退火處理對鈦╱二氧化矽╱矽結構之退化現象研究

Abstract

本論文主旨在研究熱處理過程中，鈦╱二氧化矽╱矽結構的特性退化情形 及其改進方法。一般認為在退火過程中，鈦並不會與二氧化矽反應。然而 ，在本研究中，發現介電質的退化確實發生。在超過攝氏六百度的熱處理 退火後，矽基的表面態位密度增加了，氧化層的介電強度也降低了。而且 離子佈植會強化退化情況。在移去鈦金屬層後，第二次的退火處理可降低 表面態位密度，但無法改善已經劣化的介電強度。表面態位密度增加的原 因可能是鈦╱二氧化矽介面的熱應力；而介電強度降低的原因可能是鈦和 二氧化矽之間的化學反應。 In this thesis, the dielectric degradation of Ti/SiO2/Si structure during thermal annealing is studied. Traditionally it is believed that titanium does not react with SiO2 during thermal treatment. From the results of our experiments, however, dielectric degradation of Ti/SiO2/Si structure during thermal annealing was observed. After annealing at temperatures higher than 600℃ for 60 minutes, the density of interface state increases and the dielectric strength decreases. Ion implantation through the Ti/SiO2/Si structure enhances the degradation. The second annealing after removal of the Ti film can reduce the density of surface state, but the dielectric strength can not be recovered. The electrical analysis indicates that thermal stress is presumably responsible for the increase of interface state density, and the chemical reaction between Ti and SiO2 may be responsible for the decrease of dielectric strength.