The Role of Borophosphosilicate Chemistry in Heterogeneous Nucleation

This study aims to solve the conflict between two important features of PECVD BPSG film: good flow ability and low defectiveness, which can ultimately alter the electrical characteristics of devices. The film flow associates with the amount of phosphorus and boron dopants, which, in their turn, are a source of boron phosphate imperfections. The films' compounds SiO2-B2O3-P2O3/P2O5 have to be thus kept appropriately to satisfy both requirements. Unstable glass structure carries an excessive amount of hydrogen related species, especially H2O, which is a catalyst for defects. Such films are also vulnerable to additional moisture from the air. The as-deposited film instability brings on defect generation and out-gassing / counterdoping problems during the relaxation process when film is being stored and heated. This work studies the film structure that is modulated by the deposition parameters in order to get optimized ratios of N2O/SiH4, P2O3/P2O5 and SiO2/P2O5. Special attention is paid to the oxygen-rich film's composition with low SiH4 precursor.