EFFECT OF PLASMA TREATMENT ON THE DENSITY OF DEFECTS AT AN AMORPHOUS SI-H-INSULATOR INTERFACE

Interface state density between a-Si:H and an insulating film (a-SiN1. 7:H or a-SiO2.0) was measured by photothermal deflection (PD) spectros copy and electron spin resonance. While the interface state density in a-SiN1.7:H on a-Si:H structure was smaller than the free surface stat e density on a-Si:H, that in a-SiO2.0:H on a-Si:H structure was larger than the free surface state density of a-Si:H. The difference in the surface state density between these specimens was discussed in terms o f plasma surface reaction. The effect of plasma reaction was examined by treating the surface of the a-Si:H layer by the plasma of NH3 or N2 O gas which were dominant constituents of the source gases used to dep osit the insulating layers. The PD spectral shape of a-SiO2.0 on a-Si: H was similar to N2O plasma-treated a-Si:H and that of the a-SiN1.7:H on a-Si:H structure was similar to NH3 plasma-treated a-Si:H. These re sults indicate that the interface defects in the a-SiO2.0 on a-Si:H st ructure were induced by the plasma reaction of the source gas with the surface of a-Si:H at the initial stage of deposition. The interface s tate densities in a-Si:H on a-SiN1.7:H and a-Si:H on a-SiO2.0 interfac es were smaller than those of a-SiN1.7:H on a-Si:H and a-SiO2.0 on a-S i:H, respectively. These differences in the interface defect density w ere due to the difference in the precursor used to deposit the upper l ayer. Chemical reaction on the surface of a-Si:H with a source gas ind uces interface defects at the initial stage of the deposition of the i nsulating layer. This surface chemical reaction was investigated by va rying the condition of plasma species at the surface of a-Si:H. (C) 19 98 American Institute of Physics.