Czochralski Silicon Crystals Research Articles

Defect behavior during growth of heavily phosphorus doped Czochralski silicon crystals (II): Theoretical study

Defect behavior during growth of heavily phosphorus doped Czochralski silicon crystals (II): Theoretical study

Defect behavior during growth of heavily phosphorus-doped Czochralski silicon crystals. I. Experimental study

Defect behavior during growth of heavily phosphorus-doped Czochralski silicon crystals. I. Experimental study

Influence of Thermal Conductivity and Emissivity of Heat Shield Surface Material on the Thermal Field of Czochralski Silicon Crystal Growth

Influence of Thermal Conductivity and Emissivity of Heat Shield Surface Material on the Thermal Field of Czochralski Silicon Crystal Growth

Effects of Induced Current in Crystals on the Melt Flow and the Melt–Crystal Interface during Industrial 300 mm Czochralski Silicon Crystal Growth under a Transverse Magnetic Field

Due to the high magnetic field intensity during industrial 300 mm silicon crystal growth, typically up to 0.3 T, the crystal’s rotation under this transverse magnetic field (TMF) induces a current that is strong enough to impact both the melt flow and the melt/crystal interface (m/c interface) shape. This paper investigates the influence of TMF-induced current in crystals on the melt flow, temperature distribution, and interface shape through the conduction of three sets of 3D simulations that vary in the electrical conductivity of crystals, TMF intensities, and crystal rotation rates. Combined with experiments, the accuracy of the model has been validated, and a reasonable electrical conductivity of the crystal has been predicted. The study findings reveal a shift in the driving force of forced convection from centrifugal to Lorentz force when the induced current in crystal is augmented. This alteration affects the melt flow and the m/c interface shape. Notably, this study serves as a significant complement to the conventional model, which overlooks the induced current in crystals, enhancing the accuracy and comprehensiveness of the simulation outcomes to provide a robust theoretical underpinning for industrial production.

Deep Learning Models for Data-Driven Laser Induced Breakdown Spectroscopy (LIBS) Analysis of Interstitial Oxygen Impurities in Czochralski-Si Crystals.

Analytical advantages of facile and expeditious spectral data collections from laser-induced breakdown spectroscopy (LIBS) are often offset by the low-accuracy quantitative analyses offered by the technique due to non-equilibrium plasma-matrix interactions. Herein, we developed a one-dimensional (1D) convolutional neural network (CNN) and a least absolute shrinkage and selection operator (LASSO) models for LIBS data analyses to predict trace amounts of interstitial oxygen impurities in commercial Czochralski-silicon (Cz-Si) crystals with known interstitial oxygen concentrations at 0-16 parts per million (ppm). While traditional spectral analyses from O(I) (777.2nm) atomic lines offer poor accuracy, CNN and LASSO analyses generate excellent predictions for the interstitial oxygen concentrations. Specifically, CNN-based spectral analyses uniquely identified systematic alterations in LIBS fingerprints manifested by laser-matter interactions. Our results pave the path for combining facile and voluminous LIBS data collection with deep learning driven high-fidelity data analytics.

Material evaluation for engineering a novel crucible setup for the growth of oxygen free Czochralski silicon crystals

For manufacturing of several high performance electronic devices, e.g. insulated-gate bipolar transistors (IGBT), single crystalline silicon crystals with high purity and minimum oxygen (in the range of 1015 at/cm3) concentration are required. Such silicon crystals are typically grown by the Floating Zone technique (Fz), as the more common and cheaper Czochralski technique (Cz) uses silica crucible, which leads always to a relatively high oxygen concentration in the silicon crystals (>1017 at/cm−3). Therefore, in this work potential materials were evaluated with respect to the development of a novel oxygen-free crucible system, which should enable a cost effective growth of oxygen free Cz silicon ingots. For that purpose different graphite materials as well as nitride bonded silicon nitride (NSN) were tested in contact with liquid silicon due to their infiltration behaviour and occurrence of crack formation. Functional silicon nitride (Si3N4) coatings were applied by powder based spray coating of reaction bonded silicon nitride (RBSN) and chemical vapour deposition (CVD) on graphite and NSN crucibles. Characterization of the crucible/coating systems before and after crystal growth experiments in a lab-scale casting furnace reveal information about morphology, infiltration behaviour and adhesion strength on the crucible. Further, investigations on the grown silicon crystals give information about impurity incorporation coming from the novel crucible systems. The results indicated, that especially graphite materials with low porosity and a high mechanical strength as well as NSN with polysilazane sealing in combination with a CVD Si3N4 coating have definitely a potential for application as crucible system in silicon growth processes.

Investigation on the Transformation of B-Defect in As-Grown Czochralski Silicon Crystal during Annealing Process

When a silicon ingot is grown by the Czochralski method, different defects, such as A-defect (a dislocation loop or dislocation loops cluster), B-defect (widely accepted as an interstitial atoms cluster), COP (crystal originated particle, a void), and grown-in oxygen precipitates will emerge. Nowadays most crystal defects can be characterized directly. However, due to the extremely small size and stress, B-defects can only be indirectly characterized by the formation of oxygen precipitates. What’s more, it is unclear whether B-defects transform into oxygen precipitates directly or B-defects grow and transform into A-defects firstly and further facilitate oxygen precipitation via the dislocation pinning effect. In this work, after implementing an optimized anneal at 900 °C for 3 h and HCl vapor-phase etch at 900 °C for 2 min, nano-scale defects transformed from B-defects are efficiently detected by a surface particle counter. Scanning electron microscope and energy-dispersive X-ray spectroscopy results prove that these nano-scale defects are all oxygen precipitates. This explicit result indicates that B-defects can induce the formation of oxygen precipitates directly rather than relying on the formation of A-defects, which would help to better understand the characteristic of B-defect in relatively low temperature and the transformation process between different defects in silicon ingot.

Evaluation of the Performance of Published Point Defect Parameter Sets in Cone and Body Phase of a 300 mm Czochralski Silicon Crystal

Prediction and adjustment of point defect (vacancies and self-interstitials) distribution in silicon crystals is of utmost importance for microelectronic applications. The simulation of growth processes is widely applied for process development and quite a few different sets of point defect parameters have been proposed. In this paper the transient temperature, thermal stress and point defect distributions are simulated for 300 mm Czochralski growth of the whole crystal including cone and cylindrical growth phases. Simulations with 12 different published point defect parameter sets are compared to the experimentally measured interstitial–vacancy boundary. The results are evaluated for standard and adjusted parameter sets and generally the best agreement in the whole crystal is found for models considering the effect of thermal stress on the equilibrium point defect concentration.

Electrical property of iron-related defects in n-type dislocated Czochralski silicon crystal used for solar cells

Interactions of iron atoms with dislocations in n-type Czochralski silicon have been studied by combining deep level transient spectroscopy (DLTS) and electron beam induced current (EBIC). The EBIC results indicate that dislocations facilitate the aggregation of iron atoms. The DLTS reveals three levels K1 (E c—0.17 eV), K2 (E c—0.35 eV) and K3 (E c—0.48 eV). The amplitudes of K2 and K3 peaks exhibit extended localized states. The origin of levels K2 and K3 is attributed to iron clusters around dislocations, and the existence of iron clusters in the vicinity of dislocations is further proved.

Geometric determination of direction of dislocations using synchrotron X-ray transmission topography.

When performing transmission polychromatic beam topography, the extensions to the line segments of the diffraction images of a straight dislocation are shown to intersect at a single point on the X-ray film. The location of this point, together with the diffraction pattern recorded on the film by synchrotron radiation, gives the crystallographic direction [hkl] of the dislocation unambiguously. The results of two synchrotron topography experiments are presented. Very long dislocations found in the center of a large 450 mm-diameter Czochralski silicon crystal align with the growth direction [001]. In the other silicon sample, the dislocations are of mixed type and along the [011] direction.

Recognition and Imaging of Point Defect Diffusion, Recombination, and Reaction During Growth of Czochralski-Silicon Crystals

The behavior of point defects was visualized in lightly and heavily boron (B)-doped Czochralski-silicon (CZ-Si) crystals by employing a special growth technique, namely, rapidly cooling a growing crystal after it is detached from the Si melt. In the case of crystal growth with a high pulling rate, an anomalous oxygen precipitation (AOP) region dominated by vacancies appeared, whereas in the case of crystal growth with a low pulling rate, a dislocation loop region dominated by self-interstitials appeared. In the crystals cooled rapidly after halting growth for several hours, self-interstitials flowed into the AOP region and dislocation loop regions formed and expanded, while the AOP region shrunk due to diffusion of excess vacancies to the crystal surface and void regions. These transient changes in the point defect distribution were reproduced using a point defect simulator. Defect regions related to self-interstitials could not be confirmed in the heavily B-doped crystals with resistivities of 10 mΩcm or less, where the void- and oxidation-induced stacking fault (OSF)-ring regions disappeared completely at the center of the crystal. These results show that the behaviors of point defects in heavily doped CZ-Si crystals with various impurities are important research subjects in relation to future advanced power applications.

Formation of thermal donor enhanced by oxygen precipitation in silicon crystal

The formation of thermal donors in silicon is investigated using Czochralski silicon crystals grown with different grown-in defect regions, such as voids and nuclei of oxidation-induced stacking faults. It was found that the formation rate of thermal donors during annealing at 450 °C increases with an increase in the density of oxide precipitates in the regions containing different grown-in defects. The thermodynamic model for the formation of thermal donors shows that the electrically inactive oxygen trimers as nuclei of thermal donors in an as-grown crystal increase with an increase in the density of oxide precipitates, suggesting that the formation of the nuclei is enhanced due to silicon self-interstitials emitted by oxygen precipitations during the crystal growth.

Numerical simulation and global heat transfer computations of thermoelastic stress in Cz silicon crystal

AbstractGlobal heat transfer computations were performed for the investigation of thermal stress in a Czochralski silicon crystal. The temperature distribution, thermal stress properties including maximum shear stress and von Mises stress distributions at two different axial crystal positions have been investigated with the help of heat transfer simulations. By analyzing the obtained results, the thermal stress maxima during the Czochralski growth process can be controlled by applying optimal crystal rotation of 8 rpm and counter crucible rotations of 5 and 15 rpm for a crystal position of 100 mm and 300 mm. This shows that by applying optimal crystal and counter crucible rotations throughout the growth process, the thermal stress maxima of a growing crystal can be reduced.

Boron–Oxygen Complex Responsible for Light‐Induced Degradation in Silicon Photovoltaic Cells: A New Insight into the Problem

Results available in the literature on minority carrier trapping and light‐induced degradation (LID) effects in silicon materials containing boron and oxygen atoms are briefly reviewed. Special attention is paid to the phenomena associated with “deep” electron traps (J. A. Hornbeck and J. R. Haynes, Phys. Rev. 1955, 97, 311) and the recently reported results that have linked LID with the transformation of a defect consisting of a substitutional boron atom and an oxygen dimer (BsO2) from a configuration with a deep donor state into a recombination active configuration associated with a shallow acceptor state (M. Vaqueiro‐Contreras et al., J. Appl. Phys. 2019, 125, 185704). It is shown that the BsO2 complex is a defect with negative‐U properties, and it is responsible for minority carrier trapping and persistent photoconductivity in nondegraded Si:B+O samples and solar cells. It is argued that the “deep” electron traps observed by Hornbeck and Haynes are the precursors of the “slow” forming shallow acceptor defects, which are responsible for the dominant LID in boron‐doped Czochralski silicon (Cz‐Si) crystals. Both the deep and shallow defects are BsO2 complexes, transformations between charge states and atomic configurations of which account for the observed electron trapping and LID phenomena.

Materials Research for Group IV Semiconductors: Growth, Characterization and Technological Developments

Group IV semiconductors lie at the heart of many electronic and photovoltaic devices. Issues associated with bulk silicon continue to be important, but substantial fundamental challenges also exist for other group IV bulk materials and associated alloys, nanostructures, nanocomposites, thin/thick films, and heterostructures. Advances in device performance are underpinned by new defect engineering procedures, development of novel growth techniques, and improvements in advanced diagnostic tools. Point and extended defects remain at the centre of interest, as do surfaces, and in some cases their engineering represents an option for new functionalities. This special issue contains 16 technical articles arising from selected presentations at Symposium I of the European Materials Research Society Spring Meeting held in Strasbourg, France from 18th to 22nd June 2018. This symposium was the third in the “Materials Research for Group IV Semiconductors” series. The symposium attracted 113 presenting authors from 22 countries, and 120 presentations were scheduled over five days (21 invited talks, 35 contributed talks, and 64 posters). Graduate Student Awards were presented to Audrey Morisset (Université Grenoble Alpes − INES, France) whose paper is published in this special issue, and Michael Seifner (TU Wien, Austria). In this special issue there are two feature articles from invited speakers in the silicon field. One by Hourai et al. reviews, from an industrial perspective, the development of point defect-controlled Czochralski silicon crystals and their use in power devices. The second by Kolevatov et al., focusses on the interaction between hydrogen and vacancy-related defects in silicon. The other papers cover a range of topics including the fundamentals of heat flow and transfer in semiconductors, the fundamental properties of point-like defects, surface passivation, potential new manufacturing methods, and a variety of novel heterostructures. Thanks are due to the symposium co-organisers (Chioko Kaneta, Gudrun Kissinger, Leo Miglio and Deren Yang), the members of our Scientific Committee, and the paper reviewers. We were particularly saddened to learn that Prof. Bengt Svensson, a Scientific Committee member and committed supporter of the symposium series over many years, died shortly after the symposium. An obituary to Bengt written by his colleagues and friends also appears in this special issue. John D. Murphy Guest Editor and Principal Symposium Organizer

Ground state of ultrashallow thermal donors in silicon

We have found ultrashallow thermal donors (USTDs) in carbon- and hydrogen-doped Czochralski silicon (CZ-Si) crystals, in which the electronic structure obeys the effective-mass theory. To the best of our knowledge, these are the shallowest energy levels among those of the currently reported donors in Si crystals. In addition, the ground state (1s state) of USTDs was found to be split into at least two. In this study, we measured the temperature dependence of the transmittance induced by the transition from the ground state or upper ground state to the 2p+− and 2p0 states of USTD-1 and USTD-3. It was found that the energy levels of the upper ground state of USTD-3 are shallower than those of USTD-1 despite the fact that the ground state of USTD-1 is shallower than that of USTD-3. That is, the energy levels of the upper ground state of USTD-1 and USTD-3 are inverted against those of the ground state. In addition, we compared the electron spin resonance of 13C (nuclear spin I = 1/2)- and deuterium (I = 1)-doped Si with that of 12C (I = 0)- and hydrogen (I = 1/2)-doped Si. However, no clear difference was found between the electron spin resonance spectra of the two. On the basis of these results, we briefly discuss the atomic structure of the USTDs.

Optical Properties and the Mechanism of the Formation of V2O2 and V3O2 Vacancy–Oxygen Complexes in Irradiated Silicon Crystals

The processes of the formation and annealing of VnOm (n, m ≥ 2) vacancy–oxygen complexes in Czochralski silicon crystals irradiated with fast electrons and reactor neutrons have been studied by infrared absorption Fourier spectroscopy. A number of arguments are presented in favor of identification of absorption bands at 829.3 and 844.2 cm–1 as being related to local vibrational modes of V2O2 and V3O2 complexes, respectively.

Relationship between carbon concentration and carrier lifetime in CZ-Si crystals

This paper aims to clarify the effect of carbon concentration on carrier lifetime in as-grown n-type and non-doped silicon crystals produced via the Czochralski (CZ) method. We grew n-type and non-doped silicon single crystals with 3-in. diameters along with different carbon and phosphorous contents. The resistivity, concentrations of oxygen and carbon, and lifetime were measured using four-point measurements, Fourier-transform infrared spectroscopy, and the eddy current method, respectively. The oxygen concentrations of the crystals were 6–8 × 1017 atoms/cm3, and the bulk lifetimes ranged from 10 to 20 ms. The carrier lifetime of CZ silicon crystals depended on dopant concentration but had no significant dependence on carbon concentration.

Оптические свойства и механизм образования вакансионно-кислородных комплексов V-=SUB=-2-=/SUB=-O-=SUB=-2-=/SUB=- и V-=SUB=-3-=/SUB=-O-=SUB=-2-=/SUB=- в облученных кристаллах кремния

AbstractThe processes of the formation and annealing of V_ n O_ m ( n , m ≥ 2) vacancy–oxygen complexes in Czochralski silicon crystals irradiated with fast electrons and reactor neutrons have been studied by infrared absorption Fourier spectroscopy. A number of arguments are presented in favor of identification of absorption bands at 829.3 and 844.2 cm^–1 as being related to local vibrational modes of V_2O_2 and V_3O_2 complexes, respectively.

Ground-state splitting of ultrashallow thermal donors with negative central-cell corrections in silicon

Ultrashallow thermal donors (USTDs), which consist of light element impurities such as carbon, hydrogen, and oxygen, have been found in Czochralski silicon (CZ Si) crystals. To the best of our knowledge, these are the shallowest hydrogen-like donors with negative central-cell corrections in Si. We observed the ground-state splitting of USTDs by far-infrared optical absorption at different temperatures. The upper ground-state levels are approximately 4 meV higher than the ground-state levels. This energy level splitting is also consistent with that obtained by thermal excitation from the ground state to the upper ground state. This is direct evidence that the wave function of the USTD ground state is made up of a linear combination of conduction band minimums.