Imec and Panasonic have fabricated a 2Mbit resistive RAM (RRAM) cell based on TaOx technology on a 40nm process. The approach, said to have precise filament positioning and high thermal stability, is believed to pave the way to realising 28nm embedded applications.
RRAM is based on current or voltage induced switching of a resistive element material between two metals. In developing the memory, imec and Panasonic developed a method that overcomes filament instability – one of the critical parameters that impacts the memory state during read operations.
The method uses a combination of process technologies, including low-damage etching, cell side oxidation and an encapsulated cell structure with an Ir/Ta2O5/TaOx/TaN stacked film structure with a filament at the centre of the cell.
The array is said to withstand 100k cycles and to retain data from 10 years at 85°C. Filament control and thermal stability technologies are said to be suitable for the technology to be used at 28nm.
Gosia Jurczak, director of imec's research program on RRAM devices stated: "We have proven the potential of this promising memory concept as embedded nonvolatile memory [at the] 28nm node, where conventional NOR flash shows scaling limitations. This result is a confirmation of our leadership position in research and development on resistive memory."