A new isolation method with boron-implanted sidewalls for controlling narrow-width effect

Abstract

A new isolation method for high packing density MOS devices has been developed. In this method the LOCOS technique is applied to wide isolation regions and the buried-oxide technique is applied to isolation regions less than 2 µm wide. No additional masks are needed in order to form SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> film in the wide field regions because the photoresist is thicker near steps and inside the narrow trenches. For reducing the hump that appears in subthreshold current characteristics of n-channel MOSFET's, Using buried-oxide isolation, tilt-angle implantation to each of the four sidewalls is performed as a channel stop. The Sidewall channel stop can also control the narrow-channel effect.