Characterization of Residual Strain in Si Ingots Grown by the Seed-Cast Method

The residual strain distribution in cast-grown mono-like Si ingots is analyzed. The effect of the crucible during solidification and the influence of different cooling rates is described. To clarify in which process steps residual strain accumulates, several Si ingots were grown in a laboratory scale furnace (100mm) using different cooling conditions after completion of the solidification. For the cooling, two different cooling rates were distinguished: fast cooling (12deg/min) and slow cooling (5deg/min). It was found that changes in cooling gradients greatly influence the amount of residual strain. The results show that slow cooling in any temperature range leads to strain reduction. The greatest reduction could be found when the temperature gradient was changed to slow cooling in the high temperature region.

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