Modeling of Set and Reset Operations of Phase-Change Memory Cells

Abstract

Phase-change memory elements with 25-nm Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Te <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> thickness and 25-nm heater diameter with ±2-nm protrusion/recess of the heater are studied using 2-D finite-element simulations with rotational symmetry. Temperature-dependent material parameters are used to solve current continuity and heat equations self-consistently. Melting is accounted for by including latent heat of fusion in heat capacity at melting temperature. Electrical breakdown is modeled using additional field-dependent conductivity terms to enable set simulations. Analyses on current, voltage, energy, power, and minimum pitch requirements are summarized for reset/set operations with 1-ns/20-ns voltage pulses leading to ~500× difference between the reset and set resistance states.