The electrical activity of extended lattice defects formed by interstitial oxygen precipitation in silicon is studied. Their impact on diode characteristics and on minority carrier lifetime is addressed for different initial oxygen contents and pretreatments. The carrier traps present in the substrate are studied with deep level transient spectroscopy and with photoluminescence spectroscopy. The obtained electrical results are correlated with those of structural and chemical characterization using cross-section transmission electron microscopy and Fourier transform infrared spectroscopy.

The effects of trace amounts of Fe and Cu in p-and n-type silicon were investigated with microwave photoconductance decay and surface photovoltage. The wafers received controlled amounts of surface contamination of Fe and Cu that are relevant for ultralarge scale integrated technologies. The substrate doping type has a strong impact on the effect of the metallic impurities. Fe, as expected, strongly degrades the minority carrier lifetime of p-type substrates. On the other hand, the impact of Fe on n-type silicon is at least one order of magnitude lower than on p-type. In contrast, Cu is highly detrimental to n-type material, but has no significant impact on the minority carrier properties of p-type silicon for the contamination levels studied.

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Principles of measurement of photoconductance transients by time-resolved microwave absorption and reflection mode are presented. The microwave transmission (absorption) mode is a new implementation of the time-resolved microwave conductivity method. This instrument is more sensitive with respect to microwave response signal and less critical to instabilities induced by phase modulation of the response. An adjustment of the measurement system into a local resonance for each particular sample under investigation and the whole set of experimental conditions is crucial to ensure the highest sensitivity and reliability of the instruments. The waveguide slot resonance antenna provides mapping of recombination parameters in silicon wafers of thickness d≥50 μm and resistivity ρ≥1 Ω cm with a spatial resolution of 1–2 mm. Theoretical models and validity of the approximations for carrier decay analysis and determination of the recombination parameters are discussed. The nonlinearities of the recombination processes (Shockley–Read–Hall, Auger type, or carrier trapping) arising at the moderate and high level of excitation are analyzed. Determination of the recombination parameters in this case is based on correlated measurements and numerical simulations taking into account the dominant recombination mechanisms. The activation energies of carrier traps Etb=0.16±0.02 eV and Ets=0.20±0.02 eV in neutron transmutation doped n-Si material have been derived from temperature dependent carrier lifetime measurements.

Carrier recombination centers related with iron complexes in p-type silicon are studied by microwave and light-induced absorption techniques. Both thermal- and photoactivation are used to decompose iron–boron pairs and to study the impact on the recombination lifetime. Due to photodissociation of iron–boron pairs the lifetime increases for high level injection. Efficient recombination occurs via an acceptor level at Ec−0.29 eV as derived from the temperature dependence of carrier lifetime.

Contactless techniques of infrared and microwave absorption by free carriers for the monitoring of silicon structures are described. Theoretical principles of photoconductivity decay analysis and methodology for the determination of recombination parameters are given for both homogeneous and non-homogeneous excess carrier generation. Different approximations (the methods of decay amplitude-asymptotic lifetime analysis, the simulation of the whole decay curve, the variation of effective lifetime with wafer thickness and the asymptotic lifetime measurement for stepwise varying parameters in layered structure) corresponding to real experimental conditions for various structures and treatments of materials, which are important for microelectronics, are discussed.The determined recombination parameters in the range of bulk lifetime 0.0006-230 µs, velocity of surface recombination 600-5 × 10 4 cm s −1 and diffusion coefficient 0.015-18 cm 2 s −1 are illustrated for Si wafers obtained by various doping and preparation processes. The necessity to consider carrier trapping effects and nonlinear recombination processes is demonstrated by the analysis of experimental results obtained at different excitation levels for carrier concentrations in the range 10 13 -10 18 cm −3 . The possibility of extracting the parameters of the traps (with activation energy values 0.16 ± 0.02 eV, 0.20 ± 0.02 eV and 0.28 ± 0.04 eV) from the temperature-dependent asymptotic carrier lifetime measurements is illustrated for neutron transmutation doped wafers.

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