Very high frequency plasma CVD of silicon oxide

A single-wafer parallel-plate PECVD system was developed using a 40.68 MHz excitation. The wafer temperature is controlled by a helium back side flush avoiding also a deposition at the wafer back side. A stable plasma confined between the electrodes away from the walls of the chamber, an optimised plasma density to get a sufficient deposition rate and good film uniformity, and a controlled wafer temperature which influences the plasma-surface interaction were achieved. Using a SiH4/N2O process and a deposition rate of 1 nm/s a high breakdown voltage ≥ 6 MV/cm and a refractive index of 1.46 ± 0.015 were obtained. Film thickness uniformity was < 5%. A SF6/O2 process is used for the reactor cleaning with etching rates of about 1 nm/s.