利用伸張應力陽極氧化生長技術及真空退火處理改善 超薄氧化層品質

Abstract

因為半導體技術不斷的在進步，以及摩爾定律的存在，所以元件的尺寸不斷的在縮小，根據ITRS的預測，在2012年時，金氧半元件的等效氧化層厚度會達到7.5Å，此時會因為量子效應的顯著而使得漏電流過大，因此，解決方法的提出是必要的。一般提出的解決手段是使用高介電材料來取代傳統的二氧化矽氧化層，但是卻有諸多問題尚未克服，因此，在短期中，提升二氧化矽氧化層的品質仍是必要的。在本文中，提出在成長氧化層時以伸張應力加於矽晶圓的手段來改善矽及二氧化矽之間的界面不一致，以提升成長出的金氧半元件品質。另外，由於在陽極氧化成長過程中可能會有反應未完全的氧化劑陷於氧化層中而降低氧化層品質，因此，另外給予成長完的氧化層真空熱退火處理，試圖減少氧化劑存在於氧化層中的可能性來改善元件特性。實驗結果證明，施加伸張應力的氧化層在電性及穩定度都優於一般方法成長出的氧化層；另外，經過真空熱退火處理的氧化層能更進一步改善氧化層品質及均勻性。

Because of the progress of the technology of semiconductor and the Moore’s law, the size of devices is scaling down at every moment. The equivalent oxide thickness (EOT) will be 7.5Å in 2012 according to the expectation of ITRS. In this moment, the quantum mechanical effect will be noticeable, and thus the leakage current will be exceedingly high. Therefore, method to solve this problem should be necessary. The high-κ material is one of promising candidates to replace the SiO2 as gate oxide, but there are still many problems of high-κ material to be solved. Hence, improving the quality of gate oxide of SiO2 will be required in near future. In this thesis, applying tensile stress on silicon wafer during oxidation is proposed to modify the lattice mismatch, and hence promoting the properties of MOS device. Besides, there may be residual oxidants left in the oxide after anodization due to incomplete reaction, and thus they may degrade the oxide quality. Therefore, we try to reduce the residual oxidants in the oxide by vacuum anneal treatment, and then improving the oxide quality. From the experimental results, the electrical properties and reliabilities of the tensile-stress gate oxides are superior to the non-stress gate oxides. On the other hand, the oxide quality and uniformity would be further improved by vacuum anneal treatment.