Redistribution of Boron and Fluorine Atoms in BF2 Implanted Silicon Wafers during Rapid Thermal Annealing

Abstract

Rapid thermal annealing (RTA) of 49BF2+ (70 keV, 1×1015 cm-2) implanted Si wafers (200 mm in diameter) was carried out using a single wafer furnace-type system and a lamp-based system. Sheet resistance and the uniformity of implanted wafers were measured after annealing under various annealing conditions. Boron and fluorine depth profiles were investigated using secondary ion mass spectroscopy (SIMS) after annealing. Boron atoms diffuse into bulk crystal as annealing progresses, while fluorine atoms move towards the surface and form two peculiar peaks around 65 nm and 105 nm from the surface, regardless of annealing conditions. A significant increase in sheet resistance due to boron clustering near the F peaks was observed in wafers annealed at 1100°C using a lamp-based system. The effects of annealing method, temperature and time on dopant redistribution were discussed.