Wafer-Scale Hybrid Integration of InP DFB Lasers on Si Photonics by Flip-Chip Bonding with sub-300nm Alignment Precision

Abstract

InP DFB lasers are flip-chip bonded to 300mm Si photonic wafers using a pick-and-place tool with an advanced vision system, realizing high-precision and high-throughput passive assembly. By careful co-design of the InP-Si Photonics electrical, optical and mechanical interface, as well as dedicated alignment fiducials, sub-300nm post-bonding alignment precision is realized in a 25s cycle time. Optical coupling losses of -1.5±-0.5dB are achieved at 1550nm wavelength after epoxy underfill, with up to 40 mW of optical power coupled to the SiN waveguides on the Si photonics wafer. The bonding interface adds less than 10% to the series resistance of the laser diodes and post-bonding thermal resistance is measured to be 76K/W (or 27K.mm/W), mostly dominated by heat spreading resistance in the InP lasers as suggested by in-depth thermal modeling. Although the assembled lasers suffer from significant, unintentional optical backreflection from the fiber grating couplers used for optical characterization, laser linewidths well below 1MHz have been measured under specific drive conditions, as supported by a detailed laser noise analysis. Finally, we demonstrate the ability of bonded laser assemblies to pass early reliability tests.