Effects of High Dose BF2+ Implant on the Improvement of P+ Contact Resistance

This paper describes the effect of Ti deposition/anneal and supplementary BF₂ implant/anneal on a 0.35 mum silicon CMOS process using contact silicided P+ source- drain. Thicker Ti and higher Ti/TiN annealing temperature are also required for the smaller contact sizes to get adequate P+ contact resistance. The supplementary BF₂ implant with dose of 3E14 cm^-2 and energy 20KeV helped to reduce and stabilize the contact resistance down to 150 Ohm/hole for the 0.4 mum P+ contact. The Boron profile at the TiSi₂/p⁺ interface were investigated by 2D ATHENA process simulation. The peak Boron doping level at TiSi₂/p+ interface significantly influenced the contact resistivity. Various contact chain test structures, with different contact sizes, plus single Kelvin structures were used in this investigation.