Optical thin films applied by single-target reactive magnetron sputtering

Abstract

Silicon targets as a single source for reactive magnetron sputtering provide a variety of advantages. The single-target approach offers, for example, the possibility to build very compact sputtering systems. The implementation of pulsed power results not only in non-arcing sputtering conditions but also in deposition of dense dielectric layers with smooth surfaces. Various film materials can be deposited simply by using different gases such as argon, as well as the reactive gases nitrogen and oxygen. In the visible range (380nm-780nm) silicon-oxides, silicon-nitrides and all kinds of siliconoxy- nitrides with a refractive index range of 1.44-2.05 can be used for many different optical thin film coatings. Pure silicon and silicon-sub-oxides with refractive indices up to 3.5 can be applied for coatings in the near infrared (NIR)/ infrared (IR)-region. High deposition rates of up to 2 nanometers per second, in combination with short pumping times of about 3-5 minutes, lead to extremely fast coating cycles. The machine concept and several possible applications, as for example Bragg mirrors and narrow band-pass filters in the NIR, will be presented. Anti-reflective coatings fabricated by this method have Vickers hardness values higher than 1000 HV and show superior scratch-resistance. Furthermore it is possible to produce Nd:YAG laser mirrors with high laser damage thresholds.