於傾斜陰極之陽極氧化系統中外加機械張力成長超薄閘極氧化層技術研究

Investigation of Ultra-thin Gate Oxides Prepared by Anodization with Tensile Stress in Tilted Cathode Anodization System

李宗鴻(Tsung-Hung Li)

指導教授 ： 胡振國

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.00036

摘要

本研究提出一個在氧化過程中彎曲矽晶圓的簡單技術，用以改善二氧化矽超薄閘極氧化層的品質及可靠度。此技術乃基於生長在撐大的矽晶格之上的氧化層可能會因為減少的晶格不匹配而有較好的特性之概念。本研究中的氧化程序進行於我們特別設計的傾斜陰極之陽極氧化系統。在氧化過程中，機械張力施加於矽晶圓，而在氧化層成長完畢後被釋放。

陽極氧化是一種替代的方法用以直接成長二氧化矽於矽晶圓之上。因為其在超薄閘極氧化層的厚度控制之優勢，及可在室溫下進行的特點，我們認為陽極氧化是最適合用以驗證外加張力效應的氧化方法。傾斜陰極陽極氧化系統是本研究提出的一個獨特的修改，除了能夠成長漸變厚度的氧化層，由本實驗中探討的生長機制兼可預測超薄閘極氧化層的特性趨勢。

由外加機械張力成長超薄閘極氧化層技術研究中發現，在外加張力下成長氧化層的元件之平帶電壓和對照組相比往正偏移，此處也提出氫氧根離子之混和機制以解釋。實驗結果顯示在外加張力下成長之超薄閘極氧化層其漏流明顯地被降低，可靠度也大幅改善。

關鍵字

超薄閘極氧化層 ； 陽極氧化 ； 外加機械張力

並列摘要

A simple technique to improve the quality and reliability of SiO2 as ultra-thin gate dielectrics by bending the silicon wafer during oxidation is proposed; this technique is based on the concept that the oxide grown on enlarged silicon lattice may have better property because of reduced lattice mismatch. In this work, the oxidation was carried out in a novel tilted cathode anodization system. During anodization process, mechanical tensile stress was applied to the silicon wafer, and released after gate oxide formation.
Anodization is an alternative way to directly grow SiO2 on silicon substrate; due to its superiority over thermal oxidation in the control of thickness of ultra-thin gate oxide as well as that it can be held at room temperature, we considered that anodization is the most suitable oxidation process to demonstrate the effect of the applied tensile stress. The tilted cathode anodization system, a unique modification proposed in this work, is capable of growing oxides with gradual oxide thickness and thus helpful to the evaluation of gate oxides with different thicknesses on one single wafer. In addition to avoiding many process variations, the tilted cathode anodization system makes it possible to estimate the trend of characteristics of ultra-thin gate oxides with the growth kinetics investigated in this work.
From the investigation of ultra-thin gate oxides prepared by anodization with tensile stress, the flat-band voltage of the sample grown with applied tensile stress is found to shift more positively than that without and the mechanism of OH－ incorporation is proposed. The experimental result shows that the leakage current is significantly reduced and the reliability is much improved for ultra-thin oxides prepared by tensile-stress oxidation.

並列關鍵字

Ultra-thin Gate Oxides ； Anodization ； Applied Tensile Stress

參考文獻

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