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ANALOG & DIGITAL VLSI
DESIGN
EEE/ INSTR C443/F313
MWF 11-12 noon, 1223
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ADVD
NALANDA
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Their work spawned themicroelectronicsrevolution that has changed forever theway we live, work, and communicate."
INTEGRATED CIRCUIT
George H. Heilmeier, Bell Communications
Research.
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INTEGRATED CIRCUIT
Our world is full of integrated circuits. You find
several of them in computers.
The microprocessor is an integrated circuit that
processes all information in the computer. It
mouse has been moved. It counts numbers and
runs programs, games and the operating
system. Integrated circuits are also found in almost every
modern electrical device such as cars, television
sets, CD players, cellular phones, etc4ANU GUPTA BITS PILANI,
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INTEGRATED CIRCUIT
They were born four years apart in two distant places, and yet they
were destined to start a technological revolution that changed the
world.
Without knowing each other, through two independent paths, bothinvented, almost at the same time, the Integrated Circuit (IC)
The invention of Jack Kilby and Robert Noyce, also known as "the
chip", has been recognized as one of the most important
innovations and significant achievements in the history of
humankind. 5ANU GUPTA BITS PILANI,PILANI
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Need of IC technology
Electrical engineers were aware of the potential of digital
electronics, however, they faced a big limitation known
as the "Tyranny of Numbers." This was the metaphor
that described the exponentially increasing number of
components required to design improved circuits,
of components that could be assembled together.
Both, Kilby at Texas Instruments, and Noyce at FairchildSemiconductor, were working on a solution to this
problem during 1958 and 1959.
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Tyranny of numbers
When building a circuit, it is very important that all connections areintact. If not, the electrical current will be stopped on its waythrough the circuit, making the circuit fail. Before the integratedcircuit, assembly workers had to construct circuits by hand,soldering each component in place and connecting them withmetal wires. Engineers soon realized that manually assembling the
vast number of tiny components needed in, for example, acomputer would be impossible, especially without generating as ng e au y connec on.
Another problem was the size of the circuits. A complex circuit, likea computer, was dependent on speed. If the components of thecomputer were too large or the wires interconnecting them too
long, the electric signals couldnt travel fast enough through thecircuit, thus making the computer too slow to be effective.
So there was a problem of numbers. Advanced circuits containedso many components and connections that they were virtuallyimpossible to build. This problem was known as the tyranny ofnumbers. 7ANU GUPTA BITS PILANI,
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INTEGRATED CIRCUIT DESIGN
The solution was found in the monolithic (meaning
formed from a single crystal) integrated circuit.
Instead of designing smaller components, they found the
way to fabricate entire networks of discrete components
in a single sequence by laying them into a single crystal
(chip) of semiconductor material.
Kilby used germanium and Noyce used silicon
Texas Instruments filed for a patent in February 1959.
Fairchild Semiconductor did the same in July 1959.Naturally, both firms engaged in a legal battle that lasted
through the decade of the 60s until they decided to
cross-license their technologies.
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JACK KILBY
The Patent No. 3,138,743 for Miniaturized ElectronicCircuits, were issued to Jack S. Kilby and TexasInstruments in 1964.
Kilby holds patents on sixty inventions, including the
invention of the electronic hand-held calculator in 1967. ,
and was inducted into the National Inventors Hall ofFame in 1982
In October 10, 2000, The Royal Swedish Academy of
Sciences awarded Jack Kilby the Nobel Prize in Physicsfor 2000 "for basic work on information andcommunication technology."
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ROBERT NOYCE
The Patent No. 2,981,877 for the silicon based ICwas granted to Robert Noyce,
In 1968, He founded INTEL, the companyresponsible for the invention of the microprocessor.
Dr. Noyce was issued 16 patents in the area of,
Inventors Hall of Fame in 1983. He died on June 3,1990.
Noyces circuit solved several practical problemsthat Kilbys circuit had, mainly the problem ofinterconnecting all the components on the chip.This was done by adding the metal as a final layerand then removing some of it so that the wiresneeded to connect the components were formed.10ANU GUPTA BITS PILANI,
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Moores lawdriving force
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Moores law
The law is named afterIntel co-founderGordon E.
Moore, who described the trend in his 1965 paper.
The paper noted that number of components in
integrated circuits had doubled every yearfrom the
invention of the integrated circuit in 1958 until 1965 andpredicted that the trend would continue "for at least ten
years".[10]
His prediction has proved to be uncannily accurate, in
part because the law is now used in the semiconductorindustry to guide long-term planning and to set targets
forresearch and development.
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an ou
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Previous knowledge
Digital electronics
Micro electronic circuits
Electronic devices
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Objective
VLSI circuit design and verification
Silicon implementation
Usa e of EDA tools
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Goals of this Course
Learn to design and analyze state-of-the-art digital VLSI chips using CMOStechnology
Understand design issues at the layout,, -
Performance analysis and optimization
Use commercial design software in the lab
Complexity management Understand the complete design flow
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VLSI DESIGN
Panoramic View
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What is VLSI design?
A way to design electronic circuits
Dimensionally micron, submicron, nano
range
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Why VLSI imp?
Current day technology
Micro electronics creeping in alldisciplines--- (merger of various disciplines in
system design) ra n mapp ng, ar c a
intelligence
Electromechanical systemsrobotics
Communication, Smart and secure homes,
Identification , vehicular electronics,process control 21ANU GUPTA BITS PILANI,
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Uniqueness of VLSI Design
HIGH INTEGRATION DENSITY
INTERCONNECT CROSS TALK,
MISMATCH (ON CHIP, DIE TO DIE),
COMPLEX DESIGNS,
DESIGN VERIFICATION & TESTABILITY
are important design issues now
FAST CHANGING TECHNOLOGY
PORTING DESIGN TO NEW TECH GENERATION ,
NEW SET OF DESIGN RULESmake design indep. of design rulesleverage existing work: programs ,building blocks
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VLSI design flow--Y chart (D.GJASKI)
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VLSI Design Concerns
VLSI design evolution
VLSI Design Methodologies
Structures design techniques
Design Quality
Packaging technology
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Microprocessors--------1970---- progrm/software
Digital signal processor---1980prog/hard wired
FPGA/ASIC--1990---prog, specific/ specific, vol
produc.
SOC---------------------2000
SIP------------SYSTEM in PACKAGE
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SIP/ SOC
System-on-chip (SOC) is an integrated circuit thatincludes a processor, a bus, and other peripheral
elements on a single monolithic substrate
System on Chip (SOC) design is implemented in which
various components, such as volatile memory systems,- ,
systems, mixed signal circuits and logic circuits are each
formed into units and integrated on a single chip.
The primary advantages of SOC devices are lower
costs, greatly decreased size, and reduced powerconsumption of the system
A system-on-chip is designed by stitching together
multiple stand-alone VLSI designs (cores) to provide full
functionality for an application 27ANU GUPTA BITS PILANI,PILANI
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SIP SiP permits high levels of functional density by incorporating
combinations ofwirebond, flip-chip, stacked devices,embedded devices, MEMS, and package-on-package .
This allows designers to use SiP implementation for
subsystems and systems that are not technically viable in a .
Packaging concepts include chip stacked on-chip, flip-chip
stacked on-chip, chips placed side by side in a package, as
well as other concepts. These complicate the design
partitioning process
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SIP
Additionally, SiP technology allows lower power and less
noise at the interconnect level, flexibility in mixing and
matching IC technologies, and reduced board size and
cost through inclusion of passive components,
consolidation of packaging and reduction of layers. And, ,
can be much quicker to develop.
SiP designs are typically only attempted when a wall is
reached-such as size or performance constraints-and
conventional system-on-chip (SoC) solutions are too
expensive to implement
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VLSI Design Methodology
Design MethodologyIt is a combination
of CAD tools, design strategies,
verification strategies
Strategies to ensure successful design Is
mainly guided by physical technology
(silicon implementation of the design)
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VLSI Design Styles
Programmable Logic Devices
Programmable Logic Device (PLD)
Field Programmable Gate Array (FPGA)
Standard Cell (Semi-Custom Design)
Full-Custom Design
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IMPACT OF VLSI DESIGN STYLES ON DESIGN
CYCLE TIME AND ACHIEVABLE CHIP PERFORMANCE
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PERFORMANCE IMPROVEMENT OF A
VLSI PRODUCT FOR EACH NEW GENERATION
OF MANUFACTURING TECHNOLOGY
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Analog Design
Only Full custom
Fully handcrafted design
Each design requires specific performance
Lack of Automation supporting CAD tools
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DIGITAL CMOS CHIP DESIGN
OPTIONS
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Field Programmable Gate
Arra FPGA
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Introduction
User / Field Programmability.
Array of logic cells connected via
routing channels.
.
Logic cells are mainly lookup tables
(LUT) with associated registers.
Interconnection on SRAM basis or
antifuse elements.
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Xilinx XC4000 Architecture
CLB
CLB
CLB
CLB
Switch
Matrix D Q
SlewRate
Control
PassivePull-Up,
Pull-Down
Delay
Vcc
Output
Buffer
Input
Buffer
Q D
Pad
rogramma e
Interconnect I/O Blocks (IOBs)
Configurable
Logic Blocks (CLBs)
D Q
SD
RD
EC
S/R
Control
D Q
SD
RD
EC
S/R
Control
1
1
F
G
H
DIN
F
G
H
DIN
F
G
H
H
H
Func.Gen.
GFunc.Gen.
FFunc.Gen.
G4G3G2G1
F4F3F2F1
C4C1 C2 C3
K
Y
X
H1 DIN S/R EC
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XC4000E Configurable Logic
Blocks
D Q
SD
EC
S/RControl
F
G
H
DIN
GFunc.Gen.
G4G3
G2G1
C4C1 C2 C3
YQ
H1 DIN S/R EC
2 Four-input function
generators (Look Up
Tables)
- 16x1 RAM or
Logic function
RD
D Q
SD
RD
EC
S/RControl
1
1
F
G
H
DIN
F
G
H
H
HFunc.Gen.
FFunc.Gen.
F4F3F2F1
K
Y
XQ
X
2 Registers
- Each can be
configured as Flip
Flop or Latch
- Independentclock polarity
- Synchronous and
asynchronous
Set/Reset
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Look Up Tables
Combinatorial Logic is stored in 16x1 SRAM Look Up
Tables (LUTs) in a CLB
Example:
A B C D Z
Look Up Table
Combinatorial Logic
AB
4-bit address
Capacity is limited by number ofinputs, not complexity
Choose to use each function
generator as 4 input logic (LUT) or
as high speed sync.dual port
RAM
0 0 0 1 0
0 0 1 0 0
0 0 1 1 1
0 1 0 0 1
0 1 0 1 1. . .1 1 0 0 0
1 1 0 1 0
1 1 1 0 0
1 1 1 1 1
CD
GFunc.Gen.
G4G3G2G1
WE
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XC4000X I/O Block Diagram
Shaded areas are not included in XC4000E family. 42ANU GUPTA BITS PILANI,
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Xilinx FPGA Routing
1) Fast Direct Interconnect - CLB to CLB
2) General Purpose Interconnect - Uses switch matrix
CLB CLB
CLB CLB
Switch
Matrix
Switch
Matrix
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Programmable Switches
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Design Flow
Design Entry in schematic, ABEL, VHDL,and/or Verilog. Vendors include Synopsys,
Aldec (Xilinx Foundation), Mentor,Cadence, Viewlogic, and 35 others.
Implementation includes Placement &Routing and bitstream generation using
1
XC4000XC4000XC4000
3
nx s ec no ogy. so, ana yze t m ng,view layout, and more.
Download directly to the Xilinxhardware device(s) withunlimited reconfigurations* !!
*XC9500 has 10,000 write/erase cycles
M1 Technology
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Gate Array
In view of the fast prototyping capability, thegate array (GA) comes after the FPGA. Design implementation of
FPGA chip is done with user programming,
Gate array is done with metal mask design and processing.
Gate array implementation requires a two-stepmanufacturing process:1. The first phase, which is based on generic (standard)
masks, results in an array of uncommitted transistorson each GA chip.
2. These uncommitted chips can be customized later,which is completed by defining the metalinterconnects between the transistors of the array
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Channeled vs. Channel-less(SoG) Approaches
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Small Section of a Semi-custom Base
Array Without Interconnect
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Section of Semi-custom Array with
Single Level Metal Interconnect
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The GA chip utilization factor is higher
than that of FPGA.
The used chip area divided by the total chip
area.
Chip speed is also higher.
More customized design can be achieved with
metal mask designs.
Current gate array chips can implement as
many as hundreds of thousands of logic
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Standard Cell Based Design
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CBIC
One of the most prevalent custom design styles.
Also called semi-custom design style.
Requires development of a full custom mask set.
All of the commonly used logic cells are developed,
characterized, and stored in a standard cell library.
A typical library may contain a few hundred cells
including inverters, NAND gates, NOR gates,complex AOI, OAI gates, D-latches, and flip-flops.
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Characteristic of the Cells
Each cell is designed with a fixed height.
To enable automated placement of the cells, and
Routing of inter-cell connections.
A number of cells can be abutted side-by-side to form
rows.
The power and ground rails typically run parallel to the
upper and lower boundaries of the cell.
Neighboring cells share a common power and ground bus.
nMOS transistors are located closer to the ground rail while the
pMOS transistors are placed closer to the power rail.
The input and output pins are located on the upper and
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Standard Cells
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Standard Cell Layout
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Fl l f St d d C ll
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Floor-plan for Standard Cell
Design
Inside the I/O frame which is reserved for I/O
cells, the chip area contains rows or columns of
standard cells.
Between cell rows are channels for dedicated inter-
.
Over-the-cell routing is also possible.
The physical design and layout of logic cells
ensure that
When placed into rows, their heights match.
Neighboring cells can be abutted side-by-side, which
provides natural connections for power and ground
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Full Custom Design
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Introduction
The standard-cells based design is oftencalled semi custom design.
The cells are pre-designed for general use andthe same cells are utilized in many different
chip designs. In the full custom design, the entire mask
design is done anew without use of anylibrary. The development cost of such a design style is
prohibitively high.
The concept of design reuse is becoming popular in
order to reduce design cycle time and cost.61ANU GUPTA BITS PILANI,
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Contd.
The most rigorous full custom design canbe the design of a memory cell.
Static or dynamic.
Since the same layout design is replicated,
density memory chip design.
For logic chip design, a good compromise
can be achieved by using a combination ofdifferent design styles on the same chip.
Standard cells, data-path cells and PLAs.62ANU GUPTA BITS PILANI,
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In real full-custom layout in which the
geometry, orientation and placement of every
transistor is done individually by the designer,
Full-custom layout
.
Typically 10 to 20 transistors per day,
per designer.
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Continued
In digital CMOS VLSI, full-custom design is
rarely used due to the high labor cost.
Exceptions to this include the design of high-
volume products such as memory chips, high-
masters.
Next slide shows the full layout of the Intel 486
P chip. Good example of a hybrid full-custom design.
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Small Section of a Typical Full Custom
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Small Section of a Typical Full Custom
Layout
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Comparison Among Various
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Comparison Among Various
Design Styles
Design Style
FPGA Gate
array
Standard
cell
Full
custom
Cell size Fixed Fixed Fixed Variable
Cell type Program
mable
Fixed Variable Variable
Cell
placement
Fixed Fixed In row Variable
Interconnectio
ns
Program
mable
Variable Variable Variable
Design time Very fast Fast Medium Slow
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Some important issues
Highly complex design--- structured design
strategies
Packaging
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Managing design complexity
Hierarchydivide and conquer
Regularityrepetition of blocks
Modularity---each block complete in itselfexternal details
Locality---connections are mostly between
neighboring modules (internal details)
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Structured Design Strategies
Strategies common for complex hardwareand software projects.
-> Hierarchy: Subdivide the design intomany levels of sub-modules
-> -unambiguously & well defined interfaces
-> Regularity: Subdivide to max numberof similar sub-modules at each level
-> Locality: Max local connections,keeping critical paths within moduleboundaries
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Regularity
Design the chip hierarchy into many modules ifpossible identical
Extended use of a single design simplifies thedesign process
Regularity can exist at all levels of designhierarchy
Circuit Level: uniform transistor sizes rather than
manually optimizing each device. Logic Level: identical gate structures rather than
customize every gate.
Architecture Level: construct architectures that
use a number of identical processor structures
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Modularity
Adds to hierarchy and regularity the qualities of
Well defined functions and interfaces is a must
Unambiguous functions
Well defined behavioral, structural, andphysical interfaces
Enables modules to be individually designedand evaluated.
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Locality
TIME LOCALITY: modules see a common clockand synchronous timing is applied.
Robust clock generation and distribution is
critical Critical paths, where possible, are to be kept
within module boundaries
Any global module to module signal should have
an entire clock cycle to traverse the chip. Replicate logic, if necessary, to alleviate cross-
chip crossings.
Locate modules in layout to minimize large or"global" routes between modules.
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Design for manufacturability
Design goal: All fabricated circuits meet all
performance specs under all operating
conditions.
Impediments:
Random variations in fabrication process.
Random variations in operating conditions,e.g. VDD, Temp. ambient.
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Reality: Excessive deviations of
erformance cause ield loss and increase
Why DFM important?
the
unit cost of the chip increases
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DFM Issues:
1. Parametric yield estimation.
2. Parametric yield maximization.
. - .
4. Variability Minimization.
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DFM
DFM Practice:
Consider the effects of expected randomness in
processing and operating conditions early in thedesign process.
Circuit made as insensitive to these variations as
is practical.
Design to performance specs with sufficientmargins that a large fraction of the manufactured
chips pass the chip acceptance criteria.
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Design cycle time-definition
Time period from the start of chip development until the
mask tape delivery time.
-------
desired level of chip performance.
-------Level of circuit performance achieved dependsstrongly on the design methodology
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Design Success parameters
Design is a continuous tradeoff to achieveperformance specs with adequate results in allthe other parameters.
Design Parameters By Which Design Success Is
Performance Specs - function, timing, speed, power
Size of Die - manufacturing cost
Time to Design - engineering cost and schedule
Ease of Test Generation & Testability - engineeringcost, manufacturing
cost, schedule
Manufacturability - resilient to circuit/processvariabilities 79ANU GUPTA BITS PILANI,
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Design Quality
ACHIEVE SPECIFICATIONS (Static & Dynamic)
DIE SIZE---less
POWER DISSIPATION---less
TESTABILITY--- 100% YIELD AND MANUFACTURABILITY100%
RELIABILITY
TECHNOLOGY UPDATABLE/ PORTABLE
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C
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TESTABILITY
generation of good test vectors
availablity of reliable test fixture at speed
Contd.
YIELD AND MANUFACTURABILITY
functional yield
parametric yield
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Contd.
RELIABILITY premature aging (Infant mortality)
ESD ELECTROSTATIC DISCHARGE.
latchup
-
power and ground bouncing
TECHNOLOGY UPDATABLE Easily updated to new design rules
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ESD
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ESD ESD is a transient discharge of static charge that arises from either
human handling or a machine contact.
Although ESD is the result of a static potential in a charged object,
the energy dissipated and damages made are mainly due to the
current flowing through ICs during discharge.
interconnect burn-out or oxide break-down. The basic phenomenon
of ESD is that is a large amount of heat is generated in a localized
volume significantly faster than it can be removed, leading to a
temperature in excess of the materials safe operating limits. ESD Damages
pn-junction may melt., Gate oxide may have void formation., Metal
interconnects & Vias may melt or vaporization, leading to
shorts or opens, Gate-oxide breakdown is another form of ESD damage.83ANU GUPTA BITS PILANI,
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P k i T h l
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Packaging Technology
Include important package related
parasitics in the chip design and
simulation
Packa e Power & Ground Planes On-chip power and ground bounce
Bond Wire Lengths -> on-chip inductive
effects Thermal Resistance -> temp rise due to
on-chip power dissipation
Package Cost84ANU GUPTA BITS PILANI,
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WIRE BONDINGS
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WIRE BONDINGS
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I t t k d i
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Important package design concerns:
hermetic seals to prevent penetration of
moisture
thermal conductivity shd be high
pin densityhigh keeping small size
parasitic inductance and capacitance--low
alpha-paricle protection ( especially inmemories)
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P k t
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Package types
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Custom Integrated Circuit
Specific purpose
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C t i t ti
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Custom integration
An integrated circuit that requires a full set
of masks specifically designed for a
particular function or application.
A custom IC is usually developed for a
specific customer and may have to
withstand harsh environments .
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Wh consider c stom integration?
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Why consider custom integration?
There are a number of reasons why
developing a custom Integrated Circuit is
an appropriate and often essential
ingredient to the development of asuccessful product
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Reasons
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Reasons
Size. The continued market demand to
reduce the size of electronic devices, in
particular portable and hand-held devices,
requires ever higher levels of integration. Replacing functions requiring the use of a
number of discrete components with one
IC helps achieve this goal.
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Contd
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Contd.
Performance. By utilizing the superior
matching and tracking characteristics of
integrated circuit components, manual
adjustment of circuit parameters can oftenbe eliminated, while maintaining tighter
spread on key system performance specs
over the full range of operating conditions.
Additionally, critical or high-precision
specs can be trimmed at wafer test.
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Contd
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Contd.
Cost. Replacing a number of discrete
components with a pre-tested IC
significantly reduces the test time and the
number of rejects. For large production quantities the initial
development cost will be amortized in a
short period of time, resulting in a lower
cost per unit.
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Contd
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Contd.
Reliability.An IC is significantly more
reliable than a PCB populated with the
devices necessary to provide the
equivalent functionality using discretecomponents or multiple ICs.
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Contd
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Contd.
Copy protection. This can be the most
important incentive to consider custom
integration. Simple hardware copying is
prevented because of the exclusivity of thecustom IC.
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What are the fab technology options?
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What are the fab. technology options?
The three principal technologies which are
readily accessible for custom integration
are Biploar, CMOS and BiCMOS
Choice between using a prefabricated
semi-custom array or undertaking a full
custom development
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CMOS processing
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CMOS processing
N-WELL
P-WELL
TWIN-TUB
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Wafer preparation
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Wafer preparation
defect free single crystalline lightly dopedWAFER.
Metallurgical grade silicon-electronic grade
silicon(99.99% pure) Single crystalline structure obtained bymelting and then cooling ---Czochralskimethod
Ingot cut into wafers using diamond saw Wafers are than polished to mirror finish
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Process involved
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Process involved
Photolithography
Deposition
Oxidation
Diffusion/ion implantation
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General Principles
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General Principles
Technology changes fast, so it is importantto understand the general principles whichwould span technology generations
optimization, tradeoffs
wor as par o a group
leverage existing work: programs ,buildingblocks
Concepts remain the same: Example: relays -> tubes -> bipolar transistors-> MOS transistors