Fluorine-enhanced boron diffusion in germanium-preamorphized silicon

Silicon wafers were preamorphized with 60 keV Ge+ or 70 keV Si+ at a dose of 1× 1015 atoms cm2. F+ was then implanted into some samples at 6 keV at doses ranging from 1× 1014 to 5× 1015 atoms cm2, followed by B+11 implants at 500 eV, 1× 1015 atoms cm2. Secondary-ion-mass spectrometry confirmed that fluorine enhances boron motion in germanium-preamorphized materials in the absence of annealing. The magnitude of boron diffusion scales with increasing fluorine dose. Boron motion in as-implanted samples occurs when fluorine is concentrated above 1× 1020 atoms cm3. Boron atoms are mobile in as-implanted, amorphous material at concentrations up to 1× 1019 atoms cm3. Fluorine directly influences boron motion only prior to activation annealing. During the solid-phase epitaxial regrowth process, fluorine does not directly influence boron motion, it simply alters the recrystallization rate of the silicon substrate. Boron atoms can diffuse in germanium-amorphized silicon during recrystallization at elevated temperatures without the assistance of additional dopants. Mobile boron concentrations up to 1× 1020 atoms cm3 are observed during annealing of germanium-preamorphized wafers. © 2005 American Institute of Physics.