Properties of SiO2 and Al2O3 films for electrical insulation applications deposited by reactive pulse magnetron sputtering

Alumina and silica films have been deposited using pulse reactive sputtering. Film deposition was carried out by stationary sputtering using the Double Ring Magnetron with film thickness uniformity of up to ±1% across a 200 mm diameter. In the high rate deposition process using closed loop reactive gas control, the deposition rate of dielectric compounds is in the range of 50–400 nm/min. Electrical properties of the films such as breakdown field strength, resistivity and dielectric constant have been measured in relation to pulse mode, substrate bias, deposition rate and size of contact pads. Breakdown field strength of the as-deposited Al2O3 and SiO2 films ranges from 4 to 9 MV/cm. Resistivity of the films is between 10+15 and 10+17 Ωcm measured by dc methods and between 10+10 and 10+12 Ωcm measured by ac methods (1 kHz). For the SiO2 films, an improvement of film properties due to increased energetic substrate bombardment was found. This was shown for both using bipolar pulse mode and additional rf substrate bias to enhance energetic bombardment. The results have been compared to SiO2 films deposited as reference films by conventional rf sputtering with the same arrangement at a deposition rate of 15 nm/min. Properties of the reactively deposited films with 1 order of magnitude higher deposition rate are close to those of the rf sputtered films. Results, therefore, are promising regarding the application of SiO2 and Al2O3 films deposited by reactive pulse magnetron sputtering for various insulation purposes, for example sensors with thick insulation layers and breakdown voltage up to 1000 V.