Functionalized graphene as a seeding layer for eco-friendly microvia filling technology

Abstract

Microvia filling technology becomes more important because of the increasing demand for high density interconnects. Via can be filled with copper by electroplating with the presence of a conductive seeding layer. The common process of forming a copper seeding layer requires steps involving hazardous chemicals which are difficult to be treated. Another problem is that a conductive anodic filament occurs easily with the decreasing distance between vias with a potential difference. In this thesis study, a simple and more eco-friendly method in 5 main steps is developed for microvia filling. The seeding layer is reduced graphene oxide based as it was found that it can block the migration of metal ions. The parameters in copper electroplating are optimized by changing UV reduction time, chemicals added to the bath, voltage applied and duration of electrolysis. The performance is evaluated by optical profiling, cross-section analysis and two-terminal sensing. From the results, the best-filled microvia is completed with reducing graphene oxide under UV light for 6 hours and is electroplating for 3 hours at 7.5V. The average electrical resistance of microvia reaches 0.0851 mΩ. An economic analysis is conducted to estimate its economic potential. With fewer steps and chemicals involved, this method is more environmentally friendly and cost-effective.

Date of Award	2021
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Zhengtang LUO (Supervisor)