ABSTRACT
This chapter discusses the physical mechanisms behind Phase change memory (PCM) technology, its unique characteristics, and how these characteristics can be put to use in hardware security applications. PCM utilizes the large electrical contrast between the highly resistive amorphous and highly conductive crystalline states in chalcogenide materials. Typical PCM cells consist of a thin layer of a phase change material deposited over a patterned nanoscale heater. The power required operating PCM devices scales with the device size; smaller devices mean smaller areas being amorphized/crystallized. Spontaneous crystallization of PCM devices exhibits cycle-to-cycle and device-to-device stochastic variations. Noise is typically undesired in electronic devices, especially for multibit storage, but certain properties of noise like bistable fluctuation can be useful for certain applications in hardware security. However, the feature can be utilized in the hardware security systems as physical unclonable functions (PUFs). PUFs generate unique volatile digital keys without the need for tamper-sensing mechanisms, saving area and power overhead.
