CMOS Logic Design Review Quiz

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Questions and Answers

What is the purpose of MOSFET design rules?

To define how small features can be and how closely they can be packed (correct)

To specify the exact placement of components in an IC

To determine the type of FET to be used in a circuit

To describe the manufacturing process steps in detail

Which unit process step is responsible for creating a layer of silicon dioxide on the wafer surface?

Lithography

Diffusion

Metallization

Oxidation (correct)

What do layout design rules in IC fabrication primarily govern?

Choice of components in the IC

The manufacturing cost of the IC

The electrical properties of the IC

The size and spacing of features in the IC (correct)

What makes migrating from one process to a more advanced process difficult?

Not all rules scale in the same way Signup and view all the answers

What is the main objective of creating stick diagrams for MOS circuits?

To visualize the physical layout of the circuit Signup and view all the answers

Why is it important to understand the capabilities and limitations of stick diagrams?

To optimize circuit performance Signup and view all the answers

What does CMOS stand for in Complementary CMOS Logic Style?

Complementary Metal-Oxide-Semiconductor Signup and view all the answers

What is a key topic covered in EC303 CMOS VLSI Design?

Fabrication, operation, and characteristics of MOSFET Signup and view all the answers

In building CMOS gates, what is located on the 'n-side'?

N-diffusion Signup and view all the answers

Which course outcome involves analyzing the performance of a CMOS inverter?

CO2: Analyze the performance of CMOS inverter Signup and view all the answers

What is the purpose of a stick diagram in circuit design?

To provide a high-level overview of circuit functionality Signup and view all the answers

What are some of the design techniques covered in the course for digital circuits using CMOS?

Pseudo NMOS and Dynamic logic Signup and view all the answers

What is the purpose of studying MOSFET capacitances in EC303 CMOS VLSI Design?

For analyzing circuit stability Signup and view all the answers

Which type of logic design is NOT discussed in EC303 CMOS VLSI Design?

Analog-to-digital conversion logic Signup and view all the answers

What is an essential part of the unit process steps in CMOS technology discussed in EC303?

Fabrication process flow Signup and view all the answers

What is the purpose of stick diagrams in VLSI design?

To translate circuit concepts onto silicon Signup and view all the answers

What does a poly crossing diffusion represent in a stick diagram?

Transistor Signup and view all the answers

According to the rules of stick diagrams, what does it mean when two sticks of different types cross or touch each other?

No electrical contact Signup and view all the answers

What information do stick diagrams convey through color codes or monochrome encoding?

Topography and layer information Signup and view all the answers

In CMOS stick diagrams, what is the purpose of the demarcation line drawn between p-diff and n-diff?

To prevent direct contact between p-diff and n-diff Signup and view all the answers

What aspect of MOS circuits do stick diagrams help plan and visualize?

Interconnections between components Signup and view all the answers

What should be the relationship between the placement of pMOS and nMOS in Stick Diagrams?

All pMOS must lie on one side while all nMOS must be on the other side Signup and view all the answers

What is a key component of the physical structure of an NMOS?

p+ source/drain Signup and view all the answers

Which layer is not part of the implicit layers in PMOS layout representation?

n-well Signup and view all the answers

What does Leff < Ldrawn indicate in NMOS physical structure?

Lateral doping effects are minimal Signup and view all the answers

What should be the relationship between p-substrate and n+ source/drain in physical structure of pMOS?

They must be on opposite sides of SiO2 Signup and view all the answers

Which component is common in both NMOS and PMOS layout representations?

polysilicon gate Signup and view all the answers

Study Notes

EC303 CMOS VLSI Design

Course Outcomes

Explain the fabrication, operation, and characteristics of MOSFET
Analyze the performance of CMOS inverter
Design digital circuits using CMOS gates
Design analog circuits using CMOS gates
Outline the latest trends in CMOS technology

Introduction to MOSFETs

Unit process steps of CMOS technology:
- Wafer preparation
- Oxidation
- Lithography
- Diffusion
- Ion-implantation
- Epitaxy
- Metallization
Fabrication process flow: NMOS, PMOS, Twin well CMOS
Structure and operation of the MOS transistor
I-V and CV characteristics
MOSFET capacitances
Layout and design rules
Scaling and short channel effects

MOS Inverters

Inverters with resistive, MOSFET load
CMOS inverter: Voltage transfer characteristics
Noise margins
Switching characteristics
Calculation of delay times
Effect of load on switching characteristics and driving large loads
Logical effort of paths

Digital Circuits Using CMOS

Pseudo NMOS
Pass transistor
Transmission gates
Dynamic logic
Domino logic
Differential cascode voltage switch logic
Design of combinational circuits
Design of sequential circuits
Timing requirements

Analog Circuits

Second-order effects in MOSFETs
Single stage Amplifiers:
- Common-source stage
- Source follower
- Common-gate
- Cascode stage
Differential Amplifiers
Passive and Active current mirrors
CMOS operational amplifier
Gain boosting techniques

Trends in CMOS Technology

SOI
FinFET and multi-gate FET
2D materials-based FETs
On-chip interconnects

Layout Design Rules

Definition: A schematic of the Integrated Circuit (IC) that describes the exact placement of components for fabrication
Purpose: To specify how small features can be and how closely they can be packed in a manufacturing process
Importance: Why we need layout design rules
Specification: Typically in microns, making it difficult to migrate to more advanced processes

Stick Diagrams

Definition: A means of capturing topography and layer information using simple diagrams
Purpose: Acts as an interface between symbolic circuit and actual layout
Features:
- Does show all components/vias
- Shows relative placement of components
- Goes one step closer to the layout
- Helps plan the layout and routing
Limitations:
- Does not show exact placement of components
- Does not show transistor sizes
- Does not show wire lengths, wire widths, tub boundaries
- Does not show low-level details such as parasitics

Drawing Stick Diagrams

Rule 1: When two or more ‘sticks’ of the same type cross or touch each other, it represents electrical contact
Rule 2: When two or more ‘sticks’ of different types cross or touch each other, there is no electrical contact
Rule 3: When a poly crosses diffusion, it represents a transistor
Rule 4: In CMOS, a demarcation line is drawn to avoid touching of p-diff with n-diff

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Description

Test your knowledge on CMOS logic design concepts including the structure of N-channel MOSFET, using MOSFET as a switch, building CMOS gates, Complementary CMOS logic style, and stick diagrams. Identify challenges in scaling design rules for advanced processes.