新式金屬結構技術開發研究
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2013
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本研究採用銀金屬做為半導體元件之金屬導線材料，利用原子層沉積技術製備之氮化鈦薄膜，兼具擴散阻障層與電鍍晶種層透過表面氣體電漿轟擊與稀釋氫氟酸浸泡對氮化鈦薄膜進行表面處理，藉由改善氮化鈦表面濕潤性來觀察銀電鍍於其上的變化，並利用高溫退火實驗藉由接面二極體漏電流實驗結果，顯示氮化鈦薄膜可有效阻擋銀離子於高溫400~600 oC的擴散行為。
本研究透過黃光微影系統製作出350、400以及450 nm線寬的導線模型，使用底部成長的技術，成功地將銀金屬填入導線模型。剛鍍好的銀導線結構比較鬆散、且表面粗糙。相信在退火處理後會比較完整，缺陷也會比較少。
本研究也利用傳統鑲嵌式製程製作出上開口150 nm、底部寬度84nm的導線模型，成功地將銀金屬填入導線模型中，在沒有使用任何添加劑的情況下，中央縫隙將可能會遺留，所以，我們相信在未來，添加劑的研究將會是實驗銀導線金屬化一個很重要的因素。
In this study, we investigated the silver metallization technology and feasibility of Ti-based diffusion barrier for Back-Eend-of-Line (BEOL) interconnect application. A single ALD-TiN film with bi-functional diffusion barrier and plating seed layer was developed. By way of the surface modification of TiN film with energetic plasma bombardment and DHF immersion, the wetting behavior for electroplating Ag film was effectively modified. We successfully plating Ag on treated TiN film without any catalyst or seed layer prior to the Ag deposition. Junction leakage current measurement using n+/p-Si diode showed that the titanium nitride can effectively prevent silver diffusion even after 400oC anneal process. To integrate the Ag and ALD-TiN barrier process, bottom-up Ag electroplating surrounding by TiN film was proposed. Line width of 350, 400 and 450 nm was formed via Photolithography. Post plating Ag line with distributed grain size was not as smooth as sputtering film. It is believed that the pre-treatment is necessary for better wettability and microstructure. Except the bottom-up Ag electroplating, traditional damascene metal plating was checked for electroplating condition tuning. A tapered plug with 150nm top-opening and 84nm bottom width was prepared for Ag gap-filling. We found that the seam or central void will be left without any additive added in the electrolyte. That is, the study of additive in the future will be an important issue in realizing Ag metallization.
In this study, we investigated the silver metallization technology and feasibility of Ti-based diffusion barrier for Back-Eend-of-Line (BEOL) interconnect application. A single ALD-TiN film with bi-functional diffusion barrier and plating seed layer was developed. By way of the surface modification of TiN film with energetic plasma bombardment and DHF immersion, the wetting behavior for electroplating Ag film was effectively modified. We successfully plating Ag on treated TiN film without any catalyst or seed layer prior to the Ag deposition. Junction leakage current measurement using n+/p-Si diode showed that the titanium nitride can effectively prevent silver diffusion even after 400oC anneal process. To integrate the Ag and ALD-TiN barrier process, bottom-up Ag electroplating surrounding by TiN film was proposed. Line width of 350, 400 and 450 nm was formed via Photolithography. Post plating Ag line with distributed grain size was not as smooth as sputtering film. It is believed that the pre-treatment is necessary for better wettability and microstructure. Except the bottom-up Ag electroplating, traditional damascene metal plating was checked for electroplating condition tuning. A tapered plug with 150nm top-opening and 84nm bottom width was prepared for Ag gap-filling. We found that the seam or central void will be left without any additive added in the electrolyte. That is, the study of additive in the future will be an important issue in realizing Ag metallization.
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Keywords
金屬導線製程技術, 電鍍銀, 接面電阻, 熱穩定性, Metallization technology, Silver electroplating, Contact resistance, Thermal stability