AN EXCIMER-LASER-BASED NANOSECOND THERMAL-DIFFUSION TECHNIQUE FOR ULTRA-SHALLOW PN JUNCTION FABRICATION

In this paper we review the development of nanosecond thermal diffusion (NTD), a new doping technology which utilizes excimer-laser-induced heating to incorporate and diffuse impurities in silicon wafers. With thermal anneals less than 200 ns in duration, the new laser-based method permits simple, low-temperature fabrication of the ultrashallow p-n junctions necessary for deep-submicrometer MOS and bipolar transistors. In a multifaceted research effort, we are building advanced equipment, developing accurate simulation tools, and designing effective process flows to demonstrate the viability of the NTD technique for manufacturing applications. To date we have fabricated p+-n and n+-p diodes with 300 angstrom junction depth, submicrometer PMOS transistors, and narrow-base regions in bipolar devices. Included in our results are: ultra-shallow diodes with ideality factors of 1.01-1.10 over seven decades of current, reverse leakage currents less than 10 nA/cm2 at 5 V reverse bias, and breakdown voltages in excess of 100 V, MOS devices that demonstrate excellent short channel behavior and no threshold voltage shift at submicrometer gate lengths, and bipolar transistors that incorporate base widths which range from 700 angstrom to 1200 angstrom and exhibit current gains between 50 and 200.