The effect of some impurities on the annealing behaviour of ion-implanted silicon

The annealing behaviour of ion-implanted <100> silicon containing various low-melting point, low-solubility impurities has been studied. The analysis techniques used include, Rutherford backscattering and channeling, transmission electron microscopy and time-resolved reflectivity measurements. Various annealing regimes have been identified corresponding to different implanted concentrations. For low concentrations, complete epitaxial regrowth and incorporation of the implanted impurity onto substitutional silicon lattice sites is observed. For concentrations that exceed the equilibrium solid solubility of the impurity in crystalline silicon, impurity segregation is seen at the amorphous-crystalline interface. For higher concentrations, an impurity induced amorphous to polycrystalline phase transformation is observed that is characterised by a thermal activation energy of 1.5-2.5 eV depending on the impurity. The annealing behaviour of <111> silicon implanted with low dose impurities is also discussed. In this case, the presence of impurities appears to assist the crystallisation process. 5 refs