Magnetron sputtering

Physical Vapour Deposition (PVD) processes are a set of techniques for synthesizing metallurgical coatings or ceramic films, with applications in fields as diverse as mechanics, optics, electronics, the chemical and aeronautical industries, etc. Generally speaking, coatings are produced in a rarefied atmosphere (< 10 Pa) in three stages: the creation of a metal vapour from a source (or target), its transport through a reactor and its condensation on the surface of a substrate to be coated. Although the term PVD encompasses a wide range of processes, they can be classified into three main categories, depending on how the metal vapour is obtained: by thermal effect, it's called evaporation, while by mechanical effect, it's called sputtering. In the case of low-pressure cathodic arcing, both effects are used to generate metal vapour.

A plasma-assisted physical deposition reactor comprises at least a secondary vacuum chamber, a metal vapor source, a substrate holder isolated from the rest of the installation, a flowmeter and the generators needed to create the electrical discharge and polarize the substrates. In this section, we focus on a technique that is enjoying a major industrial boom, thanks to the considerable progress made over the last twenty to thirty years in understanding the mechanisms that govern it: magnetron sputtering.

The first part will be devoted to a detailed study of the magnetron sputtering process. After an overview of the physical mechanisms involved, we will describe the various methods used to obtain coatings on metals or metal alloys, highlighting the relationships between the conditions under which they are produced and the metallurgical characteristics of the coatings, the latter conditioning their properties in use.

The second section describes the phenomena that enable ceramic coatings to be synthesized in the presence of a reactive atmosphere. The main difficulties inherent in the magnetron sputtering process under reactive conditions and the methods developed to overcome them will also be presented. Finally, we will propose two spectroscopic methods of plasma diagnosis and optical interferometry for in situ process control.