Solid State Phenomena Vols. 205-206

Abstract: Photoluminescence (PL) and deep level transient spectroscopy (DLTS) have been used to investigate carbon related defects in p–type Cz–Si induced by proton irradiation. The interstitial carbon–interstitial oxygen (C_iO_i) level in DLTS and the corresponding C–line (789.5 meV) in PL spectra are detected in as–irradiated samples. Formations of the so–called P–line at 767 meV in PL and a new defect level at about 0.39 eV above the valence band edge, E_v, in the DLTS spectra are observed in the annealed samples. The evolution of the C_iO_i and E_v+0.39 eV levels in DLTS and also the C– and P– lines in PL upon post–irradiation heat–treatment is investigated, showing that the intensity of the C_iO_i level decreases with heat–treatment, which is consistent with the PL data for the C–line. The intensity of the E_v+0.39 eV level is enhanced and then saturates with annealing duration. We tentatively assign this level to the interstitial carbon–oxygen dimer (C_iO_2i).

Abstract: Irradiation induced complexes of C-rich case in silicon crystal were examined by the highly sensitive and accurate infrared absorption spectroscopy. Low impurity concentration and high quality crystal was used and low dose was employed to make the reaction simple. Almost all possible absorption lines were revealed and their absorbance determined. The conversion coefficient from absorbance to the complex concentration was estimated by the plausible assumptions. The reaction was discussed in terms of concentration rather than absorbance. Intra-group reaction, chain reaction of successive addition of oxygen or self-interstitial, reaction yield and competition between the parallel reactions were described.

Abstract: Infrared absorption spectra of highly nitrogen doped multicrystalline float zone silicon are reported. By measuring the nitrogen content in silicon using SIMS, a calibration function of the IR absorption coefficient at 963 cm^-1 (T = 300 K) and the nitrogen concentration is deduced: c_N = (1.29 ± 0.05)×10¹⁷cm² α₉₆₃. The calibration factor is 30 % less than the calibration factor reported by Y. Itoh et al. [Appl. Phys. Lett. 47 (1985) 488].

Abstract: Effects of prior rapid thermal processing (RTP) under different atmospheres on the motion of dislocations initiated from indentations in Czochralski (CZ) silicon have been investigated. It is found that the maximum gliding distances of dislocations in the specimens with the prior RTP under nitrogen (N₂) atmosphere are much smaller than those in the specimens with the prior RTP under argon (Ar) atmosphere. This is also the case when the specimens received annealing for oxygen precipitation (OP) subsequent to the RTP at 1250 °C under N₂ and Ar atmospheres, respectively. It is believed that the nitrogen atoms introduced during the RTP under nitrogen atmosphere or the oxygen precipitates facilitated by the RTP-introduced nitrogen atoms can exhibit pinning effect on the dislocation motion, which increases the critical resolved shear stress for dislocation glide.

Abstract: In silicon several electronic levels are known which can be attributed to transition metals. Ignorance persists however about the specific nature of the defect centers. Some progress was made recently on identifying electronic levels from substitutional or interstitial lattice sites and on identifying levels from defect complexes. The sensitive Laplace DLTS technique allows us to determine depth profiles or the influence of the electrical field on the emission rate with unparalleled accuracy. Three examples will be discussed in this short review: The identification of the CoB pair, a reinterpretation of the Ti DLTS spectrum and the complex formation of interstitial Cu with substitutional Cu as the nucleation site.

Abstract: The reaction of the mobile interstitial Cu_i atom and the A-center (vacancy-oxygen complex) was recently reported to produce at 350 K the rather stable CuVO complex. Chemomechanical polishing in a copper-contaminated slurry allowed to lower the copper in-diffusion temperature down to 295K. The development of the CuVO complex is shown to proceed via formation of the metastable precursor (CuVO*) which introduces two deep levels in the lower half of the band gap. The CuVO* defect is unstable at room temperature and transforms completely into the CuVO complex by a 30 min anneal at 350 K. The proposed structure for the CuVO* complex of a Cu_i atom trapped nearby the A-center is supported by recent ab-initio calculations.

Abstract: Hydrogen incorporated into the samples by wet chemical etching interacts with platinum and forms several energy levels in the silicon forbidden band gap. Deep-level transient spectroscopy (DLTS) on Schottky diodes reveals several platinum-hydrogen related levels in p- and n-type silicon. In the n-type silicon, two new platinum-hydrogen related levels at 0.28 and 0.41 eV below the conduction band are reported. Annealing at 377 °C results in the dissociation of their corresponding platinum-hydrogen complexes.

Abstract: It has been found that association of iron-boron (FeB) pairs takes place during illumination of iron contaminated boron-doped silicon. The established FeB pair model is interpreted with respect to the quasi-Fermi level position, the stability condition of FeB pairs and the steady state reaction between interstitial iron, electrons and boron. At an excess charge carrier density of Δn = 5.4·10¹⁴ cm^-3, still 5 % of the interstitial iron associates to FeB pairs.

Abstract: In this paper, we test proximity gettering layers obtained by carbon or silicon implantation for their efficiency in molybdenum and tungsten gettering. DLTS was used to measure the impurity concentration in the solid solution and so to evaluate gettering efficiency. It was found that carbon implantation is effective in capturing these impurities, whereas silicon implantation is not. Extended defects seem not to play an important role in gettering these impurities. In addition, gettering was found to be most effective at high impurity concentration.

Abstract: Two getter tests were carried out in order to study the getter efficiency of oxygen precipitates in silicon samples contaminated with low and high Cu concentration. The samples were pre-treated by RTA followed by annealing in the temperature range between 700 °C and 1000 °C for various times in order to establish different concentrations and different sizes of oxygen precipitates in the samples. From the analysis of the results of the normalized inner surface and the gettering efficiency, it was deduced that in highly contaminated samples Cu precipitates more easily at dislocations than at the surface of oxygen precipitates. Contrarily, in the samples contaminated with low Cu concentration the presence of dislocations does not improve the getter efficiency. Cu precipitates were found at the edge of a plate-like precipitate in a sample with low Cu concentration.