The comparative study of thermal stability among silicon dioxide, fluorinated silicate glass, hydrogen silsesquioxane, and organosilicate glass dielectrics on silicon

This study investigates the thermal stability of thermally grown silicon dioxide (thermal SiO2), fluorinated silicate glass (FSG), hydrogen silsesquioxane (HSQ), and organosilicate glass (OSG). Samples with and without sputtered copper films, as-prepared and after annealing at 200 ∼ 800 °C in vacuum, have been investigated by various methods of analysis. For the as-prepared dielectrics, it is found that the densities of HSQ and OSG are less than those of SiO2 and FSG due to the greater roughness and more porous structure of HSQ and OSG. After annealing at 800 °C, the HSQ structure converts to a SiO2-like structure, which is mainly due to decomposition of HSQ. Furthermore, the methyl groups and oxygen atoms are also liberated from OSG after high temperature annealing. A plateau in the Cu profile near the Cu/dielectric interface is observed in the results of secondary ion mass spectrometry after annealing at 450 °C. On the other hand, penetration of Cu atoms across the interface between Cu and HSQ, and across the interface between Cu and OSQ, are observed for Cu/HSQ and Cu/OSG systems after annealing at 450 °C. The thermal stability of these four dielectrics are discussed and compared.