Introduction
中 文：林哲億(Che-Yi Lin)
English：楊智傑(Chih-Jie Yang)
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積體電路去除絕緣層後的俯視圖
SEM image of two-level Al(Cu) interconnect lines with W-plug vias on a Si surface.
IBM J. of Res. & Develop., July 1995 |
在積體電路(Integrated circuit, IC)的導線材料選擇中，由於銅金屬相較於其他金屬有著良好的導電性以及成本較低的優點，因此時下的積體電路製程大多是以銅做為金屬導線的材料。然而依循著摩爾定律(Moore’s law)，內部的電子元件密度不斷上升，意謂著在單位面積中要植入的電子元件數目也大幅的上升，而電路內部的金屬導線尺寸也大幅縮減。因此銅導線中單位面積所通過的電流密度也大幅提高。在銅導線中，當導線內部的電流密度到達106 A/cm2時，因大量的電子流衝擊銅原子造成動量轉移，使得銅原子會依循著的電流方向進行遷移行為，此現象稱為電遷移(Electromigration)。而銅原子的電遷移會在原本的位置留下一個空孔(Vacancy)，空孔的濃度會隨著通電時間的上升而增加。最後空孔聚集形成巨觀的孔洞(Void)，當孔洞隨著通電時間進一步擴大，最終將會造成導線的斷線，形成短路。因此銅原子的電遷移行為與元件的可靠度息息相關。
As the demand of high performance for electric component keep rising, it is necessary to scale down the integrated-circuits (IC) dimension to incorporate more semiconductor devices into a single chip. Traditional aluminum metallization has reached the limitation on fabrication of desired high speed devices. Copper metallization emerged as a promising substitution due to its low resistivity and acceptable cost. The increase in interconnect complexity together with the shrinkage of copper interconnect dimension requires finer interconnect pattern and hence increases current density passing through metal interconnect. Electromigration takes place when the current density in copper metal interconnects is over 106 A/cm2. Electromigration is the movement of the atoms in a metal line due to the momentum transfer between conducting electrons and diffusing metal atoms. Vacancies form as the atoms are bombarded away. As the momentum transfer continues, the vacancies form and coalescence into voids which might further fail the device. To increase the stability of copper interconnects, it is crucial to understand the electromigration behaviors of copper.
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電遷移示意圖
Schematically illustration of electromigration. |
C. K. Hu et al., APL, 78, 904 (2001) |
在本實驗室的研究，由超高真空穿透式電子顯微鏡的臨場觀測銅原子的電遷移行為中發現，銅原子的移動會在雙晶晶界處受到抑制。因此若能在銅金屬內部引入大量的雙晶結構，對於抑制電遷移的能力也能大幅提升。而有大量奈米尺度雙晶結構的銅膜在文獻上證明具有相當良好的機械性質以及導電性，在未來銅導線微結構選擇中是相當適合的選擇。
It was found that nano-twinns can effectively increase copper mechanical strength by one order without sacrifice it electrical conductivity. By high resolution transmission electron microscopy (HRTEM), it was founded that electromigration of copper is delayed at a twin boundary in our previous research. Effective mechanical strengthening, acceptable electrical resistivity and better EM resistance makes nanotwinned copper an ideal material for advanced microelectronic applications.
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穿透式電子顯微鏡臨場觀測雙晶晶界抑制銅原子電遷移行為
Electromigration of copper is delayed at a twin boundary.
K. C. Chen et al., Science 2008, 321, 1066-1069
(本實驗室研究成果/Our work) |
本實驗室利用電鍍的方式製備具有奈米雙晶結構的銅膜以及奈米線。可藉由電鍍液的添加物來調控銅膜的成長，或探討電鍍過程中不同的實驗參數對於雙晶結構的密度造成的影響。而藉由陽極氧化鋁模板輔助電鍍的方式可製備出大量而均勻的銅奈米線結構，而在其中也成功引入大量的奈米雙晶結構。具有大量奈米雙晶結構的銅膜具有高強度以及良好的導電性，而本實驗室亦發現對於金屬的腐蝕行為也能增加抑制的能力。
In our lab, nanotwinned copper films and nanowires are prepared by electrodeposition. It was found the growth direction of copper films can be controlled the by using proper additives. The influence of deposition parameters on twin density is another research topic. Nanotwinned copper nanowires were successfully fabricated by anodic aluminum oxide (AAO) template-assisted electrodeposition. It was also founded twinning induced grain boundary transformation can effectively delay corrosion.
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藉由添加物改成長方向，並藉由雙晶結構得到高強度的銅膜
The growth direction of copper films was controlled the by additives.
T. C. Chen et al., Cryst. Growth. Des. 2011, 11, 4970-4974
(本實驗室研究成果/Our work) |
模板輔助方式電鍍製備奈米雙晶結構的奈米線
Nanotwinned copper nanowires fabricated by AAO template-assisted electrodeposition.
(本實驗室研究成果/Our work) |
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雙晶形成伴隨的低能量晶界有效阻擋沿晶腐蝕
Twinning induced grain boundary transformation can effectively delay corrosion.
(本實驗室研究成果/Our work)
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Recent Researches (*Click on topic to read more)
Degree |
碩士 |
Name |
盧逸滄 |
| Master |
Yi-Cang Lu |
Direction |
討論電鍍溫度與電流密度對電鍍銅奈米線的微結構影響 |
| Discuss the Influence of electrodeposition temperature and current density on microstructure of
Cu nanowires. |
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電鍍溫度與電流密度對銅奈米線微結構影響之研究 |
| Influence of electrodeposition temperature and current density on microstructure of
Cu nanowires. |
本實驗探討在脈衝電鍍製程中，電鍍溫度及電流密度對銅奈米線的結晶方向及雙晶結構生成之影響。藉由模板輔助電鍍法，在商用陽極氧化鋁模板內部電鍍奈米線。並採用脈衝電鍍的方式，在不同電鍍溫度及電流密度下製備銅奈米線，再進行材料分析。而由X光結晶繞射儀和穿透式電子顯微鏡的觀察發現，在高電流密度下，降低電鍍液溫度有助於提升銅奈米線的 (111) 晶面繞射強度，同時奈米線內部的平均雙晶間距也會下降；而在低溫環境中，提高電流密度也會提升銅奈米線的 (111) 晶面繞射強度，而奈米線內部的平均雙晶間距也隨之下降。
The objective of this study is to investigate how deposition temperature and current density affect crystal orientation and formation of twinning structure of copper nanowires in pulsed electrodeposition system. X-ray diffraction (XRD) and transmission electron microscopy (TEM) are used to analyze the crystal orientation and twin structure formation of copper nanowires, respectively. Experiment results show that the (111) crystal plane diffraction intensity of copper nanowires increases, but the average twin spacing of copper nanowires decreases with the decrease of electrolyte temperature. Moreover, with increasing current density, the (111) crystal plane diffraction intensity of copper nanowires increases, while the average twin spacing of copper nanowires decrease.
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Degree |
碩士 |
Name |
曾麗倩 |
| Master |
Li-Chien Tseng |
Direction |
討論電鍍溫度與基板對電鍍銅膜的微結構影響 |
| Discuss the Influence of electrodeposition temperature and current density on microstructure of
Cu nanowires. |
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溫度與基板對脈衝電鍍製備銅膜微結構影響之研究 |
| The Effects of Temperature and Substrate on Microstructure of Copper Films Prepared by Pulsed Electrodeposition. |
因應微電子積體電路元件尺寸不斷的微縮，為了提升元件的可靠度，瞭解電鍍製程參數對銅金屬導線微結構的影響是一個重要的課題。銅的微結構與晶體成長的優選方向會受到電鍍時的過電位、電鍍液的成份、基板以及溫度的影響。在本研究中，主要是探討基板與電鍍液溫度對脈衝電鍍製程所製備銅金屬膜微結構之影響。本實驗所採用的基板，一為市售的鎳金屬箔，其具備很強的(200)晶體優選方向，另一基板為利用磁控濺鍍法在矽基板上沉積銅薄膜。電鍍液的溫度則控制在攝氏-1及20度。接著利用觀察不同條件下銅膜的表面形貌、優選方向及雙晶的間距作為探討。實驗結果發現，當溫度降低時，利用定電流模式下進行脈衝電鍍所鍍出的銅金屬膜其表面較為光滑，且在電鍍過程中整體的過電位也有所提升。推論降低溫度而造成的過電位上升使銅膜成核速率上升，進而使晶粒細化，而得到較為平整的表面。另外觀察到當電鍍液的溫度控制在攝氏20度時，初始電鍍的銅膜繼承了基板的優選方向，而當溫度下降時，初始電鍍的銅膜其基板效應較不明顯。導致此差異的主要原因在於溫度下降所造成的過電位提升使得各生長方向成核所需要的能量都大幅下降，導致晶粒各方向的成核速度沒有明顯差異而得到無特定優選方向的薄膜。最後也觀察到當溫度降低時，雙晶結構的間距大幅的下降。推論當溫度下降後，銅膜內的應力因在低溫電鍍下成核數量較多及晶界較多而有所提升，另外在低溫下，推測應力釋放將由差排滑移轉變成形成奈米雙晶的機制，使低溫下製備的銅膜內的雙晶結構更為緻密。Electrochemical deposition is commonly employed in the fabrication of copper interconnects owing to its low cost advantage and ease of mass production. To further down scaling the microelectronic device, more in-deep knowledge and process control concerning interconnect microstructure are required to improve device reliability. Copper film microstructure is known to be tailored by various process parameters such as electrodeposition overpotential, electrolyte composition, substrate and temperature. In this study, nanocrystalline copper films were fabricated by galvanostatic pulsed electrodeposition using an addictive-free sulfate solution as an electrolyte. In comparison, two types of substrate have been used: one is a commercial nickel foil with strong (200) texture and the other is copper film prepared by sputtering which has no preferred orientation. The electroplated copper films were deposited at -1 and 20�aC. The surface topology, morphology, crystallographic texture and twin spacing distribution of the copper films electrodeposited under various conditions were examined. In this experiment, we observed that as the deposition temperature decreases, the copper film showed an increase in the deposition overpotential and a decrease in surface roughness. The inheritance of substrate texture in the electrodeposited copper film was found to be tailored by deposition temperature. As the deposition temperature decreases, the deposits show less dependent on the crystallographic orientation of the substrate. It was also found that twin spacing lamella reduces with decreasing deposition temperature. We proposed that the increase of overpotential has significant influence on the nucleation behavior. The increase of overpotential leads to higher nucleation rate and lower growth rate of existing nuclei, thus a smoother surface was obtained. At lower deposition temperature, the probabilities of nucleus formation on varies planes are generally the same, thus the electrodeposited copper films did not show any preferred orientation. Finally, the decrease of twin spacing was believed to be associated with the increasing stress caused by high nucleation rate under low deposition temperature.
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Degree |
碩士 |
Name |
楊智傑 |
| Master |
Chih-Jie Yang |
Direction |
討論電鍍銅膜的中雙晶結構及Benzotriazole(BTA)對抗腐蝕能力的影響 |
| Discuss the Influence twin structures and BTA on the corrosion properties of electrodeposited copper films. |
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奈米雙晶電鍍銅薄膜之腐蝕特性研究 |
| Corrosion Properties of Nanotwinned Copper Films Prepared by Electrodeposition.
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在積體電路銅連結導線製程中，化學機械研磨是移除過多材料以及整平試片表面最重要的方法。而在化學機械研磨中採用的漿料卻為製程帶來了易腐蝕的不確定因素。化學腐蝕以及伽瓦尼腐蝕等常造成元件良率過低或是降低其可靠度，因此提高銅抗腐蝕能力成為極為重要的議題。
近年來奈米雙晶銅因具有高機械強度同時保有良好的電導率及抗電遷移的能力而被廣泛研究，但其抗腐蝕能力卻從未有人探討。因此本研究藉脈衝電鍍製程沉積具雙晶結構之銅膜，並研究雙晶結構是否能提升材料抗腐蝕能力。Benzotriazole (BTA)被廣泛應用在化學機械研磨中作為抗腐蝕劑，同時亦有應用在電鍍中作為添加劑以細化晶粒，使表面平整。但卻只有極少文獻對其作為添加劑是否能同時提升電鍍銅膜的抗腐蝕能力討論。因此於此本研究中亦針對以BTA作為添加劑的電鍍銅膜抗腐蝕能力做討論。
In copper interconnects of integrated circuit process technology, chemical mechanical polish (CMP) is the most important step to remove overburden material and planarize surface of metallization. However, the slurry adopted in CMP may introduce corrosion issue. Chemical and galvanic corrosions of copper interconnects during processing may cause the failure of device. Therefore, it is crucial to find a way to increase the corrosion resistance of copper interconnects.
Nanotwinned copper has received broad attention recently due to its high mechanical strength, reasonably low electrical resistivity, and better electromigration resistance. However, its corrosion resistance is yet to be investigated. In this research, the corrosion resistance of nanotwinned copper prepared by pulsed electrodeposition technique is studied. Benzotriazole (BTA) is widely applied as a corrosion inhibitor in CMP and an electrodeposition additive as a brightener. But there is only limited literatures addressing the corrosion resistance of copper films deposited with BTA. In this study, the corrosion resistance of copper films electrodeposited with BTA is investigated.
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Degree |
碩士 |
Name |
林哲億 |
| Master |
Che-Yi Lin |
Direction |
研究在低溫環境下，不同電流模式電鍍製備銅膜的成長方向以及表面形貌，以及奈米雙晶結構隨溫度變化的可能機制。 |
| Discuss the influence of different current modes on the growth direction, surface roughness and nano-twin structures. |
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低溫環境下電鍍銅膜之性質研究 |
| Characterization of Cu films prepared by electrodeposition at low temperature. |
在電子元件的製程中，金屬導線的填入主要是利用電鍍的方式。除了傳統的直流電鍍外，脈衝電鍍也被廣泛的應用在不同的製備需求上。然而在電鍍的研究中，關於電鍍液溫度的探討比較缺乏，尤其在室溫以下電鍍製程的研究非常稀少。此外，具有奈米雙晶的銅金屬因具有高機械強度以及良好的導電性，在近年來被廣泛的研究，而其中一種製備方式就是採用脈衝電鍍，而銅膜內的雙晶間距與脈衝電流的電流密度以及有效時間有關，但對於溫度的影響並沒有相關的研究。故在本研究中將探討直流電鍍以及脈衝電鍍在不同溫度下的影響，並探討溫度效應對於電鍍形成雙晶的影響。
Electrodeposition is the most commonly used method for depositing Cu metallization in microelectronic devices. Both direct-current and pulsed current application modes have been used in the electrodeposition process. Although electrodepostion temperature is a critical parameter to control the properties of deposited metal, very few research efforts have been dedicated to investigate the electrodeposition process at low temperature regime. Recently, Cu with high-density nanoscale twins has received extensive attention due to its high mechanical properties and decent electrical conductivity. In previous works, Cu with nanoscale twins could be fabricated by pulsed electrodeposition. Twin thickness was found to be related to the current density and duty cycle during the pulsed electrodeposition process. However, the influence of temperature has not been investigated yet. In this study, the effects of deposition temperature and deposition current mode on the microstructure of the electrodeposited Cu films are the subjects of interests.
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更新日期：
2012-08-07
