Mechanistic study of borosilicate glass growth by low-pressure chemical vapor deposition from tetraethylorthosilicate and trimethylborate

A reaction mechanism and film morphology as a function of reactor condition s and post growth thermal annealing for borosilicate glass (BSG), (SiO2)(x) (B2O3)(1-x), films deposited from tetraethylorthosilicate (TEOS), trimethyl borate (TMB), and oxygen (O-2) precursors by low-pressure chemical vapor de position (LPCVD) was determined. An empirically derived reaction model for BSG film growth is proposed that predicts the growth rate and composition o f BSG films up to 70 mole% B2O3. The BSG reaction model includes a strongly adsorbed TEOS-derived intermediate that forms SiO2 and a direct surface re action of TMB, in O-2, to form B2O3. This model is supported by growth rate and mass spectroscopic data. The BSG; film morphology, investigated using atomic force microscopy, was found to have a root-mean-square roughness of 0.5 nm, with the precise film morphology being a function of reactor condit ions. The BSG film roughness increases with film thickness, temperature, an d boron content. Thermal annealing of the films in a water-free environment leads to planarization of the BSG governed by the film composition and ann eal temperature.