Oxygen Distribution around Filament in Ta-O Resistive RAM Fabricated Using 40 nm CMOS Technology

• Published in: 2018 IEEE International Memory Workshop (IMW) pp. 1 - 4
• Main Authors: Arita, Masashi, Tsurumaki-Fukuchi, Atsushi, Takahashi, Yasuo, Wei, Zhiqiang, Muraoka, Shunsaku, Ito, Satoru, Yoneda, Shinichi
• Format: Conference Proceeding
• Language: English; Japanese
• Published: IEEE 01.05.2018
• Subjects: Brightness; Modulation; Resistance; Scanning electron microscopy; Switches; Tantalum
• DOI: 10.1109/IMW.2018.8388844

The oxygen distributions in resistive random access memory (ReRAM) cells containing one-transistor-one-resistor (1T1R) and one-resistor (1R) arrays with Ta2O5/TaOx/TaOy structures that were fabricated using 40 nm complementary metal-oxide-semiconductor (CMOS) technology were investigated. A conduction spot contributing to switching was identified through electron beam absorption current (EBAC) observation and analyzed using the scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS). A clear conductive filament (CF) was observed in a 1R cell after 1k switching cycles, while a CF remained unclear in 1T1R cells with low power injection for switching, even after 100k cycles. It was clarified that the CF region contained less oxygen than the surrounding areas in the Ta2O5 and TaOx layers, although it contained more oxygen in the TaOy layer. In this case, the TaOy layer seems to act as an oxygen reservoir. The contribution of oxygen vacancies to conduction was confirmed experimentally.