Adhesive-free bonding for hetero-integration of InP based coupons micro-transfer printed on SiO 2 into Complementary Metal-Oxide-Semiconductor backend for Si photonics application on 8 " wafer platform

Micro -Transfer printing ( mu TP) is a promising technique for hetero-integration of III -V materials into Si -based photonic platforms. To enhance the print yield by increasing the adhesion between the III -V material and Si or SiO 2 surface, an adhesion promoter like Benzocyclobutene is typically used as interlayer. In this work, we demonstrate mu TP of InP based coupons on SiO 2 interlayer without any adhesive interlayer and investigate the mechanism of adhesive free bonding. Source coupons are InP-based coupon stacks on a sacrificial layer that is removed by a chemical wet etch with FeCl 3 . For the target we fabricated amorphous -Si waveguides on 8 '' wafer encapsulated by a High Density Plasma SiO 2 which was planarized by a chemical mechanical polishing procedure. We used O 2 plasma to activate both source and target to increase adhesion between coupon and substrate. To get a better understanding of the bonding mechanism we applied several surface characterization methods. Root mean square roughness of InP and SiO 2 was measured by atomic force microscopy before and after plasma activation. The step height of the micro -transfer printed source coupon on the target wafer is estimated by optical step profiler. We used Raman peak position mappings of InP to analyze possible strain and contact angle measurements on SiO 2 , before and after plasma activation to observe a change in the hydrophilicity of the surface. X-ray Photoelectron Spectroscopy analysis was used to characterize the surface energy states of P2p, In3d, O1s for InP source and Si2p, O1s for SiO 2 target. Our results demonstrate direct bonding of InP coupons by means of mu TP without the need of a strain -compensation layer. In this way, a promising route towards Complementary Metal -Oxide -Semiconductor compatible use of mu TP for the hetero-integration of InP is provided.