Effect of vacuum ultraviolet and ultraviolet irradiation on mobile charges in the bandgap of low- k -porous organosilicate dielectrics

Capacitance-voltage ( C - V ) measurements are used to determine the effect of vacuum ultraviolet (VUV) and ultraviolet irradiation on mobile charges in porous low- k organosilicate (SiCOH) dielectrics. Hysteresis in the C - V characteristics shows that VUV irradiation increases the number of mobile charges in the dielectric. This is because VUV photons excite the trapped electrons from defect states to make them mobile carriers. Conversely UV reverses this effect by reducing the mobile charges through photoemission of free electrons and repopulation of trap states. Thus UV irradiation can be used to improve the electrical properties of plasma-processed dielectrics that are subjected to VUV irradiation.