利用鉭金屬覆蓋於鈷催化劑上自組裝成長奈米碳管連接孔之研究

An Approach to Form Self-aligned Carbon Nanotube Vias Utilizing a Ta-cap Layer on Co-catalyst

劉姿伶

指導教授 ： 游萃蓉

國立清華大學/工學院/材料科學工程學系/碩士(2013年)

摘要

本研究利用鉭金屬(Ta-cap)覆蓋於鈷催化劑(Co)之上，於400 C下利用化學氣相沉積法形成一自組裝CNT-via結構，做為未來積體電路內連線之應用。
覆蓋於Co上方的Ta-cap層能避免大氣中的氧氣直接與Co催化劑接觸，進而防止Co因氧化而降低活性，影響奈米碳管的成長。經過奈米碳管成長後，Ta-cap層會被奈米碳管頂起至上方，形成一連續Ta-cap與奈米碳管介面。一般來說，在奈米碳管內連線研究中，若欲形成CNT-via結構，在奈米碳管形成之後，會有以化學機械拋光使之平坦化，或沉積上方金屬電極等製程，而上述製程易於奈米碳管與上電極介面間形成雜質或孔洞。本研究中的Ta-cap層能提供一個連續的介面，避免奈米碳管與上方金屬電極介面產生雜質或孔洞。
本研究發現Ta-cap層厚度為主要影響奈米碳管成長之參數，故調變不同厚度並探討其影響。在奈米碳管成長後，為使電性有更好的表現，利用氧電漿去除Ta-cap層表面累積之導電性不佳的非晶形碳膜。此外，為了量測利用Ta-cap/Co結構所成長出的CNT-via電性及驗證內連線應用之可行性，本研究亦將奈米碳管成長於連接孔內。此奈米碳管連線於製程上與現行積體電路有相容性，具備未來應用之潛力。

關鍵字

奈米碳管 ； 內連線

並列摘要

This work presents an approach to form self-aligned carbon nanotube vias (CNT-vias) by chemical vapor deposition at 400 C utilizing a tantalum Ta-cap layer on Co catalyst for interconnect application.
The Ta-cap layer could protect the Co catalyst from oxidation. This protection potentially reduced the need for additional processing steps to control the size and activity of Co catalyst, which are two critical parameters for CNT formation. The Ta-cap layer was observed remaining on the top of the multi-walled CNTs as a contact layer to metal top electrode after the synthesis at 400 °C. The Ta-cap layer self-formed a continuous interface between metal top electrode layer and CNT layer, which could avoid impurities or voids caused by the conventional chemical mechanical polishing after CNT formation or metal top electrode deposition process.
The Ta-cap layer thickness was found to be the key parameter affecting CNT quality and was optimized. The O2 plasma treatment was implemented to remove residual amorphous carbon accumulated on the top of Ta-cap layer after CNT formation. CNTs were also fabricated in the via holes to measure the resistance of CNT-vias and confirm the future interconnect application. This work demonstrated a process to fabricate self-aligned CNT interconnects at low temperature, which could facilitate its future interconnect application.

參考文獻

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