Investigation of Ferroelectric Grain Sizes and Orientations in Pt/Ca(x)Sr(1–x)Bi(2)Ta(2)O(9)/Hf–Al–O/Si High Performance Ferroelectric-Gate Field-Effect-Transistors

Electron backscatter diffraction (EBSD) was applied to investigate the grain size and orientation of polycrystalline Ca(x)Sr(1–x)Bi(2)Ta(2)O(9) (C(x)S(1–x)BT) films in ferroelectric-gate field-effect transistors (FeFETs). The C(x)S(1–x)BT FeFETs with x = 0, 0.1, 0.2, 0.5, and 1 were characterized by the EBSD inverse pole figure map. The maps of x = 0, 0.1, and 0.2 showed more uniform and smaller grains with more inclusion of the a-axis component along the film normal than the maps of x = 0.5 and 1. Since spontaneous polarization of C(x)S(1–x)BT is expected to exist along the a-axis, inclusion of the film normal a-axis component is necessary to obtain polarization versus electric field (P–E) hysteresis curves of the C(x)S(1–x)BT when the E is applied across the film. Since memory windows of FeFETs originate from P–E hysteresis curves, the EBSD results were consistent with the electrical performance of the FeFETs, where the FeFETs with x = 0, 0.1, and 0.2 had wider memory windows than those with x = 0.5 and 1. The influence of annealing temperature for C(0.1)S(0.9)BT poly-crystallization was also investigated using the EBSD method.