A small area and low power true random number generator using write speed variation of oxidebased RRAM for IoT security application

A true random number generator using write speed variation of oxide-based RRAM is proposed for the first time. The signal of this physical unclonable function (PUF) is strong with long duration to be easily and accurately captured by simple circuit, of which the advantage is attributed to the mechanism that the speed variation amplifies the fluctuation of oxygen vacancy trap and de-trap. Some function parts of normal RRAM IP can be reused as entropy source cells and implementation circuit. The variation of write end point is monitored by a self-adaptive write drive circuit to trig a counter, and then serialized into a bit stream. The test chips, which are AlOx/WOx bilayer back-end RRAM fabricated in 0.18 Um logic process, passed all NIST tests with advantages of small area, low power, and not using post-processor corrector. Enough bits can be generated within the endurance limitation to ensure usual Internet of Things (IoT) security application.