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UCSB HEP ASIC Class Slide 1
CMOS Circuit Design, Layout and Simulation
Sam Burke
UCSB HEP Group
UCSB HEP ASIC Class Slide 2
References
• Text CMOS Circuit Design, Layout, and Simulation by R. J.
Baker, Li and Boyce IEEE Press Oct 2002 ISBN-81-203-1682-7
• URL http://cmosedu.com/cmos1/book.htm
UCSB HEP ASIC Class Slide 3
The Well
• P Type Wafer boron acceptor atoms (25
ohm*cm)
• Transistors Nmos Transistors on p-
substrate Pmos Transistors on n-well
• Diode formed between the n-well
and p-substrate
UCSB HEP ASIC Class Slide 4
Historical Methods
• Point Contacts 1948
• Grown Junctions 1950
• Alloy Junctions 1952
• Planar Technology or Junction Technology 1953
UCSB HEP ASIC Class Slide 5
A Little History
UCSB HEP ASIC Class Slide 6
Patterning
• Start with clean bare wafer
• Grow Oxide wet oxide dry oxide
• Apply Resist
• Photo-resist pattern
• Expose
• Develope
• Etch to remove oxide
• Ready for Diffusion
UCSB HEP ASIC Class Slide 7
Growing an N-Well
• Donor Atom Diffusion Donor valance=5
– Phosphorus Si valance=4
• N Well Resistivity 0.75 ohm*cm
UCSB HEP ASIC Class Slide 8
The N-Well
UCSB HEP ASIC Class Slide 9
The Well Resistor• R=[p/t]*L/W
R=Resistance p=resistivity
• R=Rsq*L/W Rsq=sheet resistance
(ohm/square)
• For N-Well p=0.75ohm*cm t=3um L=100um W=10um R=2500*100/10=25kohms
UCSB HEP ASIC Class Slide 10
Si Resistivity
• Experimental Data N-Type
donor concentration shown for resistor example
• Ref: Grove, A.S “Physics and Tech - -
UCSB HEP ASIC Class Slide 11
N-Well Cross Section
UCSB HEP ASIC Class Slide 12
L-Edit
• Demo the creation of an N-Well using L-Edit Error checking
UCSB HEP ASIC Class Slide 13
Design Process
UCSB HEP ASIC Class Slide 14
Well and Contacts
• N-Well contact on left metal1 active
• Bulk contact on right metal1 active P Implant
UCSB HEP ASIC Class Slide 15
PN Junction Depletion
• Carrier drift
UCSB HEP ASIC Class Slide 16
PN Junction Voltage
UCSB HEP ASIC Class Slide 17
Diode Junction Capacitance
UCSB HEP ASIC Class Slide 18
Diode V/I Equation
UCSB HEP ASIC Class Slide 19
Forward Biased Diode
UCSB HEP ASIC Class Slide 20
S-Edit
UCSB HEP ASIC Class Slide 21
T-Spice
UCSB HEP ASIC Class Slide 22
Net List of Diode Circuit
UCSB HEP ASIC Class Slide 23
Diode Storage Time
