The temporal evolution of B diffusion after ion implantation, and annealing at 800 or 900C, was studied by means of secondary ion mass spectrometry and spreading resistance profiling. The temporal evolution at 800C was monitored in both crystalline and devitrified samples. The amorphized samples exhibited near-normal concentration enhanced diffusion. The crystalline samples exhibited anomalous transient diffusion, with a rapidly diffusing low-concentration region and a static peak region above a critical concentration of 3.5 x 1018/cm3. The peak region above this critical concentration was electrically inactive. The static inactive B was released over many hours, as compared with the transient diffusion enhancement; which returned nearly to normal within 0.5h. The temporal evolution of B diffusion at 900C was studied as a function of the implantation dose. A critical concentration, for transient diffusion, of 8 x 1018/cm2 was observed at this temperature; regardless of the dose. The transient enhancement in the diffusing part of the B profile increased with increasing dose up to a value of about 5 x 1014/cm3, and saturated at higher doses. The results were explained in terms of a non-equilibrium point-defect model for diffusion which involved intermediate defect formation.

N.E.B.Cowern, K.T.F.Janssen, H.F.F.Jos: Journal of Applied Physics, 1990, 68[12], 6191-8