We report on the heterogeneous integration of electrically pumped InP Fabry-Pérot lasers on a SOI photonic integrated circuit by transfer printing. Transfer printing is a promising micromanipulation technique that allows the heterogeneous integration of optical and electronic components realized on their native substrate onto a target substrate with efficient use of the source material, in a way that can be scaled to parallel manipulation and that allows mixing components from different sources onto the same target. We pre-process transfer printable etched facet Fabry-Pérot lasers on their native InP substrate, transfer print them into a trench defined in an SOI photonic chip and post-process the printed lasers on the target substrate. The laser facet is successfully butt-coupled to the photonic circuit using a silicon inverse taper based spot size converter. Milliwatt optical output power coupled to the Si waveguide circuit at 100 mA is demonstrated.
ABSTRACT3D integration promises to reduce system form factor through direct stacking and interconnection of chips made using different technologies, into a single system. In our case, these interconnects consist of small and deep through wafer vias in the form of Cu nails. One of the enabling technologies to achieve 3D stacks, is thinning on carrier. It involves backside grinding and CMP of patterned wafers down to 20 micron, while temporarily glued to a carrier.Success of grinding on carrier is found to strongly depend on temporary glue layer properties and bonding quality. Voids in between device wafer and carrier of various origins were observed to cause thin wafer delamination and catastrophic breakage when grinding down below 50 micron. By improvements in the bonding process, we eventually enabled uniform bonding, compatible with standard grinding and CMP techniques.CMP both removes grinding-induced damage and exposes the Cu nails at the thin wafer backside. The developed CMP consists of 2 steps which are optimized to reduce Cu smearing and within-die uniformity. Both are found to correlate with the local Cu nail density variations.
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