ECN publication
Contact resistance scanning for process optimization : the Corescanner method
Published by: Publication date:
ECN Solar Energy 1-8-2001
ECN report number: Document type:
ECN-RX--01-047 Conference Paper
Number of pages: Full text:
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Presented at: 11th Workshop on Crystalline Silicon Solar Cell Materials and Processes, Ester Park CO, USA, 19-22 augustus 2001.

It is difficult to obtain screen printed grid lines on solar cells with a low contact resistance, since the contact formation is very sensitive to many parameters. To optimize the process, it is necessary to be able to measure the contact resistance for each grid line. Recently, we have introduced an instrument that can do this, called the Corescanner.In this paper, the relation between process parameters and contact resistance is investigated using this instrument. The most important finding is that poor contacting results in large inhomogeneities in contact resistance. Even for cells with very low fill factors, regions of low contact resistance can be found. Low firing temperature settings lead to a large region of high contact resistance, and an uneven printing pressure results in large contact resistance differences across the cell, although no problems were visible by microscope. In this way, we will build a problem solving library of process issues and related contact resistance scans. To conclude, the Corescanner provides us with a technique to monitor contact resistance. This instrument is a valuable tool for fault detection, error diagnosis and process optimisation.

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