Pulse Electroplating of Nanotwinned Copper using MPS-PEG Two-additive System for Damascene via Filling Process

Yu-Xi Wang, Shenzhen Institute of Advanced Electronic Materials, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China;Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215213, China;
Li-Yin Gao, Shenzhen Institute of Advanced Electronic Materials, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China;
Yong-Qiang Wan, Shenzhen Institute of Advanced Electronic Materials, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China;
Zhe Li, Shenzhen Institute of Advanced Electronic Materials, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China;
Zhi-Quan Liu, Shenzhen Institute of Advanced Electronic Materials, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China;Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215213, China;

Abstract

High density nanotwinned copper films were pulse electroplated using an optimized electrolyte. In order to find out the influencing factors of nanotwins’ formation, series content of MPS were added to electrolyte during pulse electroplating process. It was found that the copper films electroplated without MPS had large grains but a few nanotwins. And the grain size was about 0.9 μm on average and the texture components of (110) and (111) crystal orientations were calculated as 49% and 27.8% respectively. Differently, when 10 ppm MPS was added, the microstructure changed to columnar grain with high density of horizontal nanotwins and the crystal orientation also changed to highly (111) orientated one. However, when the MPS content continuously increased from 10 ppm to 40 ppm, the microstructure and crystal orientation were almost unchanged as detected by the secondary ion microscopy (SIM) of focus ion beam (FIB) and X ray diffraction (XRD). Specifically, when 40 ppm MPS was used, the grain size was 0.6 μm on average, and the texture components of (110) and (111) crystal orientations were 3.45% and 95.1%. It demonstrated that nanotwinned copper can be electroplated at a large concentration range of MPS, which also meant the filling ability of nanotwinned copper electrolyte could be adjusted by MPS content without influencing the microstructure. Finally, these electrolytes with different content of MPS were used in the Damascene via filling. The results showed that when the content of MPS was 40 ppm, the Damascus via was completely filled without voids. The achievement of via filling with nanotwinned copper makes the application of nanotwinned copper possible in Integrated Circuit(IC) fabrication, which also greatly improves the development of interconnected material for next generation.