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