The mechanisms which were involved in the gettering of Pt atoms in crystalline material were considered. By carrying out Pt implantation at various fluences, followed by thermal processing (970C, 5h), it was possible to prepare crystalline wafers which contained uniform Pt concentrations that ranged from 2 x 1012 to 2 x 1014/cm3. A heavily doped n-type region was then produced on one side of the wafer by carrying out P diffusion at 900C. A study was made of the kinetics of Pt gettering to the P-doped region, at temperatures of between 700 and 970C, during annealing times that ranged from 0.5 to 48h. Lifetime measurements, performed using a contact-less technique, detected a Pt depletion of the wafer bulk that was due to the gettering. The large range of initial Pt concentrations that were used permitted the identification and separation of the kinetic and thermodynamic constraints which determined the gettering efficiency. It was found that the gettering kinetics were driven by the dissolution of immobile substitutional Pt atoms at interstitial sites. This process was assisted by Si self-interstitials and was characterized by an activation energy of 0.4eV. The equilibrium Pt distribution was governed by the segregation coefficient of Pt atoms between the gettering sites and the matrix. This segregation coefficient, and therefore the gettering efficiency, decreased when the temperature was increased; with an associated activation energy of 2.5eV.

S.Coffa, G.Franco, C.M.Camalleri, A.Giraffa: Journal of Applied Physics, 1996, 80[1], 161-6