本論文研究以鈷鎢合金作為金屬銅製程中多功能阻障層的應用。為了降低訊號傳遞的時間延遲，現今多以銅導來取代鋁導線。但是銅導線在溫度與電場的操作下，銅極易擴散至低介電常數材料中，並與之發生反應，造成材料特性劣化與漏電流增大，甚至導致介電質崩潰。因此，必須發展具抵抗銅金屬擴散特性的阻障層材料。另外，傳統製程中必須在阻障層與銅晶種層之間再沉積一層溼潤層，確保後續沉積的銅能有良好的附著性與電鍍銅能力。
本論文研究之鈷鎢合金是以濺鍍沉積系統進行共鍍方式的薄膜成長。本論文研究首先探討鈷鎢合金的銅電鍍能力。研究中先對鈷、鎢、鈷鎢合金進行了短時間的電鍍銅實驗，從場發式電子顯微鏡所拍攝的圖像可觀察到，使用鎢鈷合金中鎢的含量為一半時的材料，可以將銅直接電鍍上去，並觀察到隨著比例調變，電鍍行為產生了變化。另外，利用了電化學分析的方法對不同比例的鈷鎢合金電鍍行為進行了分析，發現隨著鎢含量比例的增高，使得鈷鎢合金之抗腐蝕能力提高，進而讓基板之可電鍍能力提升。
本論文接著探討銅之鈷鎢合金附著能力。將已成長在二氧化矽基板上之鈷鎢合金再濺鍍一層50奈米的金屬銅，將試片進行400度30分鐘的快速退火，將退火後的試片進行場發式電子顯微鏡的觀察，發現成長在純鈷試片及鈷鎢合金中鎢含量低於30 % 之試片，其表面呈現較為平整且較少孔洞出現，代表此時銅對其試片具有較強之附著力。當鎢含量高於30 % 後，則開始有孔洞出現，代表著銅對其之附著力下降，不過其結果仍於現行製程所使用之金屬鉭結果相近。
本論文最後探討鈷鎢合金之抵抗銅擴散阻障能力。將已成長在矽基板上之鈷鎢合金再濺鍍一層50奈米的金屬銅，將試片進行升溫量測其阻值隨著溫度的變化，發現當鎢的含量比例逐漸增加時，失效溫度也隨著增高，代表鈷鎢合金的阻障能力隨著鎢的含量比例提升。另外，將試片進行400度30分鐘的快速退火，將退火後的試片進行場發式電子顯微鏡的觀察，發現鎢鈷合金中鎢的含量到達40 % 時，並不會形成矽化銅，表示此組成之鈷鎢合金具備阻障能力。

As integrated circuits (ICs) are scaled down to deep submicron regime, the impact of interconnect RC delay is becoming increasingly serious. One of the realistic methods to solve the issue is using Cu as the conductor for multi-level interconnects to reduce the resistance. However, Cu has high diffusivity. To prevent Cu from diffusing into dielectric materials under high electric fields and temperature, a barrier layer is needed. Moreover, wetting layers deposited on barriers are commonly used to enhance the Cu electroplating ability on the barrier layers.
In this study, we try to find out whether the cobalt-tungsten (CoW) alloy can be used as a combination of the barrier layer, the wetting layer and the direct electroplating layer which we call a “3 in 1 layer” to replace the traditional metal stack. To investigate its material properties, the CoW thin films were deposited by sputtering. Different W/Co content ratio was controlled by various W RF power.
In this study, the plating ability was investigated. The behaviors of direct Cu electroplating on different barrier metal including thin Co, CoW, W, and Ta/TaN films were investigated. We demonstrated that Cu could be electroplated on the CoW films with more uniform distribution of Cu nuclei. The Cu nucleation behaviors on the CoW substrates changed with the sputtering RF power. Potentiodynamic sweep methods including potential dynamic curves (Tafel plot) and cyclic voltammetry stripping (CVS) curves were used to help interpret the electroplating results.
The wetting ability was also investigated in this study. The SEM images of the Cu/Ta/SiO2, Cu/Co/SiO2, Cu/CoW/SiO2, Cu/W/SiO2 structure after annealing for 30 min at 400 °C shows that pure Co has the best wetting ability to Cu. There are less pin holes on the surface of pure Co compared to those of CoW substrates. With W adding into the Co, the wetting ability degraded due to smaller adhesion coefficient of W. The amount of pin holes on the surface of Cu/CoW/SiO2 structure with W RF power of 60 W is still comparable to the surface of Cu/Ta/SiO2 structure.
Finally, the anti-diffusion ability of the CoW films was investigated. The change in sheet resistance versus time and temperature of the Cu/CoW/Si films were used to monitor the formation of Cu3Si. It is shown that with W RF power of 50 W and 60 W, the CoW films is able to prevent Cu diffusion until annealing temperature higher than 600 °C. The SEM images of the Cu/CoW/Si films after annealing 30 min at 400 °C also indicated that W with 60 W RF power, the formation of Cu3Si can be avoided.

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