Kinetics of arsenic segregation at grain boundaries in polycrystalline silicon

By comparison between chemically and electrically active As concentrations in polycrystalline silicon thin films with a well-stabilized grain size, the equilibrium segregation coefficient relating the grain boundary and the Si grain is experimentally obtained in the 750-1000 degrees C temperature range. Moreover, by using isothermal short anneals, it has been possible to study the kinetics of the segregation phenomena. it is found that the time constant corresponding to the achievement of the equilibrium state strongly depends on the annealing temperature. The kinetics coefficients controlling the rates of exchange between the grains and the grain boundaries have been extracted on the basis of a simple kinetics model. The technological relevance of these results for the doping control of the polycrystalline silicon layers is pointed out.