Resistivity changes in laser-annealed polycrystalline silicon during thermal annealing

Polycrystalline silicon layers heavily doped with phosphorus or arsenic were irradiated with a Nd : YAG pulsed laser beam. A 40–50% reduction in sheet resistivity was obtained by laser annealing. However, during subsequent heat treatments the resistivity increased to a value which was higher than the initial value before the laser anneal. The instability of the resistivity is tentatively explained by reprecipitation of dopants both within the grains and at the grain boundaries.