TRANSIENT DIFFUSION OF ION-IMPLANTED B IN SI - DOSE, TIME, AND MATRIX DEPENDENCE OF ATOMIC AND ELECTRICAL PROFILES

The time evolution of B diffusion and electrical activation after ion implantation and annealing at 800 and 900-degrees-C is studied using secondary-ion mass spectrometry and spreading-resistance profiling. The time evolution at 800-degrees-C is observed in both crystalline and post-amorphized samples. Amorphized samples show near-normal concentration enhanced diffusion. Crystalline samples show anomalous transient diffusion, with a rapidly diffusing low-concentration region and a static peak region above a critical concentration C(enh) = 3.5 X 10(18) cm-3. The peak region above C(enh) is shown to be electrically inactive. The static, inactive B is released over a period of many hours, compared with the transient diffusion enhancement which relaxes to near-normal within 30 min. The time evolution of B diffusion at 900-degrees-C is observed as a function of implantation dose. A critical concentration for transient diffusion, C(enh) = 8 X 10(18) cm-2, independent of dose, is observed at this temperature. The transient diffusion enhancement in the diffusing part of the B profile increases with dose, up to a dose of approximately 5 X 10(14) cm-3, and saturates at higher doses. A comparison with published data shows that C(enh) approximately n(i) within a factor 2 over the temperature range 550-900-degrees-C. We interpret our observations in terms of a nonequilibrium point-defect model of diffusion and intermediate defect formation.