Reliability Impact of Chalcogenide-Structure Relaxation in Phase-Change Memory (PCM) Cells—Part I: Experimental Study

Abstract

The phase-change memory (PCM) relies on the electrical properties of the chalcogenide materials to represent the stored bit of information. As a result, data stability depends on structural relaxation (SR) in the amorphous chalcogenide phase, which results in a temperature-accelerated time evolution of the electrical properties of the active material. Here, we address the time, temperature, and bias dependence of SR effects on the amorphous 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> (GST) material used in PCM cells. Electrical measurements for increasing annealing time and temperature indicate that SR can be described by a defect annihilation process in the amorphous chalcogenide material. Finally, the stability of chalcogenide resistance as a function of the read conditions is discussed, for the purpose of reducing the impact of SR on the reliability of PCM devices.