Plasma diagnostic of an RF magnetron Ar/N 2 discharge

Abstract

Physical vapor deposition (PVD) processes are nowadays common in synthesis of hard coatings like cubic boron nitride (cBN). Precise knowledge of plasma characteristics (ion flux, ion energy distribution and plasma composition) is crucial for understanding and controlling cBN thin film growth. This work is devoted to the characterization of an unbalanced RF magnetron Ar/N 2 discharge using a Langmuir probe and an energy selective mass spectrometer. RF power and total pressure were varied from 50 to 300 W and from 0.1 to 0.5 Pa, respectively, for different Ar/N 2 mixtures. Main ionic species are found to be Ar + and N 2 + with a very low fraction of N +. The ion density increases with RF power, pressure and Ar content. The ion energy distribution consists of one single narrow peak with full-width at half-maximum of a few eV. The main neutral species are Ar and N 2. Atomic nitrogen could not be detected by mass spectrometry, indicating a low fraction of this species in the discharge.