Plasma enhanced beam deposition of thin dielectric films

A low-temperature (30-250°C) technique for depositing thin films of stoichiometric, amorphous dielectric layers with a sharp interface between the film and the substrate is proposed and demonstrated. The technique uses a combination of atomic or molecular beams of which at least one of the sources is generated by a plasma. As examples, SiO₂ and Al₂O ₃ films have been deposited on Si, GaAs, InP, InGaAs substrates. It is shown that the interface between the dielectric and the semiconductor is extremely sharp and that no native growth of oxides occurred on the semiconductor surface during film deposition. The physical properties of the deposited SiO₂ are nearly identical to those of thermal oxides grown on Si. Preliminary electrical properties show that the films have a breakdown field strength of about 5×10⁶ V/cm, and the 1-MHz C-V curves shown hystereses of 50 mV with a sweep rate of 100 mV/s. The fixed charge density is about 3.5×10¹¹ cm^{- 2}.