Strain induced (Ba,Sr)TiO3 thin films for metal-ferroelectric-insulator-semiconductor memory devices

Strain induced Metal-Ferroelectric-Insulator-Semiconductor (MFIS) has been proposed for non-volatile ferroelectric random access memory (NV-FRAM). Thi s MFIS structure employs (Ba,Sr)TiO3 (BST) thin films as a ferroelectric la yer. These BST thin films were at paraelectric composition and were transfo rmed to have a tetragonality due to the strain induced into the BST films. X-ray diffraction study on the BST layer revealed that the in-plane and pla ne normal lattice parameters of BST films were different. This suggests tha t the strain induced into the BST thin films distorts the BST lattices. In order to obtain the epitaxial nature of the BST thin films as well as to pr event charge injection from silicon to the BST film, yttria stabilized zirc onia (YSZ) thin films was used as a buffer layer. The MFIS structures with the strained BST thin films exhibited memory window, i.e., non-volatility o f 0.6 V in C-V measurements at the maximum bias voltage of 5 V. We have rep orted the ferroelectric and structural properties in the strain-induced MFI S structure.