AVS 58th Annual International Symposium and Exhibition
    Advanced Surface Engineering Division Thursday Sessions
       Session SE+PS-ThA

Paper SE+PS-ThA9
Inductively Coupled Impulse Sputtering (ICIS): A Novel Technique for Ionised PVD

Thursday, November 3, 2011, 4:40 pm, Room 104

Session: Pulsed Plasmas in Surface Engineering
Presenter: Arutiun Ehiasarian, Sheffield Hallam University, UK
Authors: A.P. Ehiasarian, Sheffield Hallam University, UK
D. Loch, Sheffield Hallam University, UK
Correspondent: Click to Email
One limitation of magnetrons is their use of inhomogeneous magnetic fields which constrains deposition of magnetic materials to thin targets, complex (magnetic) alloys by erosion-dependent stoichiometry, and oxides by build-up of arc-prone insulating layers on the target edge. Inductively Coupled Impulse Sputtering (ICIS) is a new technology for physical vapour deposition based on sputtering without magnetic fields. A plasma is generated in front of the target via an inductively coupled coil driven with a 13.56 MHz radio frequency (RF) power supply. The target is then biased to a high voltage to initiate sputtering. In order to ionise significant fractions of the sputtered flux, the RF power density is pulsed with peak values in excess of 30 Wcm-2 to produce plasma density of the order of 1012 cm-3. A low duty cycle of < 25% is used to achieve high peak powers and plasma densities at low average power. The degree of ionisation of ICIS of Cu and Ti in Ar atmosphere were evaluated using optical emission spectroscopy and atomic absorption spectroscopy and the film microstructure and coverage of vias was studied with cross sectional SEM. The effect of peak RF power density (P) was to increase metal ionisation degree hyperbolically. The rate of production of Ti1+ metal ions was proportional to ~ P1.1±0.2 and was significantly faster than that of metal neutrals of ~P0.66±0.08 indicating enhanced ionisation of the vapour with power. The mechanisms of ionisation will be discussed. The influence of pressure on the process was studied at a constant peak RF power density of P = 30 Wcm-2. The intensity of copper and argon neutral emission rose linearly for pressures of 2.95×10-2 - 1.2×10-1 mbar and saturated at higher pressures. The deposition rate was 2 nm min-1 for RF-power density of 30 Wcm-2, average target power of 67 W and a pressure of 1.2×10-1 mbar. The microstructure of Cu films was globular at 2.95×10-2 mbar and large-grain columnar at 1.2×10-1 mbar. Bottom coverage of unbiased vias with width 0.36 µm and aspect ratio of 2.5:1 increased from 15 % to 20 % as pressure increased from 2.95×10-2 to 1.2×10-1 mbar. The current work has shown that the concept of combining a high powered RF coil with a magnet-free cathode is feasible and produces very stable plasma and uniform target erosion. The experiments have shown a significant influence of power and pressure on the plasma and coating microstructure. The process is suitable for Fe, Ni and FeCo alloy deposition.