Influence of pulse duration on the plasma characteristics in high-power pulsed magnetron discharges

Abstract

High-power pulsed magnetron discharges have drawn an increasing interest as an approach to produce highly ionized metallic vapor. In this paper we propose to study how the plasma composition and the deposition rate are influenced by the pulse duration. The plasma is studied by time-resolved optical emission and absorption spectroscopies and the deposition rate is controlled thanks to a quartz microbalance. The pulse length is varied between 2.5 and 20 s at 2 and 10 mTorr in pure argon. The sputtered material is titanium. For a constant discharge power, the deposition rate increases as the pulse length decreases. With 5 s pulse, for an average power of 300 W, the deposition rate is ϳ70% of the deposition rate obtained in direct current magnetron sputtering at the same power. The increase of deposition rate can be related to the sputtering regime. For long pulses, self-sputtering seems to occur as demonstrated by time-resolved optical emission diagnostic of the discharge. In contrary, the metallic vapor ionization rate, as determined by absorption measurements, diminishes as the pulses are shortened. Nevertheless, the ionization rate is in the range of 50% for 5 s pulses while it lies below 10% in the case of a classical continuous magnetron discharge.

An introduction to thin film processing using high-power impulse magnetron sputtering

“…At the same time there is a tradeoff with the degree of ionization, where the highest reported values are found for the 20 ls pulses. 28 It is also reported that shorter pulses have beneficial consequences for reactive HiPIMS processes, 73 which are discussed in more detail in Section II F.…”

“…29 Konstantinidis et al 28 have shown that by decreasing the pulse length it is possible to increase the deposition rate, where ;70% of the DCMS deposition rate is achieved for 5 ls pulses in the case of Ti compared to ;20% of the DCMS deposition rate for 20 ls pulses, mainly due to less self-sputtering for short pulses. At the same time there is a tradeoff with the degree of ionization, where the highest reported values are found for the 20 ls pulses.…”

Argon metastables in HiPIMS: time-resolved tunable diode-laser diagnostics

“…The lower deposition rate for HiPIMS compared to conventional techniques for the same average power is often reported as a drawback, and is one of the most discussed topics in this field of research [1,4,6,7,8]. In recent publication by Samuelsson et al [4] it was found that the rates are typically in the range of 30-85 % compared to DC magnetron sputtering (DCMS) depending on source material.…”

Transition between the discharge regimes of high power impulse magnetron sputtering and conventional direct current magnetron sputtering

“…Previous publications on HiPIMS discharges have focused on the high power pulse as observed for short pulse-on times [7]. Alami and co-workers investigated the U-I characteristics for different voltages identifying different operation modes [8].…”