以臭氧水製程改善薄閘極氧化層特性之研究

Abstract

由於臭氧水具有很強的氧化力，因此可以成長緻密的薄氧化層。本論文主要研究藉由改變臭氧水的濃度、酸鹼值、浸泡時間及添加的酸性溶液，這些因素對氧化層的厚度及品質的影響。 臭氧水的濃度提高、酸鹼值降低或浸泡時間增加，都可以使氧化層的厚度增加。但是，固定酸鹼值後，無論添加哪一種酸性溶液，對氧化層的成長並沒有太大的影響。 在成長閘極氧化之前，晶片使用傳統的RCA方法後，再浸泡臭氧水，所以在成長閘極氧化層之前，就會先成長一層緻密的氧化層。使用臭氧水製程做出來的MOS電容，可以有效的降低氧化層電荷、減低漏電流及提高崩潰電壓。臭氧水的濃度提高或浸泡時間增加，都可以使元件的特性變好；但是臭氧水的酸鹼值下降，卻會使元件的特性變差。

Due to the high oxidizing ability of ozonated DI-water, a thin and dense chemical oxide layer can be grown. This thesis studies the effect of factors including the concentration, pH. value, immersion time, and additional acids on the thickness and quality of the oxide. Increasing the concentration, immersion time or decreasing the pH. value will increase the thickness of oxide. However, the addition of an extra acid does not exhibit any influence if a constant pH. value is maintained. Before gate oxide growth, wafers go through an ozonated DI-water immersion process after the conventional RCA clean. Therefore, a dense structured oxide is formed before thermal gate oxide growth. MOS capacitors formed with the ozonated DI-water immersion process exhibit low leakage currents, decreased oxide charges and a higher breakdown voltage. Increasing the concentration or immersion time show better device characteristics, while decreasing the pH. value degrades the device performance.