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超薄栅氧化层的TDDB特性与寿命评估
Characteristics and Lifetime Evaluation of TDDB of Ultrathin Gate Oxide
【作者】 廖翠萍；
【导师】 刘红侠；
【作者基本信息】 西安电子科技大学 ， 微电子学与固体电子学， 2007， 硕士
【摘要】 随着超大规模集成电路的不断发展,超薄栅氧化层的质量对器件和电路可靠性的作用越来越重要。经时绝缘击穿（TDDB）是评价薄栅氧化层质量的重要方法。本文介绍了氧化硅结构及其作为栅氧化层的击穿机理和几种主要TDDB击穿模型,重点介绍了其中的1/E模型。论述了薄栅氧化层TDDB可靠性表征方法及其相关参数。采用恒定电压法,对同一种工艺条件,沟道长为90nm,栅氧化层厚度为1.4nm的NMOSFET施加五种电压应力,测试其相应的击穿时间。比较了相同器件在不同电应力条件下击穿时间和击穿栅漏电流的差异,通过不同应力下样品的击穿时间得到与其对应的栅氧化层累积失效分布图和中位寿命,进而完成1/E模型参数的提取,最后由模型外推出器件在正常工作电压下栅氧化层的寿命,并分别从应力类别和应力大小两个方面对实验结果进行了修正。此外,栅氧化层发展的另一个方向是寻找高k栅介质替代传统的氧化硅,文中就如何选择高k栅介质材料进行了论述,并对氧化硅的理想替代物HfO2及其电学特性做了详细讨论。
【Abstract】 With the development of very large scale integrated circuit (VLSI), the quality of ultrathin gate oxide plays a very important role in the reliability of devices and circuits. Time Dependent Dielectric Breakdown (TDDB) is an important method to evaluate the quality of thin gate oxide. In this thesis, the structure and the breakdown mechanism of SiO2 and several primary breakdown models are introduced. The 1/E model is presented in detail. The reliability characterization methods of TDDB and its correlative parameters are discussed. Constant voltage TDDB test has been done on some NMOSFET which are in the same technological conditions, with the length of channel of 90nm and thickness of gate oxide layer of samples of 1.4nm, respectively. The corresponding breakdown time of gate oxide layer were tested under five kinds of gate stresses. The breakdown process of ultrathin gate oxide is analyzed according to the failure criterion of gate current. The breakdown time and gate leakage current are compared under different gate stresses, we have obtained the distribution diagram of cumulative failure probability and mid-position lifetimes of samples under five kinds of gate stresses. The parameters of 1/E model are extracted, and the lifetime of gate oxide layer of NMOSFET under normal functional mode is calculated. Taking different types and values of gate stresses into account the service lifetime from TDDB testing has been corrected. It is also necessary to find a new high-k gate dielectric to replace silicon dioxide. How to select high-k gate dielectric materials and electric characteristics of HfO2are introduced in the last chapter of this paper.