CHARACTERIZATION OF THIN TITANIUM-OXIDE ADHESION LAYERS ON GOLD - RESISTIVITY, MORPHOLOGY, AND COMPOSITION

Group 1B metal films (copper, silver and gold) are attractive for metallizations in multichip modules (MCM) and integrated circuits because they have high electrical conductivities. Unfortunately, Group 1B metals require additional bonding layers for adhesion to insulators (i.e. silicon dioxide or polymers). In this work, thin electrically insulating films of titanium oxide on titanium have been investigated as adhesion layers between gold and a wide variety of insulators. The adhesion layer does not alter the dielectric properties of the insulator surrounding the metal because it is thin. The morphology, composition, and resistivity of the titanium oxide films were studied with angle resolved X-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), and electrical resistance measurements. The results show that sputter-deposited titanium films grow by an island growth (Volmer-Weber) mechanism. The islands coalesce after 10-20 Angstrom of titanium deposition. Following deposition, the titanium films were oxidized by exposure to air at relatively low temperatures (T < 100 degrees C). Very thin titanium films (3 Angstrom) oxidized completely. When thin titanium films (10-20 Angstrom) were oxidized, a layered film formed with a sub-oxide (TiO) core and a titanium dioxide surface layer. When thicker films (> 20 Angstrom) were oxidized, a layered film was also produced with a titanium core and titanium oxide surface layer.