Solid State Phenomena Vols. 156-158

Abstract: Simulation of contrast for small spherical defects in the X-ray beam-induced current (XBIC) mode has been carried out. Under simulations the excess carrier generation function is described by the rigid cylinder with the constant generation rate inside it. The dependence of maximum contrast value on the precipitate depth, diffusion length and effective beam radius is calculated. The XBIC contrast profile as a function of diffusion length, of beam radius and of precipitate depth has been calculated that allows to evaluate the spatial resolution of the technique. The results obtained are compared with those calculated for the EBIC contrast of the same defect. It is shown that in the semiconductor materials with the small diffusion length the XBIC contrast could be comparable with the EBIC one.

Abstract: The nucleation of dislocation in semiconductors is still a matter of debate and especially in heteroepitaxial films. To understand this nucleation process the classical models of dislocation nucleation are presented and discussed. Two main points are then developed: emission of dislocations from surface steps and the role of point defects agglomeration on dislocation nucleation. Recent atomic simulation of half loops emission from surface steps and experimental evidences of anisotropic relaxation of GaInAs films deposited on vicinal (111) GaAs substrates strongly support surface steps as preferential sites for nucleation. In low temperature buffer layer structures (SiGe/Si) an original dislocation structure is observed which corresponds to the dislocation emission in different glide systems by a unique nucleation centre.

Abstract: The novel concept of “impurity engineering in CZochralski (CZ) silicon ” for large scaled integrated circuits has been reviewed. By doping with a certain impurities into CZ silicon materials intentionally, such as nitrogen (N), germanium (Ge) and even carbon (C, with high concentration), internal gettering ability of CZ silicon wafers could be improved. Meanwhile, void defects in CZ silicon wafer could be easily eliminated during annealing at higher temperatures. Furthermore, it was also found that the mechanical strength could be increased, so that breakage of wafers decreased. Thus, it is believed that by impurity engineering CZ silicon wafers can satisfy the requirment of ultra large scale integrated circuits.

Abstract: The recovery of the boron implantation damage can be very difficult. Depending on the energy and the dose many dislocations are generated at the projected range of the boron implantation. The morphology of these dislocations depends on the silicon substrate. In this work we demonstrate that the interstitial oxygen concentration ([Oi]) is related with the dislocation dimension, density end morphology. Particularly long dislocation dipoles were generated by the boron implantation in substrate with interstitial oxygen, and their density is connected with the [Oi] concentration.

Abstract: Oxygen precipitation (OP) behaviors in conventional and nitrogen co-doped heavily arsenic-doped Czocharalski silicon crystals subjected to low-high two-step anneals of 650 oC/8 h + 1000 oC/4-256 h have been comparatively investigated. Due to the nitrogen enhanced nucleation of OP during the low temperature anneal, much higher density of oxygen precipitates generated in the nitrogen co-doped specimens. With the extension of high temperature anneal, Oswald ripening of OP in the nitrogen co-doped specimens preceded that in the conventional ones. Moreover, due to the Oswald ripening effect, the oxygen precipitates in the conventional specimens became larger with a wider range of sizes. While, the sizes of oxygen precipitates in the nitrogen co-doped specimens distributed in a much narrower range with respect to the conventional ones.

Abstract: In this paper, the influence of the rapid thermal annealing of single crystalline Cz-Si wafers on the evolution of the concentration of interstitial oxygen as well as oxygen in precipitated oxide phase was investigated by infrared spectroscopy. The wafers were preliminary furnace annealed to create the precipitate seeds. The concentration of interstitial oxygen was shows to decrease considerably as a result of annealing during up to 40 min together with the growth of the concentration of precipitated oxygen. This effect depended on the purity and defect structure of initial wafers. The kinetic model was developed to account for the observed effects based on the modification of the solubility level for interstitial oxygen induced by defects as well as its diffusivity. Obtained results of simulation agree well with the experimental data.

Abstract: The results of experimental investigations of the dislocation-related DLTS-peaks originated from the dislocation networks (DN) are presented. Samples with DNs were produced by direct bonding of p-type silicon wafers and no enhancement of oxygen concentration was detected near the DN plane. Origins of the DLTS peaks were proposed and a correlation with the dislocation-related photoluminescence data was established based on known dislocation structure of the samples. Two types of shallow DLTS peaks exhibited Pool-Frenkel effect, which could be linked to the dislocation deformation potential. One of the shallow DLTS peaks was related to straight parts of screw dislocations and another - to the intersections of the dislocations.

Abstract: We used the DLTS and photoluminescence (PL) techniques to study the deep states due to dislocations and deformation-induced point defects (PDs) in plastically deformed p-type germanium single crystals containing predominantly 60 dislocations with density ND, ranging from 105 to 106 cm-2. The narrow line near the temperature 140K dominates in the DLTS spectra. The ionization enthalpy and the capture cross section for holes traps indicate that the substitution copper atoms Cus are the main type of PDs. A decrease of the Cus atoms concentration and redistribution of the intensity in the PL spectra after the heat treatment of deformed samples at a temperature 500 °C are attributed to the diffusion of copper atoms to dislocations resulting in the appearance of “dirty” regular segments of 60 dislocations.

Abstract: The IR absorption spectra and kinetics of the oxygen solid solution decay were studied in the Si1¡xGex crystals (0 · x · 0:055) plastically deformed at 680±C up to the 2{5% residual strain. It is found that the defects of non-dislocation nature, the dislocation trails, are formed during the plastic deformation of all studied SiGe crystals. The ¯ne structure of the IR absorption spectra around the 1000 cm¡1 wave number is found to be nearly identical in the pure Si (no Ge) samples and Si1¡xGex crystals with x · 0:02. At higher x the ¯ne structure was not detected due to the alloy-related broadening. In all studied crystals, the decay of the supersaturated oxygen solid solution at 650±C is determined by oxygen agglomeration at the dislocation trails as shown by the comparison with the samples annealed at 1150±C.

Abstract: Defects induced in silicon crystals by irradiations with 6 MeV electrons in the temperature range 60 to 500 oC have been studied by means of deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS. Diodes for the study were fabricated on n-type epitaxially grown Si wafers. The DLTS spectra for the samples irradiated at elevated temperatures were compared with those for samples, which were subjected to irradiation at 60 oC and subsequent isochronal anneals in a furnace. The dominant radiation-induced defects in the samples irradiated at temperatures lower than 400 oC were found to be vacancy-oxygen (VO) and interstitial carbon – interstitial oxygen (CiOi) complexes. The introduction rates of the VO and CiOi centers increased about twice upon raising the irradiation temperature from 50 to 400 oC. It is argued that this effect is associated with either a) the suppression of the annihilation rate of Frenkel pairs or b) a decrease in the threshold energy for displacement of a host Si atom upon increase in the irradiation temperature. Transformations of deep level traps due to divacancies (V2) and trivacancies (V3) to V2-oxygen and V3-oxygen complexes were found to occur upon irradiation or annealing at temperatures exceeding 250 oC. A clear anti-correlation between changes in the minority carrier life time induced in the p+-n diodes by irradiation at different temperatures and changes in the concentrations of radiation-induced vacancy- and vacancy-oxygen-related complexes was found.