p-type dopant

P-type dopants are acceptor elements from Group III of the periodic table—primarily boron (B), with indium (In) and gallium (Ga) used in specialized applications—that create holes (positive charge carriers) in the silicon lattice for forming PMOS transistors, p-wells, and p-type junctions. Boron is the dominant p-type dopant in semiconductor manufacturing due to its high solid solubility (~3×10²⁰ cm⁻³ at 1000°C), well-characterized diffusion behavior, and availability in multiple implant species. BF₂⁺ is commonly used instead of B⁺ for shallow implants—the heavier molecular ion (49 amu vs. 11 amu for boron) achieves shallower junction depths at the same implant energy, and the co-implanted fluorine reduces boron transient enhanced diffusion (TED) during annealing. Boron's light mass makes it highly susceptible to channeling in crystalline silicon—implant tilt (typically 7°) and pre-amorphization implants (PAI using Ge or Si) are employed to minimize channeling tails. Boron also exhibits significant TED during post-implant annealing, where excess interstitials from implant damage accelerate boron diffusion beyond equilibrium rates—this is a major challenge for ultra-shallow p-type junctions at advanced nodes. Indium has been investigated as an alternative p-type dopant for channel engineering due to its heavier mass (115 amu) enabling abrupt profiles, but lower solid solubility limits its application. Doses range from 1×10¹² cm⁻² for threshold adjust to 3×10¹⁵ cm⁻² for source/drain implants.