M. G. Dowsett

Diffusion of boron in germanium at 800–900°C

Diffusion of B in Ge is studied in the temperature range 800–900°C using implantation doping and B doped epitaxial Ge layers. Concentration profiles before and after furnace annealing were obtained using high resolution secondary ion mass spectroscopy (SIMS). Diffusion coefficients were calculated by fitting the annealed profiles using TSUPREM. We obtained diffusivity values which are at least two orders of magnitude lower than the lowest values previously reported in the literature. Using our values an activation energy of 4.65(±0.3)eV is calculated. Present experimental results suggest that interstitial mediated mechanism should be considered for B diffusion in Ge in accordance with recent theoretical calculations. Annealed SIMS profiles also suggest that B solid solubility in Ge is ∼2×1018cm−3 at 875°C which agrees with literature values.

Diffusion of ion-implanted boron in germanium

The diffusion of boron (B) in germanium (Ge) is studied. B was introduced in Ge wafers by ion implantation and concentration profiles after furnace annealing were obtained using secondary ion mass spectroscopy. The diffusion coefficient and solid solubility of B in Ge has been calculated to be 1.5(+/-0.3)x10-16 cm2/s and 5.5(+/-1.0)x1018/cm3, respectively at 850 degrees c by fitting experimentally obtained profiles. The value of diffusion coeffienc is at least two orders of magnitude lower than the minimum value reported in the literature for B diffusion in Ge. The results are significant as they question the general agreement about vacancy diffusion as the mechanism responsible for diffusion of B in Ge.

Secondary ion mass spectrometry analysis of ultrathin impurity layers in semiconductors and their use in quantification, instrumental assessment, and fundamental measurements

The subject of this review is the secondary ion mass spectrometry (SIMS) analysis of ultrathin or delta layers of impurity in a semiconductor matrix and their use in establishing the limitations of SIMS depth profiling, exploring the fundamental processes occurring during analysis, and enhancing the quantification of SIMS data. Methods for extracting accurate information for the grower (concerning the material) and the analyst (concerning the SIMS instrument) are described. It is demonstrated that sets of SIMS profiles obtained over a range of analytical conditions are desirable if accurate information is required. In this context, the observation of dopant interaction occurring in codoped samples during SIMS analysis is reported for the first time. It is shown that quite large discrepancies exist between different measurements of decay length and associated parameters for the same impurity/matrix combination. These need to be explained before attempting to relate delta profile shape to primary ion beam i...

Depth profiling using ultra-low-energy secondary ion mass spectrometry

The use of sub-keV primary ion beams for SIMS depth profiling is growing rapidly, especially in the semiconductor area. The first challenge in this new branch of the technique was to invent equipment capable of obtaining high quality data with sufficient rapidity to be economically viable. After a brief historical introduction, these radical developments across instrument type are reviewed. The current challenge is to obtain a good enough understanding of the experimental process to obtain accurate, interpretable, data. The elementary requirements for this are described with emphasis on data density. Finally, the physical limitations such as atomic mixing and transient effects at the surface and interfaces are discussed. Extrapolation of profile shape as a function of beam energy, combined with the use of capped samples, is discussed as a potential part of the solution.

Dopant spatial distributions: Sample-independent response function and maximum-entropy reconstruction

We demonstrate the use of maximum entropy based deconvolution to reconstruct boron spatial distribution from the secondary ion mass spectrometry (SIMS) depth profiles on a system of variously spaced boron

Secondary ion mass spectrometry depth profiling of boron, antimony, and germanium deltas in silicon and implications for profile deconvolution

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Quantification of secondary-ion-mass spectroscopy depth profiles using maximum entropy deconvolution with a sample independent response function

-layers grown in silicon. Sample independent response functions are obtained using a new method which reduces the danger of incorporating real sample behaviour in the response. Although the original profiles of different primary ion energies appear quite differently, the reconstructed distributions agree well with each other. The depth resolution in the reconstructed data is increased significantly and segregation of boron at the near surface side of the

The advantages of normal incidence ultra-low energy secondary ion mass spectrometry depth profiling

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The coordinated use of synchrotron spectroelectrochemistry for corrosion studies on heritage metals

-layers is clearly shown.

Low energy SIMS characterisation of ultra thin oxides on ferrous alloys

This article describes the shape of secondary ion mass spectrometry (SIMS) depth profiles from ultra thin ‘‘δ layers’’ in silicon, and its dependence on the impurity species and the primary beam energy. The impurities studied are boron, antimony, and germanium in epitaxial layers grown by molecular beam epitaxy. The use of the data for the assessment of depth resolution and the quantification or synthesis of SIMS profiles from thicker layers and distributions is discussed. Possible limits to deconvolution are explored.