The effect of oxygen during irradiation of silicon with low energy Cs+ ions

Abstract

The effect of oxygen flooding during ultralow energy SIMS depth profiling of silicon with Cs + primary ions is presented. New experimental data show the effective sputtering yield of silicon in the presence of oxygen, as well as the energy distribution of the secondary Si − ions. It is found that the component sputtering yield of Si is very sensitive to minute amounts of oxygen in the proximity of the sputtered surface. At these very low flooding pressures ͑in the 10 −9 -10 −8 mbar range͒, one cannot account for a full oxidation in the time frame of a typical measurement; it is concluded that in this particular case, which is technologically very relevant, small traces of oxygen will change the desorption characteristics of cesium as well as silicon. It shows that oxygen that is adsorbed to the silicon surface provides an attachment site for impinging cesium ions and thereby increases the retention capacity of cesium tremendously. Also, oxygen changes the secondary ion yield and can even promote the desorption of Si from the analysis surface.

2‐(2′‐Pyridyl)‐4,6‐diphenylphosphinine versus 2‐(2′‐Pyridyl)‐4,6‐diphenylpyridine: Synthesis, Characterization, and Reactivity of Cationic RhIII and IrIII Complexes Based on Aromatic Phosphorus Heterocycles

“…This enables comparison with other data. A more detailed validation of using this quantity to describe the amount of flooding can be found elsewhere 2. The arrival rate ratio is defined as where p O 2 is the partial pressure of the oxygen gas at the surface, J is the primary ion current and A is the raster size.…”

“…It was already demonstrated that the combination of ion implantation en consequent sputtering cannot completely describe the way cesium is retained during sputtering with low energy ions. It seems that desorption processes play an important role in removing the cesium that comes from the primary ion beam and thereby keeping the analysis surface exposed for analysis 2…”

Negative ion yield and sputter yield variations for Cs+ bombardment of Si with O2 gas flooding

“…12). Similarly, Bergmans and Vandervorst13 also observed a decrease of the useful ion yield of Si − with O 2 flooding, except at the highest flood pressure. Lösing et al 18 have reported that the secondary ion yield of P − could be increased by approximately one‐half order of magnitude for optimized O 2 gas flooding of CsC 6 − bombarded Si.…”

“…Under our experimental conditions, useful ion yields of electronegative elements U Y (M − ) (M = P, As, Sb, range of initial kinetic emission energy 65–185 eV (‘H’)) were lowered by oxygen flooding, rather than enhanced as had been reported previously in Refs 12,18,19, respectively. Kudriatsev et al 12 and Berghmans and Vandervorst13 had previously also observed that U Y (Si − ) is lowered by O 2 gas flooding of a Cs + sputtered silicon surface. For completeness, negative ion useful yield data taken from Ref.…”

“…One easy way to vary the sputter yield is to flood the surface with gas‐phase oxygen: the sputter yield of silicon, for example, drops by a factor of up to ∼4 with heavy oxygen coverage. Although the effects of oxygen on negative ion yields on cesium‐sputtered surfaces are not readily predicted11–13 it seemed worthwhile to investigate the effect of oxygen on cesium concentration and negative ion yields. (a) Three decades ago Chelgren et al 4 had suggested that additional gas flooding during Cs + bombardment should reduce the sputter yield, and thus might increase the surface cesium concentration.…”