Transcript VLSI: A Look in the Past, Present and Future

VLSI: A Look in the Past, Present and
Future
• Basic building block is the
transistor.
– Bipolar Junction Transistor
(BJT), reliable, less noisy and
more power efficient. Early
integrated circuits used BJTs.
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– Quiescent power dissipated by
the BJT is high, limiting the
number of devices that can be
integrated to make a system.
• Is there an alternative?
– Metal Oxide Semiconductor
Field Effect Transistor
(MOSFET) dates as far back as
1925.
– MOSFETs come in two flavors
nMOS (uses n-type dopants)
and pMOS (use p-type
dopants)
The Integrated Circuit Building Block
• nMOS and pMOS devices used
to construct a circuit form what
has come to be known as the
Complementary Metal Oxide
Semiconductor (CMOS).
• Modelled as switches with ON
and OFF positions allow
circuits to ideally dissipate no
power when OFF and dissipate
very little power when in
operation.
• First microprocessor to be
designed (4004 by Intel) used
strictly nMOS technology.
• Before the first microprocessor
was designed, Gordon Moore
stated that: “The complexity for
minimum component costs has
increased at a rate of roughly a
factor of two per year. Certainly
over the short term, this rate can
be expected to continue if not to
increase. Over longer term, the
rate of increase is a bit more
uncertain, although there is no
reason to believe it will not
remain nearly constant for at
least 10 years.” -1965.
VLSI Today
• Moore’s Law dictates that
device count for
microprocessors will double
every 18 months. This has been
the case for 4 decades since this
prediction was made.
• Present day microprocessors
exceed 1-billion transistors.
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Monticelo (1.72-billion)
Pentium 4 (125 million)
Cell (234 million) -IBM
Ultra SPARC IV (295 million)
• CPU speeds are at 4-5 GHz.
• Most of today’s VLSI based
systems use CMOS technology.
• Power dissipation is becoming a
major problem in these systems.
• With further scaling we are fast
approaching the physical limits
of silicon.
• It is projected that by 2018 we
will reach the atomic limit of
Silicon.
VLSI, ULSI or Tera Scale? The
FUTURE
• Are there any alternatives to
silicon based electronics?
• The so called emerging
technologies.
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Carbon nanotubes
Molecular devices
Single electron technology
Quantum dots etc.
• Basically the future is yours to
invent.
• CMOS remains the defacto for
electronics design as a result we
will study CMOS technology.
• Our main objectives:
– Understand the MOS device
operation
– Build MOS circuits (the
inverter)
– Build MOS gates (XOR, AND
etc)
– Build MOS sub-system
(Adder, Memory, Decoder)
– Study low power and highperformance issues.
VLSI DESIGN
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