Numerical simulation of flow, thermal and oxygen distributions for a Czochralski silicon growth with in a transverse magnetic field

• Main Authors: Pei-yi Chiang, 江姵儀
• Other Authors: Jyh-Chen Chen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/26192033905626159946

碩士 === 國立中央大學 === 機械工程學系 === 102 === A three-dimensional numerical simulation has been performed to understand the motion of the melt flow, thermal field and oxygen distributions during the Czochralski silicon single crystal growth process under the influence of a transverse magnetic field. With the application of a transverse magnetic, the velocity, temperature and oxygen concentration fields in the melt become three-dimensional and asymmetric. There were two different flow patterns on the plane parallel and crossing transverse magnetic field, separately. Therefore, the presence of a transverse magnetic field decreases the oxygen concentration level along the melt-crystal interface. The uniformity of oxygen concentration at the melt-crystal interface is also improved when the magnetic field is applied. However, the two flow motion will cause the different temperature distributions form distorted in the whole melt. It is hard to simulation and crystal growth. In this study, the numerical simulation has been performed to clear the mechanism of oxygen transportation, such as the distribution of oxygen concentration in the melt is related to the crystal rotation rate and crucible rate. The lower temperature at the crucible wall and the free surface velocity decrease as the crucible rotation rate decrease. When the crucible rotation rate reaches below 1 rpm, the oxygen concentration value along the melt-crystal interface decrease enlarges. The uniformity of oxygen concentration is better for higher crystal diameters. The crystal rotation rate has negligible influence on the oxygen concentration. But the radial distribution of oxygen uniformity is improved at higher crystal rotation rates. In the case of transverse field, the crucible rotation rate is a key parameter in the control of oxygen concentration in the crystal. The quantity of the oxygen transportation and silica concentration on the free surface can be increased by increasing the gas flow rate. Because the argon gas velocity affect the radial velocity and interfere the free surface flow motion. However, the crystal oxygen concentration was increased with an increase in the flow velocity of argon gas in the TMCZ. This thesis analysis silicon crystal growth process under magnetic Czochralski method, this trend is in consistence with the experimental one. The variation of the axial oxygen concentration with the growth length of the silicon crystal is related to the melt depth of the crucible, the flow structure inside the melt, the crucible temperature, and the argon flow speed along the free surface. In order to improve the axial non-uniform of oxygen concentration, the heater position and crucible rates are adjusted. The axial non-uniform of oxygen concentration can be improved approximately 24.7% and 6.6% by revising the crucible rates and modifying the heater position.