Method of forming junction-leakage free metal salicide in a semiconductor wafer with ultra-low silicon consumption

Abstract

A method for forming ultra shallow junctions in a semiconductor wafer uses disposable spacers and a silicon cap layer to achieve ultra-low low silicon consumption during a salicide formation process. A refractory metal layer, such as a cobalt layer, is deposited over the gate and source/drain junctions of a semiconductor device. Silicon nitride disposable spacers are formed over the metal layer in the region of the sidewall spacers previously formed on the sidewalls of the gate. A silicon cap layer is deposited over the metal layer and the disposable spacers. Rapid thermal annealing is performed to form the high-ohmic phase of the salicide, with the disposable spacers preventing interaction and between the cobalt and the silicon in the area between the gate and the source/drain junctions along the sidewall spacers. The silicon cap layer provides a source of silicon for consumption during the first phase of salicide formation, reducing the amount of silicon of the source/drain junctions that is consumed.