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Adhesion Investigation Between Metal and Benzocyclobutene (BCB) Polymer Dielectric Materials in 3-D Integration Applications

In this paper, the interfacial adhesion strength between metal layer and benzocyclobutene (BCB) polymer dielectric in 3-D integration applications is investigated. The effects of layer thickness, layer stacking order, and additional adhesion layer of titanium (Ti) layer between copper (Cu) and BCB polymer are investigated. Surprisingly, the conventional titanium adhesion layer commonly used in the semiconductor industry weakens the interfacial adhesion strength between copper and BCB. Additionally, to figure out the interfacial adhesion mechanisms, the interfacial structures probed by sum-frequency-generation vibrational spectroscopy are correlated to the adhesion strengths measured from corresponding sample interfaces. It is found that ordered C-H groups at the metal/BCB interface, such as titanium/BCB or molybdenum/BCB, lead to weak interfacial adhesion strength, whereas disordered interfaces, i.e., copper/BCB, lead to strong interfacial adhesion strength.