VLSI Design
Lecture 4-b: Layout Extraction
Mohammad Arjomand
CE Department
Sharif Univ. of Tech.
Gate Layout
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Layout can be very time consuming
 Design gates to fit together nicely
 Build a library of standard cells
 Must follow a technology rule
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Standard cell design methodology
 VDD and GND should abut (standard height)
 Adjacent gates should satisfy design rules
 nMOS at bottom and pMOS at top
 All gates include well and substrate contacts
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
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Example: Inverter
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
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Layout using Electric
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
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Example: NAND3
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Horizontal N-diffusion and p-diffusion strips
Vertical polysilicon gates
Metal1 VDD rail at top
Metal1 GND rail at bottom
32  by 40 
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
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Example: NAND3
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
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Stick Diagrams
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Stick diagrams help plan layout quickly
 Need not be to scale
 Draw with color pencils or dry-erase markers
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
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Stick Diagrams
 Stick diagrams help plan layout quickly
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Need not be to scale
Draw with color pencils or dry-erase markers
VDD
Vin
Vout
GND
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
Slide 8 of 50
Wiring Tracks
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A wiring track is the space required for a wire
 4  width, 4  spacing from neighbor = 8  pitch
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Transistors also consume one wiring track
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
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Well spacing
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Wells must surround transistors by 6 
 Implies 12  between opposite transistor flavors
 Leaves room for one wire track
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
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Area Estimation
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Estimate area by counting wiring tracks
 Multiply by 8 to express in 
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
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Example: O3AI
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Sketch a stick diagram for O3AI and estimate area

Y  ( A  B  C)  D
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
Slide 12 of 50
Example: O3AI

Sketch a stick diagram for O3AI and estimate area

Y  ( A  B  C)  D
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
Slide 13 of 50
Example: O3AI

Sketch a stick diagram for O3AI and estimate area

Y  ( A  B  C)  D
Modern VLSI Design 4e: Chapter 2
Sharif University of Technology
Slide 14 of 50