W. von Ammon

Influence of boron concentration on the oxidation-induced stacking fault ring in Czochralski silicon crystals

The influence of the boron doping level in the range of 1 x 10(15)-2 x 10(19) cm(-3) on the position of the oxidation-induced stacking fault ring (R-OSF) in silicon crystals has been investigated by experiments and numerical simulation. For low boron-doped crystals, the position of the R-OSF is described by a critical value C-crit defined by the ratio of the pull rate and the temperature gradient in the crystal at the solid/liquid interface. Boron concentrations higher-than 10(17) cm(-3) shift the position of the R-OSF towards the wafer center without change of growth parameters. The critical value C-crit converts into a function C-crit(C-B), depending linearly on the boron concentration C-B. Crystal-originated particles (COP) and gate oxide integrity (GOI) yield distributions which are consistent with the R-OSF pattern. A low COP density and a high GOI yield are observed outside the ring; a high COP density and a medium GOI yield in the inner region bordered by the ring. It is assumed that boron atoms modify the thermodynamical properties of vacancies and self-interstitials.

Modeling analysis of unsteady three-dimensional turbulent melt flow during Czochralski growth of si crystals

We describe a computational model based on Large Eddy Simulation to calculate 3D unsteady turbulent melt convection in Czochralski systems for Si-crystal growth. The model has been verified using temperature measurements inside the melt and along the melt-crucible surface. The effect of the crucible rotation rate on 3D turbulent structures developed in the melt is analyzed. Transformation of the melt flow with increasing argon flow rate is predicted, and the controlling effect of the argon flow on the oxygen content in the crystal is evaluated.

Analysis of magnetic field effect on 3D melt flow in CZ Si growth

Abstract Three-dimensional turbulent melt convection in an industrial Czochralski Si-crystal growth system subjected to action of an axial stationary magnetic field is numerically simulated using a hybridization of the Reynolds-averaged Navier-Stokes approach and large-eddy simulation. The proposed RANS/LES model is based on a differential model of turbulence. The results obtained with three computational models differing in the number of considered hot-zone components are presented and compared with the experimental data for temperature in the melt and along the melt-crucible surface. The influence of electrical currents in the crystal on melt motion reorganization is studied.

Modeling of transient point defect dynamics in Czochralski silicon crystals

Intrinsic point defects control the formation of grown-in defects in silicon crystals. Under steady state conditions, the type of the prevailing point defect species is exclusively determined by the ratio of pull rate and temperature gradient in the crystal at the interface. In this study, simulations have been performed for transient growing processes where the pulling rate has been abruptly changed. Large reservoirs of interstitials are formed in fast-grown, vacancy-rich crystals near the interface after abruptly reducing the pulling rate for 30 min. During further growth at high pull rate, these interstitial reservoirs are transformed into large ellipsoidal defect patterns. Experimental results are excellently reproduced if equilibrium concentrations are used as boundary conditions for interstitials and vacancies at all crystal surfaces.

Numerical study of 3D unsteady melt convection during industrial-scale CZ Si-crystal growth

We present a computational model of 3D turbulent melt convection in Czochralski Si-crystal growth systems, based on the hybridization of Reynolds-averaged approach and large eddy simulation. The effect of superimposed magnetic field action on the melt flow is introduced in the model to account for the suppression of turbulent melt fluctuations. The model has been verified using experimental data for temperature in the melt and along the melt–crucible surface. Effects of axial magnetic field on the change in melt convection are studied in an industrial configuration. r 2002 Elsevier Science B.V. All rights reserved. PACS: 81.10.Aj; 81.10.Fq; 47.27.Eq; 47.27.Rc

Silicon crystals for future requirements of 300 mm wafers

Today, the main challenge in Si crystal growth development is the transition from 200 to 300 mm diameter. While the complexity of the growth process increases with larger charge size and crystal diameter, the perfection of the growth process must significantly improve to avoid any disturbances that result in structure loss during growth and, hence, cause massive material losses. With regard to the future bulk quality, radical changes may be required as the design rule approaches the size of the prevailing grown-in defect type. Therefore, grown-in defect free wafers will be required, which can be produced either directly by pulling, by wafer annealing or by epitaxy. As substrates for annealed and epitaxial wafers, nitrogen doped and fast pulled crystals provide sufficient internal gettering capability in low thermal budget device processes. Moreover, grown-in defects in nitrogen doped crystals are so small that they are easily covered during epitaxy or annealed during high temperature treatment.

Interaction of oxygen with thermally induced vacancies in Czochralski silicon

Complexes consisting of a vacancy and four oxygen atoms, VO4, were found in oxygen-rich Czochralski silicon wafers subjected to rapid thermal annealing (RTA) at 1250 °C for 30 s in Ar/O2 atmosphere by means of Fourier transform infrared spectroscopy with enhanced sensitivity. An absorption band at 985 cm−1, previously observed only in irradiated Si and assigned to a local vibration mode of VO4, was measured reproducibly in all RTA treated wafers examined. A concentration of about 1.4×1013 cm−3 of thermally induced VO4 was estimated from the integrated intensity of the band at 985 cm−1 using the known calibration factor for interstitial oxygen.

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

Abstract 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.

Investigation of Ostwald ripening in nitrogen doped Czochralski silicon

Infrared laser scattering tomography was used to investigate Ostwald ripening in nitrogen-doped Czochralski silicon. Contrary to previous assumptions about oxide precipitation in nitrogen-doped silicon, the results clearly demonstrate that Ostwald ripening takes place during annealing of N-doped silicon wafers at 1000°C and 1100°C. The higher the nitrogen doping and the higher the temperature the faster the oxide precipitates grow and the faster they split into two fractions. One fraction is growing at the expense of the other.

N–O related shallow donors in silicon: Stoichiometry investigations

For clarification of the unknown chemical composition of the electrically active N–O defects in silicon, an ingot with variable oxygen content and fixed nitrogen concentration was investigated by infrared spectroscopy. Shallow donor spectra taken at different sample positions, i.e., oxygen concentrations, show a strong oxygen influence on the absorption of the different N–O species, allowing determination of the number of oxygen atoms for each species via the corresponding mass-action law. From that, the energetically deepest defect N–O-5 is associated with a NO configuration, whereas the strongest complex N–O-3 has NO2 composition. Further members of the shallow donor family contain three oxygen atoms.