A Mechanism for Increasing Growth Rate of Undoped SACVD Film

Sub-atmospheric SACVD undoped silicon glass (USG) inter-metal dielectric films, while having a high trench-filling ability, have a low deposition rate. At high deposition temperature and pressure, commonly recommended, however, TEOS gas precursor is fairly consumed in the gas-phase reactions without contributing to deposition on the substrate. Two growth mechanisms of the USG film are discussed. One is a direct TEOS -O3 reaction on the Si surface and another one is a result of reaction of the intermediates, which can contribute to the growing SiO2 from the gas-phase. This study targets the deposition conditions where TEOS contributes to growing SiO2 film from both the gas phase and the surface chemisorptions. This approach helps to use TEOS efficiently, to maximize the deposition rate of USG while leaving good SiO2 film quality. The film's morphology, wet etch rate, and shrinkage that are related to the film's flow capability are also discussed.