Oxygen Atoms In Silicon Research Articles

Relative concentrations of carbon related defects in silicon

Irradiation induced defects in silicon are technologically important as they impact the electronic properties. Calculations based on density functional theory employing hybrid functionals have been previously used to investigate the structures and relative energies of defect clusters formed between vacancies, self-interstitials, carbon and oxygen atoms in silicon. In this study we employ a model to calculate the relative concentrations of carbon related defects in silicon. It is calculated that the carbon content has a significant impact upon the concentration of carbon-related defects. The CiCs defect is the most populous for all the conditions considered followed by the CiOiSiI and the CiOi defects. CiOiSiI and the CiOi become increasingly important for silicon with high carbon concentrations.

Formation mechanism of grown-in defects in silicon

Problems resulting from the trend toward small-scale and highly integrated circuits used in semiconductor devices are caused by grown-in defects in the silicon crystal. Although a great many researchers have investigated the nature of these defects, their systematical formation mechanism is not clarified. Findings reveal that the intrinsic point defects and oxygen are closely related to the formation mechanism. Assuming the complex is composed of vacancies and oxygen atoms between relatively high temperatures in silicon, the formation mechanism of grown-in defects is examined, and also a system of three equations for diffusions of vacancies, self-interstitials and oxygen atoms is presented in detail, using the complex as a sink and source of vacancies and oxygen atoms in silicon.

Electronic Properties and Structure of a Complex Incorporating a Self-Interstitial and two Oxygen Atoms in Silicon

The electronic properties and structure of a complex incorporating a self-interstitial (I) and two oxygen atoms are presented by a combination of deep level transient spectroscopy (DLTS), infrared absorption spectroscopy and ab-initio modeling studies. It is argued that the IO2 complex in Si can exist in four charge states (IO− 2 , IO02 , IO+ 2 , and IO++ 2 ). The first and the second donor levels of the IO2 complex show an inverted location order in the gap, leading to a E(0/ + +) occupancy level at Ev + 0.255 eV. Activation energies for hole emission, transformation barriers between different structures, and positions of LVM lines for different configurations and charge states have been determined. These observables were calculated by density-functional calculations, which show that they are accounted for if we consider at least two charge-dependent defect structures.

A study of oxygen dislocation interactions in CZ-Si

The interaction between dislocations and oxygen atoms in silicon has been studied. The effect of immobilization of dislocations by the segregation of oxygen to the dislocation core (dislocation locking) has been investigated for different oxygen concentrations and annealing conditions. It has been revealed that oxygen locking of dislocations shows three different regimes of behaviour. A numerical model for the dislocation locking process of oxygen atoms has been presented and used to interpret the experimental results.

Interaction of hydrogen (deuterium) molecules with interstitial oxygen atoms in silicon

Formation kinetics of oxygen–hydrogen (deuterium) complexes which give rise to an infrared absorption line at 1075.1 (1076.4) cm −1 have been studied with a method of isothermal annealing in the temperature range of 30–150°C in Czochralski-grown Si crystals with different oxygen content. It was inferred that the capture of mobile hydrogen molecules (H 2) by interstitial oxygen atoms accounts for the considered formation kinetics. The values of diffusivity of hydrogen (deuterium) molecules and binding energy of O i–H 2 (D 2) complex were estimated from the analysis of the results obtained.

Formation of Grown-in Defects during Czochralski Silicon Crystal Growth

The formation behavior of grown-in defects in Czochralski silicon (CZ-Si) crystals was investigated using two crystals that were quenched during growth but in one case after crystal growth had been halted for 5 h. The distributions of grown-in defect density and size, and their micro-structures were analyzed as a function of temperature during crystal growth just before quenching by means of an optical precipitate profiler (OPP) and an atomic force microscope (AFM) coupled with a laser particle counter. The formation of grown-in defects, which are considered to be octahedral voids, was found to consist of two dominant processes. The first step involves rapid void growth in a narrow temperature range of about 30° C below 1100° C and the subsequent step consists of an oxide film growth on the inner surface of the void during the cooling process to about 900° C after void formation. It was also found that the growth of the oxide film in the voids is rate-limited by the diffusion rate of oxygen atoms in silicon. In addition, it is strongly suggested that void formation in such a narrow temperature range is due to a rapid agglomeration of vacancies.

Stoichiometric disturbances in multi-atomic multilayered structures due to ion implantation through mask openings

In this paper, a Monte Carlo computer code based on the linear cascade theory has been used to calculate Stoichiometric disturbances in multi-atomic multilayered structures. The two-dimensional excess interstitials distribution and the two-dimensional oxygen-recoil-atoms distribution in silicon substrate resulting from a 50 keV Ge + ion implantation through a thick window mask and an oxide mask window presenting tapered edge are presented. We calculate through computer simulation, the redistribution of target atoms in the vicinity of the mask edges that will influence the production of end-of-range defects in an annealing step. Recoil implantation of oxygen atoms in silicon over tens of angstroms during ion implantation through an oxide mask window is also evidenced.

Study of Oxygen Diffusion and Clustering in Silicon Using an Empirical Interatomic Potential

AbstractThe diffusion path and diffusivity of oxygen in crystalline silicon are computed using an empirical interatomic potential which was recently developed [1] for modelling the interactions between oxygen and silicon atoms. The diffusion path is determined by constrained energy minimization, and the diffusivity is computed using jump rate theory. The calculated diffusivity D=0.025 exp(-2.43eV/kBT) cm2/sec is in excellent agreement with experimental data. The same interatomic potential also is used to study the formation of small clusters of oxygen atoms in silicon. The structures of these clusters are found by NPT molecular dynamics simulations, and their free energies are calculated by thermodynamic integration. These free energies are used to predict the temperature dependence of the equilibrium partitioning of oxygen atoms into clusters of different sizes. The calculations show that, for given total oxygen concentration, most oxygen atoms are in clusters at temperature below 1300K, and that the average cluster size increases with decreasing temperature. These results are in qualitative agreement with the effects of thermal annealing on oxygen precipitation in silicon crystals.

Clustering of oxygen atoms in silicon at 450 degrees C: A new approach to thermal donor formation.

Clustering of oxygen atoms in silicon at 450 \ifmmode^\circ\else\textdegree\fi{}C has been correlated with a group of infrared vibrational absorption bands observable at room temperature. The bands are related to the formation of thermal donors and show a good correlation with results from different experimental techniques. It is suggested that three categories of thermal donors are developing corresponding to absorption bands at about 975, 988, 1000, 1006, and 1012 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$.

Monoenergetic Positron Beam Studies of Oxygen in Single Crystal Silicon - Stress Induced Clustering of Oxygen Atoms in Silicon

ABSTRACTA monoenergetic positron beam has been used to investigate the state of interstitial oxygen in Czochralski (CZ)-grown Si with either thermally grown S1O2 (100 nm thick) or silicon oxide (p-SiOx) deposited by plasma enhanced chemical vaper deposition technique on the surface. Both the growth of thermal SiO2 and the deposition of SiOx film resulted in a reduction of the doppler-broadening line shape parameter (S-parameter) for the positron annihilation in the bulk silicon region. Annealing at 450δC, the removal of oxide overlayer or long-term aging at room temperature caused the S-parameter to return to its intrinsic value. It was thought that tensile stress in silicon, induced by the thermal oxidation or the deposition of SiOx films which had compressive internal stress themselves, enhanced the rearrangement of oxygen atoms and caused the formation of oxygen clusters in silicon crystal. Oxygen interstitial clusters can trap positrons leading to the lower S-parameter value for annihilation in the bulk silicon region, because of large overlap with core electrons. The above results suggest that oxygen atoms can absorb lattice strain by clustering and thus prevent the generation of dislocations against external stress in the Si lattice. This results yield an additional explanation of the high mechanical strength of CZ Si crystal.

The Enchanting Properties of Oxygen Atoms in Silicon

In this paper we will present several new theoretical results on the properties of oxygen atoms in bulk crystalline silicon. Specifically, these properties will include (1) oxygen migration - where we will suggest that the conventional adiabatic-barrier model for oxygen migration may not be valid for this system; (2) oxygen catalysis - where we will demonstrate that certain oxygen configurations can act as “catalysts” to reactions that form silicon broken bond defects; and (3) oxygen aggregation - where we will introduce a new mechanism for the initial stages of aggregation and oxidation within the bulk of crystalline silicon.

Involvement of oxygen-vacancy defects in enhancing oxygen diffusion in silicon

We have proposed previously that the extremely high rate of single diffusion jumps of oxygen atoms in silicon during electron irradiation of crystals above 300 °C is due to the sequential trapping and detrapping of vacancies. In support of this proposal we now demonstrate thermal dissociation of up to 75% of oxygen-vacancy centers by monitoring their destruction in irradiated and annealed crystals. An important new step is the calibration of the strength of the infrared 830 cm−1 absorption band via a novel procedure to give the concentration of oxygen-vacancy complexes in crystals.

Electronic structure of the Si:O4 complex as related to the thermal donors in silicon

Rigorous self-consistent electronic structure calculations were carried out for complexes containing four interstitial oxygen atoms in silicon. The isolated tetrahedral site interstitial oxygen impurity was also investigated and the results were correlated to the complexes formation. Our calculations indicate that four oxygen impurities in Td symmetry surrounding a silicon atom at the regular lattice site are deep acceptor centers. It is also found that distortions which drive the complex to one of the observed symmetries, D2d, remove the impurity levels from the gap. Therefore, we conclude that these complexes do not show thermal donor actions in silicon as has been suggested.

Structure and Properties of The Oxygen Donor

ABSTRACTDuring aggregation, an assembly of oxygen atoms in silicon produces an electrically active site. The center is an effective mass, helium-like center (double donor) with a wave function of C2v symmetry. The formation reactions of the assembly reveal details of the invisible early stages of aggregation. The donor character of the center controls the aggregation process in heavily doped material. The atomic structure and the source of the electrical activity of the center remain unresolved.

Interaction of dislocations with impurities in silicon crystals studied byin situX-ray topography

Abstract The characteristics of dislocation locking due to the development of an impurity atmosphere have been investigated by the in situ X-ray topographic technique for silicon crystals doped with various types of impurities. Oxygen, nitrogen and phosphorus atoms are found to be effective in locking dislocations while carbon atoms are not. The dependence of the locking behaviour on the impurity concentration is investigated in detail for oxygen-doped crystals. It is known that the magnitude of the locking force is determined uniquely by the number of impurity atoms congregated on a unit length of dislocations if the species and concentration of the impurity atoms in the crystal are specified. Individual nitrogen atoms exhibit the strongest locking effect among the impurity atoms investigated. However, locking proceeds most pronouncedly in oxygen-doped crystals owing to a high diffusion rate and a higher solubility of oxygen atoms in silicon. The origins of the strong locking effects of various impurity ...

Interaction of dislocations with impurities in silicon crystals studied byin situX-ray topography

Abstract The characteristics of dislocation locking due to the development of an impurity atmosphere have been investigated by the in situ X-ray topographic technique for silicon crystals doped with various types of impurities. Oxygen, nitrogen and phosphorus atoms are found to be effective in locking dislocations while carbon atoms are not. The dependence of the locking behaviour on the impurity concentration is investigated in detail for oxygen-doped crystals. It is known that the magnitude of the locking force is determined uniquely by the number of impurity atoms congregated on a unit length of dislocations if the species and concentration of the impurity atoms in the crystal are specified. Individual nitrogen atoms exhibit the strongest locking effect among the impurity atoms investigated. However, locking proceeds most pronouncedly in oxygen-doped crystals owing to a high diffusion rate and a higher solubility of oxygen atoms in silicon. The origins of the strong locking effects of various impurity ...

Dislocation pinning effect of oxygen atoms in silicon

A definitive proof has now been obtained of the existence of a dislocation pinning effect by oxygen atoms in silicon. Ambiguities caused by uncertain material variables in different crystals or different parts of a crystal are avoided in this investigation by making oxygen out-diffusion from a wafer, creating a continuous variation of oxygen concentration in a ∼60-μm-deep surface layer. Dislocation movement at different depths of this layer was studied using indentation dislocation rosettes (IDR) on a 2° beveled surface. The method of IDR is uniquely suitable for this study because microdislocation half-loops are generated and confined to move within each ∼10-μm-deep layer in a series of precisely determined microregions down the bevel. The size of IDR increases steadily toward the sample surface, in good correlation with the steady decrease of oxygen concentration toward the same sample surface. The effect at the maximum oxygen concentration in this case increases the critical resolved shear stress in silicon by a factor of 4. This is a most beneficial effect in reducing thermal slip in the practical matter of silicon wafer processing.

Die Bestimmung des Sauerstoffgehaltes in Silizium nach Ionenimplantation durch eine SiO2-Deckschicht mit Hilfe der Reaktion18O(p, α)15N

The recoil implantation yield of oxygen atoms recoiled from18O-enriched SiO2 layers into silicon substrates has been studied using the18O(p, α)15N nuclear reaction. The method to determine the number of oxygen atoms in silicon is described in detail and the results are compared to the theoretical predictions.