Yield Enhancement by Defect Control

In the following, typical tasks in the field of optimi2ation of Bridgman-type crystal-growth processes are presented where both, thermal modeling and experimental analysis, contribute. 

The control of the shape of the solid/liquid interface during the whole growth process is, in general, and not only for Bridgman-type crystal-growth processes, of great importance for several reasons  

From Eq. (5.6) the crystal grower can estimate, for a given growth rate R, which temperature gradients in the melt and in the crystal have to be adjusted in order to grow a crystal with a flat interface, that means AQ = 0. But, Eq. (5.6) gives no information on which heater temperatures have to be chosen in order to achieve these temperature gradients and thus a flat solid/Uquid interface. 

For this purpose, the inverse modeling approach described in Section 5.2 allows the crystal grower in a very comfortable way to obtain the required information. By inverse modeling the heater temperature-time profiles can be optimized in order 

The optimization of the thermal conditions in Bridgman-type crystal growth of GaAs and InP with respect to low thermal stress conditions by using numerical simulation results mainly in a reduction of the dominant type of dislocations, the so-called 60°-dislocations with curved line vectors [49]. In Table 5.4 typical dislocation densities reported for different crystals grown by Bridgman-type growth techniques are summarized. 

---