Electron beam Annealing of Shallow BF₂ Implantations

Abstract

A multiple scan electron beam system has been used to anneal silicon implanted with BF2 (25 Kev, 1, 2 and 5 × 1015 ions × cm−2 ). The annealing temperatures range from 1000 to 1200° C and the annealing times from 3 to 18 seconds. The curves of sheet resistance as a function of annealing time show a minimum. The increase in sheet resistance at longer annealing times is due to boron outdiffusion. Junction depths have been measured by spreading resistance and are presented. For implanted doses below 2 × 1015 ions × cm−2 boron outdiffusion limits the sheet resistance value at about 100 R Ωand this minimum value corresponds to an increase in junction depths of about 500 Å. For implanted doses of 5 × 1015 ions ×cm−2, 60 Ω sheet resistance can be obtained, but with about 1000 Å increase in junction depth.