O De Gryse

Oxide phase determination in silicon using infrared spectroscopy and transmission electron microscopy techniques

Infrared absorption spectra of polyhedral and platelet oxygen precipitates in silicon are analyzed using a modified Day–Thorpe approach [J. Phys.: Condens. Matter 11, 2551 (1999)]. The aspect ratio of the precipitates is determined by transmission electron microscopy analysis. The reduced spectral function and the stoichiometry of the precipitate are extracted from the absorption spectra and the amount of precipitated interstitial oxygen. The experimental absorption spectra can be divided in a set with a Frohlich frequency of around 1100 cm−1 and in a set with a Frohlich frequency between 1110 and 1120 cm−1. It is shown that the shift in the Frohlich frequency is not due to a differing stoichiometry, but to the detailed structure of the reduced spectral function. Inverse modeling of the spectra suggests that the oxide precipitates consist of substoichiometric SiOγ with γ=1.17±0.14.

Hydrogen plasma-enhanced thermal donor formation in n-type oxygen-doped high-resistivity float-zone silicon

The impact of plasma hydrogenation on the subsequent formation of thermal donors at 450 °C in n-type oxygen-doped high-resistivity float-zone silicon is investigated by a combination of electrical and spectroscopic techniques. It is shown that the increase of the doping concentration can be explained by the creation of two sets of donors. The first one is the classical double oxygen thermal donors (OTDs), which are introduced with a nearly uniform concentration profile across the sample thickness, while the second type of donors is shallower and most likely hydrogen related. The latter show a pronounced concentration profile towards the surface and they form and disappear at a much faster rate than the OTDs at 450 °C.

Quantification of the low temperature infrared vibrational modes from interstitial oxygen in silicon.

Accurate conversion factors are obtained to determine the concentration of interstitial oxygen in silicon from the low temperature local vibrational mode absorption at 1136, 1128 and 1205 cm−1 for different resolutions and apodization functions. The absorption spectra at 6 K were fitted with fit functions in order to extract the amplitudes of interest in an accurate and reproducible manner. The ratio of the amplitude at room temperature to the low temperature amplitude then gives the conversion factors for 6 K. Based on a phonon model [H. Yamada-Kaneta Materials Science Forum, edited by G. Davies and M. H. Hazare (Trans Tech, Aveiro, 1997), 258–263, p. 355] and on occupation statistics the use of the conversion factors is extended to temperatures as high as 100 K, taking into account the broadening of the absorption peaks and the variation in the occupation of the different excited states.

Characterisation of oxygen and oxygen-related defects in highly- and lowly-doped silicon

Abstract In this paper, an overview will be given about analytical techniques which are suitable for the study of oxygen and oxygen precipitation in highly- and lowly-doped silicon. It will be shown that in the case of highly-doped silicon, the application of Fourier Transform Infrared (FT-IR) absorption spectroscopy requires the use of ultra-thinned or high-fluence irradiated samples and a dedicated data analysis. This sample preparation is necessary to reduce the free carrier absorption in the mid-IR region. It is shown that besides the interstitial oxygen concentration [O i ] and the amount of precipitated oxygen, it is possible to determine the stoichiometry of oxygen precipitates from the study of the corresponding absorption bands. Oxygen precipitation in p + silicon can also be investigated by the D1–D2 lines in photoluminescence (PL) on as-grown or heat–treated material without special sample preparation. In oxygen-doped high-resistivity float-zone silicon, standard FT-IR analysis can be applied to determine [O i ]. The presence of oxygen-related shallow donors can be probed by a combination of electrical (spreading resistance probe, SRP; capacitance–voltage, C – V ) and (quasi-)spectroscopic techniques (deep-level transient spectroscopy, DLTS).

Deep Levels in Oxygenated n-Type High-Resistivity FZ Silicon before and after a Low-Temperature Hydrogenation Step

Department of Solid-State Sciences, Ghent University, B-9000 Gent, BelgiumThe behavior of oxygen in oxygen-doped high-resistivity~HR! n-type float-zone~FZ! silicon has been studied using a combinationof analytical techniques. In the as-doped material, a large number of deep levels have been observed with deep-level transientspectroscopy. The corresponding parameters ~concentration, activation energy, and trap signature! are given, and the possibleidentity is discussed in view of the presence of oxygen and other impurities in the material. In addition, the impact of alow-temperature hydrogen-plasma preannealing on the formation of oxygen thermal donors~OTDs! and other oxygen-relatedshallow thermal donors ~STDs! at 450°C is described. It is shown that the introduction rate of OTDs in oxygenated HR FZ siliconis much smaller than in Czochralski silicon. In fact, for short anneals at 450°C following a plasma treatment, the STDs are theones which have been predominantly created near the surface of the samples.© 2003 The Electrochemical Society. @DOI: 10.1149/1.1595665# All rights reserved.Manuscript submitted July 7, 2002; revised manuscript received March 18, 2003. Available electronically July 10, 2003.

Characterization of Oxide Precipitates in Heavily B-Doped Silicon by Infrared Spectroscopy

Infrared absorption spectra of oxygen precipitates in boron-doped silicon with a boron concentration between 10 17 and 10 19 cm -3 are analyzed, applying the spectral function representation of composite materials. The aspect ratio of the platelet precipitates is determined by transmission electron microscopy measurements. The analysis shows that in samples with moderate doping levels ( 10 18 cm -3 ) samples, however, the measured spectra of the precipitates are consistent with a mixture of SiO 2 and B 2 O 3 , with a volume fraction of B 2 O 3 as high as 0.41 in the most heavily doped case.

Characterization of bulk microdefects in Ge single crystals

The work reported here concerns the characterization of bulk microdefects in germanium single-crystal wafers. From comparison with the case of silicon, it is expected that bulk microdefects are formed due to diffusion and interaction of self-interstitials and vacancies during Czochralski growth, solely dependent on the growth parameters. Unfortunately, several of the defect characterization methods, which can be used for silicon, fail in the case of germanium due to its lower band gap. Therefore, the possibilities of two alternative techniques, x-ray topography and small-angle x-ray scattering, respectively, were investigated. The results, combined with a characterization of the material surface using scanning laser reflectometry, indicate that in Ge, the same kind of intrinsic growth-related defects exist, as in Si.

Optical spectroscopy of oxygen precipitates in heavily doped p-type silicon

Results are presented on the photoluminescence (PL) characterization of heavily doped p+ Czochralski silicon, which has been subjected to a two-step, oxygen precipitation heat treatment. It will be shown that the presence of oxygen precipitates gives rise to the D1, D2 and D5 lines, where the energy of the D1 line shifts to lower values for a stronger degree of precipitation. The occurrence of these PL features is also a function of the boron concentration in the p+ material. The PL results are compared with Fourier transform infrared absorption data and with transmission electron microscopy results. From this, it is concluded that PL has a good potential for use in the assessment of oxygen precipitation in heavily doped silicon.

Accurate infrared spectroscopy determination of interstitial and precipitated oxygen in highly doped Czochralski-grown silicon

A method has been developed to determine the interstitial and precipitated oxygen concentration in highly doped n- and p-type silicon. 10–30-μm-thin silicon samples in a mechanical stress-free state and without alteration of the thermal history are prepared and measured with Fourier transform infrared spectroscopy at 5.5–6 K. The measured oxygen contents in the as-grown Si samples agree well with those obtained with gas fusion analysis. In the highly boron-doped samples, the interstitial oxygen can be determined down to 1017 cm−3.

Accurate infrared absorption measurement of interstitial and precipitated oxygen in p + silicon wafers

Abstract A novel infrared absorption method has been developed to measure the interstitial oxygen concentration in highly doped silicon. Thin samples of the order of 10–30 μm are prepared in an essentially stress-free state without changing the state of the crystal. The oxygen concentration is then determined by measuring the height of the 1136-cm−1 absorption peak due to interstitial oxygen at 5.5 K. The obtained results on as-grown samples are compared with those from gas fusion analysis. The precipitated oxygen concentration in annealed samples is also determined with the new method. It will be shown that the interstitial oxygen concentration in highly doped silicon can be determined with high accuracy and down to concentrations of 1017 cm−3.