Cu/SiO2 hybrid bonding has been developed for the application of heterogeneous bond interfaces in 3D integrated circuits in which thermal stability and bonding behavior are important. Thus, nano-twinned Cu (NT-Cu) is selected as the bonding material, and the thermal stability of NT-Cu and the bonding behavior of the interface between NT-Cu are investigated using a scanning electron microscope, electron backscatter diffraction, and focused ion beam. In addition to the microstructure analysis, nano-indentation and nano-scratch are employed to characterize the mechanical properties of the matrix and the interface between NT-Cu. As the bonding temperature increases from 200 to 300 °C for NT-Cu, the average grain sizes increase from 0.64 to 0.87 µm, and the rate of grain coarsening increases from 0.14 to 0.25 µm/h1/2. In addition, the fraction of voids at the bonding interface for NT-Cu interconnects decreases from 0.814% to 0.005%, and the penetration depth increases from 228 to 745 nm with an increase in the temperature from 200 to 300 °C. The hardness of the bonding interface obtained by nano-scratch and nano-indentation array testing is ∼1.8 GPa.

A raw electron backscatter diffraction (EBSD) signal can be empirically decomposed into a Kikuchi diffraction pattern and a smooth background. For pattern indexing, the latter is generally undesirable but can reveal topographical, compositional, or diffraction contrast. In this study, we proposed a new background correction method using polynomial fitting (PF) algorithm to obtain clear Kikuchi diffraction patterns for some applications in nonconductive materials due to coating problems, at low accelerated voltage and at rough sample surfaces and for the requirement of high pattern quality in HR-EBSD. To evaluate the quality metrics of the Kikuchi patterns, we initially used three indices, namely, pattern quality, Tenengrad variance, and spatial–spectral entropy-based quality to detect the clarity, contrast, and noise of Kikuchi patterns obtained at 5 and 15 kV. Then, we examined the performance of PF method by comparing it with pattern averaging and Fourier transform-based methods. Finally, this PF background correction is demonstrated to extract the background images from the blurred diffraction patterns of EBSD measurements at low kV accelerating voltage and with coating layer, and to provide clear Kikuchi patterns successfully.