A 1.2 V Power Supply, 2.43 Times Power Efficient, Adaptive Charge Pump Circuit with Optimized Threshold Voltage at Each Pump Stage for Ferroelectric-NAND Flash Memories

A 1.2 V power supply adaptive charge pump for the low voltage and low power ferroelectric (Fe)-NAND flash memory is proposed. The proposed circuit is fabricated with the complementary metal–oxide–semiconductor (CMOS) compatible ferroelectric-gate field-effect transistors (FeFETs) process for Fe-NAND flash memories. By using FeFETs as diodes in the charge pump and optimizing the threshold voltage (V TH) of FeFETs at each pump stage, the power efficiency of the charge pump circuit to generate the program voltage increases from 21.7 to 52.7% without the circuit area and the process step penalty. The V TH optimization of FeFETs is realized by repeating the program and the monitor operations during the testing after the fabrication. During the testing, the power efficiency is monitored to detect the optimal V TH which maximizes the power efficiency at each pump stage. FeFETs in proposed circuits are immune to the disturb and a highly reliable circuit operation is experimentally demonstrated.