利用氮處理改善鈷鈦酸高介電閘極氧化層

Abstract

本論文的重點，在利用氮處理，改善鈷鈦酸高介電閘極氧化層之電容結構特性。首先探討，利用低能量氮離子佈植的方式，對鈷鈦金屬施以氧化前氮摻雜的動作。結果顯示，氮離子佈植有效抑制了鈷鈦酸閘介電層在高溫下結晶的產生，使其漏電流得到明顯的改善。另一方面，由平帶電壓的比較可以看出，經過氮離子佈植的處理，氧化層中固定電荷的量大為減少，使平帶電壓較趨於正常值。 接著，我們也研究，利用一氧化二氮電漿後處理加上氮氣高溫快速退火，對鈷鈦酸閘極氧化層之電容結構特性的影響。由於一氧化二氮提供了一些氧原子，修復填補了鈷鈦酸閘介電層中的氧空缺，使得薄膜結構更加完整緻密，加上氮原子的作用，舒緩了介電層在高溫下結晶的產生，因此改善了電容元件的電特性及熱穩定性。

In this study, nitrogen treatment on CoTiO3 high-k gate dielectrics of MIS capacitor structure is investigated. First of all, low energy N2+ or N+ implantation was used to incorporate nitrogen into CoTiO3. Results show that samples with nitrogen incorporation exhibit better electric performance than control ones. This is due to the incorporated nitrogen atoms which suppress the crystallization of CoTiO3 film through high temperature oxidation. Furthermore, by N2+ or N+ implantation, we found that positive fixed oxide charges were decreased and flatband voltage could be controlled to the ideal value. Next, CoTiO3 gate dielectrics with post N2O plasma treatment and additional high temperature rapid thermal N2 annealing (RTN) were discussed. Experimental results show that atomic oxygen species generated by N2O decomposition can repair oxygen vacancies in the as-deposited CoTiO3 film, and nitrogen atoms can suppress crystallization of CoTiO3 film simultaneously. Consequently, improved electrical characteristics can be obtained by using nitrogen incorporation scheme.