D. W. Moon

In-depth concentration distribution of Ar in Si surface after low-energy Ar+ ion sputtering

Abstract The in-depth concentration of Ar atoms in Si surface after Ar + ion sputtering was investigated using medium-energy ion spectroscopy (MEIS) and dynamic Monte Carlo simulation. The primary Ar + ion energy was 0.5, 1 and 3 keV, and the primary Ar + ion beam direction was varied from surface normal to glancing angle. In the case of the surface normal incidence, the MEIS result shows that the maximum atomic concentration of Ar atoms increases from 6% at the depth of 2 nm to 16% at the depth of 3 nm as the primary ion energy increases from 0.5 to 3 keV. However, in the case of the incident angle of 80°, that is 2.5% at the depth of 1.5 nm when the primary energy is 3 keV, in-depth Ar distribution cannot be observable when the primary ion energy is 0.5 keV. Dynamic Monte Carlo simulation reproduced the in-depth concentration distribution of Ar atoms quantitatively.

GaAs delta‐doped layers in Si for evaluation of SIMS depth resolution GaAs

Due to the complicated artefacts in SIMS depth profiling, SIMS depth resolution is difficult to evaluate. For evaluation of the SIMS depth resolution, delta-doped layers are more useful than sharp interfaces, because the matrix effect and the sputtering rate change can be minimized in profiling through delta layers. The GaAs delta-doped layers in Si were grown and proposed as a reference material for the evaluation of SIMS depth resolution. The SIMS depth resolution was estimated using the analytical expression based on a double exponential with a Gaussian, and its dependence on SIMS analysis conditions such as ion energy, ion species and incidence angle was studied with the proposed GaAs delta-doped multilayers in Si. Copyright

Damage profiling of Ar+ sputtered Si(100) surface by medium energy ion scattering spectroscopy

Abstract To study the damage profile development due to ion bombardment as a function of the ion dose and the ion incidence angle effect on the damage profiles, MEIS spectra were taken from a clean Si surface and ion beam sputtered Si surfaces. MEIS analysis shows that the surface layer becomes amorphous initially and the amorphous surface layer gets thicker for a Si(100) surface bombarded with 3 keV Ar + ions. The damage profile of the Si(100) saturated at the ion dose of3 × 10 16 ion/cm 2 at the incidence angle of 35° from the surface normal. At the saturation ion dose, the depth of the damaged layer was 9.6 nm. The depth of the damaged layer was significantly reduced from 14.2 nm at the surface normal to 4.8 nm at the incidence angle of 80°. Though the depth of the damaged layer was minimized for the sputtering at the extremely glancing angle of 80°, the damaged layer did not disappear but remained as a very shallow surface layer. These observations were reproduce by computer simulations by the Marlowe code qualitatively.

Estimation of the electronic straggling using delta-doped multilayers

Abstract It is proposed that the electronic straggling of projectile ion beams for medium energy ion scattering spectroscopy (MEIS) can be estimated with delta-doped multilayers. From the depth dependence of the full width half maximum (FWHM) of the Ta peak of a Ta delta-doped Si multilayer, the electronic straggling of 100 keV H+ in Si could be estimated. The electronic straggling can be estimated without information on the exact thickness and the interface abruptness of the Ta delta-doped multilayers. The reduced electronic straggling, Ω e /Ω B was estimated to be 0.59. With the experimentally determined electronic straggling, the thickness of the Ta delta layer could be estimated and compared with the nominal thickness based on the growth rate determined by transmission electron microscopy (TEM).

Oxygen enhanced secondary ion emission of Fe and Co by TOF-SIMS and ISS/DR

Using secondary ion mass spectrometry (SIMS), ion scattering spectroscopy (ISS), direct recoil (DR) and X-ray photoelectron spectroscopy (XPS), we have studied the mechanism of oxygen enhancement of secondary ion emission. The secondary ion intensities were measured as a function of oxygen exposure for Fe and Co samples under static- and dynamic-SIMS conditions. In the static-SIMS, the intensity of Fe+ increased up to 60 L oxygen exposure and then slowly saturated. However, the intensity of Co+ had an additional peak at low oxygen coverage when compared with the result of Fe+. It sharply increased up to 5 L, dropping off around 20 L and increased again to saturation. Also the intensities of Fe+ and Co+ under dynamic-SIMS conditions showed similar changes to those under static-SIMS conditions. According to XPS spectra, the polycrystalline Fe surface was oxidized immediately on oxygen exposure. However the oxygen on the Co surface was changed from the chemisorbed state at low oxygen doses (0–5 L) to the oxide state at oxygen doses above 5 L. The relative oxygen coverages on Fe and Co samples estimated by DR and ISS intensities showed trends similar to the secondary ion intensities of Fe+ and Co+ as a function of oxygen dose. We applied the bond breaking model and the electron tunneling model for interpretation of the oxygen enhancement effect in the positive secondary ion emission for Fe and Co.

Medium‐energy ion scattering spectroscopy for quantitative surface and near‐surface analysis of ultrathin films

Medium-energy Ion Scattering Spectroscopy (MEISS) can provide non-destructive quantitative surface and near-surface composition with atomic layer depth resolution. The special features of MEISS can be utilized to improve quantification of conventional surface analysis techniques by studying preferential sputtering, which is one of the major problems in quantitative surface analysis using sputtering techniques. This phenomenon was studied in detail with MEISS, in situ and ex situ XPS analysis, RBS, and (inductively coupled plasma optical emission spectrometry) for WSi 2 .

Multiple As delta layered Si thin films for SIMS quantification and depth scale calibration

SIMS quantification and depth scale calibration has been based on ion implanted standards. In this work, the feasibility of using multiple delta layer reference materials for quantitative SIMS depth profiling is tested and presented. Preliminary studies on application of multiple As delta layer Si thin films to shallow junction analysis will be presented and discussed.

The incident angle effect on radiation damage and sputtering for low energy Ar+ ion bombardment

Abstract The problem of the surface damage due to ion bombardment has remained to be understood and solved. Especially for surface analysis tools such as XPS or AES sputter depth profiling, and SIMS, where sputtering processes are used, the detailed understanding of the surface damage process and the development of methods minimizing the surface damage are very important to get the original informations of the analyzed specimens. In this work, the effect of the incident angle on the formation of the altered surface layer of Ta2O5 thin film and the surface amorphization process of Si(100) surface due to Ar+ ion bombardment was studied with Medium Energy Ion Scattering Spectroscopy and Computer Simulations by Molecular Dynamics and Monte Carlo methods. Emphases were given on the extreme glancing incident angle of 80°, because it significantly minimized the radiation damage of Si and the preferential sputtering for Ta2O5.

Lattice location and damage distribution in MeV as implanted Si(100) crystals

Abstract Samples of Si(100) single crystals have been implanted with As+ ions of 1.00 MeV to a dose of ∼5 × 1014 cm−2 at room temperature. Transmission electron microscopy and combined Rutherford backscattering spectrometry and channelling experiments with a 2.10 MeV He+ beam have been performed on the implanted samples to study the lattice location of As atoms and resultant defect configuration after implantation and annealing at 850°C for 30 min. Single alignment angular distributions along [100] and [110] axes and a (110) plane for He+ scattering from both the As and Si atoms at the same depth were measured and presented. The experiments were compared with simulated scans, calculated with the use of a Monte Carlo method, for a variety of assumed lattice sites. Although an inspection of channelling profiles indicates that practically all the As are on substitutional positions, these need not be true substitutional positions as it includes defect complexes. Analysis of the data for As, by comparing with computer simulations, shows that the experimental results are consistent with the simulated ones with a possible configuration: about 83 ± 4% are on Si sites and 16 ± 3.5% occupy a site close to Si with an average displacement of about 0.014 nm along the [100] direction. A tentative explanation for these results is presented.