Quality evaluation of multi-crystalline silicon ingots produced in a directional solidification furnace with different theories

• Three methods were compared for evaluating the quality of silicon ingots produced in a DS furnace.
• The results are comparative similar for the three methods in the solidification process.
• The results vary considerably for the three methods in the annealing process.
• The thermo-plastic and thermo-creep methods are recommended for the whole process.
• Large dislocation density is generated in the annealing process.

Three methods for evaluating the quality of silicon ingots produced in a directional solidification furnace were compared. The methods are based on the thermo-elastic theory, thermo-plastic theory and thermo-creep theory. The methods use the von Mises stress, the accumulated viscoplastic strain, and the dislocation density as the evaluation parameters of ingot quality, respectively. The evaluation parameters and their distributions were calculated in the growing silicon ingots during the solidification process and in the grown ingots during the annealing process. The distributions of the quality evaluation parameters in the growing ingots are similar in the solidification process for the three methods. The evaluation method based on thermo-elastic theory is recommended because of its higher computational efficiency than the other two methods. However, in the ingot annealing process the distributions of the evaluation parameters vary considerably with the three methods. The thermo-plastic theory and the thermo-creep theory are more suitable for the whole process. It demonstrates that large dislocation density is generated in the ingot during the annealing process.