THE IMPACT OF TITANIUM SILICIDE ON THE CONTACT RESISTANCE FOR SHALLOW JUNCTION FORMED BY OUT-DIFFUSION OF ARSENIC FROM POLYSILICON

Abstract

A novel technology of Ti-polycided shallow junctions formed by out-diffusion of As+ from polysilicon was proposed and investigated. Junction depth as shallow as 0.1 mum and leakage current density as small as 0. 4 nA/cm2 can be easily obtained by this process. Contact resistance measurements show that the presence of a deliberately grown interfacial oxide leads to a significant increase in the contact resistance and small values of the specific contact resistivity (4 approximately 7 x 10(-7) OMEGA-cm2) can be obtained if Ti thicknesses are larger than half of polysilicon thicknesses. This is due to the polysilicon layer had been consumed completely and the interfacial oxide would be broken under the silicidation process. This implies that the contact resistance is mainly determined by the polysilicon/mono-silicon interface property and it is necessary to eliminate the interfacial oxide for a good contact system.