• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.7
• /
• pp.2397-2408
• /
• 1996

A numerical study was made of the control of transient oscillatory flow modes in Czochralski convection. The reduction of temperature oscillation was achieved by changing the rotation rate of crystal rod, .OMEGA.$_{S}$=.OMEG $A_{S0}$(1+ $A_{S}$sin(2.pi. $f_{S}$/ $t_{p}$t)). The temporal behavior of oscillation flow was scrutinized over broad ranges of two parameters, i.e., the rotation amplitude( $A_{S}$.leq.0.5) and the nondimensional frequency (0.9.leq. $f_{S}$.leq.1.5). The mixed convection parameter was ranged 0.225.leq.Ra/PrR $e^{2}$.leq.0.929, which encompassed the buoyancy-and forced-dominant convection regimes. Computational results revealed that the temperature oscillations could be reduced effectively by a proper adjustment of the control parameters. The uniformity of temperature distribution near the crystal rod was examined. The control of oscillatory flow modes was also made for a realistic, low value of Pr.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.4 no.1
• /
• pp.121-131
• /
• 2000

Melt flow, heat and mass transfer of oxygen have been analyzed numerically in the process of Czochralski single crystal growth of silicon under the influence of misaligned cusp magnetic fields. Since the silicon melt in a crucible for crystal growth is of high temperature and of highly electrical-conducting, experimentation method has difficulty in analyzing the behavior of the melt flow. A set of simultaneous nonlinear equations including Navier-Stokes and Maxwell equations has been used for the modelling of the melt flow which can be regarded as a liquid metal. Together with the melt flow which forms the Marangoni convection, a flow circulation is observed near the comer close both to the crucible wall and the free surface. The melt flow tends to follow the magnetic lines instead of traversing the lines. These flow characteristics helps the flow circulation exist. Mass transfer characteristics influenced by the melt flow has been analyzed and the oxygen absorption rate to the crystal has been calculated and turned out to be rather uniform than in the case of an aligned magnetic field.

• Current Photovoltaic Research
• /
• v.8 no.1
• /
• pp.17-26
• /
• 2020

It is clear that monocrystalline Silicon (Si) ingots are the key raw material for semiconductors devices. In the present industries markets, most of monocrystalline Silicon (Si) ingots are made by Czochralski Process due to their advantages with low production cost and the big crystal diameters in comparison with other manufacturing process such as Float-Zone technique. However, the disadvantage of Czochralski Process is the presence of impurities such as oxygen or carbon from the quartz and graphite crucible which later will resulted in defects and then lowering the efficiency of Si wafer. The heat transfer plays an important role in the formation of Si ingots. However, the heat transfer generates convection in Si molten state which induces the defects in Si crystal. In this study, a crystal growth simulation software was used to optimize the Si crystal growth process. The furnace and system design were modified. The results showed the melt-crystal interface shape can affect the Si crystal growth rate and defect points. In this study, the defect points and desired interface shape were controlled by specific crystal growth rate condition.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.12
• /
• pp.1667-1675
• /
• 2001

Numerical simulations are carried out for the liquid encapsulant Czochralski(LEC) by imposing a magnetic field. The use of a magnetic field to the crystal growth is to suppress melt convection and to improve the homogeneity of the crystal. In the present numerical investigation, we focus on the range of 0-0.3Tesla strength for the axial and cusped magnetic field and the effect of the magnetic field on the melt-crystal interface, flow field and temperature distribution which are the major factors to determine the quality of the single crystal are of particular interest. For both axial and cusped magnetic field, increase of the magnetic field strength causes a more convex interface to the crystal. In general, the flow is weakened by the application of magnetic field so that the shape of the melt-crystal interface and the transport phenomena are affected by the change of the flow and temperature field.

• Korean Journal of Materials Research
• /
• v.11 no.9
• /
• pp.781-785
• /
• 2001

The thermal behavior of Flow Pattern Defect (FPD) and Large Pit (LP) in Czochralski Silicon crystal was investigated by applying high temperature annealing ($\geq$$1100^{\circ}C$) and non-agitated Secco etching. For evaluation of the effect of LP upon device performance/yield, commercial DRAM and ASIC devices were fabricated. The results indicated that high temperature annealing generates LPs whereas it decreases FPD density drastically. However, the origins of FPD and LP seemed to be quite different by not showing any correspondence to their density and the location of LP generation and FPD extinction. By not showing any difference between the performance/yield of devices whose design rule is larger than 0.35 $\mu\textrm{m}$, LP seemed not to have detrimental effects on the performance/yield.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.3 no.1
• /
• pp.1-11
• /
• 1993

A suppression of turbulent fluid motion and a control of oxygen and dopants could be improved by application of magnetic field in Czochralski growth of silicon. The effect of an axial magnetic field on Czochralski system was numerically calculated. The fluid motions induced by temperature gradients and by crystal and crucible rotations were suppressed by magnetic force. The S/L interface was gradually flattened in proportion to the increase of magnetic field due to a reduced ascending velocity in the vicinity of center line. The t.emperature distributions in the melt at 8=0.3 Tesla were similar to those analyzed by the conduction heat transfer only. The dissipated amounts of heat flux from melt and crystal surfaces by Ar gas blowing was Jess than 3 %.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1996.06b
• /
• pp.239-257
• /
• 1996

$\beta$-BaB2O4는 고출력 가시광선 및 적외선을 발진시키는데 유용한, 비선형 특성을 가진 물질이다. $\alpha$-$\beta$ 상전이 온도가 녹는점보다 18$0^{\circ}C$ 낮기 때문에 보통 flux법으로 단결정을 성장시킨다. 수년전 Itoh등은 $\beta$-BaB2O4단결정을 congruent조성의 용액으로부터 Czochralski법으로 metastable한 상태에서 직접 성장시켰다. 그렇지만 그 공정은 잘 이해되지 않고 있으며 재현하기가 매우 어렵다. 저자들은 $\beta$-BaB2O4단결정을 용액표면온도도 1034$^{\circ}$-1085$^{\circ}C$, pulling rate 3mm/h, 10-30 rpm의 범위에서 성장시켰으며 융액표면의 온도구배는 $\beta$-상으로 성장시키는데 매우 중요한 인자로 여겨진다. Seed로는 직경 1-2mm의 c축방향 $\beta$-BaB2O4단결정 봉이 상용되어 성장방향을 조절하고 열응력을 최소화시켰다. 성장된 $\beta$-상의 단결정들은 6-fold모양을 하며 표면에 작은 비늘같은 것들이 붙어있고 중심부에 core가 있는 것을 알았다. Flux법으로 성장시킨 $\beta$-BaB2O4단결정을 사용한 seeds는 단결정 성장 및 냉각 중에 cracks이 자주 발생하였으며, boule의 cracks은 afterheater를 사용할 경우 다소 줄일 수 있었다. 성장된 단결정의 광학특성이 측정되었다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.6 no.1
• /
• pp.11-18
• /
• 1996

Grown-in defects like OISF and FPD in the large diameter(> 8 inch)of silicon crystal are characterized. It was revealed that the presence of the ring-patterned OISF would deterorate the minority life time of the silicon crystal. Through the cooling experiment from the $1250^{\circ}C$, the nucleation of the OISF was confirmed to follow the homogeneous nucleation and growth process. In addition to OISF nucleus, crystal originated particle, which was known to be closely related with FPD (Flow Pattern Defects), was found to depend on the pulling rate of the crystal. Combination of the lower rate of the pulling and the faster cooling near the $950^{\circ}C$ is proposed to be effective method in reducing the generation of these grown-in defects.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.6
• /
• pp.381-388
• /
• 2000

The temperature and velocity fluctuations occurred by the baroclinic instability in the melt for Czochralski crystal growth method were experimentally investigated. Wood's metal, which has similar Pr number to the silicon melt, was used as the working fluid and azimuthal velocity was measured using incorporated magnet probe. The azimuthal velocities near the free surface are faster than velocities near the bottom and the rotational velocities near the model crystal become very fast. The results of measured temperature fluctuation as increasing rotation rate were shown that baroclinic instability occurred at the region of Ro<1.01, Ta>$9.63{\times}10^8$. In these region, the fluctuations of temperature and velocity have the same frequency.

• Korean Chemical Engineering Research
• /
• v.58 no.3
• /
• pp.369-380
• /
• 2020

Most mono-crystalline silicon ingots are manufactured by the Czochralski (Cz) process. But If there are oxygen impurities, These Si-ingot tends to show low-efficiency when it is processed to be solar cell substrate. For making single-crystal Si- ingot, We need Czochralski (Cz) process which melts molten Si and then crystallizing it with seed of single-crystal Si. For melts poly Si-chunk and forming of single-crystalline Si-ingot, the heat transfer plays a main role in the structure of Cz-process. In this study to obtain high-quality Si ingot, the Cz-process was modified with the process design. The crystal growth simulation was employed with pulling rate and rotation speed optimization. Studies for modified Cz-process and the corresponding results have been discussed. The results revealed that using crystal growth simulation, we optimized the oxygen concentration of single crystal silicon by the optimal design of the pulling rate, rotation speed and melt charge level of Cz-process.