Atomic-order nitridation of Si(100) in an NH, environment (124-1400 Pa) at 300-650°C has been investigated using an ultraclean low pressure hot-wall reactor system. At 500°C or higher, the N atom concentration (nX) initially increases and tends to saturate to a certain value (d ∼ 5 Å, nX ∼ 3 × 1015 cm-2). At 400°C or lower, on the H-terminated Si surface, the Si-hydride decreases with increasing NH3 exposure time and becomes hardly observed when nX reaches nearly to the surface Si atom concentration (6.8 × 1014 cm-2). On the H-free Si surface, nX increases up to ∼2 × 1014 cm-2 with the appearance of the Si-hydride instantly after NH3 exposure. It is expected that NH3 dissociatively adsorbs on the Si dangling bonds. It is found that nX is well described by Langmuir-type physical adsorption and reaction of NH3 on the Si surface. The ultrathin nitride film shows very good characteristics as a mask against oxidation.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry