Furnace annealing behavior of B-doped poly-SiGe formed on insulating film

Furnace-annealing behavior of B-doped poly-SiGe on insulating films has been investigated. With increasing Ge fraction, thermal stability of electrically active B atoms at a supersaturated concentration was significantly improved, for example, the stability at 800°C for poly-Si_0.6Ge_0.4 films was nine times as high as that for poly-Si films. The deactivation process consists of the fast and slow processes. The fast process was due to sweeping out of B atoms from substitutional to interstitial sites, enhanced by a local strain induced by the difference in atomic radii between Si and B atoms, and the slow process was due to trapping of B at grain boundaries during grain growth by annealing. The improved thermal stability of B atoms is due to the local strain compensation by Ge doping.