Temperature Coefficients of Crystal Defects in Multicrystalline Silicon Wafers

Abstract

This article investigates the influence of crystallographic defects on the temperature sensitivity of multicrystalline silicon wafers. The thermal characteristics of the implied open-circuit voltage is assessed since it determines most of the total temperature sensitivity of the material. Spatially resolved temperature-dependent analysis is performed on wafers from various brick positions; intragrain regions, grain boundaries, and dislocation clusters are examined. The crystal regions are studied before and after subjecting the wafers to phosphorus gettering, aiming to alter the metallic impurity concentration in various regions across the wafers. Most intragrain regions and grain boundaries are found to show similar thermal characteristics before gettering. The gettering process has no substantial effect on the temperature sensitivity of intragrain regions, whereas it increases the sensitivity of most grain boundaries. Dislocation clusters exhibit both highest and lowest temperature sensitivities compared with other crystal regions before and after gettering. Images of the recombination parameter γ are created and related to the temperature sensitivity of the Shockley–Read–Hall (SRH) lifetime of the impurities in the material. The results suggest that most intragrain regions and grain boundaries are limited by SRH centers with a modest lifetime temperature sensitivity in the studied temperature range. Dislocation clusters are found to contain recombination centers with an effective lifetime that has a beneficial temperature sensitivity. The gettering process is observed to alter the composition of the recombination centers in the dislocation clusters, resulting in an SRH lifetime with an even more favorable temperature sensitivity for most clusters.