Application of Interface Deoxidization Method for the Non-Volatile Memory with Next Generation Structure

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A semiconductor based non-volatile memory with ferroelectric layer has relatively fast read/write speed like DRAM and SRAM and has been expected instead of Flash memory. Low integrated divices have been already commercialized. Such devices that are called FeRAM use electric charge accumulated in ferroelectric layer for memory operation. On the other hand, ferroelectric gate FET is expected for the new generation because scaling law used in the semiconductor field can be applied for the memory structure and it can be used for highly integrated devices with low power consumption. However, there had not been good candidate materials for such a device. In this project, the material design was done as a first step. YMnO_3/Y_2O_3/Si was selected as one of the best candidates and experiments pointed out some issues. By using interface deoxidization method, we succeeded in obtaining epitaxially grown YMnO_3/Y_2O_3/Si capacitors without any SiO_2 layer at the Y_2O_3/Si interface that deteriorates the dielectric properties of the capacitor. By optimizing the deposition conditions, we have succeeded in obtaining YMnO_3/Y_2O_3/Si capacitors with the retention time to be over 10000 sec.