Laser-Assisted Bonding with Through-Silicon Alignment for Heterogeneous Integration onto Silicon Photonic Platform

Abstract

The field of information technology currently is rapidly evolving, which in turn creates an increased demand for new application domains. Photonics plays a pivotal role in driving the expansion of the worldwide information network; however, there remains an urgent need to devise highly integrated solutions rather than relying on standalone devices and components. Commonly established microelectronics hybrid integration strategies are difficult to utilize within the silicon photonics domain. Thus, there is a growing push for more sophisticated methods that deliver accurate alignment of photonic components, rapid assembly processes, and overall reproducibility with high production throughput. Against this backdrop, Laser-Assisted Bonding (LAB) has gained traction as a compelling approach to meet stringent demands for accurate bonding, primarily because it can deliver tightly confined, localized heating and thus reduce thermal stress and warpage. Such minimized warpage is especially critical in photonic integration, since even minor structural deformations can lead to misalignment of optical axes, increased optical insertion loss, signal loss and, in severe cases, device damage. The high level of alignment precision is obtained by the implementation of through-silicon imaging technique with bottom illumination architecture, which makes it possible to simultaneously visualize the waveguides on both integrated devices (semiconductor chip and silicon substrate) and thus to enable advanced image recognition-based alignment techniques for the optimal result. Of particular note is the LAB technique's combination of speed and energy efficiency, leveraging bottom illumination/irradiation and simultaneous through-silicon imaging. This strategy supports both bonding and precise waveguide alignment - a prerequisite for effective integration in photonics. The resulting joint strength of 10.585 N(23.2 MPa) satisfies MIL-STD-883H shear strength criteria, with negligible post-bond misalignment of <0.3μ m. These findings confirm LAB as a fast, energy-efficient, and highly accurate technique for next-generation photonic packaging, capable of meeting the stringent demands of modern silicon photonics manufacturing.