Effect of Free Radical Activation for Low Temperature Si to Si Wafer Bonding

In this study, a comparison of different surface treatments for direct Si to Si wafer bonding is reported. Hydrophilic and hydrophobic Si wafers have been exposed to a range of pretreatments, involving oxygen and nitrogen radical activation before in situ wafer bonding in vacuum. After low temperature annealing at 200 and , the formation of voids has been observed by using scanning acoustic microscope inspection. A comparison of the bonding energy has been conducted and analyzed as a function of the surface treatments. Our experiments demonstrate that the remote plasma pretreatment is a very suitable process for surface modification of hydrophilic and hydrophobic Si to Si direct wafer bonding.