Improvement of Thermal Stability of Magnetoresistive Random Access Memory Device with SiN Protective Film Deposited by High-Density Plasma Chemical Vapor Deposition

Embedded magnetoresistive random access memory (MRAM) with multi-level interconnects necessitates that magnetic tunnel junction (MTJ) devices have a thermal stability of 350 °C or higher during fabrication. We have improved thermal stability of MRAM devices using SiN protective film deposited by high-density plasma chemical vapor deposition (HDP-CVD) at 200 °C. The MTJ devices with HDP-CVD SiN protective film did not degrade after post-annealing at 350 °C, which suggests that the HDP-CVD process reduced oxide metal on the etched surface of the MTJ devices and that the SiN film blocked H2O diffusion from the interlayer dielectric film during post-annealing at 350 °C. We also fabricated a 1-kbit MRAM array and experimentally demonstrated thermal stability at 350 °C.