CZ Silicon Growth Research Articles

Effect of gas flow rate on chemical reactions in Czochralski silicon crystal growth

Chemical deposits and graphite etching resulting from chemical reactions are related to crystal quality and cost reduction in CZ silicon growth. A chemical model implemented in CGSim software was applied to investigate the effect of gas flow rate on the distribution of deposited compounds and the carbon consumption for the heat shield and graphite heater. The results show that SiO2 layer is deposited only on the inside surface of heat shield, with a relatively low deposition rate of 10−19 to 10−13 μm/hr. The SiC deposition on heat shield appears an abrupt increase when gas flow rate is higher than 0.7 m/s. In terms of chemical reactions, the carbon consumption of heat shield decreases with increasing gas flow rate. Meanwhile, the heater surface is coated with Si and/or SiC layers, demonstrating neglectable effect on heating efficiency of the heater. As increasing the gas flow rate, the deposited Si layer gradually overspreads whole heater surfaces, along with decreasing the rate of graphite etching. Consequently, a medium gas flow range with inlet flow rate of 0.5–0.65 m/s is recommended as an optimum parameter for CZ silicon growth, based on a compromise between crystal quality and cost reduction.

Comment on “Investigations of interstitial generations near growth interface depending on crystal pulling rates during CZ silicon growth by detaching from the melt” by T. Abe et al. [J. Cryst. Growth 434 (2016) 128–137] and on “Observations of secondary defects and vacancies in CZ silicon crystals detached from melt using four different types of characterization technique” by T. Abe et

Comment on “Investigations of interstitial generations near growth interface depending on crystal pulling rates during CZ silicon growth by detaching from the melt” by T. Abe et al. [J. Cryst. Growth 434 (2016) 128–137] and on “Observations of secondary defects and vacancies in CZ silicon crystals detached from melt using four different types of characterization technique” by T. Abe et

Investigations of interstitial generations near growth interface depending on crystal pulling rates during CZ silicon growth by detaching from the melt

In conventional CZ crystal growth, since formation of a cone tail takes a long time, from such a crystal to have been subject the long heat treatment it is not possible to observe actual distribution of vacancies (Vs) and interstitial atoms (Is) in a straight body of a crystal during growth. This experiment attempted to observe point defect distribution frozen by rapidly cooling a crystal that had been detached from a melt during growth to eliminate the effect of the time delay. Comparison between the experimental results of these specimens and the defect distributions of a conventionally pulled crystals revealed that Vs are introduced at a growth interface and the concentration of the Vs does not depend on the pulling rate. In addition, when the pulling rate is low, Is are generated by thermal stress which increases with increasing thermal gradient G because the amount of heat transfer by mass transfer is decreased and the crystal surface near the growth interface is cooled for longer period. As a result, the generation of Is due to the increase of the thermal stress is observed in an area referred to as an interstitial generation area (IGA) located above the vacancy region on the growth interface, where the crystal temperature is 1300°C or more. This paper describes the recombination (Rc) mechanism by which these Is created in the IGA are recombined with Vs transformed through the growth interface, thereby creating an observable Rc area at a location where no defect can be detected.

Numerical study on double‐frequency TMF in Cz silicon growth

AbstractIn a typical Cz set‐up, the silicon melt sustained in a fused silica crucible is exposed to oxygen dissolving from the hot crucible walls. The reduction of oxygen incorporation into the growing silicon crystal poses one of the crucial challenges. Quartz dissolution rate can be minimized and SiO evaporation rate enhanced if melted silicon is exposed to double‐frequency upwards travelling magnet fields (TMFs) generated within KRISTMAG® heater magnet modules (HMMs) positioned around the crucible. Our numerical results show the shift of the maximum of the Lorentz force density and consequently velocity away from the crucible walls. The obtained flow patterns can be advantageous for the oxygen control in Cz silicon growth due to accelerated transport of dissolved oxygen towards melt free surface without simultaneous enhancement of oxygen dissolution rate from the silica crucible walls. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Analysis of impurity transport and deposition processes on the furnace elements during Cz silicon growth

Czochralski growth of silicon crystals is always related to transport of impurities. The main impurities are oxygen and carbon. They react with furnace elements with formation of SiO, SiO 2 and SiC deposit layers. Prediction of transport of impurities is important to detect the precise location of areas where impurity deposition may cause considerable difficulties and to avoid excessive deposition above the melt free surface. Detailed analysis of chemical processes, accompanying Cz silicon growth is under discussion in the current paper. The proposed numerical model accounts for oxygen transport in the melt and SiO deposition on the walls of the furnace. Computer analysis was provided for cases with different heat insulation of the furnace walls.

Some Remarks On CZ Silicon Growth and Dream of Ideal Growth

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Defect formation in CZ Silicon growth

Global transient heat transfer simulations are combined with transient point-defect simulations to study the influence of pull-rate variations on the defect distribution in CZ silicon crystal growth. A strong influence of pull-rate variations on the melt/crystal interface is observed. Quasi-stationary and transient results for the interface deflection are compared with experimental data. Furthermore the final point-defect distribution is compared with the defect structure of an as-grown crystal. The transient results for the interface deflection as well as the point-defect distribution show good qualitative agreement with the experimental results.

シリコン成長における固液界面の温度勾配と熱バランス

Heat balance and temperature gradient at solid liquid interface in CZ silicon growth is examined. Contribution of heat transfer due to mass transport and radiative heat flow to total heat balance is calculated to be about 10% of that of latent heat. Measurement problem is briefly discussed. The relation between the temperature gradient and the growth rate is quantitatively analyzed using the heat balance equation.

Transient computer simulation of a CZ crystal growth process

The use of numerical simulation for improving the bulk growth process is illustrated by means of two sets of investigations. On the one hand, the time dependent heat transfer during CZ silicon growth has been numerically simulated and compared to experiments for an industrial furnace. An excellent agreement between simulation and experiment is observed for both heater power and crucible temperature. On the other hand, 4″, 6″ and 8″ CZ crystals were grown with different heat shields. It has been found that the critical pull rate Vcrit, under which the oxidation induced stacking fault (OSF) ring vanishes in the wafer center, varies with the crystal diameter and the type of heat shield. A calculation of the axial temperature gradient at the solid/liquid interface for each combination reveals that the critical pull rate is proportional to this axial temperature gradient, which, in turn, is a function of the crystal diameter and heat shield. A precise law governing OSF ring formation has been established. In addition, improved processing conditions can be determined by an extensive use of simulation results.