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

Group 1B metal films (copper, silver and gold) are attractive for meta llizations in multichip modules (MCM) and integrated circuits because they have high electrical conductivities. Unfortunately, Group 1B meta ls require additional bonding layers for adhesion to insulators (i.e. silicon dioxide or polymers). In this work, thin electrically insulati ng films of titanium oxide on titanium have been investigated as adhes ion layers between gold and a wide variety of insulators. The adhesion layer does not alter the dielectric properties of the insulator surro unding the metal because it is thin. The morphology, composition, and resistivity of the titanium oxide films were studied with angle resolv ed X-ray photoelectron spectroscopy (XPS), scanning tunneling microsco py (STM), and electrical resistance measurements. The results show tha t sputter-deposited titanium films grow by an island growth (Volmer-We ber) 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). Ve ry thin titanium films (3 Angstrom) oxidized completely. When thin tit anium films (10-20 Angstrom) were oxidized, a layered film formed with a sub-oxide (TiO) core and a titanium dioxide surface layer. When thi cker films (> 20 Angstrom) were oxidized, a layered film was also prod uced with a titanium core and titanium oxide surface layer.