Implant and Anneal Methods for PMOS Gates

Processing procedures for advanced PMOS applications include growth of thin oxide or oxynitride films for the gate insulator, chemical vapor deposition of the Si film gate electrode, low-energy B implantation, and various rapid thermal anneal cycles. The anneal is intended to diffuse B dopant from the implanted region near the surface to the gate oxide interface, creating in the ideal case a high active carrier concentration in the poly-Si at the interface with negligible diffusion of B through the oxide to the Si channel. This work considers aspects of thermal annealing that may achieve the desired goals. Phenomenological diffusivities of B in poly-Si and SiO sub 2 and associated effective activation energies are determined from measurements of B distribution profiles by secondary ion mass spectroscopy and from MOS capacitance-voltage measurements.