Lateral SbTeN based multi-layer phase change memory for multi-state storage

X-ray diffraction patterns and resistivity measurement indicate that as-deposited N-doped Sb2Te3 (STN) films become amorphous while the as-deposited Sb2Te3 film is crystalline. A lateral as-deposited STN-based multi-layer phase change memory was proposed for multi-state storage. The active region of the device consists of a top 30-nm TiN/180-nm STN/20-nm TiN/bottom 120-nm STN stacked multi-layer. Static switching properties of the device with STN initially starting from the amorphous state exhibit two apparent S-shaped switchings, which correspond to two marked device resistance drops by a factor of 2–5. The first and second threshold voltages are around 2.8–3.2 and 4.3–5.4 V, respectively. Finite element analysis of the device shows that the two switchings could sequentially occur at the electrode steps from the bottom 120-nm STN layer to the top thick 180-nm STN layer.