高介電係數氧化鉿閘極介電層金氧半電容元件之不均勻特性分析

Abstract

等效氧化層厚度(EOT)通常由內含四個假設的元件參數在雙頻率電容量測下推導得出。然而, 等效氧化層厚度只是不包含有任何元件不均勻特性的有效數值。在文章中，不均勻特性將經由分析深空乏區的電壓電容(C-V)曲線而取得。當我們細察由電容電壓曲線轉換而得的表面電壓對閘極電壓( )曲線，可發現曲線斜率與理論值有所偏差。藉由不均勻假設以及引入適當的均勻度參數修改轉換公式，深空乏區的電容電壓曲線可獲得很好的模擬。因此，每個元件獨有的均勻度參數將可取得，並得以利用參數的數值分析元件的不均勻程度。在此同時，可指標與不均勻程度相消長的均勻度參數 也被定義。 至於電流電壓曲線，經由多種不同元件面積等條件及崩潰特性分析來觀察以二氧化矽及有初始界面氧化層和沒有初始界面氧化層的二氧化鉿等材料做為介電層的電容元件的不同機制，結果發現雖然高介電係數材料比傳統材料二氧化矽擁有較佳阻遏漏電流的能力，二氧化鉿介電層明顯較二氧化矽材料對實驗條件敏感。並且介於基板及二氧化鉿層之間初始界面氧化層的重要性也不容忽視。結論是對於發展對高介電係數材料的良好運用依然有許多研究空間。

The EOTs are always derived from two frequency method of capacitance measurement with four parameters. However, the EOT is just the effective value excluding any message about nonuniformity characterization of devices. In this work, the characteristic of nonuniformity was extracted by the analysis of CV curve in deep depletion region. While examining the curve transformed from C-V curve, we would find the slope deviates from the theoretical value. By modifying the transforming equations with the nonuniformity model and the injection of proper uniformity factor, the C-V curve in deep depletion would be fitted well. As a result, the uniformity factor for every definite device would be found out, and we would take advantage of the factor to analyze the nonuniformity characteristic. In addition, the uniformity parameter which could index the degree of nonuniformity was also defined. As to the I-V curves, the conditions of breakdown and various device areas were all examined to observe the mechanism differences between SiO2 and HfO2 with and without initial SiO2 dielectric layer MOS capacitors. As a result, even the high-k material would have better ability to restrain leakage current than conventional dielectric material, SiO2, the HfO2 dielectric layer is more sensitive to experimental conditions than that of SiO2 evidently. And the importance of the initial SiO2 between the substrate and HfO2 layer is also obvious. As a conclusion, there is till a lot of space to find and develop the ways to take good advantage of high-k material as dielectric layer.