Investigation of Sulfur Passivation Treatments for Direct Wafer Bonding of III-V Materials

Abstract

Bonding techniques for direct wafer bonding of III-V materials by various sulfur passivation treatments are presented. A dry sulfur passivation method utilizing elemental sulfur vapor activated by ultraviolet light in high vacuum is adapted for use in wafer bonding. Large area bonding is achieved for GaAs/GaAs and InP/InP with bulk fracture strength achieved after annealing at 400 °C and 300 °C respectively without large compressive forces. X-ray photoelectron spectroscopy measurements of the treated GaAs surface show the reduction of oxide and creation of sulfide bonds prior to bonding. The electrical conductivity across a sulfur bonded GaAs/GaAs interface is greatly improved with a short anneal (1-2 minutes) at elevated temperatures (500-600 °C) and HRTEM images reveal the interface is restructuring at lower temperatures than reported for other bonding techniques.