Photoassisted liquid-phase deposition of silicon dioxide

The deposition rate of SiO2 by liquid-phase deposition (LPD) in a H2SiF6 solution is significantly increased by 254 nm ultraviolet (UV) illumination. The photoenhancement effect is much stronger at 3.09 M H2SiF6 than at 1.34 M H2SiF6 concentration. At a constant boric acid concentration the deposition rate of SiO2 is found to increase linearly with UV light intensity. The photoassisted effect is much stronger at higher boric acid concentration. However, within the UV intensity range studied, the photoeffect on the oxide growth rate is not as strong as other parameters such as H2SiF6 concentration and boric acid addition. The UV spectrophotometric results show that the strong UV absorption of the growth solution is associated with SiF62- but not with H2O, H3BO3, or BF4- species in the solution. The observed photoenhancement effect is discussed in the light of the existing LPD models.