The formation mechanism of grown-in defects in CZ silicon crystals based on thermal gradients measured by thermocouples near growth interfaces

被引:27
作者
Abe, T [1 ]
机构
[1] Shin Etsu Handotai, Isobe R&D Ctr, Gunma 3790196, Japan
来源
MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY | 2000年 / 73卷 / 1-3期
关键词
thermal gradient; thermocouple; Voronkov's theory; interstitials and vacancies; heat flux balance equation; latent heat;
D O I
10.1016/S0921-5107(99)00428-6
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
The thermal distributions near the growth interface of 150 mm CZ crystals were measured by three thermocouples installed at the center, middle (half radius) acid edge (10 mm from surface) of the crystals. The results show that larger growth rates produced smaller thermal gradients. This contradicts the widely used heat Aux balance equation. Using this fact, it is confirmed in CZ crystals that the type of point defects created is determined by the value of the thermal gradient (G) near the interface during growth, as already reported for FZ crystals. Although depending on the growth systems the effective lengths of the thermal gradient for defect generation are varied, we defined the effective length as 10 mm from the interface in this experiment. If G is roughly smaller than 20 degrees C cm(-1), vacancy rich CZ crystals are produced. If G is larger than 25 degrees C cm(-1), the species of point defects changes dramatically from vacancies to interstitials. The experimental results after detaching FZ and CZ crystals from the melt show that growth interfaces are filled with vacancies. We propose that large G produces shrunk lattice spacing and in order to relax such lattice excess interstitials are necessary. Such interstitials recombine with vacancies which were generated at the growth interface, next occupy interstitial sites and residuals aggregate themselves to make stacking faults and dislocation loops during cooling. The shape of the growth interface is also determined by the distributions of G across the interface. That is, the small G and the large G in the center induce concave and convex interfaces to the melt, respectively. (C) 2000 Elsevier Science S.A. All rights reserved.
引用
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页码:16 / 29
页数:14
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