AMORPHISATION, CRYSTALLISATION AND RELATED PHENOMENA IN SILICON.
Abstract
This review examines recently observed phenomena associated with amorphisation and crystallisation of silicon under ion bombardment and furnace annealing. Ideally, heavy ion damage should completely amorphise the silicon surface layers so that the underlying crystal can provide a perfect template for subsequent epitaxial growth. However, in practise the ion bombardment and annealing behaviour can be decidedly more complex. During ion bombardment of silicon, several correlated processes can take place depending on the target temperature and the precise bombardment conditions. These processes include: defect production; amorphisation; diffusion and segregation of defects and impurities; and ion-beam-induced (epitaxial) crystallisation. During subsequent heat treatment, amorphous layers can exhibit anomalous impurity diffusion and precipitation effects, nucleation of random crystallites, and solid phase epitaxial growth. In addition, the kinetics of the epitaxial growth process are sensitive to the type and state of implanted impurities present in the silicon. Correlations between all of these phenomena provide considerable insight into impurity and defect behaviour in amorphous and crystalline silicon, and a better understanding of the amorphous to crystalline phase transition.