當積體電路(IC)跨入深次微米時代，元件的尺寸逐漸縮小而且導線本身也變的更薄更窄，導線中的電阻及電流密度也隨之增加，使得RC的延遲時間與焦耳熱增加。先前所使用的鋁內接導線將面臨到高性能和內接導線可靠度的問題。由於銅具備低電阻和較優良的抗電阻遷移特性，因而銅被認為是最適合用來取代鋁的金屬。當積體電路製程進入0.18微米技術節點時，銅導線更是變成金屬連線的主流。
在各種的銅導線沉積方法中，電鍍法是最被IC業者接受的技術。電鍍銅是一個非常便宜的製作法，並且有較高的生產率。目前，電鍍銅所最常使用的電解液是硫酸銅，然而使用硫酸銅電鍍之甫沉積銅膜存在著嚴重的自我退火效果，隨著時間的演進，銅膜會產生電阻的不穩定現象，因此通常必須使用沉積後退火處理來解決此種自我退火的現象。研究學者認為銅膜中的應力是造成自我退火的主因，所以若能有一種電解液能沉積出低應力的銅膜，則自我退火的現象便可消除，沉積後退火處理的步驟便可省去，積體電路中之熱預算亦可獲得改善。
在此論文中，我們比較兩種電解液－硫酸銅及六氟矽化銅，所鍍出來銅膜之特性。我們針對不同比例之硫酸銅跟六氟矽化銅之混合電解液所沉積之鍍的銅膜，比較其自我退火之效應、銅膜阻值、濕蝕刻速率、應力、雜質分析及可靠度。我們發現以六氟矽化銅所沉積之銅膜較以硫酸銅沉積之銅膜有著較低的阻值、較密緻的結構、較低的應力以及較不顯著的自我退火的現象。因此，我們認為六氟矽化銅將是未來極具潛力之應用於電鍍銅膜的電解液。

As the integrated circuits (IC) step into deep sub-half-micron regime, devices dimensions are scaled down and the interconnect lines become thinner and narrower, the resistance and current density in the wire will increase, and the RC delay time and Joule heating increasing as well. The previous used aluminum interconnect line is going to suffer from high performance and interconnection reliability problems. Copper (Cu) has been considered as the most suitable interconnect metal to substitute aluminum (Al) due to its lower electrical resistivity and better susceptibility to electromigration failure. Copper wiring has become the main stream in IC interconnect especially as the integrated circuit processing goes beyond the 0.18 um technology node.
Among the various Cu deposition methods, electroplating has been adopted by most of the IC manufactures because of its low cost and higher throughput. By far, the most common electrolyte use in IC industries is copper sulfate (CuSO4). However, the as-deposited Cu films using CuSO4 exhibit a so-called self-annealing phenomenon, in which the grains in the films grow with time and the film resistivity changes. Therefore, post-deposition-anneal is generally required to stabilize the self-annealing effect. Researchers believed that the self-annealing effect is a result of high inner film stress. If one could deposit the Cu films with low stress through some kind of electrolyte, the self-annealing effect would then be eliminated and no post-deposition-anneal is required. Of course, the thermal budget in the IC manufacturing could be improved.
In this work, we compare the properties of as-deposited Cu films prepared using two different electroplating solutions: copper-hexafluoro-silicate (CuSiF6) and CuSO4. By mixing the CuSO4 and CuSiF6 with different mix ratios, the Cu films were deposited on seed-Cu/SiO2/Si substrates and SiO2/Si substrate with different barrier layer materials. We compared the stress, resistivity, self-annealing effect, microstructure, growth rate, impurity and reliability of the as-deposited electroplated Cu films. We found that the electroplated Cu films deposited using CuSiF6 exhibit lower resistivity, denser structure, lower stress and less-apparent self-annealing effect than those using CuSO4. Therefore, we concluded that CuSiF6 is one of promising electrolyte solution for future Cu electroplating in IC manufacturing.

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