Reference Books
1. Basic VLSI Design by Douglas A. Pucknell
2. Design of VLSI Systems- A Practical Introduction by Linda E.M. Brackendary
Introduction to Microelectronics
Integrated Circuits (ICs): Resistors, Capacitors, Transistors. Many transistors in one chip.
• SSI - Small Scale Integration MSI - Medium Scale Integration
• LSI - Large Scale Integration VLSI - Very Large Scale Integration
• ULSI - Ultra Large Scale Integration GLSI - Giant Large Scale Integration
A Brief History/Microelectronics Evolution
Why VLSI/Miniaturization required in electronics?
• low size, weight and volume
• low cost (because cost depends upon size, manufacturing cost, maintenance
cost etc.)
• reduced design time and complexity (realization of complex circuits using
discrete devices are difficult and costly too)
• higher speed
• high degree of reliability, repeatability
• lower static power dissipation and sophisticated designs can be made
Moore’s Law
Gordon Moore: co-founder of Intel
1st Law:
• The number of transistors per chip roughly doubles in every two years.
• The number of transistors per chip would grow exponentially.
2nd Law:
• The cost of a semiconductor chip fabrication doubles every four years.
• The cost of a semiconductor chip fabrication increases exponentially over time.
Moore’s Law
VLSI Design Approaches
There are three approaches to implementing digital design:
1st Approach – Off the self. The chips are available “ off the self” from manufacturers.
• designer is limited to the integrated circuits on offer
• availability of specific functions influences the resulting design
2nd Approach – Full custom design. The chip design is completely depends on designer.
• total control over the chip function including the specification of the content of each layer manufactured
• associated overheads of the design time, development and manufacturing cost
3rd Approach – Semi custom design.
• design in the form of the uncommitted logic array ( ULA)
• designer specify the cell interconnection and the cell configuration to provide a user-specified function
Full Custom Design/Top down Design Hierarchy
Choice of VLSI Technology
Choice of materials:
• Low cost
• Availability
• Insulating property
Si/SoS/Ge/GaAs
Why Si is better than others?/ Why Si technology is most popular?
GeO2 – is partially soluble
GaAs – does not form a oxide, have higher mobility but high integration levels are difficult to
achieve
Choice of VLSI Technology
BJT, MOS (pMOS, nMOS), CMOS, BiCMOS
BJT
• Base current limits integration density
• More static power dissipation
MOS – low power allows very high integration
Choice of VLSI Technology
Why MOS not BJT in integration?
Features BJT MOS
Spped More Less
Area More Less
Power dissipation More Less
No. of Steps (MASKs) More Less
Processing Complex Simple
Repeatability No Yes
Dynamic storage capacity No Yes
Choice of VLSI Technology
NMOS or CMOS?
NMOS CMOS
One transistor Two transistor
Less area More area
Low speed High speed
High power dissipation Low power dissipation
Complexity few Less complexity
Less reliable More reliable
Choice of VLSI Technology
Speed-Power Product:
BJT – Speed = 10ns, Power = 2mW, Speed*Power = 20 pJ
MOS – Speed = 40ns, Power = 10nW, Speed*Power = 0.0004 pJ
Choice of VLSI Technology
EE 4121
VLSI Design and Technology
Lecture 4: Stick Diagram
Department of Electrical and Electronic Engineering (EEE)
Khulna University of Engineering & Technology (KUET)
• Design Rules: Design rules are a set of geometrical specifications that dictate the
design of the layout
Exact geometric information is known
Chips or IC are specified with mask sets.
Area is known.
• Circuit design with all dimensions is Layout
• Designer :
minimize complexity
Utilize area
Workable chip
Reliable (proper functioning)
• Process Engineer:
Controllable
reproducible
• Mask Layout: Representation of IC or stick diagram in terms of planar
geometric shapes or masks or set of masks is called mask layout.
• Properties of Mask Layout:
minimum size/width – to avoid opening or breaking
minimum spacing – to avoid shorting
minimum overlapping – for proper functioning
minimum surrounding – contact cuts
• What is HDL?
• HDL stands for Hardware Description Language. It is a programming language
that is used to describe, simulate, and create hardware like digital circuits (ICS).
HDL is mainly used to discover the faults in the design before implementing it in
the hardware.
• In computer engineering, a hardware description language (HDL) is a specialized
computer language used to describe the structure and behavior of electronic
circuits, and most commonly, digital logic circuits
Entity
• The Entity is used to specify the input and output ports of the circuit. An Entity
usually has one or more ports that can be inputs (in), outputs (out), input-
outputs (inout), or buffer.
• An Entity may also include a set of generic values that are used to declare
properties of the circuit.
