Improvements on surface carrier mobility and electrical stability of MOSFETs using HfTaO gate dielectric
Improvements on surface carrier mobility and electrical stability of MOSFETs using HfTaO gate dielectric
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DOI：
10.1109/ted.2004.839114
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发表时间：
2004-11
影响因子：
3.1
通讯作者：
Xiongfei Yu;Chunxiang Zhu;Mingbin Yu;D. Kwong
中科院分区：
文献类型：
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作者：
Xiongfei Yu;Chunxiang Zhu;Mingbin Yu;D. Kwong
首次系统地研究了HfTaO栅介质的物理和电学特性。基于X射线衍射谱和高分辨透射电子显微镜照片，HfO/sub 2/ film的晶化温度随着Ta的引入而显著提高，并且在950/spl deg/C退火30 s后，具有43% Ta的HfTaO/sub 2/ film保持非晶。X射线光电子能谱分析结果表明，随着Ta含量的增加，界面层中Si-O键的形成增多。高的Si-O键原子百分比可能导致HfTaO-Si界面向SiO/sub 2/-Si界面倾斜，并具有良好的界面性质。因此，HfTaO薄膜的界面态密度（D/sub it/）比HfO/sub 2/降低了一个数量级。此外，利用脉冲I/sub d/--V/sub g/测量技术比较了HfO/sub 2/和HfTaO薄膜中电荷俘获引起的阈值电压（V/sub th/）不稳定性，发现HfTaO薄膜的V/sub th/漂移远小于HfO/sub 2/。这表明，HfO/sub 2/薄膜中的电荷捕获被显着抑制掺入Ta。由于HfTaO薄膜中的界面陷阱和电荷陷阱都小于HfO/sub 2/，HfTaO nMOSFET的峰值迁移率比HfO/sub 2/提高了一倍以上，这是由于界面陷阱和电荷陷阱抑制了库仑散射。
Physical and electrical characteristics of HfTaO gate dielectric have been systematically investigated for the first time. Based on the X-ray diffraction spectra and high-resolution transmission electron microscope pictures, the crystallization temperature of HfO/sub 2/ film is significantly increased with incorporating Ta, and the HfTaO with 43% Ta film remains amorphous after annealing at 950/spl deg/C for 30 s. X-ray photoelectron spectroscopy results show that the formation of Si-O bonds in interfacial layer is increased with Ta concentration. The high atomic percentage of Si-O bonds may result in the HfTaO-Si interface inclining to SiO/sub 2/-Si interface, as well as good interface properties. Hence, the interface states density (D/sub it/) in HfTaO film is reduced by one order of magnitude compared with HfO/sub 2/. In addition, charge trapping induced threshold voltage (V/sub th/) instability in HfO/sub 2/ and HfTaO films is compared using a pulsed I/sub d/--V/sub g/ measurement technique, and the V/sub th/ shift in HfTaO film is much lower than HfO/sub 2/. This indicates that charge trapping in HfO/sub 2/ film is significantly suppressed by incorporating Ta. Since both of the interface traps and charged traps in HfTaO film are less than in HfO/sub 2/, more than twice higher peak mobility is achieved in HfTaO nMOSFETs, which is due to the suppression of Coulomb scattering caused by the interface traps and charged traps.