Estimation of solidification interface shapes in a boron-phosphorus compensated multicrystalline silicon ingot via photoluminescence imaging

This paper introduces a method for estimating the shape of the solidification front along the height of a directionally-solidified multicrystalline silicon ingot. The technique uses net dopant density images, obtained on wafers via photoluminescence imaging under surface limited conditions, after the impact of grain boundaries is eliminated through an image processing procedure. By modeling the dopant distribution according to Scheil's law, solidification interface images are derived sequentially along the ingot height. The technique is demonstrated on a compensated boron-phosphorus doped multicrystalline ingot. The reconstructed three dimensional interface images, together with their evolution along the ingot height, allows for subsequent optimization of the ingot growth process.