Improving Electrical Properties by Effective Sulfur Passivation via Modifying the Surface State of Substrate in HfO2/InP Systems

Abstract

The thermal stabilities and interfacial properties of HfO2 films created on conditioned i-InP surfaces using atomic layer deposition were investigated. When HfO2 was deposited on sulfur passivation InP substrate, improved interfacial properties and electrical properties were observed by suppressing the interfacial oxides and In or P dangling bonds between HfO2 and InP. X-ray photoelectron spectroscopy (XPS) and thermodynamic data indicated that the acetone-methanol-Isopropanol (AMI) pre-clean process on InP substrate before sulfur treatment helps a sulfur passivation layer on the InP surface form more effective, in comparison to hydrogen fluoride (HF) pre-cleaning. HF pre-cleaning reduces InP native oxides effectively, but In-F bonds are generated on the InP surface, which interrupts the formation of In-S bonds. Moreover, total density of states (TDOS) and electron localization function (ELF) calculation data showed that In-F bonds do not significantly decrease midgap defect states induced by the In dangling bond because fluorine does not chemically bond with In atoms. As a result, the AMI pre-clean process was proposed for effective S passivation on the substrate in the HfO2/InP system. The capacitance-voltage (C-V) data revealed that the hysteresis width and frequency dispersion in the C-V accumulation and depletion were significantly improved in the AMI+S treated sample, as compared with the HF+S treated sample. In addition, the AMI+S treated HfO2/InP showed excellent thermal stability for the interfacial, structural, and electrical properties during post annealing at 600 degrees C.