Relation between modulation frequency of electric power oscillation during pulse magnetron sputtering deposition of MoNx thin films

Abstract

This work reports the results of a study, concerning the synthesis of molybdenum nitride thin films, by DC Pulsed Magnetron Sputtering method (PMS), operating with 100 kHz main frequency, and modulated by the additional frequency, adjustable in the range of 10–1000 Hz (modulated Pulse Magnetron Sputtering – mPMS). We have studied the influence of mPMS on the state of plasma using optical emission spectroscopy technique (OES). X-ray photoelectron spectroscopic analysis (XPS) and X-ray diffractometry (XRD) were also used to investigate the relationship between phase composition and modulation frequency of Mo-N thin films. These investigations have revealed a presence of low-temperature phases of β-Mo16N7 and δ-MoN, confirming correlation between chemical state of Mo 3d3/2, 3d5/2 or 3p3/2 and amount of nitrogen incorporation in Mo-N structures. Films’ morphology was well examined by scanning electron microscopy (SEM) and consists the nanocrystalline/amorphous domains. From the utilitarian point of view, very good thermal stability, promising mechanical properties being: H ∼ 16 GPa, E∗ ∼ 180 GPa (NanoTest) and low value of resistivity below 650 μΩcm (4-point probe method) of the Mo-N, predestine them as an effective diffusion barrier in Cu-wired MOSFET structures. Results confirmed that additional modulation frequency should be considered as a significant factor of electric power oscillation during reactive synthesis by means of PMS-based method.