Ethan Muir, Arutiun P Ehiasarian¹, Yashodhan Purandare¹, Ryan Bower^2
1Sheffield Hallam University, Sheffield, United Kingdom
²Imperial College London, London, United Kingdom
This study documents the results of an investigation into the effect of pulse duration within constant-current HIPIMS discharges, specifically investigating the effects on plasma chemistry, temporal evolution and the changes to thin film texture of films produced from these discharges. Pulse durations ranging from 40-200µs were studied. Time-Averaged Optical Emission Spectroscopy (OES) has been conducted on a series of discharges with different pulse durations and multiple species identified within these discharges have been studied using Time-resolved OES to study how they develop throughout the pulse. Emissions of inert gas species, reactive gas species and metal species within the discharge were studied. The data obtained from the Time-Resolved OES shows three stages that can be used to characterise the generation of the discharge: Gas Rarefaction, Pumping and Steady State. The novel pumping stage identified is characterised by constant current but increasing electron temperature, electrons were accelerated within the pre-sheath, the high density of electrons produced led to an increased rate of collisions and increased probability of ionisation, creating larger ion populations. Time-resolved and Time-averaged mass spectrometry studies were conducted which verify the data obtained via OES. There is proof of an increase in electron temperature within the discharge whilst current remains constant. Titanium Nitride films were produced at CMOS-compatible temperatures from the discharges studied to investigate the role that pulse duration and plasma chemistry play on the texture of the films via x-ray diffraction. The films show that at low pulse durations the (111) plane is preferred, but as duration is increased, (200) increases until it is preferred. The films exhibit hardnesses in the range 31.5-34.9GPa and toughness’s in the range of Hz³/E² = 0.207-0.301GPa. Toughness and hardness have been correlated with the texture. These films have been shown to be plasmonically active when exposed to visible spectrum electromagnetic radiation.