二次イオン質量分析法によるシリコン結晶中の炭素と酸素の分析において定量性に影響する因子

抄録

The purposes of this study were to evaluate the influences of the primary ion beam current and the primary ion beam sweep area on the quantitative analyses of carbon and oxygen in silicon single crystals by secondary ion mass spectrometry (SIMS). The influences of them were examined in consideration of the slope of calibration curves and the form of craters. Five different (100) silicon single crystals, whose carbon and oxygen concentrations were determined by Fourier Transformation infrared spectrometry (FT-IR), were used as samples.
The best analytical conditions of carbon and oxygen obtained were 0.6 μA and 1.0 μA for the primary ion beam current and 200 μm×200 μm and 100 μm×100 μm for the primary ion beam sweep area, respectively. The high primary ion beam current density was suitable for the oxygen analysis, and the medium primary ion beam current density for the carbon analysis. The reason of the difference of suitable primary ion beam current density is explained with a difference of mechanism of adsorption of carbon-containing molecules and oxygen-containing molecules under the ion bombardment. Adsorption of carbon-containing molecules on the sample surface is enhanced under the ion bombardment, whereas that of oxygen-containing molecules is not enhanced. So, the high primary ion beam current density is not suitable for the carbon analysis since the background intensity is increased by adsorption of carbon-containing molecules.
At the best analytical condition of oxygen obtained, the sputtering rate was 15 nm/s and the form of crater after ion sputtering became like a corn. Therefore, the depth resolution was wrong and sensitivity is not compatible with depth resolution on SIMS analysis.