Impact of High-Energy Particle Irradiation on Polycrystalline Silicon Films

摘要

The degradation of polycrystalline silicon films, subjected to 20-MeV alpha ray irradiation, is studied. To investigate the radiation source dependence, 20MeV proton and 1-MeV electron irradiation have been performed as well. The degradation of the base resistor of a silicon bipolar transistor is also reported in order to enable a comparison of the radiation damage for different configurations and materials. The damage of alpha rays is one and three orders of magnitude large than for protons and electrons. The radiation source dependence of the performance degradation is attributed to the difference of mass and the probability of nuclear collisions for the formation of lattice defects. Poly-Si resistors are more rad-hard than base resistors. This is mainly due to the thickness difference of the junction and the oxide. The trap density for alpha rays is larger than for protons and that a negligible fluence dependence is observed. It is concluded that the degradation of the poly-Si films by high-energy particle irradiation is caused by the induced lattice defects in the grain itself rather than at its boundaries.