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VLSI

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Title: VLSI


1
VLSI TECHNOLOGY
PROJECT BY, A.POOJA SHUKLA
2
INTRODUCTION TOPICS
  • Scaling
  • Moores Law
  • 3D VLSI

3
The beginning

4
Transistor Size Scaling
MOSFET performance improves as size is
decreased shorter switching time, lower power
consumption.
2 orders of magnitude reduction in transistor
size in 30 years.
5
Significant Breakthroughs
Transistor size Intels research labs have
recently shown the worlds smallest transistor,
with a gate length of 15nm. We continue to build
smaller and smaller transistors that are faster
and faster. We've reduced the size from 70
nanometer to 30 nanometer to 20 nanometer, and
now to 15 nanometer gates.
Manufacturing process A new manufacturing
process called 130 nanometer process technology
(a nanometer is a billionth of a meter) allows
Intel today to manufacture chips with circuitry
so small it would take almost 1,000 of these
"wires" placed side-by-side to equal the width of
a human hair. This new 130-nanometer process has
60nm gate-length transistors and six layers of
copper interconnect. This process is producing
microprocessors today with millions of
transistors and running at multi-gigahertz clock
speeds.
Wafer size Wafers, which are round polished
disks made of silicon, provide the base on which
chips are manufactured. Use a bigger wafer and
you can reduce manufacturing costs. Intel has
begun using a 300 millimeter (about 12 inches)
diameter silicon wafer size, up from the previous
wafer size of 200mm (about 8 inches).
6
Major Design Challenges
  • Microscopic issues
  • ultra-high speeds
  • power dissipation and supply rail drop
  • growing importance of interconnect
  • noise, crosstalk
  • reliability, manufacturability
  • clock distribution
  • Macroscopic issues
  • time-to-market
  • design complexity (millions of gates)?
  • high levels of abstractions
  • design for test
  • reuse and IP, portability
  • systems on a chip (SoC)?
  • tool interoperability

7
Integrated Circuits
  • Digital logic is implemented using transistors in
    integrated circuits containing many gates.
  • small-scale integrated circuits (SSI) contain 10
    gates or less
  • medium-scale integrated circuits (MSI) contain
    10-100 gates
  • large-scale integrated circuits (LSI) contain up
    to 104 gates
  • very large-scale integrated circuits (VLSI)
    contain gt104 gates
  • Improvements in manufacturing lead to ever
    smaller transistors allowing more per chip.
  • gt107 gates/chip now possible doubles every 18
    months or so
  • Variety of logic families
  • TTL - transistor-transistor logic
  • CMOS - complementary metal-oxide semiconductor
  • ECL - emitter-coupled logic
  • GaAs - gallium arsenide

8
What are shown on previous diagrams cover only
the so called front-end processing - fabrication
steps that go towards forming the devices and
inter-connections between these devices to
produce the functioning IC's. The end result are
wafers each containing a regular array of the
same IC chip or die. The wafer then has to be
tested and the chips diced up and the good chips
mounted and wire-bonded in different types of IC
package and tested again before being shipped
out.
9
Moores Law
  • Gordon E. Moore - Chairman Emeritus of Intel
    Corporation
  • 1965 - observed trends in industry - of
    transistors on ICs vs. release dates
  • Noticed number of transistors doubling with
    release of each new IC generation
  • release dates (separate generations) were all
    18-24 months apart
  • Moores Law
  • The number of transistors on an integrated
    circuit will double every 18 months
  • The level of integration of silicon technology as
    measured in terms of number of devices per IC
  • This comes about in two ways size reduction of
    the individual devices and increase in the chip
    or dice size
  • As an indication of size reduction, it is
    interesting to note that feature size was
    measured in mils (1/1000 inch, 1 mil 25 mm) up
    to early 1970s, whereas now all features are
    measured in mms (1 mm 10-6 m or 10-4 cm)?
  • Semiconductor industry has followed this
    prediction with surprising accuracy

10
Moores Law
  • In 1965, Gordon Moore predicted that the number
    of transistors that can be integrated on a die
    would double every 18 to 14 months
  • i.e., grow exponentially with time
  • Amazing visionary million transistor/chip
    barrier was crossed in the 1980s.
  • 2300 transistors, 1 MHz clock (Intel 4004) - 1971
  • 42 Million, 2 GHz clock (Intel P4) - 2001
  • 140 Million transistor (HP PA-8500)?

Source Intel web page (www.intel.com)?
11
Moores Law
  • From Intels 4040 (2300 transistors) to Pentium
    II (7,500,000 transistors) and beyond

Relative sizes of ICs in graph
12
Ever since the invention of integrated circuit,
the smallest feature size has been reducing every
year. Currently (2002) the smallest feature size
is about 0.13 micron. At the same time the number
transistors per chip is increasing due to feature
size reduction and increase in chip area. Classic
example is the case of memory chips Gordon Moore
of Intel in early 1970s found that density
(bits per chip) growing at the rate of four times
in 3 to 4 years - often referred to as Moores
Law. In subsequent years, the pace slowed down a
bit, data density has doubled approximately every
18 months current definition of Moores Law.
13
Limits of Moores Law?
  • Growth expected until 30 nm gate length
    (currently 180 nm)?
  • size halved every 18 mos. - reached in
  • 2001 1.5 log2((180/30)2) 2009
  • what then?
  • Paradigm shift needed in fabrication process

14
Technological Background of the Moores Law
  • To accommodate this change, the size of the
    silicon wafers on which the integrated circuits
    are fabricated have also increased by a very
    significant factor from the 2 and 3 in diameter
    wafers to the 8 in (200 mm) and 12 in (300 mm)
    diameter wafers
  • The latest catch phrase in semiconductor
    technology (as well as in other material science)
    is nanotechnology usually referring to GaAs
    devices based on quantum mechanical phenomena
  • These devices have feature size (such as film
    thickness, line width etc) measured in nanometres
    or 10-9 metres

15
Recurring Costs
  • cost of die cost of die test
    cost of packaging
  • variable cost ---------------------------------
    -------------------------------
  • final test yield
  • cost of wafer
  • cost of die -------------------------------
    ----
  • dies per wafer die yield

? (wafer
diameter/2)2 ? wafer diameter dies
per wafer ---------------------------------- ?
---------------------------
die area
? 2 die area
16
Yield Example
  • Example
  • wafer size of 12 inches, die size of 2.5 cm2, 1
    defects/cm2, ? 3 (measure of manufacturing
    process complexity)?
  • 252 dies/wafer (remember, wafers round dies
    square)?
  • die yield of 16
  • 252 x 16 only 40 dies/wafer die yield !
  • Die cost is strong function of die area
  • proportional to the third or fourth power of the
    die area

17
Intel 4004 Microprocessor
18
Intel Pentium (IV) Microprocessor
19
Die Size Growth
Die size grows by 14 to satisfy Moores Law
Courtesy, Intel
20
Clock Frequency
Lead microprocessors frequency doubles every 2
years
10000
2X every 2 years
1000
P6
100
Pentium proc
486
Frequency (Mhz)?
386
10
8085
286
8086
8080
1
8008
4004
0.1
1970
1980
1990
2000
2010
Year
Courtesy, Intel
21
Examples of Cost Metrics (1994)?
22
VLSI
  • Very Large Scale Integration
  • design/manufacturing of extremely small, complex
    circuitry using modified semiconductor material
  • integrated circuit (IC) may contain millions of
    transistors, each a few ?m in size
  • applications wide ranging most electronic logic
    devices

23
Origins of VLSI
  • Much development motivated by WWII need for
    improved electronics, especially for radar
  • 1940 - Russell Ohl (Bell Laboratories) - first pn
    junction
  • 1948 - Shockley, Bardeen, Brattain (Bell
    Laboratories) - first transistor
  • 1956 Nobel Physics Prize
  • Late 1950s - purification of Si advances to
    acceptable levels for use in electronics
  • 1958 - Seymour Cray (Control Data Corporation) -
    first transistorized computer - CDC 1604

24
Origins of VLSI (Cont.)?
  • 1959 - Jack St. Claire Kilby (Texas Instruments)
    - first integrated circuit - 10 components on 9
    mm2
  • 1959 - Robert Norton Noyce (founder, Fairchild
    Semiconductor) - improved integrated circuit
  • 1968 - Noyce, Gordon E. Moore found Intel
  • 1971 - Ted Hoff (Intel) - first microprocessor
    (4004) - 2300 transistors on 9 mm2
  • Since then - continued improvement in technology
    has allowed for increased performance as
    predicted by Moores Law

25
Three Dimensional VLSI
  • The fabrication of a single integrated circuit
    whose functional parts (transistors, etc) extend
    in three dimensions
  • The vertical orientation of several bare
    integrated circuits in a single package

26
Advantages of 3D VLSI
  • Speed - the time required for a signal to travel
    between the functional circuit blocks in a system
    (delay) reduced.
  • Delay depends on resistance/capacitance of
    interconnections
  • resistance proportional to interconnection length

27
Advantages of 3D VLSI
  • Noise - unwanted disturbances on a useful signal
  • reflection noise (varying impedance along
    interconnect)?
  • crosstalk noise (interference between
    interconnects)?
  • electromagnetic interference (EMI) (caused by
    current in pins)?
  • 3D chips
  • fewer, shorter interconnects
  • fewer pins

28
Advantages of 3D VLSI
  • Power consumption
  • power used charging an interconnect capacitance
  • P fCV2
  • power dissipated through resistive material
  • P V2/R
  • capacitance/resistance proportional to length
  • reduced interconnect lengths will reduce power

29
Advantages of 3D VLSI
  • Interconnect capacity (connectivity)?
  • more connections between chips
  • increased functionality, ease of design

30
Advantages of 3D VLSI
  • Printed circuit board size/weight
  • planar size of PCB reduced with negligible IC
    height increase
  • weight reduction due to more circuitry per
    package/smaller PCBs
  • estimated 40-50 times reduction in size/weight

31
3D VLSI - Challenges and Solutions
  • Challenge Thermal management
  • smaller packages
  • increased circuit density
  • increased power density
  • Solutions
  • circuit layout (design stage)?
  • high power sections uniformly distributed
  • advancement in cooling techniques (heat pipes)?

32
Influential Participants - Industry
  • Mitsubishi, TI, Intel, CTS Microelectronics,
    Hitachi, Irvine Sensors, others...
  • high density memories
  • ATT
  • high density multiprocessor
  • Many other applications/participants

33
Three Dimensional VLSI
  • Moores Law approaching physical limit
  • Increased performance expected by market
  • Paradigm shift needed - 3D VLSI
  • many advantages over 2D VLSI
  • economic limitations of fabrication overhaul will
    be overcome by market demand
  • Three Dimensional VLSI may be the savior of
    Moores Law

34
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