Study of Phase Change Random Access Memory (PCRAM) at the Nano-Scale

In this paper, phase change random access memory (PCRAM) cells at the nano-scale was studied. A hybrid patterning process integrating with electron beam lithography (EBL) and optical lithography was used to fabricate nano-PCRAM cell. PCRAM cells with different feature sizes ranging from 40 nm to 200 nm have been fabricated and tested by an in-house developed tester which was capable of generation of pulse with short width. Electrical testing including programming current and speed have been conducted on the nano-cells. The resistance-current curves have shown a good scaling effect on the programming current against the cell size. Besides the current reduction, it was found that nano-PCRAM cells have shown an improved programming speed when its size reduces. RESET speed as fast as 2 ns was achieved for PCRAM cell with 45 nm. The improved speed was possible attributed to the nano-size effect due to the increasing contribution of the interfaces.