The atomic and electronic structures of the twist boundaries Σ (=3 (011), Σ=7 (111) and Σ=5 (001)) in Si have been calculated by using the transferable SETB method coupled with the supercell technique. The twist boundaries in Si contain larger structural disorder or more defects and larger interfacial energies than tilt grain boundaries. Several kinds of structural disorder or defects have been found to generate characteristic electronic states inside the gap. The present structural disorder or defects and the gap states are the candidates of the origins of the observed band-tails or mid-gap states in polycrystalline Si as well as those In amorphous Si.

In case of boron through-oxide implant, it has been shown that the knocked-in oxygen atoms segregate at initially nucleated dislocation sites during the incubation and no significant junction movement is detected. The trapping of oxygen proceeds up to a certain time at which oxygen-precipitation occurs and this leads to an ejection of excess Si interstitials and further enhancing boron diffusion. However, with fluorine addition we believe that fluorine incorporation in SiO2 and/or SiO2/Si interface not only releases the strain gradient but also suppresses the silicon interstitials ejection and by this means suppresses the oxidation-enhanced boron diffusion. Correlated results of TEM microdefect structures and spreading resistance profiles are used to further support our postulation.

Photo-Deep Level Transient Spectroscopy with 1.38 eV light reveals a new level with thermal activation energy 0.2 eV of DX centers in silicon doped Alx Ga1-xAs (x = 0.26) for the first time. The observation of this level directly proves the negative-U properties of DX centers and the existence of thermodynamically metastable state DX.

Oxygen-doped germanium crystals were used to demonstrate the interaction between implanted hydrogen or nitrogen atoms and the oxygen-related defects. The electron trap at Eo-0.26eV associated with the germanium A-center was found to be formed by electron irradiation. Another level at Eo-0.21eV also was observed on annealing at 120 °C. As for the sample implanted with hydrogen ions following electron irradiation, the trap concentration is four times as large as that for electron irradiation alone. It is probable that the germanium A-centers produced by electron irradiation capture hydrogen atoms and increase electrically active centers. After nitrogen implantation following electron irradiation, the Eo-0.26eV level almost annealed out at 140 °C and the trap at Eo-0.21eV wasn't observed. We propose that the reduction in the oxygen-related defect growth is due to the prevention of defect migration with nitrogen atoms.

We summarize here experimental results about moving dislocations and dislocations sources, in In-doped GaAs; several selective behaviours between α (As core in the glide set) and β dislocations are noticed. We try to correlate these observations with material structure and composition, and we propose a model of atomic interaction between In and α partial dislocations which could explain most of experimental observations. Some ideas about In diffusion are also developed.

The impurity effects on the creation of vacancies in GaAs and in ZnSe were investigated by monoenergetic positron beam measurements. In the case of the Si-doped MBE grown GaAs, the doping of Si atoms was found to enhance the creation of Ga site vacancies. The concentration of Ga vacancies was found to be proportional to the doped Si concentration. The observed linear relation between both concentrations supports the theoretical prediction on the creation of Ga vacancies in terms of the change in the Fermi-level position by the Si doping into GaAs and also suggests that Si atoms diffuse in GaAs as a neutral complex of Ga vacancy-Si pair rather than that of Si-Si pair. In the case of the Ga-doped MBE grown ZnSe, Zn vacancies were found to be generated in proportion to the concentration of doped Ga atoms. The observed similarity of the vacancy creation in the Si-doped GaAs and in the Ga-doped ZnSe can be well explained by the consideration of the charge neutrality condition around impurities.

The creation of radiation defects (RD's) and their interaction with shallow impurities in 3–4 MeV electron irradiated n-GaAs have been studied by means of photoluminescence (PL) and Hall effect. The irradiations were carried out at sample temperatures ranging from Ti = 30 to 500°C. It has been found for the first time that for high fluences at room temperature the shallow donor concentration starts to decrease. The behaviour of the carrier concentration (n), mobility (μ)and of the concentrations of the shallow acceptors C (As) and Ge (As) has been studied on irradiation and annealing. It was found that the behaviour of the As vacancy govern the main annealing processes observed.

An EBIC analysis is made of decorated heteroepitaxial misfit dislocations formed at the interface of Si-Si (Ge) epitaxial layers grown in a CVD reactor on Si substrates. The electrical activity of the dislocations is studied after decorating the dislocations with Ni and Au impurities introduced by ion-implantation and backside deposited metallic thin films. The impurities are activated by RTA annealing at 400, 800 and 1000°C. A model is presented for the formation of NiSi2 precipitates on misfit dislocations which suggests that the nucleation and growth of NiSi2 precipitates is a function of the cleanliness of the as-grown dislocations. It is concluded that the distribution of electrical activity of impurity decorated misfit dislocations is a strong function of the impurity type, condition of the as-grown material, and concentration of metallic impurities introduced during the process of decoration.

Deep level majority and minority carrier traps in p+/n and n+/p junction diodes have been investigated. The junctions were fabricated on n- and p- type silicon which was intentionally and uniformly doped with heavy metals Cr, Fe, Ni, and Au during Czochralski crystal growth. The activation energies of the traps in these devices has been determined using a computer based Deep Level Transient Spectroscopy system which stores and analyzes entire capacitance-time transients. The capacitance-time data sets have been analyzed using the standard rate-window method as well as by a new algorithm which is able to test for the existence of a single exponential. The new algorithm has shown that only one of the ten traps measured contained a single exponential. Rate-window analysis of all the data sets, however, yielded energy levels based on the expectation of a single-exponential, despite the inherent non-exponentiality of the transients. Implications on the reliability of results obtained by the rate window method have been discussed. Possible reasons for the observed non-exponentiality in the data have been suggested based on a study of simulated data.

An external stress field, induced at the film edge of a nitride layer, affects the defect generation in the surface-near region. Nucleation and growth of oxide precipitates and/or the generation of dislocations result in the reduction of the width of the denuded zone. The defect formation is discussed in dependence on the stress, gettering technique (annealing conditions), and on the initial oxygen concentration. The effect on electrical parameters is shown. The investigations prove that an additional oxide film (SiO2/Si3N4 films) does not relax completely the tensile stress induced by the nitride layer.

This paper presents several examples of defect analyses carried out in actual VLSI failure analyses and experiments, using TEM technique, process simulation and other advanced analytical tools. New TEM techniques are also described to observe a precise location which has failed.

Electric degradation of silicon wafer due to Cu, Fe, and Ni contamination has been studied using MCZ with low oxygen and CZ wafers. In the cases of Cu and Ni contamination, the electric properties depended on the characteristics of the starting wafers,. especially the type of conductance. The behavior of these metals in the low temperature region played an important role to understand the electric properties. On the contrary, no difference between p- and n-type wafers was observed in Fe contamination in our experiment.

The surface defects were observed with high density in the MCZ wafers in Cu contamination. These defects were sensitive to the degradation of the MOS C-t generation lifetime. Making use of this relation, the efficiency of the extrinsic gettering was evaluated.

A low-temperature, 200–300°C, plasma-assisted oxidation-deposition process sequence has been developed for formation of SiO2/Si heterostructures. Adding a nitride layer to form an ON, or ONO composite dielectric, increases the density of trapping states, Dit, at the SiO2/Si interface, unless the entire structure is subjected to a high-temperature rapid thermal anneal, e.g., 30 s at 900°C. By interrupting the nitride deposition, and using on-line Auger electron spectroscopy, AES, the increase in Dit correlates with a migration of N-atoms to the SiO2/Si interface during the nitride deposition. There is no evidence for N-atom incorporation into the oxide layer itself. In contrast, for remote PECVD deposition of oxides onto nitrides, O-atoms react with the nitride, and form an oxy-nitride alloy interfacial region layer.

CW laser beam mixed Au/Te/Au/n-GaAs contacts have been studied by RBS, Möss-bauer and Raman spectroscopy. For both low and high laser power mixing, resulting in respectively Schottky-type and ohmic contacts, the formation of non-uniformly dispersed Ga2Te3 crystallites was observed. However, for the ohmic contacts the formation of a high density of defect complexes in the GaAs surface layers was revealed. The experimental results suggest that the ohmic conduction mechanism is based on a hopping or a defect assisted tunneling process through the contact zone, consistent with the amorphous/highly defective heterojunction model.

Positron lifetime and Doppler-broadening experiments as well as Fourier-transform infrared spectroscopy (FTIR) were performed on a variety of six-inch Czochralski (CZ) silicon wafers. Measurements were done at 14 equidistant locations across the wafers which were cut from the seed-, middle-, and tail-sections of two boules grown at different pull-speeds.

In the as-grown wafers, the positron response consisted of components from small oxygen-related clusters and “perfect” bulk silicon only. Possible contributions from vacancy-type defects were at or just below the detection limit. After a two-step heat treatment (750°C/ 4 hrs + 1050°C/6 hrs in N2) FTIR showed that significant amounts of oxygen (4–8 ppma) had precipitated in wafers taken from the seed-sections of the boules but not in any of the other wafers. The positron data did not reflect this distinctive difference, however, both lifetime and Doppler-broadening results strongly indicate the creation of vacancy-type defects at concentrations in the 1016cm−3-range.

Positron lifetime results show that vacancies can be retained after growth of Czochralski silicon at concentrations of ∼x1016/cm3. Rapid thermal annealing as well as furnace annealing increase the vacancy concentration. The vacancies are predominantly trapped by oxygen interstitial clusters in lightly B-doped materials, and these complexes appear to have temperature dependent configurations which can be quenched-in by rapid cooling. Heavy Sb doping results in trapping of vacancies by the Sb impuritie

In this study the effect of oxygen agglomeration on minority carrier diffusion length in as-grown p-CZ silicon has been studied in detail. Oxygen-related defects were found acting as minority carrier traps in p-CZ silicon. These defects are not found in either oxygen-free FZ silicon or in n-type CZ silicon samples. The traps have profound effect on low excitation level diffusion length values leading to an apparent lifetime decrease by as much as an order of magnitude. This effect can be eliminated by a steady state “bias light” superimposed on the chopped excitation light. The traps can be annihilated and re-generated by thermal treatments.

Our study has also revealed oxygen-induced recombination centers. Significant improvement in lifetime is realized in p-type CZ silicon after heat treatment between 550°C and 800°C.

We investigated phenomena of oxygen precipitation in silicon single crystals by two kinds of thermal treatment, supposing a CMOS fabrication process. The one consisted of the first annealing at 1123K for 4 hrs and the second annealing at 1423K for 16 hrs. The other one consisted of the annealing at 1273K for 4 hrs and the second annealing at 1423K for 13 hrs. In the results, a single-step preannealing at 723K for 2 hrs was effective for the oxygen precipitation by the former process and nonuniform distribution profiles along crystal growth axis were well improved, however, insufficiently improved against the latter process. We considered a two-step preannealing process consisting of the first annealing at 723K for 2 hrs and the second annealing at 923K for 2 hrs. This new process was effective for the oxygen precipitation by the latter process. Especially, we could obtain uniform distribution profiles of oxygen precipitation along a crystal growth axis.

SI GaAs crystals submitted to single- or multi-step, ingot-or wafer-annealing are investigated using photoluminescence (PL) and photoacoustic spectroscopy (PA). The near-band-edge PL transitions are well resolved, with a neutral acceptor-bound exciton recombination displayed as a split doublet. The improvement induced by wafer-annealing is illustrated by the absence of additional defect-related transitions found after ingot-annealing. For the room temperature PA measurements, the intensity of a peak occuring at 1.39 eV is shown to lead to an estimation of the arsenic micro-defect density as evaluated by AB etching. The 1.39 eV PA band is also asserted to be the non-radiative recombination path of a 1.482 eV band found in the low-temperature PL spectra.

We present highly resolved photoluminescence studies on heat-treated nominally undoped InP, which was either unprotected or protected by SiO2 or Si3N4 caps during the annealing procedures. Annealing of InP above 350°C leads to six different sharp emissions in the wavelength range between 8790 and 8900 Å, which are not observed at 4 K in Zn-doped or Fe-doped samples. Based on temperature-dependent photoluminescence studies, time-resolved measurements and preliminary magnetic field studies we ascribe these emissions to isoelectronic bound exciton transitions. It is also shown that the two emissions at 8883 Å (11254 cm-1) (E) and 8889 Å (11246 cm-1) (F) belong to one center. We observe that the lines not only depend on the heat treatment but also on some unintentionally incorporated or residual impurities of a low concentration level. Possible candidates are discussed.