Electrodeposition of (111)-oriented nanotwinned Cu in Damascene vias

Due to the rapid development of advanced packaging, the size of Cu interconnection are getting smaller and smaller, traditional micro-bump technology has difficulties in narrowing the interconnection pitch due to the bridging issue of Sn based solder. The hybrid bonding has emerged to meet the reliability requirement of fine pitch interconnection. The electroplating of Damascene Cu vias is the premise of hybrid bonding. In addition, nanotwinned Cu with highly (111) orientation possessed high yield strength, good electrical conductivity and high resistance to electromigration. However, due to the significant decrease of nanotwinned's density within Damascene vias as compared to thin films, the electrolyte and electroplating process of nanotwinnedCu Damascene vias need further investigation before application. In this paper, Damascene vias of size (width 4 mu m, depth 1 mu m) was electroplated, the filled performance and the ratio of (111) orientations were analyzed. Firstly, a series of copper films were electroplated using gelatin with different molecular weight. The surface morphology and cross section of the Cu films were characterized by Scanning Electron Microscope (SEM) and Focused Ion Beam Microscopy (FIB), the orientation of the Cu films were characterized by X-Ray Diffraction (XRD), and the texture coefficients(TC) were calculated. Secondly, gelatin with different molecular weights were further characterized by Fourier Transform Infrared Spectroscopy(FTIR) and Gel Permeation Chromatography (GPC). In the end, the cross-sectional images of microstructure was observed by Focused Ion beam microscopy (FIB).