1.introduction vlsi

7/28/2019 1.Introduction VLSI

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VLSI Technology

by

SANKHA CHAKRAPAREEK


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Introduction (Lecture 1)

History of VLSI

MOS Transistor - Introduction

Transistor scaling and Moores law - BKD

VLSI Technology

MOS Technology (Lecture 2 & 3) MOS Transistor Characteristics and Short Channel Effects

Fabrication of CMOS structure

VLSI Design (Lecture 4 & 5)

Complexities involved and key design issues

VLSI Design flow (analog, digital, RF, CPLD, FPGA)

Role of design engineer in IC industry

Manufacturing trends & ITRS Roadmap


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Introduction to VLSI

(Lecture 1)

Sources:

International TechnologyRoadmap For Semiconductors -http://public.itrs.net/

INTEL-

http://www.intel.com/technology/silicon/index.htm


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High

Low

FailureR

ate

Cost

1 mm

1-5 nm High

Low

Minimum

FeatureSize

Complex

ity

1930-

1950s

1960s

1970-90

VACUUM TUBES

SEMICONDUCTOR BASEDTRANSISTORS

PLANAR TRANSISTORS

ICs LSI, VLSI

SMART STRUCTURES (MEMS)1995-

NANO STRUCTURES

2010-


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First Computer

The BabbageDifference Engine

(1832)

25,000 parts

cost: 17,470


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ENIAC - The First Electronic Computer

(1946)


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First TransistorPoint Contact Germanium Transistor

Shockley, Brattain & Bardeen - Bell Labs, 1948

Nobel Prize - 1956


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Planar Process

p-n Junction Formation

p-Si

oxidise Lithography Etch P-Diffuse

n-SiMask

Light

n+

p-Si

ox

p+

p n+

n n

n+

b e c

Bipolar transistor


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First Integrated Circuits

First IC Jack Kilby, 1958, Texas

Instruments, Nobel Prize 2000


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Early Integrated Circuits

Bipolar logic

1960s

ECL 3-input Gate

Motorola 1966


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Intel 4004 Micro-Processor

1971

1000 transistors

1 MHz operation


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IC Processor

INTEL Pentium IV IBM Corp. Power PC


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INTEL Montecito 90nm1.72 billion transistors

INTEL Prescot 90nm125 million transistors

IC Processor


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0.57 m2 cell size

>0.5 billion transistors

110 mm2 chip size

Fully functional 70 Mbit

SRAM chips have been

fabricated.

IC SRAM Chip


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Transistor Shockley, Brattain &Bardeen (Bell

Labs) in 1948 NL 1956

Bipolar transistor Schockley in 1949First bipolar digital logic gate Harris in 1956

First monolithic IC Jack Kilby in 1958 NL 2000

First commercial IC logic gates Fairchild 1960

TTL1962 into the 1990s

ECL1974 into the 1980s

Evolution of

Integrated Circuits


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Transistor Bardeen et al.(Bell Labs) in 1947

MOSFET transistor - Lilienfeld (Canada) in 1925

and Heil (England) in 1935

CMOS1960s, but plagued with manufacturingproblems

PMOS in 1960s (calculators)

NMOS in 1970s (4004, 8080) for speed

CMOS in 1980s preferred MOSFET technology

because of power benefits

BiCMOS, Gallium-Arsenide, Silicon-Germanium

SOI, Copper-Low K,

Evolution of Integrated

Circuits


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Integrated Circuits

SSI Small Scale Integrated CircuitsLess than 10 gates e.g., 7404 inverter

MSI Medium Scale Integrated Circuits

Less than 1000 gates e.g., 74161 counter

LSI Large Scale Integrated CircuitsLess than 10,000 gates e.g., 8bit -

processor

VLSI Very Large Scale Integrated Circuitsmore than 10,000 gates e.g., 64bit -

processor


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MOS Structure

metal orn+- polysilicon

p-silicon

+

+

+

+

+

+

+

+

+

oxide

Gate charge

Depletion layer charge

or Bulk charge

In a metal-oxide-silicon structure, a depletion layer

forms below the metal gate. For p-type silicon

substrate, a positive charge develops on metal side

and depletion layer is negatively charged.


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MOS Structure

M O p-Si

++++

Accumulation,VGB VT

++++

+

+++

++++

Depletion0 < VGB < VT


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MOS Transistor

p- Si

n+ poly-Si

n+ n+

depletion

region

VG

VD

Wdep n-channel

Gate

Drain

Source

VS

L channel length

oxide


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NMOS transistor (NMOSFET) behaves as a resistor when VDS is low: Drain current I

Dincreases linearly with V

DS

Resistance RDS

between SOURCE & DRAIN depends on VGS

RDS

is lowered as VGS

increases above VT

NMOS Transistor


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VDS= VGSVT Inversion-layer is pinched-offat the drain end

VGS

> VT

: Pinch-off

Electrons are swept into the drain by the E-field when theyenter the pinch-off region and saturation occurs.

NMOS Transistor


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MOS Transistor

Cut-off :

Linear region :

Saturation :

Back gate effect :

DST

DS

GSoxnD V)V2

V

V(CL

W

I

0ID

2

TGSoxnD )VV(CL2

WI

)2V2()0V(V)V(V pBSpBSGS

TBS

GS

T

0

1

2

3

4

5

6

0 0.5 1 1.5 2 2.5

VDS (V)

X 10-4

VGS = 1.0V

VGS = 1.5V

VGS = 2.0V

VGS = 2.5V

Linear Saturation

VDS = VGS - VT

cut-

off


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Without a gate voltage applied, no current can flow

between the source and drain regions.

Above a certain gate-to-source voltage (thresholdvol tageVT), a conducting layer of mobile electrons isformed at the Si surface beneath the oxide. These

electrons can carry current between the source and drain.

G

NMOS Transistor

n

p

oxide insulatorgate

n

D

S


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MOSFET as a Resistive Switch

For digital circuit applications, the MOSFET is eitherOFF (VGS< VT) or ON (VGS= VDD). Thus, we only need

to consider two IDvs. VDScurves:

1. the curve forVGS< VT

2. the curve forVGS= VDD

ID

VDS

VGS= VDD (closed switch)

VGS< VT (open switch)

Req


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For current to flow, VGS > VT

Enhancement mode: VT > 0 Depletion mode: VT < 0

Transistor is ON when VG=0V

For current to flow, VGS < VT

Enhancement mode: VT

< 0

Depletion mode: VT > 0

Transistor is ON when VG=0V

NMOS & PMOS Transistor

p-type Si

n+ poly-Si

NMOS

n+ n+

n-type Si

p+ poly-Si

PMOS

p+ p++ + + + +


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As compared to an n-channel MOSFET, the signs of all the voltages

and the currents are reversed:

PMOS Transistor


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W

L

MOS

TransistorStructure


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Source

DrainGate (contact not shown)

MOS Structure


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Transistor

for 90nm

process

InProduction

MOS Structure

After Intel Corp


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After Intel Corp

After Intel Corp

Transistor Scaling


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Generation:

Intel386 DXProcessor

Intel486 DX

Processor

PentiumProcessor

Pentium IIProcessor

1.5 1.0 0.8 0.6 0.35 0.25

Benefit of Transistor Scaling

smaller chip area lower cost

more functionality on a chip better system performance


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Moores Law

In 1965, Gordon Moore predicted that thenumber of transistors that can be integrated on

a die would double every 18 to 14 months (i.e.,

grow exponentially with time).

Amazingly visionary million transistor/chip

barrier was crossed in the 1980s.

2300 transistors, 1 MHz clock (Intel 4004) - 1971

16 Million transistors (Ultra Sparc III)

42 Million, 2 GHz clock (Intel P4) - 2001

140 Million transistor (HP PA-8500)


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40048008

80808085 8086

286386

486Pentium procP6

0.001

0.01

0.1

1

10

100

1000

1970 1980 1990 2000 2010

Year

Transistors(M

T)

2X growth in 1.96 years!

Transistors on lead microprocessors double every 2 years

Courtesy, Intel

Moores Law


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Moores Law

90 nm Montecito processor breaks through billion transistor

mark ahead of trend line with 1.72B transistors

After Intel Corp


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64

256

1,000

4,000

16,000

64,000

256,000

1,000,000

4,000,000

16,000,000

64,000,000

10

100

1000

10000

100000

1000000

10000000

100000000

1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 2010

Year

K

bitcapacity/

chip

1.6-2.4 m

1.0-1.2 m

0.7-0.8 m

0.5-0.6 m

0.35-0.4 m

0.18-0.25 m

0.13 m

0.1 m

0.07 m

encyclopedia2 hrs CD audio30 sec HDTV

book

page

4X growth every 3 years!

DRAM Chip

human memoryhuman DNA

Moores Law


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Moores Law

Processor power will keep doubling every two years.

After Intel Corp


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Moores Law

Transistor physical gate length will reach ~15 nm beforeend of this decade, and ~10 nm early next decade.

After Intel Corp


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After Intel Corp

Moores Law


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Moores Law

After Intel Corp


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40048008

80808085

8086286

386486Pentium proc

P6

1

10

100

1970 1980 1990 2000 2010

Year

Diesize(mm)

~7% growth per year

~2X growth in 10 years

Die size grows by 14% to satisfy Moores Law

Courtesy, Intel

Moores Law

Die Size


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Lead microprocessors frequency doubles every 2 years

P6Pentium proc

486386

28680868085

8080

80084004

0.1

1

10

100

1000

10000

1970 1980 1990 2000 2010

Year

Frequency(Mhz)

2X every 2 years

Courtesy, Intel

Moores Law

Clock Frequency


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Lead Microprocessors power continues to increase

P6Pentium proc

486

3862868086

80858080

80084004

0.1

1

10

100

1971 1974 1978 1985 1992 2000Year

Power(Watts)

Courtesy, Intel

Power delivery and dissipation will be prohibitive

Moores Law

Power Dissipation


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40048008

8080

8085

8086

286386

486

Pentium procP6

1

10

100

1000

10000

1970 1980 1990 2000 2010

Year

PowerDensity(W/cm2)

Hot Plate

Nuclear

Reactor

Rocket

Nozzle

Power density too high to keep junctions at low temp

Courtesy, Intel

Moores Law

Power Density


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1.E-07

1.E-05

1.E-03

1.E-01

1.E+01

68 72 76 80 84 88 92 96 00 04

Year

CostUS$/t

ransistor

Moores Law

Moores Law meansDecreasing Costs:Packing more transistors into

less space has dramatically

reduced their cost and the cost

of the products they populate.


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Lithography

Node (nm)

250 180 130 90 65 45

Process P856 P858 Px60 P1262 P1264 P1266

Ist Year ofProduction

1997 1999 2001 2003 2005 2007

Gate Length

(nm)

200 130


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Transistor

for 90nm

process

InProduction

Moores Law

After Intel Corp


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Moores Law

15nm Research Transistor

After Intel Corp


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Moores Law130 nm node

70 nm length

Production-2001

90 nm node

50 nm length

Production-2003

65 nm node

30 nm length

Production-2005

45 nm node

20 nm lengthProduction-2007

32 nm node

15nm length

Production-2009

After Intel Corp


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Moores Law - Future

Future High-k Dielectricfor Reduced Gate Leakage

30nm Tri-gate Transistor

After Intel Corp


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Silicon Nanowires

Source: Morales & Lieber,Science 279, 280 (1998)

Moores Law - Future

After Intel Corp


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Moores Law - Future

Intel SiliconOptical ModulatorConvergence of

silicon and optical

communications

MEMS-basedRF Switches

After Intel Corp


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Processed Silicon Wafer in 2000


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Why Scaling? Technology shrinks by ~0.7 per generation

With every generation can integrate 2x more functions ona chip; chip cost does not increase significantly

Cost of a function decreases by 2x

But How to design chips with more and more functions?

Design engineering population does not double every two

years Hence, a need for more efficient design methods

Exploit different levels of abstraction

Moores Law & IC Design


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Design Levels

n+n+

S

GD

+

DEVICE

CIRCUIT

GATE

MODULE

SYSTEM


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Investment into IC Manufacture


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IC Manufacture Trend

Source ITRS

1.introduction vlsi

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