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2019
Conference Paper
Titel
Approach to Clarify the Cause of Handling Defects in Silicon Heterojunction Cell Production through the Interplay of Different Imaging Techniques
Abstract
Within this paper, a systematic approach will be presented to clarify the origin of locally reduced carrier lifetime caused by conveyor belts and vacuum grippers used for automated wafer handling. The most sensitive handling step in silicon heterojunction production is between wet-chemical cleaning and amorphous-Silicon (a-Si) layer deposition by plasma enhanced chemical vapor deposition (PECVD). In this state the wafer surface should be clean, defect-free and H-terminated what should not be altered by the automation. The handling takes place at room temperature before first side a-Si layer deposition and at elevated temperatures, resulting from residual heat of the previous deposition, before second side deposition. This paper focuses on the interplay of different imaging techniques to identify the cause of conveyor belt and gripper induced locally reduced carrier lifetime. Photoluminescence imaging (PL) is used to display the electrical properties of the passivated silicon surface in a spatially resolved manner. In addition micro photoluminescence imaging (µ-PL) images were taken to examine details in a small area. These images are applied to navigate to the handling system induced defects on the wafer surface by image navigation in a scanning electron microscope (SEM). At the end of the investigation chain, electron dispersive X-ray spectroscopy (EDX) is used to analyze the found irregularities concerning their chemical composition.