Silicon wafers were pre-amorphized with 60keV Ge+ or 70keV Si+ at a dose of 1015/cm2. F+ was then implanted into some samples at 6keV at doses ranging from 1014 to 5 x 1015/cm2, followed by 11B+ implants at 500eV, 1015/cm2. Secondary-ion-mass spectrometry confirmed that F enhanced B motion in germanium-preamorphized materials in the absence of annealing. The magnitude of B diffusion scales with increasing F dose. Boron motion in as-implanted samples occurred when F was concentrated above 1020/cm3. Boron atoms were mobile in as-implanted, amorphous material at concentrations up to 1019/cm3. Fluorine directly influences B motion only prior to activation annealing. During the solid-phase epitaxial regrowth process, F did not directly influence B motion, it simply alters the recrystallization rate of the Si substrate. Boron atoms could diffuse in germanium-amorphized Si during recrystallization at elevated temperatures without the assistance of additional dopants. Mobile B concentrations up to 1020/cm3 were observed during annealing of Ge pre-amorphized wafers.

Fluorine-Enhanced Boron Diffusion in Germanium-Preamorphized Silicon. J.M.Jacques, K.S.Jones, L.S.Robertson, A.Li-Fatou, C.M.Hazelton, E.Napolitani, L.M.Rubin: Journal of Applied Physics, 2005, 98[7], 073521 (6pp)