Temporal evolution of spatial optical emission characteristics by inductively-coupled impulse sputtering (ICIS) using high power-burst 155kHz-ICP

Abstract

A copper target was negatively-biased and was sputtered by bombardment of argon ion species produced 155 kHz-inductively-coupled plasma (ICP) in a burst-pulse mode for a duration of 800 μs. This system was called ICIS (Inductively-coupled impulse sputtering). The plasma density was on the order of 1019 m−3 in the ICP region. The target current density and the power density were about 0.8 A/cm2 and about 0.3 kW/cm2, respectively. Temporal evolution of the optical emission of the plasma species was discussed. The observed species were argon ions, excited argon and excited copper. The entire region consisted of the ICP, a bulk plasma and a target plasma. Argon ions produced in the ICP were transported by an ambipolar diffusion toward the target and excited argon and excited copper species were mainly produced in the target plasma. A plateau emission by argon ions and spike emission by energetic electrons which were originated from secondary electrons were seen. Gas rarefaction of argon gas also influenced the temporary evolution particularly near at the target. This was discussed using a carbon target.