Low temperature InP (chip) / Al2O3 / Si (wafer) direct bonding

• Main Author: Lin, Yiding
• Other Authors: Tan Chuan Seng
• Format: Theses and Dissertations
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Microelectronics
• Online Access: http://hdl.handle.net/10356/65369
• Institution: Nanyang Technological University

Direct chip-to-wafer bonding of Indium Phosphide (InP) on Silicon (Si) using Aluminium Oxide (Al2O3) as an intermediate layer has been investigated. Thermal superiority of Al2O3 material over SiO2 as bonding intermediate layer has been demonstrated with respect to thermal dissipation and thermally-induced stress relief, using COMSOL Multiphysics. Successful InP/Al2O3/Si bonding has been achieved, via both O2 plasma and UV/Ozone activation techniques. Multiple characterization results support the good quality of bonding. Die shear test shows strong bond strength higher than 2.5 MPa. Cross-sectional Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) results reveal void-free and seamless bonding interface. Energy-dispersive X-ray Spectroscopy (EDX) as well as elemental mapping results show minimal material inter-diffusion at the interface. X-Ray Diffractometer (XRD) scan confirms minimal stress induced in the transferred film without significant crystal quality degradation. To resolve bonding interfacial void issue, in-plane outgassing channels on Si were designed, fabricated and studied. COMSOL simulation shows more significant outgassing-channel-induced InP/Al2O3/Si thermal and thermal-mechanical characteristics degradation, with decreasing channel Spacing-to-width (S/W) ratio. Successful InP/Al2O3/channel-patterned-Si bonding has been demonstrated, with void density suppression more significantly with decreasing S/W ratio. To compromise between the thermally-induced degradation and void density suppression, optimal S/W ratio of 2.5 has been proposed, with mild (10%) thermal stress increase and efficient (90%) void density suppression. Uniform InP film coverage was observed on Si at this ratio, with rigid suspension above outgassing channels. Therefore, the overall advantages of InP/Al2O3/Si bonding prove that it could be a promising candidate for future silicon photonics integrated circuit applications.