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Structures and Generation Mechanisms of Defects in High-k Dielectric Films for Silicon ULSIs

硅超大规模集成电路用高k介质薄膜的结构及缺陷产生机制

基本信息

批准号：
16360160
负责人：
OHKI Yoshimichi
金额：
$ 9.54万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360160/
关键词：
gate insulator high-k dielectrics hafnium silicate zirconium silicate hafnia zirconia plasma CVD photoluminescence

项目摘要

For the coming sub-65 nm complementary metal-oxide-semiconductor (CMOS) technology, high-k materials such as hafnia (HfO_2), hafnium silicate (Hf_xSi_<1-x>O_y), zirconia (ZrO_2), and zirconium silicate (Zr_xSi_<1-x>O_y) are expected to take the place of SiO_2 as the basic material for gate dielectrics. However, there is a high possibility that a lot of localized states due to defects are present in the band gap of these high-k candidates. These localized states are assumed to cause various dielectric malfunctions such as high leakage current, low breakdown voltage, and threshold variation. Therefore, detailed and systematic research on the localized states is indispensable to understand the effects of the defects on electrical properties.From this viewpoint, we have carried out basic studies on HfO_2, Hf_xSi_<1-x>O_y, ZrO_2, and ZrxSi_<1-x>O_y, using photoluminescence (PL) as a common tool that can provide fundamental information about the band gap energy and localized states. X-ray ph … More otoelectron spectroscopy (XPS) analyses were also carried out to investigate the band profiles. Furthermore, the effects of postannealing on the electrical properties of the high-k materials were also studied.Energy band profiles were investigated by XPS for amorphous hafnia and hafnium silicate films sandwiched between an evaporated Au electrode and a Si substrate. Valence band offset and conduction band offset decrease until they become almost constant with an increase in hafnium content at both Si and Au sides. In literature, similar decrease in the valence band offset was reported in zirconium silicate.Photoluminescence spectra induced by UV photons were measured for amorphous hafnia and zirconia deposited by plasma-enhanced chemical-vapor deposition, amorphous hafnia deposited by pulse laser deposition, and crystalline yttria-stabilized zirconia (YSZ). A PL peak appears around 2.7 to 2.9 eV similarly in all hafnia and zirconia samples, irrespective of the difference in crystallinity, oxygen deficiency, source alkoxide, deposition method, or the substrate material. The decay profile of the PL is also similar in all the samples. These results indicate that the PL is inherent in hafnia and zirconia, and is not due to impurities, oxygen vacancy, or interface defects between the sample and the substrate. From PL excitation (PLE) and vacuum-ultraviolet (VUV) absorption measurements, the PL was found to be excited by UV photons to tail states at the band edges. When the samples were annealed at 900℃, a new PL peak appears around 4.2 eV in all the samples except YSZ. The PLE and VUV absorption measurements indicate that the 4.2-eV PL is excited due to the interband absorption.Mechanisms of PLs induced in hafnium and zirconium silicates were also discussed. A broad PL spectrum was observed from 2.0 to 5.0 eV similarly in both silicates. This PL has two components with peaks around 2.8 to 3.0 eV and 3.8 eV for hafnium silicates and those around 2.7 to 3.0 eV and 3.8 eV for zirconium silicates. Time-resolved PL and PL decay measurements indicate that the origin of the PL component around 2.7(2.8) to 3.0 eV is the same as that of the PL component around 2.7 to 2.9 eV in hafnia and zirconia. Furthermore, PLE and VUV absorption measurements show that both the PL components around 2.7(2.8) to 3.0 eV and 3.8 eV are excited to tail states at the band edges. Through these studies, it is assumed that hafnium silicate, zirconium silicate, hafnia, and zirconia have luminescent centers in their band gaps with their respective upper and lower states that have a certain fixed energy difference irrespective of the hafnium or zirconium content.Furthermore, effects of postannealing on the electrical properties of hafnium and zirconium silicates were investigated. When the samples were postannealed in nitrogen monoxide (NO). leakage current and capacitance-voltage (C-V) hysteresis width are decreased drastically. From ESR measurement, it is assumed that paramagnetic defects at the interface between the sample and the Si substrate are responsible for the leakage current and the C-V hysteresis. Furthermore, depth profile by XPS shows that the postnitridation effectively terminates these interface defects and contributes to the improvement in electrical properties. Less

对于即将到来的亚65纳米互补金属氧化物半导体（CMOS）技术，高k材料如氧化铪（HfO_2）、硅酸铪（Hf_xSi_O_y）、氧化锆（ZrO_2）和硅酸锆（Zr_xSi_O_y）有望取代SiO_2作为栅介质的基本材料。<1-x><1-x>然而，在这些高k候选物的带隙中存在由于缺陷而导致的大量局域态的可能性很高。这些局部状态被假定为引起各种介电故障，如高漏电流，低击穿电压，和阈值变化。因此，详细而系统地研究局域态对于理解缺陷对电学性质的影响是必不可少的，从这个角度出发，我们对HfO_2，Hf_xSi_O_y，ZrO_2和ZrxSi_O_y进行了基础性的研究，利用光致发光（PL）作为一种常用的工具，可以提供关于带隙能量和局域态的基本信息。<1-x><1-x>X射线ph值 ...更多信息还进行了光电子能谱（XPS）分析以研究能带分布。此外，还研究了退火处理对高k材料电学性能的影响，用XPS研究了蒸发Au电极和Si衬底之间的非晶SiO2和SiO2薄膜的能带分布。随着Si和Au两侧铪含量的增加，价带偏移和导带偏移减小，直到它们变得几乎恒定。在文献中，类似的价带偏移的减少在硅酸锆中被报道。测量了由等离子体增强化学气相沉积法沉积的非晶氧化钇和氧化锆，由脉冲激光沉积法沉积的非晶氧化钇和结晶氧化钇稳定的氧化锆（YSZ）的紫外光子诱导的光致发光光谱。PL峰出现在2.7至2.9 eV附近，类似地在所有氧化铈和氧化锆样品中，而不管结晶度、氧缺乏、源醇盐、沉积方法或衬底材料的差异。PL的衰减曲线在所有样品中也是相似的。这些结果表明，PL是固有的氧化铈和氧化锆，而不是由于杂质，氧空位，或样品和衬底之间的界面缺陷。从PL激发（PLE）和真空紫外（VUV）吸收测量，PL被发现是由紫外光子激发到带边的尾态。当样品在900 ℃退火时，除YSZ外，所有样品都在4.2eV附近出现一个新的PL峰。PLE和VUV吸收测量表明，4.2eV的PL是由带间吸收激发的，并讨论了铪和锆硅酸盐中PL的产生机理。在两种硅酸盐中，从2.0至5.0 eV类似地观察到宽的PL光谱。该PL具有两个分量，其中对于硅酸铪，峰值在2.8至3.0 eV和3.8 eV附近，对于硅酸锆，峰值在2.7至3.0 eV和3.8 eV附近。时间分辨的PL和PL衰减测量表明，PL组件的起源约2.7（2.8）至3.0 eV的是相同的PL组件的约2.7至2.9 eV的氧化铈和氧化锆。此外，PLE和VUV吸收测量表明，在2.7（2.8）至3.0 eV和3.8 eV附近的PL分量被激发到带边的尾态。通过这些研究，我们假设硅酸铪、硅酸锆、氧化铈和氧化锆在其带隙中具有发光中心，且其各自的上、下态具有一定的能量差，而与铪或锆的含量无关。此外，我们还研究了退火后处理对硅酸铪和硅酸锆电学性能的影响。当样品在一氧化氮（NO）中退火后。漏电流和电容-电压（C-V）滞后宽度显著减小。从ESR测量，它被认为是在样品和Si衬底之间的界面处的顺磁缺陷是负责的漏电流和C-V滞后。此外，XPS深度分布表明，后氮化有效地终止这些界面缺陷，并有助于改善电性能。少