Low-K factor of SiO2 layer on Si irradiated by YAG:Nd laser

The change of optical and electrical properties of SiO2 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 SiO2 layer with thickness 0.75 mu m 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 mu m did not change color after irradiation. We explain such peculiarities of optical properties by change of optical path. Capacity (C) measurements of SiO2 layer with thickness 0.21 mu m 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 SiO2 layer increases. Atomic force microscope and profilemeter measurements did not show any change of surface roughness for the SiO2 layer with thickness 0.21 mu m. We suppose that after irradiation of the SiO2 layer decrease of K takes place due to the formation of nanopores in SiO2 or/and generation of the charged point defect at the interface Of Si-SiO2. Particularly the first is in agreement with measurements of micro hardness and capillary effect. (c) 2007 Elsevier B.V. All rights reserved.