Effects of substrate temperature on the electrical and physical properties of silicon dioxide films deposited from electron cyclotron resonant microwave plasmas

Abstract

Silicon dioxide films have been fabricated at growth temperatures ranging from 25 to 330 °C from an electron cyclotron resonant microwave plasma. Films were deposited from a SiH4/Ar/N2O reactant gas mixture. The minimum temperature required to fabricate high-electrical-quality silicon dioxide films is between 255 and 290 °C. In metal-oxide-semiconductor devices, electron injection field strengths and breakdown field strengths were as high as 5 and 8 MV/cm, respectively, for oxides grown above this temperature range. Films grown at temperatures slightly below the 255–290 °C range have much poorer electrical integrity. A concomitant increase in the refractive index was observed with the improvement in the electrical integrity of these films. The refractive index increased with increasing growth temperature and was in the range of 1.44–1.47. In the 255–290 °C temperature range, the refractive index of the silicon dioxide films reached approximately 1.46–1.47, and saturates thereafter. Infrared spectroscopy indicated a hydrogen content in these films of approximately 4 at. %. The hydrogen was bonded as SiOH, while no SiH impurity groups were detected. The dependence of the deposition rate on the substrate temperature was dependent on the location of the substrate. For films grown on substrates in contact with the plasma, the deposition rate was found to decrease with increasing substrate temperature. In contrast, for films grown on substrates located in the plasma afterglow, the deposition rate increased with increasing substrate temperature.