Patternig method for silicides based on local oxidation

Abstract

Oxidation of CoSi2 layers on Si~100! using oxidation masks has been investigated. It is shown that local oxidation can be used to pattern the silicide layer. This method allows the formation of buried interconnects and metallized silicon mesa structures. Epitaxial CoSi2 silicide layers were grown by molecular beam epitaxy on Si~100!. The SiO2/Si3N4 oxidation mask was patterned photolithographically with linewidths of typically 1.5 mm. During thermal oxidation, SiO2 forms in the unprotected regions of the silicide layer. The silicide is pushed into the substrate in these regions. At a critical oxide thickness, the oxidized region of the silicide layer separates from the unoxidized, in conformance with the structure of the oxidation mask. The oxide capped silicide maintains its uniform layer structure and its single crystallinity in spite of the large shift into the substrate. The method should be applicable also to polycrystalline silicides, such as TiSi2.