Introduction to Layout

Jack Ou, Ph.D.CES 522 V

VLSI DesignSonoma State University

Flow Chart

Cross Sectional of an Inverter

Mask SetD D

S S

Basic Ingriedents

• n-well (N_WELL)• Polysilicon (POLY)• n+ diffusion• p+ diffusion• contact• metal

Manufacturing the n-well• Grow a protectiveLayer of oxide.• Remove oxidein selected region• Ion Implantation

• Poly silicon(doped to makegood conductor,Block n+ diffusion)• n-diffusion

p-diffusion, contacts and metal

Thick metal oxide provides insulationp+ diffusion is made selectively using silicon dioxide and photo resist

λ

• λ is half of the smallest feature size– In 0.18 um, λ is 0.09 um

• λ based design rules makes it easy to migrate from one process to process.

• Industrial design rules are usually specified in microns, which makes it difficult to migrate to a more advanced process.

Simplified λ based design rules

Example from tsmc 0.18 um process

POLY has a width of 2 λContacts are 2 λ x 2 λ

Design Rules

Schematic/Layout of an Inverter

p+ diffision

n+ diffision

Ground

VDD

Schematic/Layout of a NAND2

p+ diffision

n+ diffision

Ground

VDD

Substrate Contact

P_WELL

P_WELL+P_PLUS_SELECT

P_WELL+P_PLUS_SELECT+Active(43)

P_WELL+P_PLUS_SELECT+Active(43)+Contact to Active

P_WELL+P_PLUS_SELECT+Active(43)+Contact to Active+Metal1

Nwell Contact

NWELL

NWELL+N_Plus_Select+

NWELL+N_Plus_Select+Active Layer

NWELL+N_Plus_Select+Active Layer+Contact to Active Layer

NWELL+N_Plus_Select+Active Layer+Contact to Active Layer+Metal 1

DRC

DRC

Check: to run DRCFirst: to see the first DRC violationNext: to step through the DRC errors

DRC Results

DRC violation

Use the Rule Deck to Repair the Layout

Repaired Layout

Enlarged N Plus Select

Reduced Result Count