TaSixNy 薄膜對銅原子擴散之阻障特性

Abstract

本論文主要包含兩部分。第一部份探討以TaSi2 靶材在氮(N2)/氬(Ar)混合氣體中濺鍍沈積、厚度為10奈米之氮化鉭矽(TaSixNy)的擴散阻障特性；第二部份探討在濺鍍沈積之TaSixNy阻障層作後續處理，對於阻障層之擴散阻障能力的改善，其中後續處理的方式包括氮氣熱退火、氮氣電漿處理、以及氮氣熱退火結合氮氣電漿處理。吾人利用「銅/阻障層/p+n」接面二極體在氮氣中熱退火處理後測得之電性劣化情形來評估阻障層對銅原子擴散之阻障特性。實驗結果顯示，在N2/Ar流量比為15到20%的N2/Ar混合氣體中濺鍍所得之TaSixNy(15~20%)阻障層具有最佳的擴散阻障特性。厚度10奈米的TaSixNy(15%)阻障層，可使「銅/阻障層/p+n」接面二極體在450℃熱退火後仍然保有原來的電特性。經過氮氣熱退火處理(500℃，30分鐘)的阻障層，其「銅/阻障層/p+n」接面二極體的熱穩定溫度可達到500℃；而經過氮氣電漿處理(150W，10分鐘)之TaSixNy(15%)，則可使接面二極體的熱穩定溫度提升到550℃。結合上述兩項後續處理，即氮氣熱退火處理後接著作氮氣電漿處理，可得一最佳阻障層，使接面二極體的熱穩定溫度進一步提升到600℃。阻障層特性的改善主要是因為氮氣熱退火處理對於在濺鍍沈積TaSixNy阻障層時所產生的局部性缺陷具有修補的作用；而氮氣電漿處理則可以在阻障層表面形成富有氮原子的表面層，藉由氮原子之填塞在晶粒邊界和局部缺陷，可阻斷銅原子的擴散路徑。

This thesis studies the barrier property of 10-nm-thick TaSix-based TaSixNy layers sputter deposited from a TaSi2 target in various N2/Ar mixing gases, using electrical measurement on Cu/TaSixNy/p+-n junction diodes as well as various techniques of material analysis. The study also includes the barrier capability improvement of the thin TaSixNy layer by various post-deposition treatments, including N2-thermal-annealing, N2-plasma-treatment and N2-thermal-annealing followed by N2-plasma-treatment on the surface of the barrier layer. It was found that the TaSixNy film sputter deposited in a N2/Ar gas mixture with the N2/Ar flow ratio of 15 to 20% has the most efficient barrier property. The Cu/TaSixNy/p+-n junction diodes with this optimal 10-nm-thick TaSixNy barrier layer were able to remain stable after thermal annealing at temperatures up to 450℃. The post-deposition N2-thermal-annealing at 500℃ for 30min made the TaSixNy(15%) layer (sputter deposited in N2/Ar mixed ambient with the N2/Ar flow ratio of 15%) capable of raising the thermally stable temperature of the Cu/TaSixNy(15%)/p+-n junction diodes up to 500℃. With 150W N2-plasma-treatment for 10min on the TaSixNy(15%) barrier layer, the Cu/TaSixNy(15%)/p+-n junction diodes were able to remain thermally stable at temperatures up to 550℃. Moreover, the combined post-deposition-treatment of N2-thermal-annealing followed by N2-plasma-treatment resulted in the most efficient barrier property, making the Cu/TaSixNy(15%)/p+-n junction diodes capable of remaining stable at temperatures up to 600℃. The improvement in the diffusion barrier property may be attributed to the healing of localized defects in the reactively sputter deposited TaSixNy layer by the post-deposition N2-thermal-annealing, and the formation of a nitrogen rich surface layer by N2-plasma-treatment such that nitrogen atoms are stuffed into the grain boundaries and localized defects, thus obstructing the diffusion paths of Cu atoms.