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Improvement of ferroelectric and insulator layers in ferroelectric/insulator/semiconductor stacked gate structure

铁电/绝缘体/半导体叠栅结构中铁电体和绝缘体层的改进

基本信息

批准号：
12450147
负责人：
NODA Minoru
金额：
$ 9.02万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

1. It is suggested that leakage current through layer of ferroelectric such as SrBi_2TaO_9 and Sr_2 (Ta_<1-x>, Nb_x)_2O_7 has a dominant effect on memory retention properties of Metal-Ferroelectric-Insulator-Semiconductor (MFIS) structure. Furthermore, it is confirmed especially for the. SBT film that suppression of the leakage improved drastically retention properties, then increased the time by an order of magnitude, more than 2x10^4 s. with some post-oxygen annealing process.2. We proposed a dynamic model where carriers flow though ferroelectric layer and inject into the interface between ferroelectric and insulator layers, thus electric field imposed on the ferroelectric film gradually cancelled and decreased. As a result, experimental results shown above was qualitatively explained.3. A new analysis instrument utilizing ionization potential measurement was proposed and fabricated, which enables us to evaluate the SBT sutface with and without post-oxygen annealing, then to consider the band diagram of MFIS structure. It reveals that, before the annealing, hole conduction dominates the leakage through the SBT film, and that, after the annealing, barrier height against hole increases from 1.6 to 2.0 eV. This result agrees well with the mentioned above, where a reduction of leakage by the annealing improves the memory retention characteristics.4. A Rapid Thermal Annealing process with oxygen atmosphere improved greatly the retention time of MFIS diode. With a very high temperature and short time of 1000℃ and 30 s, the retention time became more than 6x10^5 s (about 1 week), and was extrapolated to about 3x10^7 s (about 1 year).5. A high pressure (7 atm) oxygen annealing was examined in order to improve the retention properties furthermore: It was found that the annealing is effective to reduce the leakage and estimated that Bi_xO_y layer, different from (Bi_2O_2)^<2+> layer, was fermed and suppress the leakage.

1.结果表明，在<1-x>金属-铁电-绝缘体-半导体（MFIS）结构中，通过SrBi_2TaO_9和Sr_2（Ta_，Nb_x）_2O_7铁电层的漏电流对MFIS的存储保持性能有着重要的影响。此外，特别是对于。SBT薄膜的泄漏抑制大大提高了保持性能，然后将时间增加了一个数量级，超过2 × 10^4 s。与一些后氧退火工艺。提出了一种动态模型，即载流子通过铁电层注入铁电层和绝缘层的界面，从而使施加在铁电膜上的电场逐渐抵消和减小。对上述实验结果进行了定性解释.提出并研制了一种利用电离势测量的新的分析仪器，它使我们能够评估SBT表面有和没有后氧退火，然后考虑MFIS结构的能带图。结果表明，在退火前，空穴传导主导通过SBT膜的泄漏，并且，在退火后，对空穴的势垒高度从1.6增加到2.0 eV。这个结果与上面提到的一致，其中通过退火减少泄漏改善了存储器保持特性。采用氧气氛快速退火工艺，大幅度提高了MFIS二极管的保留时间。在很高的温度和1000℃和30 s的短时间内，保留时间超过6x10^5 s（约1周），并外推至约3x10^7 s（约1年）。为了进一步提高保持性能，我们研究了高压氧退火（7atm）：发现退火对降低漏电流是有效的，并估计Bi_xO_y层（不同于（Bi_2O_2）^<2+>层）的形成抑制了漏电流。