Finite Element Simulations of Phase Change Memory Devices Using Semiconductor Physics

Phase change memory (PCM) is a non-volatile memory in which data is stored as resistance contrast between amorphous and crystalline phases. Many simulation models have been developed to study crystalline to amorphous transition (reset) and amorphous to crystalline transition (set) operations. Ge2Sb2Tes (GST) is the most widely used phase change material, which is a p-type semiconductor in both phases. This work presents a finite element simulation platform that uses semiconductor physics to calculate charge carrier concentration during device operation, along with heat transport physics to estimate temperature. Crystallinity is tracked by solving a simple ordinary differential equation. A PCM line cell, which has experienced a reset pulse of 3.5 V, shows melting, bandgap collapse, and amorphization in the middle. Carrier trapping in the amorphous portion and Schottky barrier formation in the amorphous-crystalline boundary are observed. This type of modeling will be particularly useful in investigating carrier kinetics during set and reset operations and charge trapping-detrapping inside the PCM devices.