Thermal activation of shallow boron-ion implants

Boron implanted into n-type Si at 10(15) cm(-2) dose and energies from 500 eV to 1 keV was activated by annealing in nominally pure N-2 and in N-2 wit h small admixtures of O-2. Effective process times and temperatures were de rived by thermal activation analysis of various heating cycles. The lowest thermal budgets used "spike anneals" with heating rates up to 150 degrees C /sec, cooling rates up to 80 degrees C/sec, and minimal dwell time at the m aximum temperature. Dopant activation was determined by sheet electrical tr ansport measurements. Surface oxidation was characterized by film thickness ellipsometry. P-n junction depths were inferred from analysis of sheet ele ctrical transport measurements and secondary ion mass spectroscopy profiles . Boron activation increases with boron diffusion from the implanted region . Electrical activation has a thermal activation energy near 5 eV, while bo ron diffusion has an activation energy near 4 eV. Surface oxide can retard boron diffusion into the ambient for high-temperature anneals.