PV06000 - SEMI PV60 - Test Method for Measurement of Cracks in Photovoltaic (PV) Silicon Wafers in PV Modules by Laser Scanning
This Standard was technically approved by the Photovoltaic – Materials Global Technical Committee. This edition was approved for publication by the global Audits and Reviews Subcommittee on November 11, 2014. Available at www.semiviews.org and www.semi.org in January 2015.
Multicrystalline and monocrystalline silicon wafers for photovoltaic (PV) cells are manufactured by casting, Czochralski technique or other controlled solidification methods.
In PV cell fabrication process using these silicon wafers, macroscopic defects such as chips, scratches, and cracks are often generated due to mechanical and thermal stresses. Chips and scratches can be origins for crack generation.
Cracked wafers are sometimes broken in module fabrication process causing lower productivity and cost increases. Also broken wafers in a module may result in degradation of the module reliability.
Therefore, in-line characterization methods are required that allow discriminately inspecting cracks with high through put and repeatability, and that measure the number and the length of those.
This method is based upon the measurement of laser beam induced current (LBIC) and can detect only cracks in wafers of a module by controlling bias voltage applied to the module.
This Test Method identifies and measures cracks in crystalline silicon wafers of a module.
This Test Method employs an in-line, noncontacting and nondestructive method for characterizing multi- and monocrystalline silicon wafers of a module supported by a mechanism that moves the test specimen through the measurement equipment.
This Test Method covers square and pseudo-square silicon wafers of PV cells with nominal edge length ≥125 mm and a nominal thickness ≥100 µm.
It is more effective to operate this Test Method under the statistical process control (SPC) [e.g., ISO 11462] to obtain the data with high reliability and repeatability.
This Test Method detects cracks from the distribution of leakage current density on the PV cell obtained by scanning its front side by laser.
Other measurement methods may also provide similar information about the number and the length of cracks of wafers with this Test Method. Their subjects are, however, different from that of this Test Method.
This Test Method is also applicable to off-line measurement provided that the requirements of the test method are satisfied.
Referenced SEMI Standards
SEMI E89 — Guide for Measurement System Analysis (MSA)
SEMI M59 — Terminology for Silicon Technology
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