Passivation of Silicon Surfaces by Formation of Thin Silicon Oxide Films Formed by Combination of Induction-Coupled Remote Oxygen Plasma with High Pressure H2O Vapor Heat Treatment

Abstract

ABSTRACTWe report formation of thin silicon oxide films on the silicon surfaces by combination of oxygen radical and high pressure H2O vapor heat treatment for passivation of silicon surfaces at a low temperature. Oxygen plasma was generated by 13.56 MHz radio frequency induction-coupled remote plasma with mixed gases of O2 and Ar at 2 sccm, 2x10-2 Pa and at a power of 50 W. Oxygen radical was produced from the plasma via a metal mesh closing plasma in the reactor. The top surfaces of 20 Wcm n-type silicon substrates with the rear surface coated by thermally grown SiO2 layers were exposed by oxygen radical from 1 to 5 min to oxidize the silicon surface. The samples were subsequently annealed with 9.0x105 Pa H2O vapor heat treatment at 260oC for 3 h. The effective minority carrier lifetime estimated using photo-induced carrier microwave absorption system in the case of 635 nm light illumination at 1.5 mW/cm2 to the top surface increased from 1.3x10-4 to 5.1x10-4s as the oxygen radical treatment duration increased from 1 to 5 min. The recombination velocity decreased from 380 to 90 cm/s. 500 kHz capacitance response with bias gate voltages characteristics of metal oxide semiconductor structure resulted in the effective oxide thicknesses (EOT) ranging from 1.3 to 1.7 nm. These results indicate a capability of thin oxide formation and effective passivation of silicon surfaces at a low temperature.