Bonding of lithium niobate to silicon in ambient air using laser irradiation

In this paper, we introduce a bonding method in ambient air using laser irradiation to the face-to-face interface of dissimilar materials. This method is performed while keeping whole wafers of the materials at room temperature. We demonstrate the bonding of LiNbO₃ to Si using pulsed nanosecond green laser irradiation. Laser use can minimize thermal stress owing to a large thermal expansion mismatch. The bonding characteristic obtained by an irradiation laser up to 2.5 J/cm2 in fluence is investigated. It is found that a LiNbO₃ chip is strongly bonded to a Si chip by setting the laser fluence at the optimum range. A bond strength of over 2MPa, which may be enough for the device applications, can be obtained.