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Boron trifluoride BF3 is one of the commonly used materials for p-type implant. In the plasma, there
are combinations of dissociative, ionized radicals, and recombined molecules. Boron has two
isotopes, which are boron 10 10B (19.9%) and boron 11 11B (80.1%). Thus, in the plasma state are a
number of ion types, which are 10B (10g), 11B (11g), 10BF (29g), 11BF (30g), F2 (38g), 10BF2 (48g),
and 11BF2 (49g). The figure in the parenthesis indicates the atom weight or molecular weight. For pwell implantation, the lighter weight 11B + is preferred because it can penetrate deeper into silicon
substrate. For shallow junction implant, 11BF2 + is preferred because of it large size and heavy
weight. At the lowest energy level, an ion implanter can provide 11BF2 + ion for shallowest ptype
junction implant.