Nano Group, Southampton Nanofabrication Centre, Department of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UK.
Nanotechnology. 2016 Aug 26;27(34):345705. doi: 10.1088/0957-4484/27/34/345705. Epub 2016 Jul 15.
Resistive random access memory (RRAM) is considered an attractive candidate for next generation memory devices due to its competitive scalability, low-power operation and high switching speed. The technology however, still faces several challenges that overall prohibit its industrial translation, such as low yields, large switching variability and ultimately hard breakdown due to long-term operation or high-voltage biasing. The latter issue is of particular interest, because it ultimately leads to device failure. In this work, we have investigated the physicochemical changes that occur within RRAM devices as a consequence of soft and hard breakdown by combining full-field transmission x-ray microscopy with soft x-ray spectroscopic analysis performed on lamella samples. The high lateral resolution of this technique (down to 25 nm) allows the investigation of localized nanometric areas underneath permanent damage of the metal top electrode. Results show that devices after hard breakdown present discontinuity in the active layer, Pt inclusions and the formation of crystalline phases such as rutile, which indicates that the temperature increased locally up to 1000 K.
阻变随机存取存储器（RRAM）因其具有竞争力的可扩展性、低功耗操作和高开关速度，被认为是下一代存储设备的有吸引力的候选者。然而，该技术仍面临着一些挑战，总体上阻止了其工业应用，例如低产量、大的开关变异性，以及由于长期操作或高压偏置导致的最终硬性击穿。后一个问题特别值得关注，因为它最终会导致器件失效。在这项工作中，我们通过结合全场透射 X 射线显微镜和软 X 射线能谱分析，对薄片样品进行了研究，以研究软击穿和硬击穿对 RRAM 器件内部发生的物理化学变化。该技术具有高的横向分辨率（低至 25nm），可以在金属顶电极的永久性损坏下，对局部纳米区域进行探测。结果表明，硬击穿后的器件在活性层中存在不连续性，Pt 夹杂和金红石等结晶相的形成，这表明局部温度升高到 1000K 左右。
