EFFICIENCY AND THERMAL-STABILITY OF PT GETTERING IN CRYSTALLINE SI

We have investigated the efficiency and the thermal stability of Pt ge ttering at different sites in crystalline Si, In particular we compare d the gettering performances of heavily n-type doped regions formed by P diffusion, cavities formed after high-temperature annealings of He implanted Si, and damage induced by ion implantation of B, C, or Si. T hese sites were introduced on one side of wafers containing a uniform Pt concentration in the range 1x10(13)-5x10(14) atoms/cm(3). The unifo rm concentration of Pt was attained by means of Pt implantation follow ed by a high-temperature thermal process. The gettering efficiency of the different sites was monitored during thermal processes at 700 degr ees C for times ranging from 1 to 48 h. Thermal stability of gettering was investigated with a subsequent thermal process in the temperature range 750-900 degrees C during which part of the gettered Pt is relea sed in the bulk of the wafer. The kinetics of Pt gettering at the diff erent sites is found to be similar since it is fully dominated by the kick-out diffusion mechanism of the metal impurity. The thermal stabil ity is instead site-dependent and can be described in terms of an effe ctive binding enthalpy of 1.9, 2.6, and 3.0 eV between Pt atoms and ca vities, P-doped region, and ion-implantation damage, respectively. The physical meaning of the binding enthalpy is investigated and discusse d. (C) 1996 American Institute of Physics.