ULSI嵌入式銅導線無砥粒化學機械平坦化技術

Abstract

為提升元件之效能，在新的ULSI積体電路製程中，以銅導線取代原始之鋁導線已成為不可避免的趨勢，這主要是由於銅金屬具有較低之電阻值及較高抵抗電子遷移的能力。然而，在多層銅金屬導体連線的製作上，化學機械研磨技術雖是達成全域性平坦化的關鍵技術，但漿料組成中之砥粒卻極易造成元件製作上的缺陷，例如刮痕與疊層薄膜的剝離等等。於是，近年來無砥粒化學機械平坦化技術便被積極的研發，以期能取代原本的化學機械研磨技術做為多層金屬銅導体連線進行平坦化製程。此論文中，將對鑲嵌式金屬銅導線連線無粒砥化學機械平坦化技術進行深入的探討。 由於漿料中不含研磨砥粒，無砥粒化學機械平坦化技術可以避免在研磨過程中因砥粒的存在對金屬銅導線造成刮痕，同時也能有效降低研磨時對基材所造成的強大應力。這樣的優點有利於低機械強度的多孔性低介電值材料取代氧化矽成為元件的介電層。於本論文的前半部，將就影響無砥粒化學機械平坦化技術之平坦化效能的諸多重要因素，諸如金屬銅導線於漿料中的腐蝕行為與抗腐蝕鈍化層的性質等等做深入的討論。 此外，於金屬導線化學機械研磨平坦化過程中，圖形效應(Pattern Effect)來自於不同設計樣式之導線於研磨過程中造成不同的有效局部壓力。而當圖形效應明顯作用於金屬導線之平坦化過程中時，各不同樣式形貌與線寬大小不同之金屬導線將具有不同的平坦化效能。然而近來發現，藉由調整無砥粒金屬銅導線化學機械平坦化製程中的研磨正壓力，能夠使銅導線的移除機制不受有效局部壓力的影響，進而能有效降低於導線平坦化過程中之圖形效應。於本論文的後半部，將深入的探討如何以無砥粒化學機械平坦化技術來解決金屬銅導線平坦化製程中圖形效應的問題。

In order to optimize the efficiency of ULSI IC device, copper has be developed as an alternative to aluminum as interconnects because of its high ability against electron migration and low resistance. However, in a damascene chemical mechanical polishing (CMP) process, Cu planarization suffers some damages resulting from mechanical abrasion by abrasives, such as scratching and peeling. In recent years, in order to avoid mechanical damages and achieve stress-free Cu planarization, Cu abrasive free polishing (Cu AFP) technology is developed as an alternative to CMP. In this thesis, we deeply study on the mechanism of Cu AFP technology. Owing to lack of mechanical abrasion by abrasives, Cu AFP could benefit a scratch-free Cu surface for Cu planarization. In situ, the pressure done on the polished substrate would be significantly reduced and it helps enhance the potential of porous low-k material used as dielectric layers. In this thesis, the first half part would focus on the some important issues those have significant influence on the planarization efficiency of Cu AFP technology. After Chapter 4, this thesis focuses on how to optimize pattern effect in Cu planarization with Cu AFP technology. Pattern effect, a critical issue in metal planarization, results from different pattern designs bringing a variation of effective local pressure. In order to optimize pattern effect in Cu planarization, Cu removal should be pressure independent. In this thesis, it was found that Cu abrasive free polishing (AFP) technology could benefit pressure independent Cu removal for Cu planarization by controlling down force. By pressure independent Cu removal with AFP slurries, the problem of pattern effect in Cu planarization could be significantly optimized.