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|Title: ||摻雜砷柴氏法生長單晶矽之雜質傳輸數值分析;Numerical Study of Impurity Transport during Czochralski Arsenic-doped Silicon Crystal Growth|
|Authors: ||阮氏懷秋;Thu,Nguyen Thi Hoai|
|Keywords: ||砷摻雜於矽熔湯;摻雜技術;矽晶體;Arsenic doped-silicon melt;Doping technique;Silicon crystal|
|Issue Date: ||2014-10-15 17:20:17 (UTC+8)|
;Nowadays the Czochralski (Cz) technique has become a main method to grow large single silicon crystal. In order to enhance the quality of crystal, the level of oxygen concentration in the ingot as well as its electric properties has to be controlled. The optimal resistivity for the silicon epitaxial wafers can be obtained by adding directly some common dopants (boron, arsenic, phosphorus, antimony …) into the liquid silicon during the growth process.
In this study, the effect of doping arsenic on the oxygen concentration along the freezing interface is numerically investigated by finite volume method (FVM). In order to compare with the experimental resistivity provided by SAS Company, the conversion of crystal resistivity from arsenic concentration is made by using the standard transformation formulation. It is clear that the simulation predictions have similar tendency with the experimental ones in crystal resistivity.
The computational results show the mechanism of oxygen content reduction in heavily arsenic-doped Cz silicon melt as compared with non-doped melt. This is because arsenic doping decreases the thermodynamic activity coefficient of oxygen dissolved into the bulk melt from silica. Arsenic content also increases along the length of crystal due to its small segregation coefficient (k0=0.3). The arsenic atoms concentrated in the ingot center are much more than their concentration in the region of crystal edge.
Furthermore, the increase in doping level causes a decrease of oxygen content in the growth direction while this increases the radial segregation of arsenic. There is an inverse relationship between dopant concentration and crystal resistivity.
Last but not least, the effect of pulling rate and rotation rate on the resistivity is also predicted numerically. The results indicate that the radial resistivity variation of ingot increases with increasing the growth rate as well as crucible rotation rate while this trend is reversed as the crystal rotation rate is accelerated.
|Appears in Collections:||[機械工程研究所] 博碩士論文|
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