ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Effects of 35Cl+ bombardment of Si (100) surfaces were studied with a mass-separated low energy ion beam system operated under ultrahigh vacuum and with in situ x-ray photoelectron spectroscopy (XPS). Before ion bombardment, each silicon sample was etched with a hydrofluoric acid solution and rinsed in deionized water. XPS showed that the surface received no ion bombardment was effectively hydrogen passivated and had no silicon with an oxidation number higher than 2. However, oxygen was found which was probably present in the form of Si—OH or adsorbed water. Chlorine ion bombardment at room temperature initially drove the surface oxygen to the formation of silicon oxide which was subsequently etched off by further ion bombardment. The surface oxidation was initiated by the formation of Si—Cl bonds followed by the thermodynamically favorable replacement of Si—Cl with Si—O. The removal of the surface oxygen depended critically on the bombardment energy. At a bombardment energy of 1±0.6 eV, oxygen bonding was still observed even with a dose of 1018/cm2. The critical dose for oxygen depletion was found to be about 1×1018/cm2 for 40 eV bombardment, and about 1×1016/cm2 for 100 eV bombardment. Physical sputtering was the main oxide removal mechanism. Once the surface oxygen atoms were consumed, the silicon surface was etched by the chlorine ions with an enhancement by the chlorine chemistry. However, the absence of Si—Clx (x(approximately-greater-than)1) was clearly shown by XPS. Hence, bombardment must have promoted the desorption of the surface silicon chlorides.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.356160
