Transcript No Slide Title

Nanomagnetic Logic
Wolfgang Porod
Center for Nano Science
and Technology
University of Notre Dame
http://www.nd.edu/~ndnano
Supported by NSF, ONR, and SRC-NRI
1st Berkeley Symposium on Energy Efficient Electronics ● 11 June 2009
SRC-NRI Funded Centers
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“Magnetic components are rather attractive to the
computer designer for several reasons:
•They posses an inherent high reliability
•They require in most applications no power
other than the power to switch their state
•They are potentially able to perform all
required operations, i.e., logic, storage and
amplification “
H. W. Gschwind, Design of Digital Computers © 1967 by Springer-Verlag.
The Elliott 803 computer
The machine was compact (requiring around 400 square feet of floor-space) had
undemanding power requirements (3.5 kilowatts plus at least 10 kilowatts of air conditioning)
and, most importantly, offered hardware floating point arithmetic as an option, so the Elliott
could be used as a low cost scientific machine.
Several aspects of the machine's technology are rather unusual.
Such as, the basic switching technology is built from germanium transistors and a large
number of ferrite core logic elements used, not as memory, but as a logic gate. The most
common configuration is illustrated below.
Quantum-Dot Cellular Automata
A Quantum-Dot Cell
A cell with 4 dots
2 extra electrons
Represent binary
information by
charge configuration
An Array of Cells
Neighboring cells tend to
align due to direct
Coulombic coupling
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QCA Devices
Binary wire-1
1
Majority gate
-1
1
Inverter
-1
1
A
B
C
-1
1
M
A
B
Out
C
Programmable 2-input
AND or OR gate.
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From metal-dot to molecular QCA
Metal tunnel junctions
“dot” = metal island
70 mK
“dot” = redox center
Mixed valence compounds
room temperature+
Metal-dot QCA established proof-of-principle.
but …low T, fabrication variations
Molecular QCA: room temp, synthetic consistency
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First room temperature magnetic
“quantum-dot cellular automata”
The circular dots, each of diameter 110 nm, placed on a pitch of
135 nm. The dots were 10 nm thick and were made from
the common magnetic alloy supermalloy (Ni80Fe14Mo5X1,
where X is other metals) by e-beam lithography and lift-off.
Evolution of a soliton propagating along a chain
of coupled nanomagnets under the action of a
30Oe field applied:
R.P. Cowburn and M.E. Welland SCIENCE,
VOLUME 287, 1466 (2000)
R.P. Cowburn JOURN MAGNETISM MAGNETIC MAT,
VOLUME 242, 505 (2002)
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Coupled Nanomagnets
Magnetostatic energy
M

20nm
kT
100 nm
50nm
300
15nm
150
0
90
Strong Coupling
270

Stable Patterns
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Observe Magnetic Field Coupling
Atomic-Force and
Magnetic-Force
Microscopy
(AFM and MFM)
Gary H. Bernstein, Alexandra Imre, Zhou Ling, George Csaba
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Approx. 36 µm
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Magnetite Biomineralization
Biomineralization in
Magnetotactic Bacteria
Bob Kopp, 2001
Joseph L Kirschvink et al.
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Experimental demonstration of
antiferromagnetic ordering
SEM
AFM
MFM
16 dots long chain contains 30 nm thick permalloy nanomagnets
made by e-beam lithography and lift-off
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Experimental demonstration of
ferromagnetic ordering with input
AFM
MFM
H
16 dots long chain contains 30 nm thick permalloy nanomagnets
made by EBL and lift-off
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Majority gate geometry
A different version off the majority “cross” geometry was proposed by
M.C.B. Parish and M. Forshaw,
APPL. PHYS. LETT. 83, 2046 (2003)
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Demonstration of
majority gate operation
A. Imre et al, SCIENCE, VOL. 311, 205 (2006)
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Proposed Drive Circuitry
1 wire controls 1000s of magnets
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Aggregate Energy
Sources of Energy
Nanomagnet Studies
1. Hysteresis loss in magnets
G. Csaba, J. of
Comp. Elec.,
vol. 4(1/2), pp.
105–11, 2005.
2. Cu wire resistance, parasitics
3. Clock generation circuitry (not shown)
Clock Wire Studies
1010 magnets switch 108 times/s, ~ 0.1 W
Wire Drivers
• Hclock is a function of current density
•Greater J [ > Hclock [ > I [ > P (as a function of I2)
•Niemier, et. al., “Clocking structures and power analysis
for nanomagnet-based logic devices,” ISLPED, pp. 26–
31, 2007.
• Should be most significant energy
We add
25% energy
overhead
per wire to
estimate
consumer in a computation
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Energy Delay Product (EDP)
Estimates
EDP Estimate for 32-bit CMOS Ripple Carry Adder
Magnets with feature sizes
can outperform CMOS
equivalents in EDP
Scaling should
further reduce
MQCA EDP
Can also
investigate
materials to
increase relative
permeability
Pierambaram, “Enhanced Permeability
Device Structures and Methods”, Dec.
17, 2007, US Patent Application US
2007/0284683 A1
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Thanks to …
• Magnetic QCA
–
–
–
–
–
Edit Varga and Tanvir Alam (NDnano) … Fabrication and MFM
Alexandra Imre (ANL) … Fabrication and MFM
George Csaba and Paolo Lugli (TUM) … Theory and Modeling
Gary Bernstein and Alexei Orlov (NDnano) … Fabrication and Testing
Michael Niemier and Sharon Hu (NDnano) … Architectures
• Sponsors
– Office of Naval Research
– National Science Foundation
– Semiconductor Research Corporation
Center for Nano Science and Technology