以伸張應力及直流疊加交流之陽極氧化法成長超薄閘極氧化層

Abstract

在先進的半導體製程技術，金氧半元件縮小至深次微米區域，矽氧化層的厚度也隨之縮小。根據國際半導體技術藍圖（ITRS）的預測，西元2012年時，元件的等效氧化層厚度將會是0.75奈米，此時的矽氧化層因為太薄而導致大量漏電流，因而有高介電質材料作為金氧半元件絕緣層的考慮。然而，由於高介電質材料的不穩定等問題，矽氧化層仍是非常重要的課題。在本篇論文中，我們採用另一種直接成長二氧化矽於基板上的方法－陽極氧化。陽極氧化的優點在於超薄閘極氧化層的厚度控制及可在室溫下成長氧化層的特點。在成長氧化層的過程當中，我們藉著機械應力彎曲矽晶圓的方式及交直流增進金氧半元件氧化層的品質。元件的電特性及穩度度分析在利用傾斜陰極之陽極氧化系統生長不同厚度之氧化層將會被仔細地探討。實驗結果證明，無論是機械張力或是交直流電技術成長氧化層，都能增進元件的電特性及穩定度。最後，我們對這篇論文給予結論及建議未來的研究方向。

In advanced technology of semiconductor, MOS devices are scaled down to deep-submicrometer region. As a result, thickness of silicon oxide also scales down. Based on the International Technology Roadmap for Semiconductor (ITRS), the equivalent oxide thickness (EOT) should be scaled to 0.75 nm in 2012. It is too leaky for ultra-thin gate silicon oxide so high-k films are introduced to solve the problem. However, silicon dioxide is still of interest due to the existing problems in high-k gate dielectrics. In the thesis, we introduce an alternative way to directly grow SiO2 on silicon substrate, i.e., anodization. The advantage of anodization includes good control of the thickness of ultra-thin gate oxides as well as the process can be held at room temperature. In addition, we improve the quality of oxide by applying mechanical tensile stress on silicon wafer and giving direct current superimposed with alternating-current (DAC) during anodization. The electrical characteristics and reliability of different oxide thickness prepared by tilted cathode anodization system will be discussed. From the experimental results, we demonstrate the quality of gate oxides would be improved in electrical characteristics and reliability test by either tensile-stress or DAC. Finally, conclusions and some other suggestions for future work about this thesis were given.