Stress and Microstructure Evolution in Mo Thin Films Without or with Cover Layers During Thermal-Cycling

• Main Authors: Eunmi Park, Marietta Seifert, Gayatri K. Rane, Siegfried B. Menzel, Thomas Gemming, Kornelius Nielsch
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Materials
• Subjects: molybdenum thin films; high-temperature behavior; intrinsic stress
• Online Access: https://www.mdpi.com/1996-1944/13/18/3926

The intrinsic stress behavior and microstructure evolution of Molybdenum thin films were investigated to evaluate their applicability as a metallization in high temperature microelectronic devices. For this purpose, 100 nm thick Mo films were sputter-deposited without or with an AlN or SiO₂ cover layer on thermally oxidized Si substrates. The samples were subjected to thermal cycling up to 900 °C in ultrahigh vacuum; meanwhile, the in-situ stress behavior was monitored by a laser based Multi-beam Optical Sensor (MOS) system. After preannealing at 900 °C for 24 h, the uncovered films showed a high residual stress at room temperature and a plastic behavior at high temperatures, while the covered Mo films showed an almost entirely elastic deformation during the thermal cycling between room temperature and 900 °C with hardly any plastic deformation, and a constant stress value during isothermal annealing without a notable creep. Furthermore, after thermal cycling, the Mo films without as well as with a cover layer showed low electrical resistivity (≤ 10 μΩ·cm).