Patent ID: 6087227
Filing Date: 2000-07-11
Classification: H01L

Abstract:
A method for fabricating an electrostatic discharge (ESD) protection circuit on a substrate, which includes an internal circuit region and an ESD protection circuit region, in which a first MOS transistor is formed at the internal circuit region, and a second MOS transistor is formed at the ESD protection circuit region, wherein the first MOS transistor isolated by a first isolation structure includes a first gate structure, a first spacer on each sidewall of the first gate structure, and a first source/drain region with a first lightly doped drain (LDD) structure located in the substrate at each side of the first gate structure, and the second MOS transistor isolated by a second isolation structure includes a second gate structure, a second spacer on each sidewall of the second gate structure, and a second source/drain region with a second LDD structure located in the substrate at each side of the second gate structure, the method comprising:forming a metal layer over the substrate, wherein the metal layer is conformal to the substrate;forming a patterned photoresist layer on the metal layer;patterning the photoresist layer to expose a portion of the metal layer, wherein under the exposed portion of the metal layer it comprises the second spacer, a portion of the second source/drain region, and the second isolation structure;removing the exposed portion of the metal layer, using the photoresist layer as a mask;continuously removing the second spacer so as to expose the second source/drain region and the second LDD structure;performing an ion implantation process, still using the photoresist layer as a mask, so as to merge the second LDD structure with the second source/drain region into a third source/drain region for the second MOS transistor;removing photoresist layer so as to expose the remaining metal layer; andforming a self-aligned silicide (Salicide) layer on the first source/drain region, the first gate structure, the second gate structure, and a portion of the third source/drain region through using the metal layer.