Efficiency and thermal stability of Pt gettering in crystalline Si

Abstract

We have investigated the efficiency and the thermal stability of Pt gettering at different sites in crystalline Si. In particular, we compared 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. These sites were introduced on one side of wafers containing a uniform Pt concentration in the range 1×1013–5×1014 atoms/cm3. The uniform concentration of Pt was attained by means of Pt implantation followed by a high-temperature thermal process. The gettering efficiency of the different sites was monitored during thermal processes at 700 °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 °C during which part of the gettered Pt is released in the bulk of the wafer. The kinetics of Pt gettering at the different sites is found to be similar since it is fully dominated by the kick-out diffusion mechanism of the metal impurity. The thermal stability is instead site-dependent and can be described in terms of an effective binding enthalpy of 1.9, 2.6, and 3.0 eV between Pt atoms and cavities, P-doped region, and ion-implantation damage, respectively. The physical meaning of the binding enthalpy is investigated and discussed.