J un 2 01 9 Ultraslow Dynamic Annealing of Neutron-induced Defects in n-type Silicon

Neutron bombardments with equivalent fluence (1×10 cm) and different fluxes have been performed on one kind of bipolar transistor and two kinds of bipolar circuits. The base currents or input bias currents of almost all samples are found to decrease with increasing neutron flux, implying that the strength of the dynamic annealing of divacancy defects (V−2 ) in n-type silicon follows a positive flux dependence. Such flux dependence is the same as that observed in ions implantation using protons, boron, carbon, and other heavy ions, but the transition flux in our experiment (∼ 1×10 cms) is 4 orders of magnitudes lower than that of proton bombardment, despite the similarity in the masses and energies of the two particles. A new model considering dissipation of diffused Si interstitials was proposed for the flux effect, in which the huge discrepancy in transition fluxes is attributed to the presence of vast charge carriers in proton bombardments, which strongly accelerate the dynamic annealing of defects by enhancing the diffusion velocity of Si interstitials. Our work would contribute to the understanding of the defect buildup processes in silicon.