Diffusion of cesium in silicon during SIMS experiments investigated by numerical simulations

Philipp, Patrick; Barry, Peter R.; Wirtz, Tom

doi:10.1002/sia.5608

Cited by 3 publications

(2 citation statements)

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“…This is not obvious because the cluster ion bombardment creates a much larger perturbation of the surface than monatomic ion bombardment. The large atomic radius of cesium which allows only for a low solubility in silicon and leads to its diffusion from the bulk to the sample surface on time scales smaller than the time difference between two consecutive and overlapping impacts may help at this point. , The diffusion of cesium to the sample surface is also supported by the formation of cesium oxide dots once the sample is taken out of vacuum, although this happens on much longer time scales over several days . In addition, the adhesion of cesium on cesium is low, facilitating its surface diffusion to areas with low cesium surface concentrations.…”

Section: Resultsmentioning

confidence: 99%

Significant Enhancement of Negative Secondary Ion Yields by Cluster Ion Bombardment Combined with Cesium Flooding

et al. 2015

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In secondary ion mass spectrometry (SIMS), the beneficial effect of cesium implantation or flooding on the enhancement of negative secondary ion yields has been investigated in detail for various semiconductor and metal samples. All results have been obtained for monatomic ion bombardment. Recent progress in SIMS is based to a large extent on the development and use of cluster primary ions. In this work we show that the enhancement of negative secondary ions induced by the combination of ion bombardment with simultaneous cesium flooding is valid not only for monatomic ion bombardment but also for cluster primary ions. Experiments carried out using C60+ and Ar4000+ bombardment on silicon show that yields of negative secondary silicon ions can be optimized in the same way as by Ga+ and Cs+ bombardment. Both for monatomic and cluster ion bombardment, the optimization does not depend on the primary ion species. Hence, it can be assumed that the silicon results are also valid for other cluster primary ions and that results obtained for monatomic ion bombardment on other semiconductor and metal samples are also valid for cluster ion bombardment. In SIMS, cluster primary ions are also largely used for the analysis of organic matter. For polycarbonate, our results show that Ar4000+ bombardment combined with cesium flooding enhances secondary ion signals by a factor of 6. This can be attributed to the removal of charging effects and/or reduced fragmentation, but no major influence on ionization processes can be observed. The use of cesium flooding for the imaging of cells was also investigated and a significant enhancement of secondary ion yields was observed. Hence, cesium flooding has also a vast potential for SIMS analyses with cluster ion bombardment.

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Section: Resultsmentioning

confidence: 99%

Significant Enhancement of Negative Secondary Ion Yields by Cluster Ion Bombardment Combined with Cesium Flooding

et al. 2015

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“…This is due not only to the partial mixing of cesium into the sample, but also to the diffusion of cesium to the sample surface on short time scales. In DFT calculations, using some configurations where cesium was only a few atomic layers below the sample surface, the diffusion to the silicon surface took only some picoseconds [23], which is related to the large size of cesium compared to silicon and the stress produced in the silicon lattice [23,24]. Previous results are valid not only for Cs + and Ga + bombardment, but for any monatomic primary ion species, including He + and Ne + , where yield enhancements of up to 5 orders of magnitude were observed (figure 5(b)).…”

Section: Secondary Ion Mass Spectrometrymentioning

confidence: 99%

High-resolution high-sensitivity elemental imaging by secondary ion mass spectrometry: from traditional 2D and 3D imaging to correlative microscopy

et al. 2015

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Secondary ion mass spectrometry (SIMS) constitutes an extremely sensitive technique for imaging surfaces in 2D and 3D. Apart from its excellent sensitivity and high lateral resolution (50 nm on state-of-the-art SIMS instruments), advantages of SIMS include high dynamic range and the ability to differentiate between isotopes. This paper first reviews the underlying principles of SIMS as well as the performance and applications of 2D and 3D SIMS elemental imaging. The prospects for further improving the capabilities of SIMS imaging are discussed. The lateral resolution in SIMS imaging when using the microprobe mode is limited by (i) the ion probe size, which is dependent on the brightness of the primary ion source, the quality of the optics of the primary ion column and the electric fields in the near sample region used to extract secondary ions; (ii) the sensitivity of the analysis as a reasonable secondary ion signal, which must be detected from very tiny voxel sizes and thus from a very limited number of sputtered atoms; and (iii) the physical dimensions of the collision cascade determining the origin of the sputtered ions with respect to the impact site of the incident primary ion probe. One interesting prospect is the use of SIMS-based correlative microscopy. In this approach SIMS is combined with various high-resolution microscopy techniques, so that elemental/chemical information at the highest sensitivity can be obtained with SIMS, while excellent spatial resolution is provided by overlaying the SIMS images with high-resolution images obtained by these microscopy techniques. Examples of this approach are given by presenting in situ combinations of SIMS with transmission electron microscopy (TEM), helium ion microscopy (HIM) and scanning probe microscopy (SPM).

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Temperature dependent Cs retention, distribution, and ion yield changes during Cs+ bombardment SIMS

Giordani

Lee

et al. 2016

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Combining Cs+ bombardment with positive secondary molecular ion detection (MCs+) can extend the analysis capability of secondary ion mass spectrometry (SIMS) from the dilute limit (<1 at. %) to matrix elements. The MCs+ technique has had great success in quantifying the sample composition of III–V semiconductors. However, the MCs+ has been less effective at reducing the matrix effect for group IV materials, particularly Si-containing compounds. The lack of success in quantifying group IV materials is primarily attributable to the high Cs surface concentrations overloading the sample surface and lowering ion yields. The Cs overload issue is caused by the mobility and relocation of the implanted Cs to the surface during an analysis. Critical to understanding the material-dependent success of the MCs+ technique and elucidating the Cs mobility is understanding how Cs is incorporated and distributed into the sample and how the Cs surface concentration affects the ionization processes. The authors provide both new insight for improving the MCs+ technique by investigating the Cs retention, distribution, and ion yield differences between group III–V and IV materials and a greater understanding of the temperature-dependent mobility and relocation of the implanted Cs. There have been many studies on improving the MCs+ technique; however, our novel approach to use temperature as a means of controlling the Cs mobility has not been previously explored. Cesium build-up curves were acquired to assess the in situ Cs incorporation differences. By utilizing the newly developed variable temperature stage on our SIMS, cesium build-up curves were acquired over a wide range of temperatures (−150 to 300 °C) to show the temperature-dependent relocation of Cs and the effect it has on the ionization processes. Additionally, Cs ionization and neutralization were quantified as a function of Cs fluence and temperature. The Cs retention and distribution differences were determined ex situ by measuring the Cs concentration using heat-treatment x-ray photoelectron spectroscopy and heat-treatment medium energy ion scattering. These results allow for a more thorough understanding of the material-dependent success of the MCs+ technique, the Cs+-sample interaction, and the temperature component of the Cs mobility.

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Diffusion of cesium in silicon during SIMS experiments investigated by numerical simulations

Cited by 3 publications

References 24 publications

Significant Enhancement of Negative Secondary Ion Yields by Cluster Ion Bombardment Combined with Cesium Flooding

Significant Enhancement of Negative Secondary Ion Yields by Cluster Ion Bombardment Combined with Cesium Flooding

High-resolution high-sensitivity elemental imaging by secondary ion mass spectrometry: from traditional 2D and 3D imaging to correlative microscopy

Temperature dependent Cs retention, distribution, and ion yield changes during Cs+ bombardment SIMS

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