Densification of chemical vapor deposition silicon dioxide film using oxygen radical oxidation

Abstract

Silicon dioxide (SiO2) films formed by chemical vapor deposition (CVD) were treated with oxygen radical oxidation using Ar/O2 plasma excited by microwave. The mass density depth profiles, carrier trap densities, and current-voltage characteristics of the radical-oxidized CVD-SiO2 films were investigated. The mass density depth profiles were estimated with x ray reflectivity measurement using synchrotron radiation of SPring-8. The carrier trap densities were estimated with x ray photoelectron spectroscopy time-dependent measurement. The mass densities of the radical-oxidized CVD-SiO2 films were increased near the SiO2 surface. The densities of the carrier trap centers in these films were decreased. The leakage currents of the metal-oxide-semiconductor capacitors fabricated by using these films were reduced. It is probable that the insulation properties of the CVD-SiO2 film are improved by the increase in the mass density and the decrease in the carrier trap density caused by the restoration of the Si-O network with the radical oxidation.

Effect of microwave plasma treatment on silicon dioxide films grown by atomic layer deposition at low temperature

“…Plasma-treated oxide films consist of layers with differing mass densities because near the surface, the oxide film increases in density more easily as a result of the plasma treatment. 10 Since O (1D) atoms relax to O (3P) atoms by diffusing through the oxide films, 18 the atoms have less of an affect on the film layers far from the surface. The mass density in Figure 2 is the mean value since the bonding state concentrations determined from the IR absorbance are averaged over the entire oxide film.…”

“…[8][9][10] Plasma treatments generate a high density of excited oxygen atoms, which react with the SiO 2 network at temperatures typically too low for oxygen molecules reaction. 11 In previous reports, it was concluded that the SiO 2 network was reconstructed by SPA plasma treatments, which led to a reduced leakage current.…”

Mass densification and defect restoration in chemical vapor deposition silicon dioxide film using Ar plasma excited by microwave

“…[1][2][3] We also reported that the treatments using active oxygen species generated by Ar/O 2 plasma excited by the microwave is extremely effective. 4 We clarified that the mass density of the CVD-SiO 2 film is increased and the carrier trap density of the film is decreased by the Ar/O 2 plasma treatment with X-Ray Reflectivity (XRR) analysis and X-ray Photoelectron Spectroscopy (XPS) time-dependent measurement. In addition, we also clarified that the leakage current of the CVD-SiO 2 films in metal-oxide-semiconductor (MOS) capacitors is decreased more than two orders of magnitude by the Ar/O 2 plasma treatment.…”

“…5,6 This mechanism is the same as that of the mass densification and phase transition of the bulk SiO 2 during cooling down process in ambiences containing the flux. 4 On the other hand, we presumed that the decrease in the carrier trap density is caused by the restoration of the defects with the active oxygen species because it is probable that the active oxygen species oxidize the oxygen vacancy defects in the CVD-SiO 2 film. However, the influence of the active argon species on the carrier trap center is unclear.…”

“…[4][5][6][7] It is probable that the increase in the mass density of the CVD-SiO 2 film is caused by not only the restoration of the defects but also the reconstruction of the Si-O bond network with the active species acting as the flux. 4 The Si-O bonds in the SiO 2 film can be dissociated by the Ar/O 2 plasma at low temperatures because the active argon or oxygen species have high energy. The Si-O-Si bond angles are decreased by the release of the strong constraint of the Si-O bond network because the Si-O-Si bond angle in the stable bulk SiO 2 at the low temperatures is smaller than that in the CVD-SiO 2 film.…”