Vacuum‐free fabrication of a low‐voltage multi‐bit memory device based on a ferroelectric polymer and photosensitive film

Abstract

A multi-bit memory device was fabricated using a ferroelectric polymer. For multi-bit storage, a capacitive-type memory was configured to have two different thicknesses: a thinner sub-capacitor to represent the polarization reversal at a lower voltage and a thicker sub-capacitor that allows the two sub-capacitors to operate in different voltage ranges. The thin film was composed of a single ferroelectric polymer film and the thick film was composed of a hybrid film of a ferroelectric polymer and a photosensitive polymer. The photosensitive polymer reacted with ultraviolet light, so it was patterned by a conventional lithography process. The external voltage was divided into two layers, the ferroelectric layer and the photosensitive layer, which resulted in polarisation reversal at a higher voltage region. The most important feature of this work is that no vacuum equipment was used in the manufacturing process of the memory device. In the manufacturing process of the conventional multi-bit memory device, vacuum equipment was required to remove the polymer film. Therefore, the size of the substrate is limited and the productivity is inevitably lowered. The proposed multi-bit memory device and its fabrication process will be useful because it has many advantages in terms of productivity compared to existing processes.