Energy Deposition at the Substrate in a Magnetron Sputtering System

Abstract

In any deposition process, the effective energy deposited onto a surface of a substrate material by the depositing and reactive particles is essential to understanding the mechanism of film growth on the surface [1–4]. For low-pressure plasmas, such as with the magnetron sputtering process, these particles include electrons, ions, neutrals, etc. [2,5–9], which interact with the surfaces and each other through collisions and or chemical reactions. It should be evident therefore that the energy flux onto a substrate depends on the process conditions, such as magnetron power, pressure, geometry, etc. [2, 5, 8]. The deposited energy causes the effective temperature of the growing film to rise [10]. As the particles arrive at the substrate, they transfer momentum, and increase the mobility of the particles at the surface of the growing film [3, 4]. They also cause peening, increasing density and comprehensive stress [11–17]. Apart from surface mobility, the reaction rates/pathways are greatly influenced by this incident energy, and hence the micro- and nanostructure and the properties of the growing film depend strongly on the energy management [18-24]. The relationship between substrate temperature and film properties, such as columnar structure, grain size, etc., has been well established [25–31]. The density and temperature of the plasma species at the substrate region have been shown to also affect the properties of the deposited film [32–34]. Gas pressure, as a process parameter, affects the kinetic energy of the deposited species as well as the characteristics of the plasma [7, 8, 35, 36], hence it may be said to have an important indirect effect on the micro- and nanostructural evolution of the film. Since these effects determine the effective energy deposited [36], then, energy flux onto the substrate is one of the important parameters in many high performance thin films.