Room temperature photo-oxidation of NH4F-prepared H–Si(111)(1×1) and Hx–Si(100)

Abstract

This work discusses the room temperature photo-oxidation of hydrogen-passivated silicon surfaces. Specifically, photoemission spectroscopy is used to investigate how the factors present in cleanrooms, including ultraviolet (UV) light, oxygen (O2), and water (H2O), lead to the photo-oxidation of the hydrogen-passivated silicon surface. Results indicate that both the H–Si(111)(1×1) and Hx–Si(100) surfaces oxidize when exposed to UV light in the presence of O2 only, H2O only, or humid air (both O2 and H2O). We propose that UV light assists in the photo-oxidation of the hydrogen-terminated silicon surfaces by cleaving the H–Si surface bond. This process generates silicon surface radicals that can then be scavenged by either O2 to form peroxyl radicals (Si–O–O∙) or by H2O to form silanols (Si–OH). Results also show that photo-oxidation is most significant when the surface is exposed to both O2 and H2O in the presence of UV light. Results from the humid air photo-oxidation experiments indicate that after the H–Si surface bond is cleaved by UV light, H2O reacts with the generated silicon surface radical to form a silanol. This is followed by a subsequent step involving UV light and O2.