Determination of the characteristics of the metallic bonding interface and the bonding strength of a Cu interlayer by using atomic force microscopy

초록

We report a low-temperature thermo-compression bonding process that utilizes chemical surface activation and is useful in 3D integration processing of wafers. Cu possesses desirable properties, such as ideal electrical properties, good thermal conductivity, and longer electro-migration times, making it an attractive interlayer material for the 3D integration process. However, in general, a high thermal energy of 400 A degrees C or more is required for Cu-Cu bonding to be successful. In order to address this problem, this investigation sought to confirm chemical activation of a Cu surface during the bonding process by using atomic force microscopy (AFM) to measure the bonding strength. The reliability of AFM has been established in previous research. The bonding strength of the Cu was determined to be about 6.7 J/m(2) at 150 A degrees C. This bonding strength can be used for 3D integration applications, and the possibility of low-temperature thermo-compression was confirmed by chemical surface activation.

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