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標題: Characterization of Amorphous TaSiN Diffusion Barrier Deposited by Dual Ion Beam Sputtering
作者: 劉協宗
Liu, Hsieh Tsung
關鍵字: TaSiN;鉭矽氮;Diffusion barrier;Dual ion beam;擴散阻障層;雙離子束
出版社: 材料工程學研究所
非晶質TaSiN薄膜因缺乏晶界的存在,具有極高之熱穩定性,且不易與銅互溶和產生反應的特性,加上能幫助後續鍍製的銅膜形成較緻密(111)織構,被認為是銅金屬化中最有效的擴散阻障層材料。本研究利用雙離子束濺鍍(Dual Ion Beam Sputtering,DIBS)系統以不同的濺鍍參數,在矽基板上沉積不同成份之TaSiN薄膜及製備不同複層Cu/ Ta-Si-N/ Si系統,以探討濺鍍製程與TaSiN薄膜性質之關聯性與非晶質TaSiN薄膜組成對熱穩定性的影響及其擴散阻障行為。同時,我們對於非晶質TaSiN薄膜的結晶化行為與對銅的擴散阻障性能也提出機制加以說明。
實驗結果顯示,以雙離子束濺鍍系統可獲得厚度均勻、緻密且表面平整的非晶質結構之TaSiN薄膜,表面粗糙度可降低到只有0.16nm。在組成比例上,所有鍍膜的氮原子含量皆在50~60 at%,為富氮之TaSiN薄膜,其中以含矽量較多的Ta9Si36N55薄膜具有較高的熱穩定性,即使經1000℃/60分鐘的退火處理,仍保持非晶質結構。而以Ta33Si16N51薄膜不僅具有較低的電阻率,同時對銅有最佳的阻障性能,在700℃/30分鐘的退火處理下,仍可有效防止銅原子擴散。此外,我們認為組成中矽含量的增加,會抑制TaN立方晶的出現,進而提高TaSiN薄膜的結晶化溫度。而Ta33Si16N51 與 Ta9Si36N55組成對銅的失效機制,是由於基材中的矽原子往外擴散所致,但造成Ta34Si7N59對銅的失效機制卻是因非晶質基地中發生再結晶所導致。

Amorphous Ta-Si-N films have been considered to be the most effective barriers for Cu metallization because of the absence of grain boundaries, their high thermal stability against crystallization, immiscibility with copper, and the enhancement of (111) texture formation of the Cu film. In this study, we use a dual ion beam sputtering (DIBS) system to deposit several Ta-Si-N films with different compositions by changing the deposition parameters and prepare Cu/TaSiN/Si multi-layered structures to study the relationship between deposition parameters and properties of the as-deposited TaSiN films, and the effects of film composition on the thermal stability and barrier performance of the amorphous Ta-Si-N film. We also proposed mechanisms to explain the crystallization behavior of amorphous TaSiN films and the failure of TaSiN barrier layer against Cu diffusion.
The results showed that all the TaSiN thin films prepared by a dual ion beam sputtering system exhibited a dense amorphous structure with a smooth surface and uniform thickness in which the surface roughness of as low as 0.16 nm can be achieved. In addition, the TaSiN thin films were found to be nitride-riched where nitrogen concentration varied from 50 to 60 at %. The amorphous Ta9Si36N55 film, remaining an amorphous structure even after being annealed at 1000℃ for 60 min. showed the highest thermal stability, however, failed to stop Cu diffusion at 800℃ for 30 min. Meanwhile, the Ta33Si16N51 film showed not only the lowest resistivity but also the best barrier performance where Cu diffusion can be effectively stopped until being annealed at 800℃ for 30 min. In addition, we believe that increasing the Si content in the composition could suppress the nucleation of TaN phase to raise the temperature of crystallization. The failure mechanism of Ta33Si16N51 and Ta9Si36N55 films were because of the Si outdiffusion from certain regions of the amorphous matrix. However, the failure mechanism of Ta34Si7N59 film is due to the crystallization in the amorphous matrix.
Appears in Collections:材料科學與工程學系

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