高密度铌酸锂单晶薄膜铁电二极管存储器

Present commercial nonvolatile ferroelectric thin-film memories utilize a transistor and a capacitor as a storage unit, where the data can be read out destructively through charge integration. This limits the high-density integration of the memories. To overcome this problem, we fabricated a LiNbO3 single-crystal memory using ion injection and film peeled-off techniques on Si substrates with the film thicknesses of 50-500 nm in large area. The cell can be shrunk with the size of <50 nm in contacts with left and right electrodes on the film surfaces. Under the application of an in-plane electric field, the domain within each cell can be switched towards the left or the right electrode for the realization of nonvolatile data storage. The switched domain can form an erasable wall against the underlying unswitched matrix of the bulk domain. The domain wall is conductive, which enables the nondestructive readout of the data within the cell. After the optimization of the film composition and crystal orientation, the maximum readout current can exceeds 1A with on/off current ratio of >1000 , write voltage of <5 V, write time of <5 ns, endurance cycles of 10 orders, and retention time of 10 years.

目前商业化非挥发铁电薄膜存储器采用了一个晶体管和一个铁电电容(1T/1C)的单元结构以及电荷积分的破坏性读取技术，限制了存储器集成密度的提高。为了克服以上困难，我们基于离子注入和剥离技术，在Si衬底上低温制备一层50-500nm厚的大面积铌酸锂单晶铁电薄膜；运用电子束直写和离子刻蚀技术，在以上单晶薄膜表面制备尺寸小于50纳米的存储单元和左右读写电极；通过左右电极施加面内电场，控制存储单元内电畴向左或向右取向，实现信息非挥发性写入，并与底层不翻转的电畴形成可擦写畴壁；该畴壁导电，通过畴壁开关电流可以非破坏性地读出存储单元中逻辑信息。通过优化铌酸锂单晶薄膜的组分和晶体取向，实现可读出开态电流大于1微安，开关电流比大于1000，读写电压小于5V，读写时间小于5ns，擦写次数达10个量级，信息保持时间能够满足10年要求。

采用高度绝缘的铌酸锂单晶薄膜材料实现与硅基电路的低温键合，突破存储单元一致性和可重复性等关键工艺，提出一种全新概念的非易失性铁电畴壁存储器。通过在薄膜表层与底部参考层间形成平行和反平行的畴结构，实现“0”和“1”信息的非易失性写入，同时在它们二者之间形成可擦写的导电畴壁。通过可擦写畴壁的高低电阻，实现信息的非破坏性电流读出，区别于传统的电荷积分的破坏性读取技术。发现存储单元的表面层具有天然选择管功能，可限制畴壁电流的单向导通，适用于大规模交叉棒阵列集成，从而能够大幅提高存储密度。通过优化铌酸锂单晶薄膜的组分和晶体取向，开态电流可达1-10微安，开关电流比大于10000。发现存储器的读写电压随器件尺寸等比例减小，41nm单元在3V时读写时间可小于5ns，抗疲劳强度大于10的10次方，掉电数据保持能力大于10年。获得授权发明专利8项，另申请8项。培养硕、博研究生6名。在Nature Materials、Nature Communications等国际知名刊物发表受本项目标注的科技论文19篇。

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