On-Wafer Monitoring of Vacuum-Ultraviolet Radiation Damage in High-Density Plasma Processes

Abstract

Vacuum-ultraviolet (VUV) radiation damage was investigated in inductively coupled Ar, He, and O2 plasmas by measuring the hole currents generated in SiO2 film. The hole currents strongly depended on the irradiated plasma VUV wavelength and photon flux (electron density). When the electron density was increased, larger hole currents were observed in the SiO2 film. A VUV wavelength of 58.4 nm in the He plasma and of 130.5 nm in the O2 plasma generated more holes in the SiO2 film than that of 104.8 and 106.6 nm in the Ar plasma did. That is believed to be due not only to the photon energy but also to the dependence of VUV transmittance in SiO2 films on the VUV wavelength. We found that pulse-time-modulated plasma is very effective in reducing the number of holes generated in SiO2 film by plasma VUV irradiation. Compared to the result obtained in the cw plasma, the VUV spectrum intensities and hole currents in the pulse-time-modulated plasma decreased drastically when the electron density was maintained.