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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

在未来的65 nm以下互补金属氧化物半导体（CMOS）技术中，高钾材料如半氧化锆（HfO_2）、硅酸铪（Hf_xSi_<1-x>O_y）、氧化锆（ZrO_2）和硅酸锆（Zr_xSi_<1-x>O_y）有望取代SiO_2作为栅极电介质的基础材料。然而，这些高k候选者的带隙中很有可能存在由于缺陷而产生的大量局域态。假设这些局部状态会导致各种介电故障，如高泄漏电流、低击穿电压和阈值变化。因此，要了解缺陷对电学性能的影响，必须对其局部化状态进行详细而系统的研究。从这个角度出发，我们对HfO_2， Hf_xSi_<1-x>O_y, ZrO_2, ZrxSi_<1-x>O_y进行了基础研究，利用光致发光（PL）作为一种常用的工具，可以提供带隙能量和局域态的基本信息。并用电子能谱（XPS）对其谱带进行了分析。此外，还研究了后镀工艺对高k材料电学性能的影响。用XPS研究了夹在蒸发金电极和硅衬底之间的非晶铪和硅酸铪薄膜的能带谱。价带偏置和导带偏置随着Si和Au两侧铪含量的增加而减小，直到它们几乎保持不变。在文献中，类似的价带偏移在硅酸锆中也有报道。测量了等离子体增强化学气相沉积法、脉冲激光沉积法和钇稳定氧化锆（YSZ）的非晶半氧化锆和非晶半氧化锆的紫外光子诱导发光光谱。在所有的半氧化锆和氧化锆样品中，PL峰都相似地出现在2.7至2.9 eV附近，而不考虑结晶度、氧缺乏、源醇氧化合物、沉积方法或衬底材料的差异。在所有样品中，PL的衰减曲线也是相似的。这些结果表明，PL是固有的半氧化锆和氧化锆，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）吸收测量中，发现PL被紫外光子激发到带边缘的尾态。900℃退火后，除YSZ外，其余样品均在4.2 eV左右出现新的PL峰。PLE和VUV吸收测量表明，4.2 ev的PL是由于带间吸收而被激发的。还讨论了在硅酸铪和锆中诱导PLs的机理。在这两种硅酸盐中观察到从2.0到5.0 eV的宽PL谱。该PL有两个组分，其中硅酸铪的峰约为2.8至3.0 eV和3.8 eV，硅酸锆的峰约为2.7至3.0 eV和3.8 eV。时间分辨PL和PL衰减测量表明，在半氧化锆和氧化锆中，2.7（2.8）至3.0 eV的PL成分的起源与2.7至2.9 eV的PL成分的起源相同。此外，PLE和VUV吸收测量表明，2.7(2.8)~ 3.0 eV和3.8 eV附近的PL组分在带边缘被激发到尾态。通过这些研究，我们假设硅酸铪、硅酸锆、铪和氧化锆的带隙中都有发光中心，无论铪或锆的含量如何，它们各自的上下态都有一定的固定能差。此外，还研究了电镀后对硅酸铪和锆电学性能的影响。当样品在一氧化二氮（NO）中进行电泳时。漏电流和电容-电压滞回宽度显著减小。从ESR测量可以推测，泄漏电流和C-V滞回是样品和Si衬底之间界面的顺磁缺陷造成的。此外，XPS深度剖面显示，后氮化有效地消除了这些界面缺陷，有助于提高电性能。少