Ion assisted selective thin film deposition

Abstract

Ion bombardment of a growing film is one known way of changing film properties. Also in reactive etching, ions may assist surface reactions. We will present a study where different substrates are bombarded by energetic argon ions during deposition of titanium. If titanium is deposited onto three different substrates without influencing the substrate by any ion irradiation, a thin titanium film, equally thick, will be formed on all three substrates. If, however, the substrates are bombarded by energetic argon ions (500–800 eV) during deposition of titanium, we have found that quite different film thicknesses may be obtained on different substrates. In fact, a balance may be found where actually one substrate is sputter etched while another substrate under identical deposition conditions (same run) is deposited by titanium. Results from rf-bias sputtering in argon shows selectivity, e.g., between Si and Pt at 10 mTorr pressure, 1600 V target voltage and 800 V substrate bais. Ti is deposited onto silicon but the net surface effect on Pt is substrate etching. This demonstrates that selective deposition is possible to achieve by ion assisted thin film growth.