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Improvement of Wafer-Level Cu-to-Cu Bonding Quality Using Wet Chemical Pretreatment

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Abstract:

We have evaluated the effect of wet chemical treatment on the interfacial bonding strength of Cu-to-Cu direct bonding. The oxide on a Cu-deposited wafer can be removed by a solution made of hydrofluoric acid and sulfuric acid (HF/H2SO4) or diluted hydrochloric acid (HCI/H2O), which can also improve the bonding quality of Cu-to-Cu bonds. Two 4-inch Cu-deposited wafers were bonded at 250 °C via the thermo-compression method. The interfacial adhesion energy of Cu-to-Cu bonding was quantitatively measured by the four-point bending method. After chemical pretreatment for 30 seconds with HF/H2SO4 and HCI:H2O solutions, the measured interfacial adhesion energies were 4.91 J/m2 and 5.51 J/m2, respectively. Microstructural examination of the Cu bonding interfaces showed that the interfacial bonding quality of Cu-to-Cu bonds improved under proper wet chemical etching conditions. Wafer-level cleaning by wet chemical treatment of the Cu surface was found to be a very effective way to improve the bonding quality of Cu bonds, even at bonding temperatures lower than 300 °C.

Document Type: Research Article

DOI: https://doi.org/10.1166/jnn.2012.5619

Publication date: 2012-04-01

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  • Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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