Surface and Interface Characterization of Sequentially Plasma Activated Silicon,Silicon dioxide and Germanium Wafers for Low Temperature Bonding Applications

摘要

ermanium (Ge) has recently drawn considerable interest because of its large absorption coefficient at near infrared frequency range, and high carrier mobility [1]. On the other hand, silicon (Si) and silicon dioxide (SiO_2) offer a low cost solution for microelectronic and micro-electromechanical systems. Integration of Ge with Si and SiO2 can find important applications in high performance photodetectors, solar cells, and Ge on insulator (SiO_2) (GeOI) structures. However, epitaxial growth of Ge on Si is not preferable because of high temperature (~700-900°C), high cost and large lattice mismatch (4.2 %). To address these issues, low temperature bonding of Ge/Si and Ge/SiO_2 has been proposed. Currently, direct bonding of Ge/Si and Ge/SiO_2 require high temperature (~300-400°C) at prolonged annealing (~48 hours) [2, 3]. The high bonding temperature creates thermal stress, interfacial voids and hence is not preferable for delicate structures and materials with large differences in thermal expansion coefficients. In addition to these problems, device throughput can be reduced by prolonged annealing, hence a low temperature, fast and spontaneous bonding technique for Ge/Si and Ge/SiC>2 is needed for practical applications.