A Study of Novel 3 Dimensional Architecture Modeling for Phase Change Memory toword Low Current Operation

Abstract

Phase Change Random Access Memory (PCRAM) of a three-dimensional (3D) vertical cell type for next-generation large-capacity storage was developed. In this paper, we present novel 3D architecture for more efficiently low set and reset currents in PCRAM. In 3D architecture, the sidewall of phase change film is contacted to the vertical heating layer. In special, to realize the small contact areal of under 50 nm2 for low reset current, this structure includes the stacked layers consisting of extremely thin Phase Change Material (PCM) and conduction films, and its fabrication method is proposed. The excellent scalability of the vertical PCRAM's phase-change material makes it possible to reduce the cell size beyond the scaling limit of flash memory. And, we estimated set and reset currents for the proposed structure by 3D simulation method. Here, we confirmed that contact area of 30 nm2 in this structure using Ge2Sb2Te5 as PCM provides reset current of 13.5 uA and set current of 4 uA, which be expected to scaling trend of PCM. Furthermore, it is confirmed that thinner PCM in this structure provides less thermal disturbance to neighboring cell. From this estimation, we expect that this structure can be a promising candidate for high density nonvolatile memory architecture with PCM.