Microdefects in striated (swirl defects) and nonstriated distribution (D-defects) have been observed in float-zoned crystals doped with various impurities by x-ray topography following copper decoration. A new type of defects were found to be present in swirl-free and D-defect-free regions and to become invisible by doping gallium. This gallium effect led to the conclusion that they are microprecipitates produced from residual oxygen impurity in FZ crystals. Effects of various impurities on defect formation indicate that D-defects are of vacancy agglomerates. It was observed that swirl defects are formed when the temperature gradient near the interface is high, and that their formation is suppressed by doping nitrogen. Formation processes of microprecipitates, swirls, and D-defects are discussed on the basis of observation of their mutual interaction and the impurity effects.

The properties of transition metals in silicon are reviewed, emphasizing those observations which allow conclusions to be drawn with respect to microscopic defect models. 3d metals diffuse interstitially into silicon and stay predominantly in these sites at high temperatures. 3d elements lighter than Co can be quenched into these interstitial sites, giving rise to well-established energy levels. First theoretic calculations for these ions yield promising results. Co, Ni and Cu vanish out of the interstitial solution during quenching; an appreciable fraction of Cu may form pairs. The understanding of 4d and 5d metals in silicon is much less advanced at present, even for the technologically important elements Au and Pt. Some observations indicate that for Au and Pt pair formation might as well be important.

The paper highlights recent progress in understanding the role of vacancies and self-interstitials in self- and impurity diffusion in silicon above about 700°C. How surface oxidation of silicon leads to a perturbation of the pointdefect population is described. An analysis of the resulting oxidationenhanced or -retarded diffusion of group III and group V dopants shows that under thermal equilibrium as well as under oxidation conditions both vacancies and self-interstitials are present. For sufficiently long times vacancies and self-interstitials attain dynamical equilibrium which involves their recombination and spontaneous thermal creation in the bulk of silicon crystals. The existence and the nature of a recombination barrier slowing down the recombination process are discussed in this context. Recent experimental and theoretical results on the diffusion of gold in silicon enable us to determine the selfinterstitial component of silicon self-diffusion and to obtain an estimate of the respective vacancy contribution. The two components turn out to be of the same order of magnitude from 700°C up to the melting point.

Research in the area of dopant diffusion in Si has focused on identifying the specific mechanisms and point defects involved. Recent approaches include observing the effects of diffusion and doping on oxygen precipitation, stacking fault growth or shrinkage, enhanced/retarded diffusion of one dopant in the presence of another. Very few of these studies have yielded unambiguous interpretations as a result of the indirect nature of the experiments. However, taken together we can infer the relative importance of vacancies versus Si selfinterstitials in the diffusion of each dopant species.

In this paper we argue that amorphous silicon can be treated as a relaxed continuous random network. The optical and electronic properties are controlled by localized gap states which arise from characteristic features of a disordered tetrahedrally-bonded covalent network. Experimental results are reviewed which indicate that the dominant (perhaps only) electrically-active defect in hydrogenated amorphous silicon is the topologically distinct, silicon dangling bond. Finally, we suggest that the same, disorder-related characteristics might also typify the electronic properties of some macroscopic crystalline silicon defects.

High temperature (1200°C) HCI oxidation treatment has been employed to float-zone (FZ) silicon wafers (625μm thick) containing swirl defects in order to study their diffusion characteristics. In treated wafers, swirl defects can be eliminated from both surfaces up to a depth of ∼30μm. In the bulk of the wafers, however, large swirl defects (A-swirls) rearrange themselves into many small defects. The untreated portions of wafers contain large swirl defects (A-swirls) that extend up to both surfaces. Since swirl defects are primarily clusters of silicon self-interstitials, their rearrangement in the bulk and elimination from the surfaces demonstrate that migration of interstitials takes place on a large scale and is not confined to SiO2/ silicon interface only. The above observations appear to provide direct evidence for the dominant role of self interstitials for diffusion mechanism in silicon at high temperature and can be rationalized in terms of an interstitialcy mechanism. Alternatively, however, dominance of interstitials can be related to a higher migration energy of vacancies proposed in a model where both species coexist at high temperature. The preference of one model over another must await theoretical calculations of diffusion energetics derived from both models.

Deep Level Transient Spectroscopy is used to examine the stability of defect configurations in Si and InP. A systematic approach has been developed to study alternate structures of metastable defects through their representative electronic states. Regulation of defect charge state prior to analysis reveals dramatic transformations in the resulting spectra. These defect states are metastable and can be controlled with thermal or electronic energy. Model studies in electron irradiated InP and Si are presented. The barriers to configurational change are determined from the reaction kinetics. The roles of electric field, minority carrier injection and charge state are explored through junction bias techniques. It is believed that the observed behaviors represent a new class of defect reactions. The systematics of detecting and studying these reactions are presented. Model defect structures are discussed.

An experimental study of high concentration (1019 –1021 /cm3 shallow diffusion was undertaken using TEM to investigate the nature of these diffusion-related defects. Phosphorous from a wide variety of sources (PBr3, POCl3, etc.) other than ion implantation was used in temperature range from 950°– 1100°C and for times of 15 minutes to 1 hour. Care was taken in surface preparation and material selection to avoid extraneous defects from sources other than the diffusions.

A high concentration of small dislocation loops (1012/ cm2) was present in the top few microns of the wafers. Diffraction contrast on the loops revealed that they are of edge character with Burger's vector b = ½<110>. Identification of the nature of these loops by tilting method [(g·b)·s] and anomalous dark-faced black-white lobes show they are of the interstitial type, i.e. the observed defects place the surrounding matrix in a compressive state.

Our knowledge of phenomena connected to the early stages of oxygen clusters, especially their electrical activity is reviewed. In addition to the well-known 450°C thermal donors, 'new oxygen donors', which occur in ca. 650°C annealing, have emerged in conjunction with low temperature processing for VLSI and are discussed. The existing models of thermal donors are reviewed. In a new model of thermal donor formation, thermal donors are viewed as metastable oxygen clusters which lower the compressive strain of the surrounding silicon matrix via bonding of 2p oxygen lone pair orbitals. It is shown how this bonding can result in shallow double donor states.

This paper describes recent progress on nucleation and growth of oxide precipitates and stacking faults in Czochralski silicon. Conclusions on the growth kinetics of oxide precipitates are drawn from the experiments and analysis of growth kinetics of two-dimensional precipitates: The experimentally obtained growth kinetics, three-quarter power law is theoretically derived and the precipitate growth is demonstrated to be diffusion-limited by oxygen interstitials. The formation mechanism of stacking faults is the Bardeen-Herring mechanism. Based on diffusional growth model, the growth kinetics of stacking faults are analyzed, assuming a coexistence of self-interstitial supersaturation and vacancy undersaturation. It is found that the growth is driven by vacancies in undersaturation. Vacancy component of self-diffusion has been determined and found to be predominant at low temperature. The possibility of growth model proposed for increase of oxide precipitate density during annealing has been excluded. Both processes, homogeneous and heterogeneous nucleation, have been taking place during annealing.

An experiment was performed to study the oxidation-enhanced and -retarded diffusion (OED and ORD) of Sb in silicon wafers oxidized in dry O2 at 1160°C. The ORD data of (100) wafers agree well with the prediction of a model assuming that Si self-interstitials (I) and vacancies (V) coexist in thermal equilibrium at high temperatures. An adjustment of the I supersaturation values is needed to bring the ORD/OED data of (111) wafers to fit with the model satisfactorily. This indicates the existence of a mechanism which injects V into (111) wafers in addition to the normal mechanism of I injection due to SiO2 growth.

Oxygen precipitation in Czochralski silicon has been studied as a function of anneal time, oxygen concentration and carbon concentration using FTIR. It was found that the oxygen supersaturation controls the precipitation kinetics in high oxygen content samples, whereas the carbon concentration is of prime importance in low oxygen content samples. The decrease in sustitutional carbon concentration after nucleation and its subsequent increase with extended growth anneals supports the view that carbon affects precipitate nucleation, but not precipitate growth. The measured oxygen solubility at 1000°C was found to depend on both the initial oxygen concentration and the initial carbon concentration.

We suggest that thermal donor formation in silicon involves fast-diffusing, gas-like molecular oxygen in dynamical equilibrium with atomic oxygen in interstitial position. We will discuss still remaining difficulties in understanding thermal donor formation in the light of recent experimental observations by Stavola, Patel, Kimerling and Treeland, indicating that the diffusivity of interstitial oxygen apparently depends on the thermal history of the silicon sample.

Low-energy ion bombardment has been used to enhance diffusion of phosphorus and antimony atoms in silicon. Oxygen free silicon crystals both containing phosphorus and antimony doped surface layers and original crystals were bombarded at 400–700°C with 400 eV oxygen or argon ions. Impurity and electrical carrier profiles were measured to analyse the role of oxygen in the radiationenhanced diffusion. The results obtained are explained on assuming complexes such as vacancyoxygen and vacancy-substitutional impurity to be involved in the process.

Cz silicon samples heated to 450 ° C or higher temperatures for several hours exhibit many sharp photoluminescence lines well below the band edge. We study the production of the lines in terms of carbon and oxygen doping and of the heating temperature and duration. First results as to a level scheme of the P (0.7672 eV) line are reported.

Thermal donors generated in CZ-silicon by annealing at 450° C are investigated by infrared absorption spectroscopy.Up to nine double-donors can be distinguished due to their line spectra characteristic for effective-mass-like donors.Their number and their concentrations depend on the duration of the thermal treatment. The formation of the different donors is ruled by complicated kinetics.

Quantitative microprofiles of the interstitial oxygen concentration and of the excess carrier lifetime, with a spacial resolution of about 20 μm, were obtained in as-grown dislocationfree CZ-Si crystals employing a double laser absorption technique. It was found that maxima (minima) in oxygen concentration along the crystal growth direction coincide with minima (maxima) of the lifetime. It was further found that the relation between changes in oxygen concentration and in lifetime varies in the radial direction indicating that “as-grown” oxygen precipitates are involved in lifetime limiting processes.

In this paper we report preliminary observations of oxygen precipitation in degenerately-doped silicon using etching, optical microscopy and transmission electron microscopy. It was found that n+ material was resistant to precipitation, but p+ material precipitated readily. A multistep heat treatment starting with a low temperature step to achieve a high supersaturation ratio was sucessfully used to induce precipitation in n+ material.

The effects of oxygen precipitation on the minority carrier recombination lifetime (TR) and the carrier generation lifetime (TG) have been characterized for a ‘typical’ silicon crystal grown with the Czochralski method. Infrared (IR) absorption measurements were obtained on polished wafers, before and after 2 step thermal anneals at 800°C and 1050°C to characterize the axial distribution of interstitial and precipitated oxygen in the ingot. Computerized measurements on NMOS diode and capacitor arrays were used to characterize the axial and radial distributions of carrier lifetime. The results indicate that oxygen precipitation is the dominant mechanism contributing to the degradation of both minority carrier recombination andgeneration lifetime.