Influence of hydrogen incorporation on the structure and stoichiometry of chemically vapor deposited silica films

Hydrogen incorporation into SiO2 films grown by low-pressure chemical vapor deposition (CVD) from SiH4/O-2 mixtures is investigated by means of infrar ed spectroscopy (IRS), nuclear magnetic resonance (NMR), elastic recoil det ection analysis (ERDA), X-ray photoemission spectroscopy (XPS), and nuclear reaction analysis (NRA). We find that hydrogen atoms are preferentially bo nded to O atoms, forming bulk SiOH groups, either isolated or clustered, an d H2O groups, with a minor incorporation of SiH groups, as well as geminal and surface isolated SiOH groups. The proportion of clustered SiOH groups d ecreases upon increasing the deposition temperature, which has been attribu ted to the faster dehydroxylation reactions and higher surface mobility of the hydrogenated species involved in the film growth. Using a novel method based on the combination of NRA and ERDA, we verify quantitatively that the predominance of O-H over Si-H bonding implies a slight overstoichiometric character (O/Si atomic ratio > 2) that is accentuated with increasing OH co ncentration.