Role of an encapsulating layer for reducing resistance drift in phase change random access memory

Abstract

Phase change random access memory (PCRAM) devices exhibit a steady increase in resistance in the amorphous phase upon aging and this resistance drift phenomenon directly affects the device reliability. A stress relaxation model is used here to study the effect of a device encapsulating layer material in addressing the resistance drift phenomenon in PCRAM. The resistance drift can be increased or decreased depending on the biaxial moduli of the phase change material (YPCM) and the encapsulating layer material (YELM) according to the stress relationship between them in the drift regime. The proposed model suggests that the resistance drift can be effectively reduced by selecting a proper material as an encapsulating layer. Moreover, our model explains that reducing the size of the phase change material (PCM) while fully reset and reducing the amorphous/crystalline ratio in PCM help to improve the resistance drift, and thus opens an avenue for highly reliable multilevel PCRAM applications.

Phase Change Random Access Memory for Neuro‐Inspired Computing

“…[144] The design of encapsulating layer (in Figure 9f) using SiO 2 , [145] TiN, or Al 2 O 3 , whose biaxial moduli is much different to that of the phase change materials, is demonstrated to block oxygen penetration and mitigate the resistance drift. [145][146][147][148] Recently, a number of advanced systematic R-drift mitigation approaches, such as reference-cell-based resistance tracking, [149] DRAM-like refresh resistance drift, [150] resistance drift compensation (RDC) scheme, [151] and R-SET technique, [139] have been verified by IBM, Samsung Electronics, Macronix, and CEA-LETI, respectively. These approaches have been successfully demonstrated in the application of multilevel cell PCRAM as storage, and are serving for high-precision neuro-inspired computing.…”