3D stacked IGZO 2T0C DRAM array with multibit capability for computing in memory applications

Traditional dynamic random access memory (DRAM) technology faces grand challenges in power consumption due to the constant data refresh and in density due to the physical limit for dimension scaling. Recently, two-transistor zero-capacitor (2T0C) DRAM based on amorphous indium gallium zinc oxide (IGZO) exhibits long data retention owing to its extremely low off-state leakage current. Furthermore, the low thermal budget of the IGZO channel enables the monolithic three-dimensional (3D) stacking for higher bit density beyond the planar scaling limit. However, the demonstration of 3D stacking for IGZO has been limited to 2T0C DRAM single cell. In this work, an 8 by 8 3D stacked IGZO 2T0C DRAM array was designed and manufactured with optimized electrical characteristics, exhibiting 3-bit storage with over 100-second retention time. Furthermore, a neural network model has been demonstrated to achieve an accuracy of 94.95% in image recognition, providing for promising pathway toward computing in memory to overcome the “memory wall.”