Time-Resolved Ionisation Studies of the High Power Impulse Magnetron Discharge in Mixed Argon and Nitrogen Atmosphere

Abstract

Magnetron sputtering technology is widely used to grow thin films on a range of substrate materials. High power impulse magnetron sputtering (HIPIMS) technology differentiates itself from other types of magnetron sputtering by the high degree of ionisation of the sputtered material achieved by applying high peak powers of 3 kW · cm−2 (4 A · cm−2) at duty cycles of <1%. The current paper discusses HIPIMS of Ti in mixed argon and nitrogen atmosphere, commonly used for hard coatings deposition. Estimation of the composition of the ion deposition flux arriving at the substrate position is extracted from energy-resolved mass spectrometry data. The measured time-resolved ion mass and ion energy distribution functions were compared for the HIPIMS discharge and industry-standard direct current (DC) and medium frequency pulsed DC magnetron discharges operated at the same average power of 2 W · cm−2. In inert Ar atmosphere, HIPIMS produced a metal-dominated ion flux with Ti1+ concentration of 46%, compared to 10% in DC operation. In reactive atmosphere of Ar and 10% N2 the HIPIMS discharge produced an ion flux with significantly increased content of ionised film-forming species such as Ti1+, Ti2+ and N1+. The atomic ion N1+ was the most abundant species representing 40% of the total flux with Ti1+ 19% and Ar1+ 19%. In contrast, the ion flux in DC and pulsed DC discharges was dominated by Ar1+ and molecular ion N.