High power impulse magnetron sputtering (HIPIMS) and related self-sputtering techniques are reviewed from a viewpoint of plasma-based ion implantation and deposition (PBII&D). HIPIMS combines the classical, scalable sputtering technology with pulsed power, which is an elegant way of ionizing the sputtered atoms. Related approaches, such as sustained self-sputtering, are also considered. The resulting intense flux of ions to the substrate consists of a mixture of metal and gas ions when using a process gas, or of metal ions only when using 'gasless' or pure self-sputtering. In many respects, processing with HIPIMS plasmas is similar to processing with filtered cathodic arc plasmas, though the former is easier to scale to large areas. Both ion implantation and etching (high bias voltage, without deposition) and thin film deposition (low bias, or bias of low duty cycle) have been demonstrated.
Introduction: Plasma sources for PBII&DPlasma-based ion implantation and deposition (PBII&D) is a family of surface modification and thin film deposition techniques overlapping with other plasma-based technologies known under various other names. The basic idea is to immerse a substrate in a plasma and apply a usually rather high voltage to it; as a result, a high voltage sheath forms between plasma and substrate, enabling controlled acceleration of plasma ions after they cross the plasma-sheath boundary (sheath edge). Depending on the voltage amplitude and the character of the plasma, ion implantation and/or deposition occurs [1].An early form, or predecessor, of PBII&D is ion plating where metal vapor is partially ionized and the growing metal film is subject of ion bombardment [2]. Instead of trying to ionize atoms from a metal evaporation source, metal plasma can be readily produced using high-current pulsed arc or spark discharges in vacuum [3]. These early, pioneering attempts inspired the much-cited work by Conrad and coworkers [4] who used non-condensable (not film-forming) nitrogen plasma for surface modification: the implantation of nitrogen facilitated the formation of nitrides in the surface layer with the well-known advantageous features of enhanced hardness and improved wear and corrosion resistance.Without further reviewing the many papers that appeared on the subject, one can see that the plasma sources can be generally classified in gaseous and those leading to film growth (condensable, usually containing metal or carbon ions). Gaseous plasma can be further classified in noble and reactive gases, while metal plasmas can be quite different in their properties, especially in terms of ion charge states and ion energy distribution functions. Examples of gas plasma sources include radio-frequency (RF) sources [4][5] and distributed electron cyclotron resonance microwave (DECR) sources [6].