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BAYINDIR RESEARCH GROUP
JOURNAL CLUB
Nanotech 2011, Boston
PRESENTER(S): OSAMA TOBAIL
ARTICLES:
Carbon Nanotube Computer (Nature Sep. 2013)
Sub 10-nm Carbon Nanotube Transistor (ACS Nano Jan 2012)
http://bg.bilkent.edu.tr/jc/jc.html10/7/2013
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
TITLE
210/7/2013
The miniaturization of electronic devices has been the principal driving force behind the semiconductor industry,and has brought about major improvements in computational power and energy efficiency. Although advanceswith silicon-based electronics continue to be made, alternative technologies are being explored. Digital circuitsbased on transistors fabricated from carbon nanotubes (CNTs) have the potential to outperform silicon byimproving the energy–delay product, a metric of energy efficiency, by more than an order of magnitude. Hence,CNTs are an exciting complement to existing semiconductor technologies1, 2. Owing to substantial fundamentalimperfections inherent in CNTs, however, only very basic circuit blocks have been demonstrated. Here we showhow these imperfections can be overcome, and demonstrate the first computer built entirely using CNT-basedtransistors. The CNT computer runs an operating system that is capable of multitasking: as a demonstration, weperform counting and integer-sorting simultaneously. In addition, we implement 20 different instructions from thecommercial MIPS instruction set to demonstrate the generality of our CNT computer. This experimentaldemonstration is the most complex carbon-based electronic system yet realized. It is a considerable advancebecause CNTs are prominent among a variety of emerging technologies that are being considered for the nextgeneration of highly energy-efficient electronic systems3, 4.
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
First computer made of carbon nanotubes is unveiled
310/7/2013
First computer made of carbon nanotubes is unveiledBy James Morgan Science reporter, BBC News, 25 September 2013
Cedric
Max Shulaker with Cedric, the first carbon computer: "There is no limit to the tasks it can perform".
Max
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Cedric, Is it the start of Si age end?
410/7/2013
Cedric's vital statistics• 1 bit processor• Speed: 1 kHz• 178 transistors• 10-200 nanotubes per transistor• 2 billion carbon atoms• Turing* complete• Multitasking
How small is a carbon computer chip?• 100 microns - width of human hair • 10 microns - water droplet• 8 microns - transistors in Cedric• 625 nanometres (nm) - wavelength of red light• 20-450 nm - single viruses• 22 nm latest silicon chips• 9 nm - smallest carbon nanotube chip• 6 nm - cell membrane• 1 nm - single carbon nanotube
The transistors in Cedric are built with "imperfection-immune" designCedric can only count to 32, but in principle it could count to 32 billion
*After Alan Turing: general purpose computer is called Turing equivalent or Turing complete.
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Background
510/7/2013
MIPS (Microprocessor without Interlocked Pipeline) Architecture, From Wikipedia
How Microprocessor execute programs?
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
TITLE
610/7/2013
The miniaturization of electronic devices has been the principal driving force behind the semiconductor industry,and has brought about major improvements in computational power and energy efficiency. Although advanceswith silicon-based electronics continue to be made, alternative technologies are being explored. Digital circuitsbased on transistors fabricated from carbon nanotubes (CNTs) have the potential to outperform silicon byimproving the energy–delay product, a metric of energy efficiency, by more than an order of magnitude. Hence,CNTs are an exciting complement to existing semiconductor technologies1, 2. Owing to substantial fundamentalimperfections inherent in CNTs, however, only very basic circuit blocks have been demonstrated. Here we showhow these imperfections can be overcome, and demonstrate the first computer built entirely using CNT-basedtransistors. The CNT computer runs an operating system that is capable of multitasking: as a demonstration, weperform counting and integer-sorting simultaneously. In addition, we implement 20 different instructions from thecommercial MIPS instruction set to demonstrate the generality of our CNT computer. This experimentaldemonstration is the most complex carbon-based electronic system yet realized. It is a considerable advancebecause CNTs are prominent among a variety of emerging technologies that are being considered for the nextgeneration of highly energy-efficient electronic systems3, 4.
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
SUBNEG and program implementation
710/7/2013
MM Shulaker et al. Nature 501, 526-530 (2013) doi:10.1038/nature12502
SUBNEG = Subtract and Branch If Negative
Example of non-pre-emptive multitasking
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Schematic of CNT computer
810/7/2013
MM Shulaker et al. Nature 501, 526-530 (2013) doi:10.1038/nature12502
Timing diagram of the CNT computer:The lines show the waveforms corresponding to each signal; of particular note are the transitions of the lower five signals with respect to the clock signals.
Schematic of the entire CNT computer:composed of the four subunits: 1. instruction fetch, 2. data fetch, 3. arithmetic operation4. write-back.
All components apart from the memory are implemented entirely using CNFETs.
Logic gates and latches are built fromTransistors (CNFETs)
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Characterization of CNFET subcomponents
910/7/2013
MM Shulaker et al. Nature 501, 526-530 (2013) doi:10.1038/nature12502
The CNFET computer is composed of 178 CNFETs, with each CNFET comprising ,10–200 CNTsAll p-type-transistors logic circuits
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
CNT computer results
1010/7/2013
MM Shulaker et al. Nature 501, 526-530 (2013) doi:10.1038/nature12502
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Extended Data Figure 1: Fabrication flow for the CNT computer
1110/7/2013
I. prepare the final substrate for circuit fabrication
II. transfer the CNTs from the quartz wafer (where highly aligned CNTs are grown) to the final SiO2 substrate
III. continue final device fabrication on the final substrate
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Extended Data Figure 2: Multibit arithmetic unit
1210/7/2013
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Extended Data Figure 2: Multibit arithmetic unit
1310/7/2013
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Extended Data Figure 3: Internal versus external connections of CNT computer
1410/7/2013
a, Schematic of the CNT computer, showing that all connections are fabricated on-chip and that only signals reading or writing to or from an external memory are connected off-chip. b, SEM of the CNT computer, showing which connections are made to and from the CNT computer from the probe pads. The SEM is colour-coded to match the coloured wires in a.
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Extended Data Figure 4: PMOS-only logic schematics
1510/7/2013
a, Schematic of PMOS-only inverter. b, Schematic of PMOS-only NAND gate.
A B O/P0 0 10 1 11 0 11 1 0
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
VLSI-compatible Metallic CNT Removal (VMR)
1610/7/2013
N. Patil et.al. IEEE Transaction on Nanotechnology (2011)
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Title
1710/7/2013
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Motivation
1810/7/2013
Within the next decade, computing technology will require transistors with channel length below 10 nm
ROBERT F. SERVICE, 20 FEBRUARY 2009 VOL 323 SCIENCE
New material needed for sub 10nm devices
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Single Wall Carbon Nanotubes provide a solution
1910/7/2013
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Device Fabrication
2010/7/2013
Figure S1. (a) SEM image of aligned CNTs after transfer onto substrate with local bottom gates. CNTs are ~50 µm long, extending from one catalyst stripe (bright, vertical line) to another. (b) AFM image of nanotube used for diameter extraction. Average diameter was obtained from several AFM images. (c) SEM image of a set of devices on a single CNT showing how the staggered source/drain contacts enable a variety of channel lengths, including sub-10 nm. (d) Cross-sectional TEM image showing the sidewall structure of the contacts and a sub-10 nm channel.
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Device characterization
2110/7/2013
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Device characterization - evaluation
2210/7/2013
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
Device characterization - evaluation
2310/7/2013
BAYINDIR RESEARCH GROUP | bg.bilkent.edu.tr
What can we do?
2410/7/2013
Device modelling based on experimental results
Tube separation, alignment for better quality devices
SiNW devicesgr
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