Evolution of film temperature during magnetron sputtering

Abstract

We report on the results of measurements of the temperature TFsurf which developed on the surface of films deposited by magnetron sputtering of chromium and copper targets on cooling and non-cooling silicon substrates. The TFsurf and substrate temperature (Ts) were simultaneously measured using high-resolution IR camera and thermocouple, respectively. We revealed that the TFsurf steeply grows, keeps constant when it achieves saturation level, and rapidly drops to the value of the Ts after stopping the deposition. At the same time, the Ts either does not change for the case of cooling substrate or increases to a certain level for noncooling substrate. However, in both cases the Ts remains several times lower than the TFsurf. The TFsurf is proportional to the flux of energy delivered to the growth surface by sputtered atoms and other fast particles, weakly depends on the depositing metal and can achieve several hundreds of °C. This phenomenon is explained by a model assuming formation of a hot thin surface layer (HTSL) on the top of the growing film, which exists only during film deposition and exhibits extremely low thermal conductivity. Due to this unique property the temperature TFsurf of HTSL is several times higher than the Ts. Variations in the TFsurf fairly correlate with structure changes of Cr films along thickness investigated in detail previously.