Abstract
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.