High power pulsed magnetron sputtering: Fundamentals and applications

Abstract

Direct current magnetron sputtering (dcMS) is a widely used technique for deposition of a large number of compound and metallic coatings with specified mechanical, electrical and optical properties. Although dcMS is a successful coating technique, it suffers from fundamental problems, such as low target utilization and target poisoning during reactive sputtering, which results in process instabilities and poor deposition rates. In order to alleviate some of these problems, alternative techniques, such as radio frequency magnetron sputtering, additional ionization by rf coils or microwaves, or increased magnetic confinement by a multipolar magnetic setup are used. High power unipolar pulsing of the target voltage is another approach that has been used of late, in order to increase the ionization fraction in the discharge. In this deposition technique, known as high power pulsed magnetron sputtering (HPPMS), the power supply operates at low (or zero) power level and pulses to a high voltage for a short time each cycle. Thus, high electron densities are generated leading to increased ionization of the sputtered material. With peak power densities typically of several kW cm −2, ionization fractions of the sputtered material ranging from 4.5% for C to 70% for Cu are achieved. HPPMS has been used to grow metallic and compound coatings. In the present work, a summary over some of the important results related to this technique are presented. The mechanisms taking place in the discharge and at the coating surface during deposition are discussed and the benefits of using HPPMS are reviewed: tailoring of coating properties, control of the coating bombardment during deposition, enhancement of the coating mechanical properties and morphology. Finally, TiAlN coatings are deposited using an industrial coater, and the coating's properties are studied.