Composition of oxygen precipitates in Czochralski silicon wafers investigated by STEM with EDX/EELS and FTIR spectroscopy

Kot, Dawid; Kissinger, G.; Schubert, Markus Andreas; Klingsporn, Max; Huber, Andreas; Sattler, Andreas

doi:10.1002/pssr.201510194

Cited by 13 publications

(23 citation statements)

References 25 publications

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“…In agreement with the above, it has been reported [88] that a thin oblate spheroid (simplification of a platelet) with an aspect ratio ~0.01 gives rise to an absorption band at 1227 cm −1 . The gradually change of the morphology from plate-like to more spheroidal shapes with larger aspect ratio shifts the frequency to lower wavenumbers [88]. Remarkably however, the 1230 cm −1 band has not been detected in the spectra in a number of previous experimental works [32,37,71,87,[89][90][91].…”

Section: Resultssupporting

confidence: 86%

“…The structure becomes IR active only when its size is smaller than 0.36 μm and it is shifted towards lower wavenumbers when the precipitates structure becomes more spheroidal [77]. In agreement with the above, it has been reported [88] that a thin oblate spheroid (simplification of a platelet) with an aspect ratio ~0.01 gives rise to an absorption band at 1227 cm −1 . The gradually change of the morphology from plate-like to more spheroidal shapes with larger aspect ratio shifts the frequency to lower wavenumbers [88].…”

Section: Resultssupporting

confidence: 77%

“…Instead, a band at 1170 cm −1 found in our spectra is related to platelet morphologies [71,75,76,78]. The latter band is considered to originate from a thin oblate spheroidal morphology, which approximates that of a platelet [71,88]. Apparently, its aspect ratio is larger than that of the platelet precipitate morphology related with the 1230 cm −1 band.…”

Section: Resultsmentioning

confidence: 56%

“…Regarding thermal treatments, it has been observed [11,87,89,[93][94][95][96][97] that when the samples were subjected to long term pre-annealing treatments at low temperatures [11,[87][88][89][93][94][95] i.e. at ~ 750 °C or even lower temperatures [37,90,96] i.e.…”

Section: Resultsmentioning

confidence: 99%

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IR studies of the oxygen and carbon precipitation processes in electron irradiated tin-doped silicon

Sgourou

Angeletos

Chroneos

et al. 2017

J Mater Sci: Mater Electron

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Section: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 56%

Section: Resultsmentioning

confidence: 99%

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IR studies of the oxygen and carbon precipitation processes in electron irradiated tin-doped silicon

Sgourou

Angeletos

Chroneos

et al. 2017

J Mater Sci: Mater Electron

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“…We think that more reliable results can be obtained applying a direct method like EDX and EELS as we did in our previous work. 18 The EDX results showed that the composition of plate-like precipitates and transitional forms between plate-like precipitates and octahedral precipitates is close to SiO 2 . Moreover, the EELS measurements of the characteristic plasmon loss energy show that the oxygen precipitates consist of amorphous SiO 2 .…”

mentioning

confidence: 93%

Current Stage of the Investigation of the Composition of Oxygen Precipitates in Czochralski Silicon Wafers

Kot

Kissinger

Schubert

et al. 2017

ECS J. Solid State Sci. Technol.

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In this work, we look on the current stage of the investigation of the composition of oxygen precipitates obtained with the help of different techniques. Moreover, we present our recent and new investigation of the composition of oxygen precipitates carried out by means of energy dispersive X-ray spectroscopy, electron energy loss spectroscopy, and Fourier transform infrared spectroscopy. The FTIR spectra measured at liquid helium temperature are compared with the spectra simulated on the basis of experimental results obtained by scanning transmission electron microscopy. Oxygen precipitates formed in Czochralski (CZ) silicon wafers in consequence of the thermal treatment were investigated since many decades (see e.g. Ref. 1). The main reason why so much effort was directed toward these defects was the impact which they have on integrated circuits and the properties of the silicon wafer itself. Oxygen precipitates can increase the resistivity of CZ silicon, change the wafer strength and cause warpage of the wafers. [2][3][4] It was also demonstrated that metallic impurities can be effectively trapped at oxygen precipitates in the process of gettering. [5][6][7][8][9] All these features of the oxygen precipitates require the control of precipitation in the production process of silicon devices. However, this cannot be optimally executed if the features of oxygen precipitates like their composition are not fully known. In spite of the wide knowledge about oxygen precipitation, the composition of oxygen precipitates SiO x still remains under ongoing discussion. This is due to the different x values varying from x = 1 to x = 2 which can be found in the literature. [10][11][12][13][14][15][16][17][18][19][20] In 1986, Skiff et al. investigated plate-like precipitates by electron energy loss spectroscopy (EELS) in the near-edge and ionization edge range. 10 The composition which they found was SiO 0.95 . At the beginning of the 90ies, Borghesi et al. modeled Fourier transform infrared spectroscopy (FTIR) spectra by an effective medium approach and concluded that the absorption band of precipitates at 1230 cm −1 can be well reproduced if SiO 1.8 is used.11 However, in 1995 Vanhellemont investigated the growth kinetics of oxygen precipitates based on the solubility and diffusivity of oxygen in silicon using precipitate sizes determined by transmission electron microscopy (TEM). He demonstrated that the precipitated phase is closer to SiO than to SiO 2 .12 The later works, exploiting again FTIR spectroscopy and effective medium theory for the determination of the composition of the oxygen precipitates and carried out by De Gryse et al., confirmed the thesis of Vanhellemont. In the beginning the authors obtained SiO x with x = 1.1-1.2 but in their more recent work they modified the algorithm and concluded that the precipitated phase behaves optically as a mixture of amorphous silicon and amorphous SiO 2 .13,14 Meduňa et al. investigated the composition of oxygen precipitates in silicon wafers characterized by different th...

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STEM EELS plasmon imaging ( SEPI ) for mixed phase silicon / silicon‐oxides systems

Klingsporn

Schubert

Kirner

et al. 2016

European Microscopy Congress 2016: Proceedings

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Plasmon imaging using energy filtered transmission electron microscopy (EFTEM) has been a well‐established technique for investigating mixed phase silicon systems for more than a decade [1]. To image the silicon distribution typically an energy window of 4 eV centered at 17 eV is used. With this approach the signal contains significant contributions of the silicon monoxide and dioxide plasmons which deteriorates contrast and prohibits quantitative imaging. As alternative approach we developed SEPI. A method, based on the combination of scanning transmission electron microscopy (STEM) with electron energy loss spectroscopy (EELS). SEPI allows to separate the contributions of Si, SiO and SiO 2 (see Fig. 1(a)) and, thereby, to map them individually. This was achieved by a spectrum‐by‐spectrum evaluation routine of EELS data cubes including the extraction of the single scattering distribution (SSD) and the subsequent fitting with reference spectra of silicon monoxide and dioxide and the analytical Drude model for silicon. In this work we present the successful application of SEPI for investigations of three silicon / silicon oxides systems. All measurements were performed on FEI Tecnai Osiris microscope equipped with a FS‐1 electron energy spectrometer. In Fig. 1(b) the silicon nanostructure of a nanocrystalline hydrogenated SiO x (nc‐SiO x :H) layer deposited on a silicon wafer using PECVD is shown. During the last years nc‐SiO x :H was under investigation for several applications in silicon thin film solar cells [2], as it offers high electronic conductivity compared to other silicon alloys. The electrical properties are commonly explained by the presence of silicon nanofilaments [3], which can be seen in Fig. 1(b). In Fig. 2, a line scan across the interface of a 14.5 nm thick silicon oxide layer on a silicon wafer is shown. The oxide layer was thermally grown at 900 °C partially using HCl atmosphere. The distribution of the three components Si, SiO, and SiO 2 demonstrate that between the silicon substrate and the SiO 2 layer an intermediate SiO layer exists. Fig. 3 (a) shows the oxygen distribution measured using energy dispersive X‐ray spectroscopy (EDX) of an oxygen precipitate in silicon. Oxygen precipitates in silicon are generated by precipitation of the supersaturated interstitial oxygen during thermal processing. Their stoichiometry was under discussion for decades and the compositions found were ranging from SiO 2 to SiO. Recently, it was shown that the center of the precipitate consists of SiO 2 [4]. The SiO plasmon ratio distribution of the oxygen precipitate, shown in Fig. 3 (b), demonstrates that the oxygen precipitate is also surrounded by an SiO layer similar to the oxide layer.

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Composition of oxygen precipitates in Czochralski silicon wafers investigated by STEM with EDX/EELS and FTIR spectroscopy

Cited by 13 publications

References 25 publications

IR studies of the oxygen and carbon precipitation processes in electron irradiated tin-doped silicon

IR studies of the oxygen and carbon precipitation processes in electron irradiated tin-doped silicon

Current Stage of the Investigation of the Composition of Oxygen Precipitates in Czochralski Silicon Wafers

STEM EELS plasmon imaging ( SEPI ) for mixed phase silicon / silicon‐oxides systems

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