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Development of Low-Temperature MOCVD Technology for Ferroelectric Thin Films

铁电薄膜低温MOCVD技术的发展

基本信息

批准号：
11555085
负责人：
TOKUMITSU Eisuke
金额：
$ 7.55万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

The objective of this research project is to develop a low-temperature MOCVD (metalorganic chemical vapor deposition) technology for ferroelectric thin films which will be used for future nonvolatile memory applications. In this research project, we introduced RF plasma in the growth of ferroelectric SrBi_2Ta_2O_9 (SBT) films by liquid-delivery MOCVD to reduce the crystallization temperature. We first used Sr[Ta(OC_2H_5)_6]_2 as a Sr-Ta source and showed that low-temperature (350℃) deposition of the film followed by high-temperature (750℃) crystallization annealing is necessary to obtain ferroelectric SrBi_2Ta_2O_9 (SBT) films. This is because Sr[Ta(OC_2H_5)_6]_2 can be easily decomposed at high temperatures, which makes the composition control difficult. Hence, we next used a novel Sr-Ta source precursor, Sr[Ta(OC_2H_5)_5(OC_2H_4OCH_3)]_2, which is more thermally stable than the conventional source, to overcome this problem. Using the Sr[Ta(OC_2H_5)_5(OC_2H_4OCH_3)]_2, we grew good ferroelectric SBT films with a remanent polarization of 6.2 μC/cm^2 and a coercive field of 62 kV/cm at 750℃ without RF plasma. By applying the RF plasma during the growth, we succeeded in reducing the crystallization temperatures to as low as 615℃. This temperature is about 150℃ lower than the temperature required in the conventional techniques. Remanent polarization of the ferroelectric SBT film grown by the plasma-assisted MOCVD technique at 615℃ with an RF power of 20W was 5.8 μC/cm^2, which is comparable to the remanent polarization obtained by the conventional techniques around 750℃.

本研究项目的目标是开发一种用于铁电薄膜的低温MOCVD(金属有机化学气相沉积)技术，该技术将用于未来的非易失性存储应用。在本研究项目中，我们将射频等离子体引入到液态MOCVD法生长铁电薄膜中，以降低薄膜的晶化温度。我们首次使用了Sr[Ta(OC_2H_5)_6]_2作为Sr-Ta源，证明了低温(350℃)沉积薄膜和高温(750℃)晶化处理是获得铁电薄膜所必需的。这是因为锶[Ta(OC_2H_5)_6]_2在高温下很容易分解，这给成分控制带来了困难。因此，我们接下来使用了一种新型的锶-钽源前驱体，锶[Ta(OC_2H_5)_5(OC_2H_4OCH_3)]_2，它比传统的源更热稳定，以克服这个问题。用锶[Ta(OC_2H_5)_5(OC_2H_4OCH_3)]_2，在没有射频等离子体的情况下，获得了剩余极化为6.2μC/cm~2，在750℃下的矫顽场为62 kV/cm的铁电薄膜。通过在生长过程中使用射频等离子体，我们成功地将结晶温度降低到了615℃。该温度比传统技术中所需的温度低约150℃。在射频功率为20W、频率为615℃的条件下，用等离子体辅助MOCVD技术生长的铁电薄膜的剩余极化为5.8C/cm2，与传统工艺获得的约750μ的剩余极化相当。