This presentation discusses stick diagrams and lambda-based design rules for VLSI system design. It begins with an overview of the top-down design hierarchy and then defines stick diagrams as a way to represent different layers of a layout using colors or monochrome lines. Common stick encodings are presented along with examples of drawing a CMOS inverter. Design rules are then covered, with lambda serving as a size-independent unit and rules specifying dimensions for wires, transistors, and contacts between layers. The goal is to convey key layer information and spacing requirements for mask layouts in a standardized way.

1. Stick Diagram
&
Lambda Based Design Rules
Presented by:
TAHSIN AL MAHI
Student ID: 140934
Year: 4 Term: I
ECE Discipline
Khulna University
Khulna
7/29/2018 ECE KU 1

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Presentation Outline
Top Down Hierarchy of System Design in VLSI
What is Stick Diagram
Stick Encodings
A CMOS inverter
Color Codes
Some Rules
What is Lambda Based Design Rule
Design Rules

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Top Down Hierarchy of System Design in VLSI
System Specifications
System Design
Subsystem Design
Logic Design
Logic Circuit Electronic Circuit
Stick Diagram
Mask Layout
Fabrication
Chip

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What is Stick Diagram?
o Stick diagram is a cartoon of a layout.
o Conveying layer information through the use of a color code or
monochrome encoding.
o Monochrome encodings are black and white lines.
D
S
G G
S
D
a b
Fig: (a) nMOS; (b) Stick Diagram of the nMOS

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Stick Encoding Layer
Diffusion Layer (n-type or p-type)
Polysilicon
Metal
Contact Cut (Diffusion layer with Metal)
Buried Contact (Diffusion layer with polysilicon)
Implant (Channel between drain and source)
Demarcation line (between n and p type)
VIA (Contact between metal 1 and metal 2)
Body to substrate connection
Stick Encodings

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A CMOS Inverter
D
S
G
S
D
G
a b
Fig: (a) CMOS inverter; (b) Stick diagram of the CMOS inverter
DDV
outVinV
GND
DDV
GND
inV outV

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Color Codes
Layer Layer Name
Metal 1
Polysilicon
n-type diffusion
p-type diffusion
Demarcation line

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Some Rules
Rule 1: When two or more ‘sticks’ of the same type cross or touch each
other that represents electrical contact.
Fig: Same type of sticks are crossing

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Some Rules…
Rule 2: When two or more ‘sticks’ of different type cross or touch each
other there is no electrical contact. If electrical contact is needed we have to
show the connection explicitly.
Fig: Electrical contact between two different sticks

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Some Rules…
Rule 3: When a poly crosses diffusion it represents a transistor.
Fig: Transistor made out by crossing over diffusion and polysilicon

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Some Rules…
Rule 4: In CMOS a demarcation line is drawn to separate the nMOS and
the pMOS.
Fig: Demarcation line separating nMOS and pMOS

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What is Lambda Based Design Rule
o Setting out mask dimensions along a size-independent way.
o Mead and Conway provided these rules.
o (Lambda) is a unit and can be of any value.
o According this rule line widths, separations and extensions are
expressed in terms of .
o Mask layout is designed according to Lambda Based Designed Rule.
o Nowadays, .


nm14

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Design Rules
Fig: Design Rules for wires (nMOS and CMOS)
3
2
2
2
2
1
2
n-diffusion p-diffusion
Minimum
width
Minimum separation
(where specified)
Polysilicon

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Design Rules…
Fig: Design Rules for wires (nMOS and CMOS)
3
Minimum
width
3
4
4
Minimum separation
(where specified)
4
Metal 2
Metal 1
3

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Design Rules…
Fig: Transistor Design Rules (nMOS and pMOS)
 22   22 
2
2
 66 
nMOS
(enhancement)
pMOS
(enhancement)
pMOS
(depletion)

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Design Rules…
2 Minimum
Implant for an nMOS
depletion mode
transistor to extend 2y
minimum beyond
channel in all
directions
2 Minimum
minimum
2
2 minimum
2
Fig: Transistor Design Rules (CMOS)

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Design Rules…
minimum3
2
minimum
Fig: Transistor Design Rules (Metal 1 to Polysilicon or to Diffusion)

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Design Rules…
Metal 2
Metal 1
2 minimum separation
(if other spacings allows)
Cut
 44  area of overlap with
 22  via at center
Fig: Transistor Design Rules (contact from metal 2 to metal 1 and thence to other layers)

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Reference
 Basic VLSI Design by Douglas A. Pucknell & Kamran Eshraghian
 Stick Diagrams, Maharishi Markandeshwar University, Haryana, India

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Any Questions?

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