嵌入式補償性金屬對超薄氧化層金氧半穿隧二極體之電特性影響

Abstract

本篇論文主要是探討嵌入式補償性金屬使超薄閘極氧化層金氧半穿隧二極體之橫向不均勻的降低以及飽和電流對電荷捕捉和照光反應的靈敏度提升之效果。在本文的第二章，為了要去減少氧化層橫向不均勻對於金氧半元件的衰退效應，我們提出了一種解決氧化層橫向不均勻的方法。藉由陽極氧化補償的方式去補償氧化層以及金屬的介面，並且利用電流密度以及電容密度對電壓的特性結果，我們觀察到氧化層均勻度被大幅改善。此外，進一步對於累積區的電流密度及電流密度在不同面積下的發散百分比統計結果也提供了一個佐證。相關的崩潰可靠度測試結果亦證明了氧化層橫向均勻度受到改善。因此，受惠於均勻度的改善，少數載子免除了橫向不均勻電場的干擾，使我們觀察到較顯著的反轉區電容反應。在第二章最後，為了要證明陽極氧化補償的有效性，我們利用部分硝酸氧化的方法去來製作具有相同結構的元件並比較其結果，我們發現不管是在電流密度對電壓的特性、電容對電壓的特性以及可靠度的測試上，使用陽極氧化補償的元件皆具有較佳的氧化層橫向均勻度，因此陽極氧化補償這項技術對於製作可靠的金氧半元件相當具有參考性。而在本文的第三章，我們主要探討元件邊緣電場所扮演的角色。在具有嵌入式金屬的金氧半穿隧二極體中，因為結合了高介電常數絕緣層以及嵌入式金屬提供的電場屏蔽效應之優點，我們發現其邊緣電場有被增強的現象。此邊緣電場的增強現象導致元件邊緣的空乏區被拓寬，進一步造成了在正負定電壓應力操作後更多的氧化層邊緣電子被抓陷或釋放。為了要去維持電中性，被多餘抓陷的電子使矽基板內部的電荷量下降而更進一步調變了多數載子蕭特基位障。因此，在具有嵌入式金屬的金氧半穿隧二極體中，我們就觀察到了更顯著的雙態飽和電流特性。此外，我們也在具有嵌入式金屬的金氧半穿隧二極體中觀察到較顯著的光靈敏度；因為金氧半穿隧二極體的光電流和元件邊緣電場直接相關，所以這個結果也提供了一個邊緣電場增強了的佐證。在第三章最後，我們也使用精準的電腦輔助設計工具去驗證我們提出的假設，而模擬出來的現象也和實驗結果相當吻合。

In this thesis, we demonstrate the effect of compensatory embedded aluminum in metal-insulator-semiconductor (MIS) tunnel diodes on the reduction of lateral non-uniformity and sensitivity enhancements to charge trapping and illumination. In chapter 2, in order to reduce the degradation caused by lateral non-uniformity (LNU) of gate oxides in MIS devices, a method to ameliorate the lateral oxide uniformity was proposed. By adopting the anodic oxidation compensation technique to compensate the interface of oxide and embedded aluminum layer, significant uniformity improvements were found in capacitance per unit area-voltage and current density-voltage characteristics, and the percentage dispersions of capacitance per unit area and current density in accumulation regime also give the support to uniformity improvement. Besides, the outcomes of reliability tests also evidence that the LNU is reduced. Hence, with the advantages of superior oxide uniformity, the enhanced response in inversion capacitance was observed. At last, nitric acid solution is used for validating the effectiveness of anodic oxidation compensation, and the current density-voltage, capacitance-voltage reliability characteristics were compared to show that anodic oxidation compensation is necessary for fabricating reliable MIS-based devices. In chapter 3, because of high permittivity dielectric and electric field screening effect by the embedded aluminum, fringing field of the MIS tunnel diode is believed to be enhanced. The enhancement of fringing field leads to the broadening of depletion region at device edge, which intensified the amounts of electron trapping/de-trapping after negative/positive constant voltage stressing. For maintaining charge neutrality, more charge attenuation in silicon bulk due to charge trapping in oxide further modulates Schottky barrier height of majority carriers. As a result, more significant two-state saturation current behavior of the MIS tunnel diode with embedded aluminum was observed. In addition, enlarged photosensitivity was also detected in the MIS tunnel diode with embedded aluminum to serve as another evidence of fringing field enhancement. Finally, accurate TCAD simulations were employed, and the outcomes are consistent with the experimental results.