Phase‐Change Memory: A Historic Perspective

The phase‐change memory (PCM) technology is one of the most studied emerging technologies for both the stand‐alone and embedded memory markets. It is based on the peculiar properties of a chalcogenide material, able to make reversible transitions between a poly‐crystalline, high conductivity phase, and an amorphous, high resistivity phase, thus enabling the storage of the logical bit. PCM allows for an analog‐oriented storage as well, opening the way to an employment on inference for AI applications. The research on PCM began in the late 1960s, driven by the pioneering work of Stanford Ovshinsky, who discovered the threshold and memory switching effects in amorphous materials. An overview of the early work, the cell and array demonstrators all the way to more recent implementations of PCM proves the depth of the research done on this technology. The implementation of different cell architectures and the research on the core material represent the key points for PCM development.