CZ-Si Crystal Growth Research Articles

Effects of crystal rotation rate on the melt–crystal interface of a CZ-Si crystal growth in a transverse magnetic field

A series of computations were carried out to study the effect of crystal rotation rate on the melt–crystal interface shape and temperature gradient at the interface during CZ-Si crystal growth in a transverse magnetic field (TMCZ). A three-dimensional (3D) global model was used in this study. It was found that the interface deflection changes from non-uniformity in the azimuthal direction to an axisymmetric distribution with increasing crystal rotation rate. The mechanism of this effect is mainly attributed to the spatial fluctuations of local growth rate, which is derived as a function of crystal rotation rate and non-uniformity of interface deflection in the azimuthal direction. It contributes to the formation of the shape of the melt–crystal interface through the heat release of solidification at the melt–crystal interface. Even though the melt–crystal interface shape is nearly axisymmetric at a high crystal rotation rate, local growth rate fluctuations are still noticeable and play an important role in the characteristics of heat transfer and impurity segregation at the melt–crystal interface.

Dislocation-free CZ-Si crystal growth without the thin Dash-neck

It is found that dislocation-free Si crystal growth is possible without a thin neck. Dislocation behaviour in a heavily B-doped CZ-Si crystal has been analysed, and it is found that three kinds of dislocations generated due to thermal shock, lattice misfit and incomplete seeding must be suppressed to grow dislocation-free crystal without the thin Dash-neck. Heavily B-doped or Ge-doped Si seeds are useful in suppressing dislocation generation due to thermal shock, and heavily B- and Ge-codoped Si seeds not only suppress dislocation generation due to thermal shock most effectively but can also suppress that due to lattice misfit. A relative higher melt temperature at the start of pulling is suggested for suppressing the dislocation generation due to incomplete seeding. Dislocations were observed in crystals grown from an annealed heavily B-doped Si seed, and they were probably induced by the dislocation loops in the annealed seed.

Global analysis of effects of magnetic field configuration on melt–crystal interface shape and melt flow in CZ-Si crystal growth

In order to clarify the effects of configuration of magnetic field on the melt–crystal interface shape and the melt convection in a crucible, a set of numerical computations was conducted for a Czochralski furnace for silicon crystals of small diameter by global modeling. Under different combinations of crucible/crystal rotation rates, numerical comparisons were carried out for four configurations of magnetic field: a transverse magnetic field, a vertical magnetic field and two types of cusp-shaped magnetic fields. The computations revealed that each magnetic-field configuration has its own feature in affecting the melt convection and the melt–crystal interface shape when combining with variation in crystal/crucible rotation rates.

Prediction of solid–liquid interface shape during CZ Si crystal growth using experimental and global simulation

In the Czochralski process, the prediction of characteristics of point defects in growing crystal strongly depends on the geometry of the solid–liquid interface. As the shape of the solid–liquid interface is not known a priori, melt convection and other forms of global simulation are used to determine the interface geometry. Conventional 2D models cannot realize interface shapes precisely, and unsteady 3D models require high large expenditure of both time and money for computer simulation and calculation. To surmount this problem, we found a new parameter ( G ave) that could be used to determine the interface height by means of a simple procedure. By deriving G ave from the average axial temperature gradients in the crystals, we can characterize the thermal ambiance surrounding the crystal by hot zone geometry or the process condition. Interface heights h and G ave are formularized as h= a( V/ G ave)+ b. Fitting parameters a and b were obtained statistically by a number of sets of actual interface heights and calculated temperature distributions with various hot-zone types and process conditions. Pairs of fitting parameters were classified according to the crystal diameter and magnetic field strength.

Prediction of the growth interface shape in industrial 300 mm CZ Si crystal growth

A model approach for a modification of the effective heat conductivity in the turbulent melt flow simulation for 28″ Si CZ crucibles is presented, which helped to overcome deficiencies in the growth interface shape prediction for industrial 300 mm Si CZ growth. The model has been incorporated into a CZ simulation tool based on the simulation software codes FEMAG for the global heat transfer and CFD-ACE for the turbulent melt flow simulation. The model predictions are compared to results from 300 mm Si CZ growth experiments with 200 kg charge weight in 28″ crucibles in a growth parameter range covered by standard industrial processes. The model is an engineering approach. Nevertheless, some physical background is briefly discussed on a phenomenological basis, including results of recent model experiments.

Reactions at the liquid silicon/silica glass interface

Experiments have been carried out to determine the nature and origin of the spots growing on silica glass surfaces in contact with liquid silicon during CZ–Si crystal growth. Silica glass ampoules were filled with silicon and tempered between 5 min and 40 h at a temperature (1693 K) slightly above the melting point of silicon. Cross sections of the ampoules with solidified silicon have been examined by scanning electron microscopy and optical polarization microscopy. In addition cross sections from commercial silica glass crucibles used in the Czochralski process or dipped into the silicon melt were investigated with the same methods. At the silicon/silica glass interface different reaction zone morphologies were detected. A solution-precipitation mechanism is suggested for the fast lateral growth of the reaction zone, which is proposed to consist of small cristobalite crystals embedded in a silica glass matrix.

Calculation of bulk defects in CZ Si growth: impact of melt turbulent fluctuations

We present 3D unsteady analysis of melt turbulent convection coupled with heat transfer in the crystal and crucible during 300 mm CZ Si crystal growth. The 3D analysis includes the calculation of the crystallization front geometry, validated by comparing to experimental data and results obtained with a conventional 2D model. At the second step, an analysis of defect incorporation and evolution in the crystal has been performed within a 2D model.

Ga-doped CZ-Si crystal growth

Ga-doped CZ-Si crystal growth

Prediction of bulk defects in CZ Si crystals using 3D unsteady calculations of melt convection

We present 3D unsteady analysis of melt turbulent convection coupled with heat transfer in the crystal and crucible during CZ Si crystal growth. The 3D analysis includes the calculation of the crystallization front geometry, validated by comparing experimental data and results obtained with a conventional 2D model. At the second step, an analysis of defect incorporation and evolution in the crystal has been performed within a 2D model.

Investigations of seeding condition in dislocation-free CZ-Si crystal growth without necking

Investigations of seeding condition in dislocation-free CZ-Si crystal growth without necking

Modeling of Impurity Transport and Point Defect Formation during Cz Si Crystal Growth

Modeling of Impurity Transport and Point Defect Formation during Cz Si Crystal Growth

無ネッキング無転位CZ-Si結晶成長 : バルク成長I

無ネッキング無転位CZ-Si結晶成長 : バルク成長I

In situ observation of the Si melt–silica glass interface concerning CZ-Si crystal growth

An in situ observation was carried out for investigating the interfacial phase of so-called ‘brownish rings’ formed at the Si melt–silica glass interface concerning Czochralski (CZ) silicon crystal growth. It is found that some small dots appeared at the interface immediately after the Si melting, and grew gradually. The growth rate of the interfacial phase increases with increasing temperature, and it is almost the same when the silica dissolution rate is lower than a critical value. It can be concluded, therefore, that the growth rate of the interfacial phase does not depend on the silica dissolution rate in a practical CZ-Si crystal growth by considering that the silica dissolution rate in CZ-Si crystal growth is also lower than the critical value. Crystalline phase forms from the central region of the interfacial phase, and the amount of the crystalline phase increases with increasing temperature and reaction time.

Oxygen transportation during Czochralski silicon crystal growth

Oxygen transportation processes concerning CZSi crystal growth have been investigated, including dissolution from silica crucible to silicon melt, evaporation from silicon melt to ambient Ar atmosphere and incorporation (segregation) from silicon melt to silicon crystal. It is found that almost all of the dissolved oxygen evaporates as the form of SiO from the surface of the silicon melt to the atmosphere of Ar gas in a conventional CZSi crystal growth. The quantity of the oxygen incorporated into the silicon crystal is only a very small amount compared to the dissolved oxygen or evaporated oxygen. The equilibrium segregation coefficient of oxygen was obtained by comparing the oxygen concentration in the silicon crystal to the oxygen saturation concentration in the silicon melt and the result is suggested to be 0.8±0.1. It is confirmed experimentally that the oxygen distribution in the CZSi crystal becomes much uniform and the oxygen concentration decreases gradually with increasing the cusp magnetic field, which indicates that the application of a cusp magnetic field is an effective method to control the convection in the silicon melt.

Silica Dissolution and Oxygen Segregation Concerning CZ-Si Crystal Growth(<Special Issue>Control of Oxygen-atoms Transport and Micro-defects Generation during Si Crystal Growth)

Silica Dissolution and Oxygen Segregation Concerning CZ-Si Crystal Growth(<Special Issue>Control of Oxygen-atoms Transport and Micro-defects Generation during Si Crystal Growth)

Relationship between grown-in defects and thermal history during CZ Si crystal growth

An abrupt change of the crystal growth rate at temperatures in the range 1150–1080°C affects the annihilation or the agglomeration of grown-in defects such as flow pattern defects (FPD), crystal originated particles (COP), laser scattering defects (LSTD) and the defects measured by an optical precipitate profiler (OPPDs). Moreover, it is demonstrated that the densities of FPDs and LSTDs correlate with each other, and also with the cooling rate in such a temperature range. These relationships were investigated by growing several silicon single crystals in 10 kinds of hot-zone (HZ) configurations designed by using a numerical simulation. The cooling rate from 1412°C, the melting point of silicon, to 1150°C does not seem to be so important for the generation or the annihilation of these defects.

The ESR Investigation of Brownish Ring at the Surface of Quartz Crucible Used for Cz-Si Crystal Growth

Abstract An ESR spectrum was observed for brownish rings formed at the surface of quartz crucible used in Cz-Si crystal growth. A signal assignable to the E′-center has been detected in the brownish ring. This result is explained by the dissolution of oxygen atoms of vitreous quartz crucible into liquid silicon.

Relationship between Grown-In Defects and Thermal History during CZ Si Crystal Growth

Relationship between Grown-In Defects and Thermal History during CZ Si Crystal Growth

The Formation of Defects Degrading Gate Oxide Integrity During CZ-Si Crystal Growth

AbstractThe formation of grown-in defects degrading the gate oxide integrity (GOI) has been studied. The growth-halting experiments were carried out to investigate the temperature ranges at which the formation of the defects was promoted or suppressed. GOI is improved in the crystal regions slowly cooled above 1330°C and between 1060°C and 1100°C. It is degraded in the crystal regions held below 1060°C. In the peripheral of the crystals, those temperature ranges are about 30°C lower. The defects are formed and grown below 1060°C in the center part of the crystal. The defect density is decreased with cooling time between 1060°C and 1100°C. These phenomena are considered to be closely related with reactions of intrinsic point defects, that is, the pair annihilation or the aggregation. The temperatures at which the pair annihilation and the aggregation of the point defects occur are dependent upon the supersaturation of the point defects.

Formation of nitrogen-oxygen donors in N-doped Czochralski-silicon crystal

The behavior of nitrogen and the formation of nitrogen-oxygen donors in nitrogen-doped Czochralski-silicon crystals (Cz-Si) were studied by the electrical and infrared-absorption measurements in samples annealed in different conditions. Experiments showed that nitrogen-oxygen shallow donors are formed during the nitrogen-doped Cz-Si crystal growth. Nitrogen-oxygen thermal donors are generated in temperature range of 300–550 °C, and the behavior of these thermal donors resembles that of the thermal donors in Cz-Si crystals [P. Wagner, C. Holm, and E. Stirtl, Festkoperprobleme 24, 191 (1984)], but they are monovalent donors with the same levels as those of neutral thermal donors; no new electrically active center is generated in the temperature range of 600–900 °C.