Low- K factor of SiO 2 layer on Si irradiated by YAG:Nd laser

Abstract

The change of optical and electrical properties of SiO 2 layer on Si single crystal exposed to YAG:Nd laser radiation has been found experimentally. The second harmonic of YAG:Nd laser was used as a source of light. Before irradiation the SiO 2 layer with thickness 0.75 μm had red color in reflecting light due to the interference. After irradiation with the laser with intensity of more than 3.5 MW/cm 2 red color changed to yellow. However, samples with thickness 0.21 μm did not change color after irradiation. We explain such peculiarities of optical properties by change of optical path. Capacity ( C) measurements of SiO 2 layer with thickness 0.21 μm by the method of capacity–voltage characteristics have shown a decrease of C to more than 40%. It is possible if real part of dielectric permittivity ( K) decreases or thickness of the SiO 2 layer increases. Atomic force microscope and profilemeter measurements did not show any change of surface roughness for the SiO 2 layer with thickness 0.21 μm. We suppose that after irradiation of the SiO 2 layer decrease of K takes place due to the formation of nanopores in SiO 2 or/and generation of the charged point defect at the interface of Si–SiO 2. Particularly the first is in agreement with measurements of micro hardness and capillary effect.