Influence of Annealing and Argon Pressure on the Microcrystalline Structure of Magnetron-Sputtered Textured Cobalt Films

Abstract

The influence of argon pressure P (0.13 ≤ P ≤ 1 Pa) and vacuum annealing on the microstructure and texture of d ≈ 300 nm thick cobalt films magnetron-sputtered on a SiO₂/Si substrate has been investigated. It has been shown that the films deposited at 0.26 ≤ P < 1 Pa have a columnar microstructure with a mixed hcp-Co(002)/fcc-Co(111) phase. Annealing results in a more uniform microstructure owing to the grain size growth and improves the hcp-Co(002)/fcc-Co(111) texture. The films deposited at 0.13 ≤ P < 0.18 Pa have a mixed crystalline phase: the hcp-Co(002)/fcc-Co(111) and hcp-Co(101) phases coexist with an fcc crystalline phase and fcc-Co(200) texture. Finally, films grown at P ≈ 0.13 Pa are characterized by the fcc-Co(200) texture, and their microstructure is nonuniform over the thickness: at the film–substrate interface, there exists a d_c ≈ 100–130 nm thick layer with a quasi-uniform microstructure, which becomes granulated at d > d_c. Annealing results in a more uniform microstructure of these films due to grain growth, improves the fcc-Co(200) texture, and causes the appearance of the fcc-Co(111)/hcp-Co(002) phase.