CYCLIC ALKYLSILANES AS LOW-PRESSURE CHEMICAL-VAPOR-DEPOSITION SILICONDIOXIDE PRECURSORS

Silacyclobutane and silacyclopentane were synthesized for evaluations as precursors for silicon dioxide films under low pressure chemical va por deposition conditions at low temperatures. Both silacyclobutane an d silacyclopentane were studied in the temperature range from 300 degr ees C to 500 degrees C in the presence of oxygen. Deposition rates fol low an Arrhenius behavior at constant reactor pressure, and the activa tion energies were found to be 41.8 kJ mole(-1) for silacyclobutane an d 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 a s the temperature is increased. The films were analyzed by Fourier tra nsform infrared spectroscopy for the presence of hydroxyl and hydrocar bon bands. The refractive indices were measured by ellipsometry. Carbo n concentrations and Si:O ratios were estimated by Auger electron spec troscopy. Quantum mechanical semi-empirical AM1 calculations were carr ied out to determine the relative ring-strain energies and reactivitie s. These results estimate the propensity of these molecules to ring op en under mild thermal conditions. The experimental results are in agre ement with the calculations.