Improvement of the spin-on-glass process by ion implantation for highly reliable MOS devices

We have developed a novel process for intermetal dielectrics (IMD) using ion-implanted organic spin-on glass (SOG). Ion implantation into the SOG films improves the hot carrier (HC) reliability, which deteriorates from the use of organic SOG films. The content of mobile water-related species in the organic SOG films, which was examined by thermal desorption spectrometry (TDS), is reduced by Ar+-ion implantation under the conditions of 140 keV, 1 × 1015 ions/cm2; while on the contrary, the content of mobile hydrogen in SOG is increased by ion implantation. The change in the mechanical stress due to ion implantation is small, because ion implantation shrinks SOG only in the direction vertical to the wafer surface. Thus the change in stress due to ion implantation scarcely affect the electrical characteristics of the underlying MOS-FET. Therefore the deterioration of HC reliability for the MOS devices with SOG as IMD is well explained by a water diffusion model rather than by a hydrogen diffusion and mechanical stress model.