Influence of inert gas species on the growth of silver and molybdenum films via a magnetron discharge

Argon is the process gas of choice for most magnetron sputtering applications due to its large atomic mass, inert chemistry, and relatively low cost. Other inert gases are available for use in sputtering deposition that have varying mass and hence different momentum behaviour during ion bombardment of solid surfaces — affecting sputter yield, particle implantation and incorporation of process gas into deposited films. The plasma discharges generated from these gases vary in terms of the nature and energy of species incident at both target and substrate. In particular, the contribution from energetic neutrals varies as a consequence of the atomic mass of the process gas in comparison to the target material to be sputtered. ron plasma discharges were generated from neon, argon, krypton and xenon gases in DC and mid-frequency pulsed-DC modes with both silver and molybdenum cathodes. The electrical characteristics, such as potential and current at the target and substrate were measured and compared. Thin metallic films were then deposited and analysed in terms of structure; mechanical, optical and electrical properties; and process gas incorporation. The data generated is used to establish the relationship between process gas species, plasma discharge characteristics of those gases, and the subsequent growth and properties of deposited coatings.