Electron holography study of voids in self-annealed implanted silicon (original) (raw)

The effect of ion-beam specimen preparation techniques on vacancy-type defects in silicon

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2006

Ion bombardment is frequently used in the preparation of thin foils of a variety of materials for analysis by transmission electron microscopy (TEM) and related techniques. We have studied in detail the effects of such specimen preparation techniques on nanometre-sized cavities in silicon by comparing ion-beam milled cross-sectional specimens with those prepared using a small-angle cleavage technique. The cavities have been formed by a prior implantation of energetic helium ions and a high-temperature anneal. In the specimens prepared by ion-beam techniques in two different commercial systems, there is a clear effect on the small cavities. Specifically, the cavities are observed to migrate away from the original surface at both room temperature and liquid nitrogen temperature. The effect is discussed in the context of the interaction of the cavities with mobile vacancies and interstitials injected by the ion bombardment. We believe this to be an important effect that must be taken into account when using TEM techniques to study defects in semiconductors.

The formation, migration, agglomeration and annealing of vacancy-type defects in self-implanted Si

Journal of Materials Science: Materials in Electronics, 2007

The evolution of vacancy-type defects has been studied by variable-energy positron annihilation spectroscopy (VEPAS) in samples of high-quality FZ p-type (001) silicon wafers implanted with 4 MeV Si 2+ ions at room temperature to doses of 10 12 -10 14 cm -2 . The average vacancy concentration increases as (ion dose) 0.70 ± 0.06 . Progressive isochronal annealing measurements show that open-volume point defects (having a VEPAS signature close to that for divacancies) anneal between 500-600°C. VEPAS with enhanced depth sensitivity (via progressive etching) verified that single 30 min anneals to 550 and 600°C lead to the formation of buried clusters V N with an average N of 3.5 lying between depths of 2.2 and 3.6 lm (both ± 2 lm), close to the peak of vacancy damage just shallower than the ion range predicted by simulation. The concentration of these clusters increases as (ion dose) 2.6 ± 0.1 . Single anneals to higher temperatures reduce all open-volume point defect concentrations to below the limit detectable by VEPAS.

Investigation of inhomogeneous structures of near-surface-layers in ion-implanted silicon

The ion implantation as a subject of investigations attracts increasing interest because of its technological applications. For example, the ion implantation and the adequate thermal treatment are the basic processes for fabrication of a new so-called delta-BSF solar cell. In this silicon solar cell, the continuous sub-structure of modified material _planar amorphous-like layer of nanometric thickness with very thin transition zones. is inserted into the single-crystal emitter. From earlier high resolution electron microscopy studies, it is evident that these two Si phases coexist in the form of well-defined layers separated by sharp heterointerfaces wZ.T. Kuznicki, J. Thibault, F. Chautain-Mathys, S. De Unamuno, Towards ion beam processed single-crystal Si solar cells with a very high efficiency, E-MRS Spring Meeting, Strasbourg, France, First Polish–Ukrainian Symposium, New Photovoltaic Materials for Solar Cells, October 21–22, Krakow, Poland, 1996.x. The aim of this paper is the further structural characterisation of silicon single crystal with buried ‘amorphous’ layer. The non-destructive X-ray diffraction methods as well as the transmission electron microscopy were used to investigate the quality of the a-Sirc-Si heterointerfaces, structural homogeneity of the layers and distribution of the stress field. The measurements were carried out on an initial, as-implanted and annealed material. The _100:-oriented Si single crystals were implanted with 180 keV energy P ions at room temperature.

Electron - beam annealing of B-, P-, As-, Sb-, and Ga-implanted silicon by multiple-scan method

IEE Proceedings I Solid State and Electron Devices, 1982

Data are presented on the sheet resistance of ion-implanted silicon following isothermal electronbeam annealing by the multiple-scan method. Anneals were performed on implanted 5 mm square chips for times around 5 s, with anneal temperatures up to 1350°C. Implants of As, P, B, Sb and Ga were annealed, ranging in doses from 10 13 cm" 2 to 10 16 cm" 2 in both (100) and (111) orientation silicon, and the sheet resistance was measured with a four-point probe. The measurements are presented as a plot of sheet resistance against electron-beam power, for a given dopant and anneal time, and the corresponding temperatures are also shown. Above a threshold temperature region of 750°C to 950°C near-full electrical activation is obtained, except in cases where the doping level approaches the solid solubility limit, or for certain high-dose boron implants. Slightly lower sheet resistances are obtained for implants in (100) material than (111) material, and at temperatures exceeding 1100°C diffusion effects are expected to be significant. The activation of ion implants without significant redistribution of dopant during annealing can be used to improve the performance of ion-implanted devices.

Cavities at the Si projected range by high dose and energy Si ion implantation in Si

Materials Science and Engineering: B, 2009

Two series of n-type Si samples ␣ and ␤ are implanted with Si ions at high dose (1 × 10 16 ) and high energies, 0.3 and 1.0 MeV, respectively. Both sort of samples are then implanted with 5 × 10 16 He cm −2 (at 10 or 50 keV) and eventually with B atoms. Some of the samples are annealed at temperatures ranging from 800 to 1000 • C to allow the thermal growth of He-cavities, located between sample surface and the projected range (R p ) of Si. After the triple ion implantation, which corresponds to defect engineering, samples were characterized by cross-section transmission electron microscopy (XTEM). Voids (or bubbles) are observed not only at the R p (He) on all annealed samples, but also at the R p (Si) on ␤ samples implanted with He at 50 keV. The samples are also studied by positron annihilation spectroscopy (PAS) and the spectra confirm that as-implanted samples contain di-vacancies and that the annealed ones, even at high temperature have bigger open volumes, which are assumed to be the same voids observed by XTEM. It is demonstrated that a sole Si implantation at high energy and dose is efficient to create cavities which are thermally stable up to 1000 • C only in the presence of He.

Off-axis electron holography of unbiased and reverse-biased focused ion beam milled Si pn junctions

2005

Abstract: Off-axis electron holography is used to measure electrostatic potential profiles across a silicon pn junction, which has been prepared for examination in the transmission electron microscope~ TEM! in two different specimen geometries using focused ion beam~ FIB! milling. Results are obtained both from a conventional unbiased FIB-milled sample and using a novel sample geometry that allows a reverse bias to be applied to an FIB-milled sample in situ in the TEM.

DLTS and EPR study of defects in H implanted silicon

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002

Single crystal CZ Si samples were implanted with hydrogen ions to the dose of 2E16 He ions/cm 2 at room temperature and subsequently annealed in vacuum in the temperature interval from 100 to 900°C. The aim of the experiment was to determine the conditions for bubble formation within the solid film, which may have important technological application. Defects produced in such samples were studied by deep-level transient spectroscopy (DLTS) and electron paramagnetic resonance (EPR) spectroscopy. It is shown that high dose hydrogen implantation produces vacancy-related and silicon selfinterstitial clusters. The latter are thought to be responsible for the formation of the weak displacement field. The annealing at higher temperatures creates multivacancy-related clusters responsible for the strong displacement field formation. Ó