Sputter-initiated resonance ionization spectroscopy (SIRIS) is an analytical technique with extremely high sensitivity, selectivity, dynamic range, and quantitation accuracy. SIRIS also provides good spatial resolution, and freedom from matrix effects on surfaces and at interfaces. In this paper we report the capability of SIRIS to quantitate, with high accuracy and high depth resolution, dopant and impurity concentrations in semiconductor devices at the 1013–1020 atoms/cm3 level. By utilizing layered GaAs/AlGaAs/GaAs samples grown by molecular beam epitaxy, a depth resolution of ∼2 nm has been demonstrated using 0.5 keV Ar+ primary ion energy. Depth profiles of boron in Si implants showed dynamic ranges up to 2×106. The correlation between B concentration and B SIRIS signal demonstrated high quantitation accuracy. The lateral imaging capability of SIRIS was demonstrated. We concluded that an optimized instrument could produce high depth-resolved quantitative measurements over a 1012–1021 atoms/cm3 concentration range.
A scanning ion beam instrument equipped with a gas field ionization source (GFIS) has been commercialized, but only helium and neon are currently available as GFISs. The characteristics of krypton ion emission from a single atom tip (SAT) have not been reported yet. In this study, the characteristics of krypton ion emission were investigated by field ion microscopy. At 65 K, the krypton ion emission current reached approximately 40 pA, which is 1 order of magnitude higher than that at 130 K. As the krypton gas pressure was increased, the krypton ion current increased. At a pressure of 0.3 Pa, the emission current was anticipated to reach 200 pA, which may be high enough for nanofabrication. The variation of the krypton ion current was as low as 5% in one hour. We concluded that a krypton ion beam instrument equipped with a GFIS will be a powerful tool for nanofabrication.
Depth profiles of 30Si negative secondary ions were measured at Cs+ ion impact energies of 10.5 keV, 14.5 keV and 17.5 keV and a 45° impact angle by means of secondary ion mass spectrometry (SIMS). Yield changes due to surface topography changes occurred at 14.5 keV and 17.5 keV impact energy, although no surface topography change has ever been reported during Cs+ ion bombardment. No yield change was detected at 10.5 keV impact energy. The topography changes and ion yield changes are obviously affected by the Cs+ ion impact energy.
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