3.35V High Voltage Electroforming Generator in 28nm with 5.3mV ripple and 46% efficiency for HfO2-based Memristors

A high voltage (HV) that is usually not available in modern nodes is required to form memristors. A scalable implementation requires the HV to be generated on chip and this work proposes such a generator. In a 28 nm CMOS process, a three-stage charge pump (CP)) is designed in the absence of HV transistors. For the HfO2 based memristor electroforming (EF), a developed CP runs with an efficiency of 46.5% at an output voltage of 3.35 V and a load current of $184.9 \mu \mathrm{~A}$ from a 1.8 V supply. The optimum design strategy for a cross-coupled charge pump (CC-CP) is explained for a low ripple $\lt6 \mathrm{mV}$, while at the same time ensuring lower capacitor value and high reliability. The results of an over-voltage analytical investigation have important ramifications for lowering the overall area without compromising output voltage or CP efficiency. Monte Carlo simulation for 200 samples were also performed to verify the design’s robustness. However, the proposed design can be readily extended to any memristor application or material, thereby paving the way for the integration of fully integrated chips (ICs) for memristor EF in smaller technology nodes.