Demonstration of a Wafer Level Face- To-Back (F2B) Fine Pitch Cu-Cu Hybrid Bonding with High Density TSV for 3D Integration Applications

We have successfully fabricated a 2-Layers Face-To-Back (F2B) test vehicle (TV) by combining fine pitch Cu-Cu hybrid bonding technology with high density (HD) TSV. Three different stacked structures, built on 300 mm wafers, are needed to achieve the F2B TV. There are different Cu damascene levels that simulate back-end-of-line (BEOL) layers commonly used in 3D integration. Morphological characterizations have been carried out and highlighted the integrity of the 3D structure. Furthermore, results of electrical tests on Kelvin and Daisy-Chain structures demonstrated a high connectivity. Kelvin and Daisy-Chain test structures are designed with either standard or fine pitch configuration (Pitch: 6 µm and 4 µm respectively) with hybrid bonding pad dimensions of 3 µm and 2 µm respectively. HD TSV dimensions are 1µm in diameter and 10 µm in height.