奈米壓印技術應用於多孔性低介電質材料之研究

在現今積體電路製程中，於高階製程常須導入至少八層以上的銅金屬連接導線製作，若使用光學微影的方式於每一層結構皆須耗費許多繁雜的步驟，與良好的製程控制，才能達到理想的圖形轉移與性能。因此，應用奈米壓印來直接圖型化於介電層結構中之技術在近幾年來得到許多注意與研究興趣。主要由於奈米壓印技術應用於壓印功能性材料可大幅降低後段製作導線之步驟，並且節省製程成本。根據過去研究指出，奈米壓印技術應用於壓印低介電層材料中，多屬於無孔性之低介電質材料，然而於下世代技術中，具微孔性之超低介電質材料才符合現今奈米元件技術發展之需要。但是在整合超低介電材料於多層內連接導線技術時，仍有許多技術障礙及可靠度等議題待解決，因此極具挑戰性。本研究主要為探討奈米壓印技術應用於多孔性超低介電質材料之議題。在本實驗中，我們以MSQ為主體之功能性材料，其具有彈性模數可達7 GPa、介電常數值為2.82等特性，利用添加CTAB來作為孔洞犧牲層，可將其介電常數值降低至2.2。由實驗結果可得知，退火步驟為影響奈米壓印圖型轉移是否成功最大要素之一，同時，並找出奈米壓印製程參數之最佳化。因此，本研究成功地證明奈米壓印技術應用於多孔性超低介電質材料之可行性與發展性。

關鍵字

多孔性低介電質材料；奈米壓印技術

並列摘要

Optical lithography routes based on the dual damascene method require many complicated processing steps for each wiring layers in modern integrated circuit fabrication. There is a great interest in directly patterning multi-tier dielectric structures for semiconductor applications by nanoimprint lithography (NIL), which offers a potential cost savings in the number of process steps required to manufacture Back-End-Of-The-Line (BEOL) through the ability to imprint functional materials. To the best of our knowledge, the past studies involved directly patterning functional materials have mainly focused on imprinting non-porous low dielectric (low-k) thin films, however, next generation devices require ultralow-k dielectric materials with nanoscopic pores. The integration of these ultralow-k materials proves to be a challenge because the fabrication of the multilevel interconnects structures of ultralow-k dielectric material brings numerous technical obstacles and reliability concerns. This study focus on discussing NIL apply to porous low-k materials, and we choose the methylsilsesquioxane (MSQ)-based functional material, which has a high modulus (7 GPa) and low dielectric constant (k=2.82). The dielectric constant can be down to 2.2 by adding Cetyltrimethylammonium Bromide (CTAB, (C16H33)N(CH3)3Br) as the porogen. According to the experimental results, the annealing step will be one of the important factors of whether the patterns transform successfully or not, and we could optimize the NIL procedure parameters. Finally, this study successfully demonstrates the development and feasibility of directly patterning on porous low-k materials by using NIL.