VUV radiation flux from argon DC magnetron plasma

Vacuum ultraviolet (VUV) flux of argon plasma radiation in a DC magnetron discharge with a plane circular titanium cathode is measured. It is found that the intensity of VUV radiation, mainly indicated by the resonance lines of argon atoms at 104.8 and 106.7 nm and ions at 92 and 93.2 nm, is proportional to the discharge current and decreases with pressure. Following the results of the measurements, a numerical model of resonance radiation transport is developed to determine the VUV flux to the substrate placed near the sputtering cathode where direct measurements are impossible due to the fast contamination of the detector by sputtered atoms. In the case of a substrate located 10 cm opposite the cathode surface, the upper limit of estimated VUV flux is of the order of 10¹⁵ photons cm⁻² s⁻¹ at a coating deposition rate of 1.5 nm s⁻¹ for 2 and 12 mTorr gas pressures. Based on the measurements, the damage to a porous low-k dielectric by VUV radiation during the deposition of barrier layers in the DC magnetron discharge is first estimated. (paper)