Depth-dependent self-annealing behavior of electroplated Cu

• Published in: Surface & coatings technology Vol. 320; pp. 489 - 496
• Main Authors: Chen, Chang-Chih, Yang, Cheng-Hsien, Wu, Ying-Syuan, Ho, Cheng-En
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.06.2017; Elsevier BV
• Subjects: Annealing; Bottom-up grain growth; Copper; Crystal defects; Crystallography; Diffusion; EBSD; Electron backscatter diffraction; Electroplated Cu; Evolution; Grain boundaries; Grain growth; Grain size distribution; Microstructure; Orientation; Residual stress; Self-annealing; Stress concentration; TOF-SIMS; Self-annealing; Bottom-up grain growth; TOF-SIMS; EBSD; Electroplated Cu
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2016.11.057

The remarkable microstructure evolution of as-electroplated Cu in a few hours at room temperature is generally termed Cu self-annealing, which might induce transitions of the resistivity, internal stress, impurity distribution, and crystallographic defects that govern the physical/chemical characteristics of an entire Cu film. In this study, we performed a cross-sectional investigation of this time-dependent phenomenon to investigate the crystallographic/microstructure transition during the Cu self-annealing procedure. The crystallographic evolution of electroplated Cu, including grain size distribution, crystallographic orientation, and grain boundary (GB) characteristics, with respect to various Cu deposition depths and self-annealing times (t), were investigated using a scanning electron microscope (SEM) combined with an electron backscatter diffraction (EBSD) analysis system. The initiation of Cu grain growth was from the bottom of electroplated Cu (i.e., the substrate side), and the orientation of the newly developed Cu grains correlated with the substrate (Cu) orientation. The bottom-up Cu grain growth accompanying the GB elimination provided a rationalization for the redistribution (out-diffusion) of impurities with t. This knowledge advances our understanding of the overview of the electroplated Cu microstructure evolution during its self-annealing procedure. •Self-annealing behavior of electroplated Cu.•Depth-dependent Cu self-annealing.•Strong orientation relationship between recrystallized Cu and substrate.•Bottom-up grain growth during Cu self-annealing.•Out-diffusion of impurities during Cu self-annealing.