Rapid thermal annealing of boron-implanted silicon using an ultrahigh power arc lamp

Abstract

We have used an ultrahigh powered, 100-kW vortex cooled arc lamp to anneal 75-mm-diam 〈100〉 silicon wafers implanted with various doses of 50-keV B+ and BF+2 ions. Sheet resistivity measurements, secondary ion mass spectrometry, and transmission electron microscopy have been used to characterize the annealed wafers. Standard diffusion coefficients predict little dopant movement in the temperature (∼1200°C) and time (∼1 s) region we studied. However, boron atoms which have been channeled relatively deep into the silicon and left in interstitial positions move ∼100 nm in ∼1 s at low temperatures, then stop. We presume that they encounter a vacancy and become substitutional. The dopant diffusion rate then is close to equilibrium values, and there is little measurable movement between 900 and 1250°C. A 3-s lamp cycle with maximum wafer temperature 1230°C is sufficient to fully activate a 10 14 cm-2 BF+2 implant and leave the material with no extended defects. The dopant half-width and junction depth are 50 and 250 nm for the as-implanted sample, and 90 and 340 nm for the annealed sample.