Application of VUV irradiation to promote the wet etch resistance of PSZ-SOG film inside the gap

In this paper, we demonstrate that vacuum ultraviolet (VUV) irradiation was effective to promote the wet etch resistance of perhydro-polysilazane-based inorganic spin-on-glass (PSZ-SOG) film inside the gap. The baking condition of VUV irradiation was chosen at 150 °C in 0.2 Pa before furnace curing process. Observed the densification characteristics of various trench sizes (aspect ratio (AR) = 3.1–0.13), all densification coefficient (Deff) of the samples with VUV irradiation were larger than 0.90. On the contrary, for the sample without VUV irradiation, a remarkable reduction of Deff values from 0.99 to 0.58 was found while the AR increasing from 0.13 to 3.1. The better densification characteristics of PSZ-SOG films were mainly contributed to the VUV photon. Compared with the reaction mechanisms during VUV irradiation and furnace curing, VUV photon is responsible for triggering the Si–N bond dissociation and accelerating the conversion rate of PSZ. Finally, the new reaction mechanism makes SOG films denser at STI region without additional thermal budget.