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

Abstract

InP DFB lasers are flip-chip bonded to 300 mm 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-300 nm post-bonding alignment precision is realized in a 25 s cycle time. Optical coupling losses of -1.5 +/--0.5 dB are achieved at 1550 nm 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 76 K/W (or 27 K.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 1 MHz 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.