Thermal Stability and Electrical Resistivity of SiTaN[sub x] Heating Layer for Phase-Change Memories

Highly resistive amorphous films were studied focusing on their use as heating layers for phase-change random-access memory (PCRAM). The measured electrical resistivity of films between 0.069 and fulfills the requirements of a suitable heating layer suggested by simulations and is determined by nitrogen content which is tunable up to 52.8%. The films with higher nitrogen contents showed excellent thermal stability with amorphous structure sustained until at least . However, these samples exhibited a high degree of temperature-dependent resistivity and showed a negative temperature coefficient of resistance (TCR) at the temperature range . The negative TCR increases with increasing N content and ratio. The binding energy of films changes with nitrogen content and ratio, conforming with the performance of electrical resistivity. By considering electrical resistivity at the range and low TCR, compositions, 33.5–34.5 Si, 15.0–16.0 Ta, and 48–50 N in atom %, are recommended optimal for PCRAM heating layers. The single cells with a heating layer underwent preliminary testing.