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^oC in 0.2Pa before furnace curing process. Observed the densification characteristics of various trench sizes (aspect ratio (AR)=3.1-0.13), all densification coefficient (D"e"f"f) of the samples with VUV irradiation were larger than 0.90. On the contrary, for the sample without VUV irradiation, a remarkable reduction of D"e"f"f 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.