cmos n p twin tub well formation
Post on 25-May-2015
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CMOS WELL FORMATIONAZMATH MOOSA
M. TECH 1ST YEAR
DEPARTMENT OF ELECTRONICS ENGINEERING
SCHOOL OF ENGINEERING AND TECHNOLOGY
INTRODUCTION
• Well refers to a region within a p or n type substrate of opposite dopant type
N WELL FORMATION
P WELL FORMATION
TWIN TUB FORMATION
• Provide separate optimization of the n-type and p-type transistors • Makes it possible to optimize "Vt", "Body effect", and the "Gain" of n, p
devices, independently.
TWIN TUB• Steps:
• Start with lightly doped n or p type material
• "epitaxial" or "epi" layer to prevent "latch up"
• Process sequence • a. Tub formation
• b. Thin-Oxide construction
• c. Source & drain implantations
• d. Contact cut definition
• e. Metallization
Concentrated PHOSPHOROUS AmbientConcentrated BORON Ambient
TWIN TUB FORMATION
N+ substrate
Epitaxial Layer
Photoresist
Mask
Photoresist
P - well N - well
Mask
Oxide Oxide
THANK YOU
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