Cyclic alkylsilanes as low-pressure chemical vapor deposition silicon dioxide precursors

Abstract

Silacyclobutane and silacyclopentane were synthesized for evaluations as precursors for silicon dioxide films under low-pressure chemical vapor deposition conditions at low temperatures. Both silacyclobutane and silacyclopentane were studied in the temperature range from 300 °C to 500 °C in the presence of oxygen. Deposition rates follow an Arrhenius behavior at constant reactor pressure, and the activation energies were found to be 41.8 kJ mole −1 for silacyclobutane and 75.3 kJ mole −1 for silacyclopentane below 66.6 Pa. Silacyclobutane is susceptible to homogeneous nucleation, so obtaining optimum oxide film properties with this precursor requires lower reactor pressures as the temperature is increased. The films were analyzed by Fourier transform infrared spectroscopy for the presence of hydroxyl and hydrocarbon bands. The refractive indices were measured by ellipsometry. Carbon concentrations and Si:O ratios were estimated by Auger electron spectroscopy. Quantum mechanical semi-empirical AM1 calculations were carried out to determine the relative ring-strain energies and reactivities. These results estimate the propensity of these molecules to ring open under mild thermal conditions. The experimental results are in agreement with the calculations.