Phase change memory technology

Abstract

We survey the current state of phase change memory (PCM), a non-volatile solid-state memory technology built around the large electrical contrast between the highly-resistive amorphous and highly-conductive crystalline states in so-called phase change materials. PCM technology has made rapid progress in a short time, having passed older technologies in terms of both sophisticated demonstrations of scaling to small device dimensions, as well as integrated large-array demonstrators with impressive retention, endurance, performance and yield characteristics. We introduce the physics behind PCM technology, assess how its characteristics match up with various potential applications across the memory-storage hierarchy, and discuss its strengths including scalability and rapid switching speed. We then address challenges for the technology, including the design of PCM cells for low RESET current, the need to control device-to-device variability, and undesirable changes in the phase change material that can be induced by the fabrication procedure. We then turn to issues related to operation of PCM devices, including retention, device-to-device thermal crosstalk, endurance, and bias-polarity effects. Several factors that can be expected to enhance PCM in the future are addressed, including Multi-Level Cell technology for PCM (which offers higher density through the use of intermediate resistance states), the role of coding, and possible routes to an ultra-high density PCM technology.Comment: Review articl

Improved structural and electrical properties in native Sb2Te3/GexSb2Te3+x van der Waals superlattices due to intermixing mitigation

“…[1][2][3][4] The most promising materials are the alloys along the GeTeSb 2 Te 3 pseudo-binary line. An impressive achievement has been accomplished when it was realized that PCM memory cells based on superlattices (SLs), structures made of alternating GeTe and Sb 2 Te 3 layers, showed dramatically improved performance in terms of reduced switching energies with ultra-low energy consumption, enhanced write-erase cycle lifetimes, and faster switching speeds.…”

Crystal growth within a phase change memory cell

“…In particular, phase change memory (PCM) has recently emerged as the most promising new nonvolatile solid-state memory technology [1][2][3] . Phase-change materials are also being investigated as building blocks of neuromorphic computing hardware [4][5][6] .…”

Ultra-fast calorimetry study of Ge2Sb2Te5 crystallization between dielectric layers

“…The present work is motivated by the current interest in chalcogenidebased PC-RAM for non-volatile memory. 2,3 For this application, crystallization must be rapid, preferably taking less than the 10 ns switching time typical for DRAM. 3 Yet, in a possibly contradictory requirement, 3 under ambient conditions crystallization must be suppressed to permit long-term (>10 yr) data retention.…”