Highly electrical resistive SiTiNx heating layers and diffusion barriers for PCRAM

Abstract

Highly electrical resistive amorphous SiTiNx films were explored as both heating layers and diffusion barriers for the cells of phase-change random-access memory (PCRAM). The measured electrical resistivity of SiTiNx films, determined by the nitrogen content x tunable up to 38.68%, is between 0.039–0.69 Ω cm which fulfils the requirements of a suitable heating layer suggested by simulations. SiTiNx films with a medium range of nitrogen content showed excellent thermal stability, very smooth surface and amorphous structure sustaining until at least 800 °C, thus suitable for application in PCRAM. However, SiTiNx films exhibit a high degree of temperature dependent resistivity, and show a different temperature coefficient of resistance with different N contents at the temperature range 400–500 °C. The chemical binding characteristics of SiTiNx films with such higher electrical resistivity were also investigated. The binding energy of Ti 2p spectra in SiTiNx films changes with nitrogen content and shifts to higher energies confirming their susceptibility to oxidation. Besides, interface analysis showed that these films perform excellently as a diffusion barrier between a W bottom electrode and the Ge2Sb2Te5 phase-change layer after evaluation annealing at 600 °C for 30 min.