Highly insulating Al2O3, SiO2, and Si3N4 films for sensor applications deposited by reactive pulse magnetron sputtering

Applications in sensor, automotive and aviation technology require thin films that exhibit electrical insulating properties at room temperature but also at elevated temperatures. One technology for the deposition of such films is reactive pulse magnetron sputtering. Because of the high deposition rate this technology is especially interesting for the deposition of thick insulating films of several microns allowing high insulation voltages up to 800V or deposition onto relatively rough substrates e.g. stainless steel. In this paper the breakdown field strength and resistivity of such sputter deposited Al2O3, SiO2 and Si3N4 films are investigated in the temperature range between room temperature and 400°C. All investigated films show excellent insulation properties at room temperature. At high temperatures films remain insulating at slightly reduced breakdown voltage. The combination of different film materials allows fulfilling the requirements not only on insulating but also on thermo mechanical properties. One example of industrial application is the deposition of electrical insulation films onto the membranes of pressure sensors using cluster type sputter equipment