Deposition of stress-free Co-Cr alloy thin films on thin tape substrate by Kr ion sputtering

Co₇₉Cr₂₁ and Co₈₀Cr₁₇Ta₃ films were deposited on the substrate of thin polyethylene naphthalate (PEN) tape by using Kr and Ar ions and the facing targets sputtering (FTS) system. It is important to release the internal stress of Co-Cr films without deterioration of the crystallinity to avoid the curling of magnetic recording tape. Kr ions could make a stable discharge at the working gas pressure as low as 10 ^-5 Torr because of their large ionization cross section, and suppress the recoil of Kr atoms from the target plane surface because of their large mass. Therefore, stress-free Co₈₀Cr₁₇Ta₃ films could be deposited at low Kr pressure of 0.1~0.3 m Torr where Δθ₅₀ of the films deposited on the PEN tape was 8°. The sputtering technique by using Kr ions and the FTS system proved useful for fabricating curl-free magnetic recording tape from crystalline films of Co-Cr alloy such as Co₇₉Cr₂₁ and Co₈₀Cr₁₇Ta₃