Transcript Introduction to VLSI Design

Digital Integrated Circuits
A Design Perspective
Jan M. Rabaey
Outline (approximate)
– Introduction and Motivation
– The VLSI Design Process
– Details of the MOS Transistor
– Device Fabrication
– Design Rules
– CMOS circuits
– VLSI Structures
– System Timing
– Real Circuits and Performance
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
The First Computer
The Babbage
Difference Engine
(1832)
25,000 parts
cost: £17,470
Digital Integrated Circuits
Introduction
© Prentice Hall 1995
ENIAC - The first electronic computer
(1946)
Digital Integrated Circuits
Introduction
© Prentice Hall 1995
Evolution in Complexity
Digital Integrated Circuits
Introduction
© Prentice Hall 1995
What is “CMOS VLSI”?
– MOS = Metal Oxide Semiconductor (This used
to mean a Metal gate over Oxide insulation)
– Now we use polycrystalline silicon which is
deposited on the surface of the chip as a gate.
We call this “poly” or just “red stuff” to
distinguish it from the body of the chip, the
substrate, which is a single crystal of silicon.
– We do use metal (aluminum) for interconnection
wires on the surface of the chip.
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
CMOS:Complementary MOS
– Means we are using both N-channel and Pchannel type enhancement mode Field Effect
Transistors (FETs).
– Field Effect- NO current from the controlling
electrode into the output


FET is a voltage controlled current device
BJT is a current controlled current device
– N/P Channel - doping of the substrate for
increased carriers (electrons or holes)
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
N-Channel Enhancement
mode MOS FET
– Four Terminal Device - substrate bias
–The “self aligned gate” - key to CMOS
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
VLSI:Very Large Scale
Integration

Integration: Integrated Circuits
» multiple devices on one substrate

How large is Very Large?
– SSI (small scale integration)

7400 series, 10-100 transistors
– MSI (medium scale)

74000 series 100-1000
– LSI 1,000-10,000 transistors
– VLSI > 10,000 transistors
– ULSI/SLSI (some disagreement)
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
Intel 4004 Micro-Processor
Digital Integrated Circuits
Introduction
© Prentice Hall 1995
Evolution in Transistor Count
Digital Integrated Circuits
Introduction
© Prentice Hall 1995
Scale Example
Consider a chip size of 20mm X 20mm
 Consider a transistor size of 2um X 2um

» With area for wires, etc.
1x108 transistors / chip
 Or - plot at 1 transistor : 1 mm

– 1 chip : 20 meter x 20 meter plot
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
Intel Pentium (II) microprocessor
Digital Integrated Circuits
Introduction
© Prentice Hall 1995
VLSI Design
– But the real issue is that VLSI is about
designing systems on chips.
– The designs are complex, and we need to use
structured design techniques and sophisticated
design tools to manage the complexity of the
design.
– We also accept the fact that any technology we
learn the details of will be out of date soon.
– We are trying to develop and use techniques
that will transcend the technology, but still
respect it.
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
The Process of VLSI Design:
Consists of many different representations/Abstractions
of the system (chip) that is being designed.
– System Level Design
– Architecture / Algorithm Level Design
– Digital System Level Design
– Logical Level Design
– Electrical Level Design
– Layout Level Design
– Semiconductor Level Design (possibly more)
Each abstraction/view is itself a Design Hierarchy of
refinements which decompose the design.
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
Design Abstraction Levels
SYSTEM
MODULE
+
GATE
CIRCUIT
DEVICE
G
S
n+
Digital Integrated Circuits
Introduction
D
n+
© Prentice Hall 1995
Help from Computer Aided
Design tools

Tools
»
»
»
»
»
»
»

Editors
Simulators
Libraries
Module Synthesis
Place/Route
Chip Assemblers
Silicon Compilers
Introduction to VLSI Design
Experts
» Logic design
» Electronic/circuit
design
» Device physics
» Artwork
» Applications - system
design
» Architectures
Introduction
© Steven P. Levitan 1998
New Design Methodologies

Methodologies which are based on:
» System Level Abstractions v.s. Device
Characteristic Abstractions
– Logic structures and circuitry change slowly
over time

trade-offs do change, but the choices do not
» Scalable Designs
– Layout techniques also change slowly.

But the minimum feature size steadily decreases with
time (also Voltage, Die Size, etc.)
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
Design Approaches
– Custom


full control of design
best results, slowest design time.
– Semi-custom (std cell)


use Cell libraries from vendor
cad tools, faster design time
– Gate Array



fastest design time
worst speed/power/density
best low volume (worst high volume)
– EPLA/EPLD - FPGA - electrically programmable
(in the field) Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
Close up of Intel Chip?
Time Magazine, July 1998
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
Evolution in Speed/Performance
Digital Integrated Circuits
Introduction
© Prentice Hall 1995
Technologies
– Bipolar (BJT)



TTL, Schottky
ECL
I^2 L
– Dual Junction, current controlled devices

MOS (FET unipolar)
» NMOS, PMOS
» CMOS <== our course
– Single Junction voltage controlled devices


GaAs (typically JFET’s)
OEIC’s - MQW’s, Integrated Lasers,?
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
Silicon in 2010
Density AccessTime
(Gbits/cm2)
(ns)
Die Area:
2.5x2.5 cm
DRAM
8.5
10
Voltage:
0.6 V
DRAM (Logic)
2.5
10
Technology: 0.07 m
SRAM (Cache)
0.3
1.5
Density
Max. Ave. Power Clock Rate
(Mgates/cm2)
(W /cm2)
(GHz)
Custom
25
54
3
Std. Cell
10
27
1.5
Gate Array
5
18
1
Single-Mask GA
2.5
12.5
0.7
FPGA
0.4
4.5
0.25
Digital Integrated Circuits
Introduction
© Prentice Hall 1995
SIA -National Technology
Roadmap for Semiconductors
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
SIA -National Technology
Roadmap for Semiconductors
8 inch
Introduction to VLSI Design
Introduction
18 inch
© Steven P. Levitan 1998
SIA -National Technology
Roadmap for Semiconductors
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
SIA -National Technology
Roadmap for Semiconductors
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
SIA -National Technology
Roadmap for Semiconductors
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998
SIA -National Technology
Roadmap for Semiconductors
Introduction to VLSI Design
Introduction
© Steven P. Levitan 1998