フォーミングを必要としない抵抗変化メモリ（ReRAM）の作製に関する研究

摘要

Generally, a resistance change effect in transition metal oxides appear after the forming process. Here, a conducting filamentary path in which resistive switching occurs is formed in the forming process. However, there are resistive random access memory devices which do not need the forming process. These devices are initially in the low resistance state and start with a reset process, where reset means the switching from a low resistance state to a high resistance state. In these devices, the filaments are considered to be formed already in an initial state and, therefore, we call this kind of filaments "native filaments (NFIs)". The initial resistance of devices containing NFIs and the probability that NFI is observed in as-prepared devices, P_(NFI), as a function of the device area were measured. As a result, it was suggested that NFIs exist in a certain averaged interval around the electrode. On the other hand, the memory layer thickness dependence of P_(NFI) suggests that NFI consists of metal or oxygen vacancies which connect top and bottom electrodes. These vacancies are considered to be introduced during the reactive ion etching process of the top electrode and the memory layer fabrication.%SRAM,DRAM,NAND型フラッシュメモリに代わる次世rn代不揮発メモリとして，高集積，高速動作が見込める抵抗変rn化メモリ（ReRAM）は有力な候補の一つである．ReR-rnAMの動作枚構解明はその性能を最大限に引き出すためのrn大きな課題であるが，近年，抵抗変化現象はフォーミソグrn（Forming）によって遷移金属酸化物中に形成されたフィラrnメソトの陽極端の酸化/還元によって生じるとの考え方が一rn般的となっている．ここで，フォーミングとは絶縁破壊rnと類似の現象であり，これにより低抵抗から高抵抗へと変化rnするリセット，高抵抗から低抵抗へと変化するセットの繰りrn返しが可能となる．