stick diagrams
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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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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
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