Dielectric Thin Films through rf Sputtering

Insulators cannot be sputtered with standard dc glow discharge techniques, because the accelerating potential cannot be directly applied and because the positive charge which accumulates on the surface during ion bombardment cannot be neutralized. Direct sputtering of insulators can be achieved by applying a high‐frequency potential to a metal electrode behind the dielectric target. This technique was used to deposit thin insulating films. With a properly optimized electrode configuration and a superimposed magnetic field, deposition rates up to 2000 A/min were obtained. Electrode potentials between 700 and 5500 V peak‐to‐peak were used. In all experiments described herein, the frequency was 13.56 Mc/sec and the pressure was 5×10−3 Torr. It was found that the introduction of oxygen into the argon sputtering atmosphere greatly reduced the deposition rate. Most experiments were carried out with borosilicate glass (Corning Pyrex 7740) and fused quartz. Without any special measures, films with a low pinhole density were obtained.