Olga V. Feklisova

Transformation of deep-level spectrum of irradiated silicon due to hydrogenation under wet chemical etching

The effect of wet chemical etching in acid solutions on the energy spectrum of n- and p-type silicon crystals previously irradiated with high-energy electrons is studied by deep-level transient spectroscopy. It is observed that together with the well known radiation defects a number of novel deep-level centres appear near the etched surface. The depth profiles of the deep-level centres are investigated depending on the irradiation dose and the temperature of subsequent annealing. The novel centres observed are shown to be complexes of radiation defects with the hydrogen atoms which penetrated into the crystal during etching. The origin of some of these centres from the particular vacancy-related defects is established. A simple quantitative description is given of hydrogen atom penetration during the etching and formation of the hydrogen - radiation defect complexes. Based on this analysis, the radius of hydrogen capture to the well known A-centre (vacancy - oxygen complex) is estimated and the centre with an energy level of eV is identified as a complex of the A-centre with two hydrogen atoms.

Dissociation of iron-related centers in Si stimulated by hydrogen

The interaction of hydrogen with Fe-related centers in p-type Si was investigated by deep level transient spectroscopy (DLTS). After wet chemical etching (WCE) of iron diffused Si samples the interstitial iron concentration exceeds the equilibrium concentration close to the surface. The iron depth profiles exhibit an exponential dependence with a characteristic length identical to the hydrogen penetration depth, which is about ten times larger than the iron diffusion length. On the other hand, after reverse bias annealing (RBA) the iron profile deviates clearly from the exponential distribution. Our results give evidence for a release of iron by a hydrogen-stimulated dissociation of iron-related defects.

Electrical and Optical Properties of Dislocations Generated under Pure Conditions

The PL, DLTS and EBIC investigations of p-Si samples plastical ly deformed in the clean conditions were carried out. For a comparison the samples deformed using set-up made from steel were studied. Oxygen effect on the PL spectra of samples deformed in the clean conditions is revealed. The effect of contamination during deformation was observed by the all thr e methods.

Simulation of hydrogen penetration into p-type silicon under wet chemical etching

Penetration of hydrogen into p-Si and formation of hydrogen-containing defects under wet chemical etching were simulated. The simulated concentration profiles of hydrogen-containing defects were compared to the measured profiles. It is shown that the hydrogen-distribution relaxation after termination of etching is important in the crystals with a low trap concentration. Consideration of such relaxation makes it possible to describe all experimental profiles without assuming that the hydrogen diffusivity is anomalously high. However, the experimental profiles can also be described assuming that the hydrogen diffusivity is high, with the effect of relaxation being less important in this case. It is shown that a comparative analysis of concentration profiles for the hydrogen-containing centers makes it possible to determine the number of hydrogen atoms in these centers in the cases where these profiles are either formed mainly in the course of etching or are modified significantly by transient hydrogen diffusion.

Annealing kinetics of boron-containing centers in electron-irradiated silicon

The annealing kinetics of BiOi pairs created by fast-electron irradiation in Si wafers is studied. The wafers are grown by the Czochralski method and doped with boron to different levels. It is found that, at a particular temperature, the annealing rate steadily increases with increasing boron concentration. The results are described with a simple model that takes into consideration the interaction of interstitial boron atoms with oxygen atoms and substitutional boron atoms. In the context of the model, the temperature dependence of the dissociation rate of the BiOi complex is calculated.

XBIC Investigation of the Grain Boundaries in Multicrystalline Si on the Laboratory X-Ray Source

It is shown that the X-ray beam induced current method (XBIC) can be realized at the laboratory X-ray source using the polycapillary x-ray optics. The images of iron contaminated grain boundaries in multicrystalline Si are obtained. It is shown that the grain boundary XBIC contrast is 2-3 times smaller than the EBIC one. A simulation of XBIC and EBIC contrast values for two-dimensional defects is carried out and a good correlation between the experimental and calculated values is obtained. The dependence of grain boundary XBIC contrast on the X-ray beam width is calculated.

X-ray beam induced current method at the laboratory x-ray source

The x-ray beam induced current method (XBIC) is realized on the laboratory x-ray source using the polycapillary x-ray optics. It is shown that rather good images of grain boundaries in Si can be obtained by this method. The parameters of x-ray beam are estimated by the simulation of Schottky diode image. A good correlation between the experimental and calculated grain boundary XBIC contrast is obtained. The possibilities of laboratory source based XBIC method are estimated.

Oxygen Effect on Electrical and Optical Properties of Dislocations in Silicon

(a) Institute of Microelectronics Technology, Russian Academy of Sciences,142432 Chernogolovka, Russiae-mail: yakimov@ipmt-hpm.ac.ru; Fax: 00709596280(b) Laboratoire MATOP associe´ au CNRS, Universite´ d’Aix-Marseille III, case 142,Faculte´ des Sciences St. Je´roˆme, F-13397 Marseille cedex 20, Francee-mail: gmariani@matop.u-3mrs.fr; Fax: 0033491288775(Received September 28, 1998)The DLTS (Deep Level Transient Spectroscopy) and PL (Photoluminescence) spectra of disloca-tions introduced in Cz-Si (single crystal grown by the Czochralski method) under clean conditionshave been studied. The oxygen effect on the formation of both spectra has been revealed. For thefirst time, a concomitant decay of both PL and DLTS signals with deformation duration in therange of 0.25 to 14 h was observed. Preliminary results show that one of the important parametersresponsible for the electrical and optical properties of the dislocations could be the distance cov-ered by the dislocations.

Gold Diffusion as a Tool for Defect Characterization in Si

An application of gold diffusion investigations for the defect struc ture characterization in Si is illustrated by the experiments carried out on samples containing different types of defects. A possibility to obtain information about grown-in defects in Si from gol d diffusion experiments is demonstrated by studies of Cz and FZ crystals and crystals doped with nitrogen. The results of gold diffusion application for the study of gettering efficiency of nanocavities produced by light ion implantation and for the characterization of extended defects are p res nted. The efficiency of gold diffusion experiments for investigations of intrinsic point defect ge neration and annihilation in Si is demonstrated.

A Comparison of EBIC, LBIC and XBIC Methods as Tools for Multicrystalline Si Characterization

A comparative study of multicrystalline Si based solar cells and plastically deformed single crystalline Si by the EBIC, LBIC and XBIC methods as well as a computer simulation were carried out. The XBIC measurements were realized on a laboratory X-ray source. Simulations of LBIC and XBIC contrast values for grain boundaries, dislocations and spherical precipitates were carried out for different diffusion length and beam diameter values. It is shown by a computer simulation that the LBIC and XBIC contrast of two-dimensional defects in the crystals with a large enough diffusion length can be a few times higher than that in the EBIC mode, i.e. these methods in recent multicrystalline Si structures allow to reveal grain boundaries with the lower recombination strength. The contrast of dislocations perpendicular to the surface can be comparable in all three methods. The XBIC and LBIC contrast of precipitates usually is essentially smaller than that in the EBIC mode and could approach it in the structures with the small diffusion length only. Experimental data confirming the results of simulations are presented.