Study for low-temperature formation of high-quality STNO high-k films for non-volatile memories

本课题的研究目的是利用微波激发高密度等离子体和径向线槽天线，在500℃以下的极低温度下，在大直径晶圆上制备均匀性在±2%以内的高质量高k薄膜（Sr_2(Ta_<1-x>, Nb_x)_2O_7: STNO）。采用溶胶-凝胶、PE-CVD（等离子体增强化学气相沉积）、CVD、溅射等常规的高k成膜方法，在低温条件下难以形成均匀、高速率的高质量栅极绝缘子。在本研究项目中，我们开发了以下新型高k栅极绝缘子形成技术。流程顺序如下。首先，利用微波激发高密度等离子体减轻高k薄膜与硅衬底之间的反应，在低温500℃下在硅衬底上形成高质量的超薄氮化硅薄膜作为阻挡膜。然后利用低能离子轰击平衡电子漂移磁控管等离子体溅射技术在衬底上形成Sr，…More Ta， Nb合金薄膜。然后在微波激发高密度等离子体设备中直接氧化形成高k膜。我们成功地形成了高质量的氮化硅栅极绝缘子膜，具有优异的阻挡能力，极低的泄漏电流（比传统的热生长栅极氧化膜低3个数量级），极低的1/f噪声（比传统的栅极氧化膜低2个数量级），以及优异的电流应力强度（Qbd: 100 C/cm^2）。此外，我们还成功地通过直接氧化各种表面取向的单晶硅、多晶硅和涉及Sr、Ta、Nb合金的金属，形成了具有优异电性能的氧化膜。这些成果不仅实现了高k栅极场效应管的超高速器件，而且建立了一系列先进的加工技术，这些技术必将成为亚100纳米时代微电子领域的主流，对未来的半导体制造技术产生重大影响。少

The purpose of this research project is to develop film formation process technologies for high-quality high-k films (Sr_2(Ta_<1-x>, Nb_x)_2O_7 : STNO) with excellent uniformity within ±2 % over large diameter wafers at very low-temperatures below 500 ℃ by utilizing a microwave excited high-density plasma with a radial line slot antenna.By using the conventional high-k film formation methods such as sol-gel, PE-CVD (plasma enhanced chemical vapor deposition), CVD, and sputtering, it is difficult to form uniform high-quality gate insulator with high-rate at low-temperatures. In this research project we have developed following novel high-k gate insulator formation technologies. The process sequence is as follows. At first, a high-quality ultra-thin silicon nitride film as a barrier film is formed on a silicon substrate at low temperature of 500 ℃ by utilizing the microwave excited high-density plasma to mitigate the reaction between the high-k film and the silicon substrate. Then a Sr, … More Ta, Nb alloy film are formed on the substrate by using a novel sputtering technology with balanced electron drift magnetron plasma utilizing low-energy ion bombardment. Then, high-k film is formed by direct oxidation in the microwave excited high-density plasma equipment.We have succeeded to form high-quality silicon nitride gate insulator films with excellent barrier ability, very low leakage current (3 order of magnitude lower than the conventional thermally grown gate oxide films), very low 1/f noise (2 order of magnitude lower than the conventional gate oxide films), and excellent strength for current stress (Qbd : 100 C/cm^2) by low-temperature direct-nitridation process with NH^* radicals. Furthermore, we have succeeded to form oxide films with excellent electric properties by directly oxidizing the single-crystal silicon with every surface orientation, poly silicon, and metal involving the Sr, Ta, Nb alloys. These results lead not only to the realization of ultrahigh-speed devices with high-k gate FET but also to the establishment of a number of advanced processing technologies which certainly will become the main stream in microelectronics in sub- 100 nm era, impacting greatly the semiconductor manufacturing technology in future. Less