Working temperature dependence of metal-ferroelectric-insulator-semiconductor capacitors using a poly(vinylidene fluoride-trifluoroethylene) copolymer for nonvolatile memory applications

The working temperature dependence of organic ferroelectric capacitors using poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] thin films was investigated for the nonvolatile memory operations. High-frequency C-V characteristics and memory operations, including the ferroelectric memory windows, for the Au/P(VDF-TrFE)/SiO2/Si capacitors were measured as a function of the measurement temperature from RT to 130 .deg. C. In order to confirm the effect of the initial crystallinity of the P(VDF-TrFE), we prepared two types of capacitors by varying the temperature of the final heat treatment for the P(VDF-TrFE) to 70 and 140 .deg. C. For the capacitor with the 70 .deg. C-dried P(VDF-TrFE) film, the observed characteristics were affected by complex effects such as temperature-dependent ferroelectric properties, a temperature-induced crystallization process, and undesirable charge injection. On the contrary, for the capacitor with the 140 .deg. C-annealed P(VDF-TrFE) film, the memory window decreased and finally vanished with increasing working temperature. The memory window width of 1.58 V was very stable even at 80 .deg. C, and the C-V curve was almost recovered to the initial state after cooling from 130 .deg. C to RT.