Formation of epitaxial yttrium and erbium silicide on Si(111) in ultra-high vacuum

The growth of epitaxial yttrium and erbium silicide on Si(111) in ultra-high vacuum is studied. Resistivity, epitaxial quality, and pinhole distributions are studied as a function of annealing temperature. The best films result from the growth of a thin template layer (< 50 Å) which is annealed to 700°C, followed by thicker film growth by depositing Y or Er onto a Si substrate heated high enough to induce silicide formation (∼ 300°C). Annealing YSi2−x to 900°C and ErSi2−x to 850°C results in the lowest resistivities (48 μΩ cm for 425 Å YSi2−x and 30 μΩ cm for 200 Å ErSi2−x films). Furthermore, these films have Rutherford backscattering minimum channeling yields χmin ≈ 3% and 2% for Y- and Er-silicides,respectively. YSi2−x appears to have a sharper interface with Si(111) than does ErSi2−x from RBS, while pinhole sizes increase with annealing temperature for both silicides, with well-defined hexagonal features prevalent in the ErSi2−x films only. These are perhaps indicative of the differences in lattice matching with Si(111) of the two silicides.