Method of forming ultra-shallow junctions in a semiconductor wafer with deposited silicon layer to reduce silicon consumption during salicidation

摘要

A method for forming ultra shallow junctions in a semiconductor wafer with reduced silicon consumption during salicidation supplies additional silicon during the salicidation process. After the gate and source/drain junctions are formed in a semiconductor device, high resistivity metal silicide regions are formed on the gate and source/drain junctions. Silicon is then deposited in a layer on the high resistivity metal silicide regions. An annealing step is then performed to form low resistivity metal silicide regions on the gate and source/drain junctions. The deposited silicon is a source of silicon that is employed as a diffusion species during the transformation of the high resistivity metal silicide (such as CoSi) to a low resistivity metal silicide (such as CoSi2). Since the additional silicon provided in the deposited layer is consumed, there is reduced consumption of the silicon from the ultra-shallow junctions, thereby preventing the bottom of the silicide regions from reaching the bottom of the source/drain junctions.