【作者】 张维；

【导师】 周白杨；

【作者基本信息】 福州大学 ， 材料物理与化学， 2014， 硕士

【摘要】 随着半导体工艺的技术节点不断地向前推进,以基于浮栅结构的闪存为代表的传统非挥发性存储器面临着越来越严重的技术瓶颈。目前,学术界已对下一代非挥发性存储器展开了广泛的研究,阻变存储器因具有高读写速度、高集成度、多值存储能力和低成本等优势,被认为是下一代非挥发性存储器的有力竞争者。本文采用(反应)磁控溅射方法在ITO玻璃衬底上沉积(AlCu掺杂型)Ti02薄膜阻变介质层和上电极以制备薄膜阻变元件,通过采用掺杂技术及不同的上电极(W、Cu、Al、Ti)组合,以期进一步改善元件的阻变特性。研究结果表明：通过更换不同的上电极材料会给TiO2薄膜阻变元件的阻变特性造成很大影响：W上电极元件呈现出了稳定的双极阻变特性,且阻变窗口稳定、耐受性良好,元件的阻变机理符合导电细丝机制；Cu上电极消除了元件的Forming过程,并带来了非常稳定的高、低阻值,但同时也导致了不利于实际操作的“非典型性”Reset过程；Al上电极使得元件的耐受性变差,并因-的迁移率较低而改变了元件的阻变机理；以Ti作为上电极的元件没有发现阻变特性,可能与界面的欧姆接触有关。A1掺杂能有效提升Ti02薄膜的阻变特性：Al的掺入降低了TiO2薄膜内的漏电流,将元件的阻变窗口值提高了一个数量级；由于掺入的Al3+离子能降低薄膜中氧空位的形成能,使得氧空位导电细丝的形成更容易,进而降低了元件的操作电压。但在不同上电极材料的匹配下Al掺杂达到的效果不尽相同,具体表现为：Al掺杂可消除Cu上电极元件的“非典型性”Reset过程,因此增强了元件的可操作性；由于Al的掺入使得Ti/Ti02界面的欧姆接触转换为肖特基接触,从而使以Ti作为上电极的元件呈现出了双极阻变特性。Cu掺杂在很大程度上影响了TiO2薄膜阻变元件在高阻态时的导电机制,使得所有元件均或多或少的受到肖特基发射机制的影响；而TiO2及Al掺杂TiO2薄膜大多以空间电荷限制电流效应为主导机制。与Al掺杂的作用相似,Cu掺杂同样使Ti/TiO2界面呈现肖特基接触,从而使Ti上电极元件也呈现出阻变特性。综合对比各元件的阻变特性,发现无论是TiO2薄膜还是Al、Cu掺杂TiO2薄膜,采用金属W作为上电极对薄膜的阻变特性最为有利；而在各阻变介质层中,Al掺杂TiO2薄膜的阻变特性优于TiO2薄膜及Cu掺杂TiO2薄膜。更多还原

【Abstract】 With semiconductor process technology nodes continue to move forward, the traditional non-volatile memory that represented by flash memory is facing increasingly serious bottleneck. Nowadays, the next generation non-volatile memory has been studied widely in academia. Resistive random access memory is one of the strong contenders for next generation non-volatile memory because of its fast switching speed, high integration density, multilevel storage, low cost and other advantages. In this paper, (reactive) magnetron sputtering was utilized to prepare thin film Resistive Random Access Memory including (Al, Cu-doped) TiO2 film which was deposited on ITO glass substrate with different top electrode materials (W, Cu, Al, Ti) to further improve the resistive switching properties of elements.Relevant results showed that changing top electrode materials had a significant impact on the resistive switching properties of elements. The W/TiO2/ITO structure element displayed a stable bipolar resistive switching behavior as stable memory window and good endurance were performed in electrical testing, and the resistive switching mechanism of the element could be explained by conductive filament model. Cu top electrode had eliminated the Forming process of element, and gained the stable resistance value, but also led to the "atypical" Reset process which has a bad effect to actual operation. Al top electrode made the endurance characteristic deteriorated, and changed the resistive switching mechanism of element. TiO2 film wouldn’t be found the resistive switching behavior if the top electrode adopted metal Ti.Al-doped can effectively improve the resistive switching properties of TiO2 film, as the memory window is increased by one order of magnitude, by reducing the leakage current of TiO2 film. The Al3+ ions reduced formation energy of oxygen vacancies so that the conductive filament of oxygen vacancies formed more easily, and therefore the operating voltage of the element is reduced. But Al-doped would achieve different results with different top electrode materials, as follows. The "atypical" Reset process of Cu/TiO2/ITO structure element had been eliminated by Al-doped, thus the practicability of element had been enhanced. The work function of had been reduced by Al-doped so that the Ohmic contact Ti/TiO2 interface was changed into Schottky contact, and then element showed a bipolar resistive switching behavior.Cu-doped greatly influenced the conduction mechanism of element on high-resistance state so that all elements were more or less affected by the Schottky emission mechanism, while TiO2 and TiO2:Al film were mostly controlled by Space Charge Limited Current theory. Similar to the Al-doped, Cu-doped also reduced the work function of TiO2, and the Ti/TiO2/ITO structure element showed a bipolar resistive switching behavior consequently.By comprehensive comparison of resistive switching characteristics of each elements, we found that the use of W top electrode on the characteristics of the film as the most beneficial for both TiO2 film or Al, Cu-doped TiO2 thin film; in various insulator layers, the overall performance of Al-doped TiO2 film was better than the TiO2 film and Cu-doped TiO2 film.更多还原