Inductively Coupled Plasma Atomic Emission Spectroscopy: A bulk analysis and process monitoring technique for silicon solar cell fabrication

Abstract

We report on the investigation of Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP AES), a trace element analysis technique, as a bulk impurity characterization and process monitoring technique in silicon solar cell fabrication. Various impurities may be inherent to the nascent silicon material itself or get introduced during the fabrication process. These may be present at the surface or in the bulk of the silicon wafer and would degrade performance of the solar cells. The distribution of impurities varies throughout the wafer during the solar cell fabrication process. The analysis of the etchant solutions obtained by layer-wise digestion of the solar cell precursor after each step of fabrication using ICP AES elucidates how the distribution of impurities changes during the process. Also monitoring the impurity content in various chemical baths, such as the chemicals used for wafer cleaning, saw damage etching (SDE) or phosphosilicate glass (PSG) removal, after processing batches of wafers offers an insight about performance of chemical processes. Thus it would be a powerful tool for monitoring impurity content in the starting wafers, those introduced during cell processing and hence useful for improving efficiency and yield.