Method of low-temperature conversion of pehydropolysilazane into amorphous SiO_x in aqueous solutions

We investigated low-temperature SiO_x conversion methods for the spin-coated perhydropolysilazane (a diluted dibutyl-ether solution) films prepared on (100) Si substrates under different curing schemes. From the Fourier transform-infrared (FTIR) spectroscopy and refractive index (RI) measurements, conversion to high-density SiO_x was observed for the curing methods of dipping the coatings into various aqueous solutions such as H ₂O₂, NH₄OH, and deionized water with or without 405-nm ultraviolet irradiation at near room temperature. The SiO_x films cured in H₂O₂ solution at 80 °C for 10 min exhibited a high conversion efficiency for the SiOx network, as observed from FTIR spectra, RI measurement (∼1:46), O/Si stoichiometry (∼1:5), surface smoothness (roughness < 1:1 nm), and mechanical property (nanoindenter elastic modulus ≃ 42 GPa), which are comparable to those of the conventional chemical-vapor-deposited SiO_x films.