EFFECTS OF RAPID THERMAL ANNEALING ON THE FORMATION OF SHALLOW P+N JUNCTION BY IMPLANTING BF2+ IONS INTO THIN METAL-FILMS ON SI SUBSTRATE .2. THIN COBALT FILMS

Abstract

The effects of rapid thermal annealing (RTA) on the formation of shallow p+ n junctions by the implantation of BF2+ ions into thin Co films and subsequent silicidation/drive-in have been studied. The junction formation by various implant conditions has been characterized to correlate with the dopant drive-in efficiency, defects in junctions, and junction depth under different anneal conditions. Optimum junctions were achieved by the 700-degrees-C anneal in all the present implant conditions. Annealing at 800-degrees-C degraded the junction formation due to the considerable formation of Co-B compounds caused by the high heating rate and high-temperature processings. Higher implant energy greatly lessened the dopant confinement due to deeper as-implanted dopant profile. Conventional furnace annealing (CFA) considerably enhanced the drive-in efficiency, while RTA is superior to CFA in annihilating damage, activating dopant, and forming shallow junctions. The benefits of RTA are particularly obvious for the implants of low-energy, low-dosage and high-energy, high-dosage. Consequently, low-temperature RTA processings can achieve silicided shallow p+ n junctions with good rectifying characteristics.