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Ravikiran

STICK DIAGRAMS

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VLSI DESIGN FLOW

D.Ravikiran babu

Assoc.ProfessorDept of ECE.,

JITS, Karimnagar.drkbabu1@gmail.com

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D.R.K.Babu

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VLSI DESIGN FLOW

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D.R.K.Babu

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Stick Diagrams

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Stick Diagrams

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Stick Diagrams

Objectives:

To know what is meant by stick diagram.

To understand the capabilities and limitations of stick

diagram. To learn how to draw stick diagrams for a given MOS

circuit.

Outcome: At the end of this module the students will be able

draw the stick diagram for simple MOS circuits.

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Stick Diagrams

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Stick Diagrams

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N+ N+

Stick Diagrams

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Stick Diagrams

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Gnd

VDD

xx

X

X

X

X

VDD

x x

Gnd

Stick

Diagram

Stick Diagrams

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Stick Diagrams

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Gnd

VDD

xx

X

X

X

X

VDD

x x

Gnd

Stick Diagrams

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Stick Diagrams

VLSI design aims to translate circuit conceptsonto silicon.

stick diagrams are a means of capturingtopography and layer information using simplediagrams.

Stick diagrams convey layer informationthrough colour codes (or monochrome

encoding). Acts as an interface between symbolic circuit

and the actual layout.

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Stick Diagrams

Does show all components/vias.

It shows relative placement of components.

Goes one step closer to the layout

Helps plan the layout and routing

A stick diagram is a cartoon of a layout.

Stick Diagrams

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Stick Diagrams

Does notshow

Exact placement of components

Transistor sizes Wire lengths, wire widths, tub boundaries.

Any other low level details such as parasitics..

Stick Diagrams

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Stick encoding(n-mos & p-mos)

N-diffusion

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P-diffusion

Metal 1

Contact Cut

Implant

Polysilicon

N-diffusion

P-diffusion

Metal 1

Contact Cut

Implant

:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

Poly Silicon

Buried contact

Color Coding Monochrome Coding

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Stick diagram:

green,,yellow n-diffusion, p-difffusion

Red Polysilicon

Blue Metal

Yellow Implant

Black Contact areas

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Contact cuts

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Electrical connections

Rule 1.

When two or more sticks of the same type

cross or touch each other that represents

electrical contact.

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Contact cuts

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Contact cutBuried contact

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).

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Contd.

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Butting Contact

Via

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N-diffusion

Ploy silicon

Nmos enhancement transistor:

Rule 3.When a poly crosses diffusion it represents a transistor.

Note: If a contact is shown then it is nota transistor.

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N-diffusion

Ploy silicon

Implant

Nmos depletion transistor:

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pmos enhancement transistor:

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p-diffusion

Ploy silicon

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pmos DEPLETION MODE transistor:

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P-diffusion

Ploy silicon

Implant

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Stick diagram for nmos inverter:

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vin

gnd

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Step1:

Draw metal(blue) VDDand GND rails in parallel

with enough separation

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VDD

GND

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vin

Step2:

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Forming transistors

gnd

VDD

GND

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Step2-1:

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vin

gndVin

VDD

GND

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Step3:

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vin

gnd

Vout

Vin

VDD

GND

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Step4:

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vin

gnd

VDD

GND

Vout

Vin

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Vdd

Vss

N mos NAND GATE

A

Ploy(G)

Ploy(G)

s

s

D

D

B

Ploy(G)

Vout(A nand B)

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Vout(A nor B)

N mos NOR GATE

3333

Vdd

Vss

A

Ploy(G)

Ploy(G)s s

DD

B

CMOS ENCODING

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CMOS ENCODING

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Cmos inverter:

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Demarcation line

VDD

GND

input output

Vdd contact

Vss contact

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Demarcation

Line

Vdd contact

Vss contact

Vdd

Vss

Vout(A nand B

A

Ploy(G)

Ploy(G)

Ploy(G)

Ploy(G)

B

s s

s

s

D

D D

D

Cmos NAND GATE

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Vdd contact

Vss contact

Vdd

Vss

DemarcationLine

Vout(A nor B)A

Ploy(G)

Ploy(G)

Ploy(G)

Ploy(G)

s

s

s s

D

D

D

D

B

Cmos Nor GATE

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Vss contact

Vdd

Vss

Demarcation

Line

Vout

Vdd contactBiCmos inverter

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Vdd

Vout

Vdd contactBiCmos inverter