Process for formation of shallow silicided junctions

A method for forming semiconductor junctions in a silicon substrate, comprising:

• forming a region of a first conductivity type in the substrate;
• forming a conductive layer on the substrate having a top surface and a sidewall;
• forming a conformal layer of refractory metal on the substrate and the conductive layer;
• reacting the portion of the refractory metal contacting the surface of the silicon to form a silicide;
• implanting impurity materials of a second conductivity type through the surface of the silicide;
• after said implanting removing the portions of the refractory metal layer not reacted to form silicide;
• and
• driving the implanted impurities downward into the substrate to form a metallurgical junction between the first and second conductivity types beneath the silicide.

A method for forming a semiconductor device in a silicon substrate, comprising:

• forming a plurality of active areas on the substrate, each separated by a layer of thick field oxide;
• forming at least one gate electrode of polycrystalline silicon having a top surface and sidewalls on one of the active layers and separated from the surface of the silicon by a layer of gate oxide;
• selectively forming a layer of oxide on the sidewalls of the gate electrode;
• forming a conformal layer of refractory metal on the substrate;
• reacting the portions of the layer of refractory metal contacting the surface of the silicon and the top surface of the gate electrode to form a silicide;
• implanting impurity materials of a second conductivity type through the surface of the silicide to a first dosage;
• after said implanting removing the portions of the refractory metal layer not reacted to form a silicide;
• and
• driving the implanted impurities into the silicon to form a metallurgical junction between the first and second conductivity types beneath the silicide.

A method forming silicided source/drain regions in an MOS transistor having an active region formed on a substrate and a gate electrode disposed over the active region and separated therefrom by a layer of oxide to define a channel region, comprising:

• forming a sidewall oxide on the vertical surfaces of the gates;
• forming a layer of refractory metal over the substrate;
• reacting the refractory metal layer to form a silicide at the portions of the refractory metal layer contacting the silicon and the active regions on the opposite sides of the gate electrode;
• implanting impurities of a conductivity type opposite that of the substrate through the surface of silicided layers and the unsilicided portions of the refractory metal layer;
• after said implanting removing the unsilicided portions of the refractory metal layer;
• and
• driving the impurities down into the substrate.