HIGH TILT ANGLE PLUS TWIST DRAIN EXTENSION IMPLANT FOR CHC LIFETIME IMPROVEMENT

摘要

An integrated circuit containing an analog MOS transistor may be formed by implanting drain extensions with exactly four sub-implants wherein at least one sub-implant implants dopants in a substrate of the integrated circuit at a source/drain gate edge of the analog MOS transistor at a twist angle having a magnitude of 5 degrees to 40 degrees with respect to the source/drain gate edge of the analog MOS transistor, for each source/drain gate edge of the analog MOS transistor, wherein a zero twist angle sub-implant is perpendicular to the source/drain gate edge. No more than two sub-implants put the dopants in the substrate at any source/drain gate edge of the analog MOS transistor. All four sub-implants are performed at a same tilt angle. No halo implants are performed on the analog MOS transistor.

主权项

1. A method of forming an integrated circuit, comprising the steps:
providing a substrate comprising semiconductor material at a top surface of said substrate; forming a gate of an analog metal oxide semiconductor (MOS) transistor over said substrate, said analog MOS transistor having a first source/drain gate edge at said top surface of said substrate directly under a first lateral surface of said gate and having a second source/drain gate edge at said top surface of said substrate directly under a second lateral surface of said gate, so that said first source/drain gate edge and said second source/drain gate edge are on opposite sides of said gate; forming an implant mask over said substrate so as to expose at least a portion of said gate and expose a portion of said substrate adjacent to said gate, so that said implant mask is separated from said first source/drain gate edge, and is separated from said second source/drain gate edge, by substantially equal lateral spaces; and forming drain extensions in said substrate adjacent to, and partially underlapping, said gate at said first source/drain gate edge and said second source/drain gate edge by implanting dopants in four sub-implants, wherein:
a first sub-implant of said four sub-implants is at a tilt angle of at least 15 degrees, referenced to a perpendicular line to said top surface of said substrate, and at a first twist angle having a magnitude of 5 degrees to 40 degrees referenced to a horizontal normal line which lies in said top surface and is perpendicular to said first source/drain gate edge, wherein said first sub-implant clears said implant mask to implant a portion of said dopants into said substrate at said first source/drain gate edge, said first sub-implant being blocked from said second source/drain gate edge by said gate;a second sub-implant of said four sub-implants is at said tilt angle of at least 15 degrees and at a second twist angle referenced to said horizontal normal line opposite from said first twist angle, wherein said second sub-implant clears said implant mask to implant a portion of said dopants into said substrate at said first source/drain gate edge, said second sub-implant being blocked from said second source/drain gate edge by said gate;a third sub-implant of said four sub-implants is at said tilt angle of at least 15 degrees and opposite from said first sub-implant, wherein said third sub-implant clears said implant mask to implant a portion of said dopants into said substrate at said second source/drain gate edge, said third sub-implant being blocked from said first source/drain gate edge by said gate;a fourth sub-implant of said four sub-implants is at said tilt angle of at least 15 degrees and opposite from said second sub-implant, wherein said fourth sub-implant clears said implant mask to implant a portion of said dopants into said substrate at said second source/drain gate edge, said fourth sub-implant being blocked from said first source/drain gate edge by said gate; andsaid drain extensions are free of halo implanted regions having dopants of an opposite conductivity type from said dopants of said four sub-implants.