In vacuo fabrication of thin-film cobalt monosilicide (CoSi) on 300 mm wafer level

Abstract

Materials that demonstrate high spin-orbit torque are central to the functionality of next-generation spintronic memory and logic technologies. A promising class of materials for this purpose are topological semimetals. While first experimental results have shown the high spin hall angle of Weyl semimetals such as WTe2, these materials are not readily CMOS-compatible and cannot be easily integrated into existing industry-standard cleanroom processes on a 300 mm wafer level. Cobalt silicides are transition metal silicides that are already well-established in the semiconductor industry. Further applications have opened up with the recent identification of cobalt monosilicide (CoSi) as a chiral topological semimetal. Here, we present material properties of CoSi thin films fabricated on 300 mm wafers using industry-standard cleanroom tools. Metalorganic chemical vapor deposition (MOCVD) was used to deposit Co layers of varied thickness onto wafers with an amorphous Si (a-Si) layer. The stacks were then annealed in the same tool in a vacuum atmosphere. We were able to control the thickness of the fabricated silicide films by adjusting the thickness of the a-Si and deposited Co layers. Relative to the a-Si thickness, the Co thickness was adjusted to obtain silicide films with a 1:1 Co:Si stoichiometry on a nanometer scale. The sensitivity of the composition of the formed silicide to the initial Co to a-Si ratio was investigated using GIXRD. The resistivity of the silicide films was also investigated. Therefore, we speculate that the CoSi film may possess topological properties for efficient charge-to-spin conversion for use in low-power spintronic applications. This methodology paves the way for fabricating large-scale silicide films on a CMOS platform for spintronic applications.