Film Deposition by Energetic Condensation

Abstract

When the plasma ions arrive at a surface, they do so with considerable kinetic energy, which is typically in the range 20–150 eV without bias. A bias voltage can increase this energy even further. Energetic condensation involves subsurface processes when the arriving ions displace surface and near-surface ions to come to rest below the surface. Shallow ion implantation or “subplantation” occurs, leading to dense and hard coatings that are generally under high compressive stress. Hardness and compressive stress are related. Excessive compressive stress is detrimental because it can lead to catastrophic failure of the coating by delamination. Stress control becomes paramount for high-performing coatings. This can be addressed by utilizing the high degree of ionization: biasing the substrate is very efficient in giving ions controlled, high energy capable of generating small collision cascades in the subsurface layer of the solid. Stress can be relieved through atom rearrangement facilitated by the short period of high mobility. This is best controlled by sophisticated biasing techniques, such as pulsed biasing with optimized pulse duration and duty cycle. One can maximize stress relief while maintaining an overall high level of hardness and elastic modulus.