Phosphorus redistribution in P-doped polycrystalline silicon/tantalum silicide system during high temperature sintering

Abstract

We studied redistribution of phosphorus between layers of P-doped polycrystalline silicon and TaSi2 during sintering of the silicide at 900 °C. Because of the loss of phosphorus to the silicide, the sheet resistivity of polysilicon layers is increased. We attempted a systematic study of this effect using polysilicon layers of varying thicknesses (from less than 1000 to more than 6000 Å). The experimental results are in excellent agreement with our model which regards the concentrations of phosphorus in both polysilicon and silicide as dilute solutions and assumes that during sintering of the silicide these solutions come to equilibrium. From the equilibrium condition of uniform chemical potential with respect to the solute, we were able to determine the distribution coefficient of P between the two solvents.