Miniaturizing Computers: Evolution of Processors Matt Cohen Chris Rousset

Report
Miniaturizing Computers:
Evolution of Processors
Past
Matt Cohen
Chris Rousset
Abdallah Rahman
Present
The Processor
A central processing unit (CPU), or sometimes simply
processor, is the component in a digital computer that
interprets computer program instructions and processes
data. CPUs provide the fundamental digital computer
trait of programmability, and are one of the necessary
components found in computers of any era, along with
primary storage and input/output facilities. Beginning in
the mid-1970s, microprocessors of ever-increasing
complexity and power gradually supplanted other
designs, and today the term "CPU" is usually applied to
s o m e t y p e o f m i c r o p r o c e s s o r.
The 65nm Processor
The technology of today
Benefits of the 90-65nm cross-over
Increase in multimedia performance (video, audio, data
streaming)
Two new layers of hardware based security (protection
against hackers and viruses)
Advanced manageability for IT (remote problem
resolution)
Acceleration technology that improves the speed for
network traffic (faster download and communication)
The 65nm Processor
The 65nm technology
35nm gate length
1.2nm gate oxide
NiSi for low resistance
2nd generation strained Silicon
for enhanced performance
These features prevent transistor leakage and
reduce power consumption
The 45nm Processor
Benefits of the 65-45nm cross-over
Twice improvement in transistor density
Five times reduction in source-drain leakage power
20% improvement in transistor switching speed
30% reduction in transistor switching power
Ten times reduction in transistor gate oxide leakage for
lower power requirements and increased battery life
More performance for exponentially less cost
The 45nm Processor
The production
Intel is on track for 45nm production in the second half of
2007
AMD and IBM expect the first 45nm products using
immersion lithography and ultra-low-K interconnect
dielectrics to be available in mid-2008
The Future
Intel plans to use extreme ultra-violet lithography to print
elements as small as 32 nm and beyond (expectations
2009)
AMD and IBM will cooperate to devise techniques for
manufacturing chips using the 32-nanometer and 22nanometer processes (expectations 2009 and 2011)
Other options include replacing the use of Silicon by
other materials such as Germanium
Another development relates to the use of Graphene
The Use of Germanium
Why replacing Silicon?
For the past four decades the silicon industry has delivered a
continuously improving performance at ever-reduced cost
Those breakthroughs were achieved by physical scaling of the
silicon device
Physical limitations such as off-state leakage current and power
density pose a potential threat to the performance enhancement that
can obtained by geometrical scaling
Strain engineering has quickly emerged as a new scaling vector for
performance enhancement to extend the life of silicon
But what will happen next?
The Use of Germanium
Why using Germanium?
As seen in class mobility is one of the most important characteristics
for electronic applications
According to the International Technology Roadmap for
Semiconductors, even with strain engineering, metal gates and
high-k dielectrics, semiconductors with higher mobility will be
needed to continue scaling beyond the 22nm technology node
III/IV compounds such as InSb, InAs or InGaAs have high electron
mobility but same hole mobility as Si which is an issue for p-MOS
devices
Germanium is one solution
The Use of Germanium
Properties
Si
Ge
GaAs
5.02 x
1022
4.42 x
1022
4.42 x
1022
Effective mass electrons (m/m0)
0.26
0.082
0.067
Effective mass holes (m/m0)
0.69
0.28
0.57
Electron affinity (V)
4.05
4.0
4.07
Energy gap (eV)
1.12
0.67
1.42
Mobility electrons (cm2/V s)
1500
3900
8500
Mobility holes (cm2/V s)
450
1900
450
Atoms/cm3
The Use of Germanium
Problems with the use of Ge
Germanium use will allow research and development to reach the
22nm node however:
The low bandgap (0.67eV) and low melting point (937C) poses
challenges for device design and process integration
Ge wafers offer poor mechanical strength and are much more
expensive than Si wafers
For n-MOS devices the presence of specific surface defects directly
degrade the channel mobility and limit the current drive
The Use of Graphene
Carbon nanotubes



Metallic nanotubes display quantized ballistic
conduction at room temperature
conductance can be controlled by applying an
electrostatic gate
Have already been used to make simple transistors
and logic gates
Low-dimensional graphite structures


Have almost identical properties of carbon nanotubes
EX: Graphene Ribbon
Nanotubes
Nanotubes – many limitations
- limited consistency in size and electric properties
- Difficulty integrating nanotubes into electronics efficiently
- High electrical resistance at junctions between nanotubes and the
wires connecting them.
The solution – Using Graphene layers or ribbons
- Exact same properties as Carbon nanotubes with out
the limitations.
Graphene layers
Advantages –



The graphene layers are only 10 atoms thick
(Miniaturization)
High efficiencies and low power consumption
Devices made from graphene layers can be made
using standard micro-electric processing techniques
(Mass production of graphene devices)
Such standard lithographic methods
The Progress of Graphene
Transistors
Many universities have created transistors
from graphene, approximately 80nm
The goal is to make these transistors 10nm
where the devices will display ballistic
transport.
Single-electron logic: A single-electron transistor carved
entirely in a graphene sheet. The central element is a socalled quantum dot, which allows electrons to flow one by one.
The dot is connected to wider regions that have contact pads
used to turn the transistor on and off.
Credit: University of Manchester
Problems with Graphene
Early Graphene resistors leaked current

Working on single electron transistor using quantum
dots to solve this problem.
Quantum dots at room temperature are not
stable enough.
No fabrication techniques available to produce
the 3nm quantum dots needed for the single
electron transistor.
This requires the manufacturer to once again
rely on luck to produce the right sized quantum
dot. This brings us back to square one as it is a
similar problem with nanotubes.
Quantum Computers
The future
Qubits – can similtaniously be 1 and 0 at the same time, compared to bits which can only
be 1 or 0.
Quantum computer processes information using atoms and other tiny
particles (Qubits), rather than transistors
-EX: electron (Spin up down), Photon (Polarization of light horizontal, vertical)
Entanglement- quantum mechanical phenomenon where the quantum states of two or
more objects or qubits have to be described with reference to each other.
- For example, two photons can be entangled such that if one is horizontally polarized,
the other is always vertically polarized
-key to quantum computers
-this is what gives the quantum computer its advantage along with being simultaneously
on and off.
In principle a quantum computer will be able to outperform a classical computer in certain
tasks
Problems of the Quantum
Computer
Controlling the interaction between many
qubits
"The issue isn't how many qubits, it's how
many well-controlled qubits," Steane says
Detecting what stat the qubits are in
Sources
http://www.nature.com
http://physicsweb.org/articles/news/8/6/18
http://gtresearchnews.gatech.edu/newsrelease/graphene.htm
http://www.technologyreview.com/Infotech/18264/page1/
http://www.physics.gatech.edu/npeg/npeg.html
http://en.wikipedia.org/wiki/Moore's_law
http://www.eetimes.com/news/semi/showArticle.jhtml?articleID=1
96901271
http://www.amd.com/usen/Processors/ProductInformation/0,,30_118_9485_13041%5E1
4633,00.html
http://www.intel.com/technology/silicon/65nm-cross-over.htm

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