the mask-carrying reticle onto a resist-covered silicon wafer.

Advantage –small patterns, can be reasonably fast; Limits – can be very expensive.

11/10/05 10 Electron Beam Lithography

High energy electrons (30-200 KeV) have Quanta 600 FEG (FEI Company) much shorter wavelength (~ pm). Beam size can be sub-nanometer.

Primary beam secondary electrons

e- e- beam exposure ebeam resist Substrate

post-development ebeam resist Substrate JBX-9300FS Electron

11/10/05 Beam Lithography System11 Electron Beam Lithography

4 nm

Muray, Isaacson, and Adesida, Appl. K. Yamazaki and H. Namatsu, Jpn J. Phys. Lett., Vol 45, 589 (1984). Appl Phys,Vol 43, 6B, 3767 (2004).

10-15 nm

Wavelength is not an issue. Beam size can be sub-nanometer.

Done here at CMU ! Advantage – small arbitrary patterns, no mask is needed. Limits – serial process, slow.

11/10/05 12 Nano-Imprint Lithography SB6e - Suss A schematics introduction

2 1 Master/Mold

Master/Mold polymer Si Si

hυ or/and heat 3 4 Master/Mold

Master/Mold

Si Si

11/10/05 13 NPS 300 -Suss 11 2 Pt Cross-bar Memory – 10 bit/cm

1 Kbit

Si

Ordered Nanowires array with extremely high density Heath Group – Caltech

Imprint mold with Holes imprinted Metal dots 10nm diameter pillars in PMMA fabricated by NIL 11/10/05 J M DeSimone Group – UNC/NCSU S.Y. Chou Group - Princeton14 Techniques to make nanoscale patterns from top-down – lithography with:

UV light, ebeam, EUV, X-ray, Imprint, etc.

It is likely that the scaling of CMOS will continue down to 22nm node (~10nm channel length).

11/10/05 15 11/10/05 16 Bottom-up Approach

• SPM – imaging, and building structures atom by atom;

• Synthesis and applications of nanocrytal, nanotube, nanowire, and supramolecule;

• Self-Assembling of nano-components;

• Nanoelectronics with molecules.

11/10/05 17 SPM – Microscopes that can “see” and move atoms

STM Tunneling Current

Fe atom position

A

Quantum Corral AFM Source: IBM Laser beam deflection

Laser position Ge/Si(105) surface (NCAFM image )

11/10/05 Si(111) 7x7 reconstruction surface 18 Source: Omicron Atoms and molecules can be precisely manipulated by STM tips

Low-temperature STM image of -CH3 on Si(111) surface. (Heath, Caltech) C60 , ~ 1nm

“nano-abacus” formed by C60 molecule along single atomic steps on copper surface. (Jim Gimzewski, UCLA)

Development of One-Dimensional Band Structure 11/10/05 in Artificial Gold Chains, W. Ho Group, UC Irvine. 19 Nanocrystal / Nanoparticle

Brus, Columbia

Bawendi Group, MIT

Quantum confinement 11/10/05Optoelectronic applications - size effect 20 Fullerenes

A whole family of Bucky Balls C28, … C60, C70,… C240… C60

Carbon NanoTubes

11/10/05 http://www.photon.t.u-tokyo.ac.jp/~maruyama/agallery/agallery.html 21 Carbon Nanotubes

Carbon Nanotubes H. Dai Group, Stanford Univ.

Carbon Nanotube sensor and transistor C. Dekker Group, Delft Univ of Tech 11/10/05 22 Semiconductor Nanomaterials

Semiconductor Tetrapod Alivisatos Group, Berkeley

Chemical and biochemical sensing

Semiconductor11/10/05 Nanowires, Lieber Group, Harvard Peidong Yang Group, Berkeley 23 Self-Assembled Molecular Monolayer

Atomic Force Microscope Image of SAM on Au

S S S S S S S S S Au

11/10/05 24 DNA Nanotechnology

Specifically designed DNA building blocks

11/10/05 Seeman, NYU 25 DNA-Based Computation and Algorithmic Assembly

-a cool example: Yi = XOR [Yi-1,Xi]

11/10/05 Seeman - NYU & Eric Winfree - Caltech 26 Supramolecules – advanced multifunctional molecules

Molecular Borromean Rings

M. FUJITA Group Molecular Muscles University of Tokyo J. Fraser Stoddart Group, UCLA 11/10/05 27 Bi-stable molecules polymer

O O O O O N N SS

SS O N N O O O O O O O O O MeS S 4+ N N N N C1 SS SS V=0 volt V=+1 volt V=-1 volt SS SS N N N N O N O O O O O O O O O O O N N SS O O O S SS O N N O O O O O O OH O

4+ 4+ 4+ C2 R1 R2 O O O O O OMeO MeO MeO solution

Figure 1 Absorbance

400 500 600 700 800 900 λ / nm

Fraser Stoddart’s Group

11/10/05 CNSI / UCLA 28 Cross-bar Memory – 1011bit/cm2

MS Schematics MS MS MS 1 Kbit

Device Structure

molecule 1.0 All bits OFF Science, December 21, 2001 ) 0.8 A p-type 0.6 (n t

n-type n

e 0.4 rr

u 0.2 C 0.0 0 100 200 300 400 500 600 Bits Si 1.0 0.8 Selective bits ON ) A 0.6 (n t n e

rr 0.4 u C Metal 0.2

0.0 0 100 200 300 400 500 600 Bits

11/10/05 Heath Group – Caltech 29 10 single-molecule transistor 7nm Ag nano-particle

5 Schematic energy diagram

Molecular states

(volt) 0 G V

VS-D Ef

-5

drain source -10 -0.2 -0.1 0.0 0.1 0.2 VS-D (volt)

0.10 VG gate 0.05

0.0 Molecular energy levels

(V) -0.05 can be tuned by gate potential. G V

-0.10

Break-junction with single molecule (gap -0.15 5nm long molecule size can be controlled between ~1 to 10 nm). -20 -10 0 10 20

VSD(mV)

30 nm silicon oxide Au or Pt electrode Gate electrode 11/10/05 (degenerately doped poly-Si) 30 Fabry-Perot measurement for electron wave Single Molecule Transistor

P.L. McEuen Group, Cornell Univ.

HK Park, Harvard Univ.

11/10/05 31 A True Single Molecule Transistor

Opportunities to go much smaller than 10 nm where top-down and bottom-up meet ! <10 nm

H H H H N N N N Pt S N N N S Pt n n H H LUMO source drain

NH source HOMO drain

NH

H N Tunneling Tunneling PO 4 barrier gate barrier TiO2/Ti gate LUMO-lowest Unoccupied Molecular Orbital HOMO-highest Occupied Molecular Orbital • Built-in gate to increase gating efficiency • Tunneling barriers to adjust coupling • Anchoring groups to realize Selective-Self- Attachment

Conductive and Semiconductive acetylene Oligomers phenylene • bandgap ~ 1-3 eV • chemically or electrically doped S S S S thiophene • polymer conductivity ~ 5x102 (S cm-1) 11/10/05 32 Just in the world of electronics

In six decades, device features have been reduced by x 106!

1947, Shockley, Bardeen, & Brattain

1958, Kilby

1971, Intel 4004 Entering the world where molecules and chemistry work the current, Intel Xeon best! (65nm generation, 36nm channel length) Number of transistors on a chip approaching 1 billion vs. 100 billions to (Source: Intel) What’s next? 1 trillion neural networks in an average (< 10nm) human brain. How to get there?

11/10/05 33