EFFECT OF STRENGTH TEST METHODS ON SILICON WAFER STRENGTH MEASUREMENTS

摘要

In recent years, the boom in the photovoltaic industry is restricted by the solar silicon feedstockmaterial available. This has been reflected in the price of silicon and so on the solar modules. The solution is toreduce the thickness as well as the kerf loss of the silicon wafers during the processing by means of mutli-wire slurrysaw (MWSS) technology. However, the reduction of the wafer thickness without increasing the wafer strength leadsto a larger breakage during the subsequent handling of these wafers. Hence, it is necessary to improve the sawingprocess to minimize the influence of the sub-surface defects which can be quantified by measuring the waferstrength. In this paper, several aspects related to the strength measurements of silicon wafers are presented: Thedifferences between the 4-lines bending and ring-on-ring tests, the effects of the edge defects, as well as the testmethodology on the stress-to-rupture. The main conclusions of this study can be summarized as follow: (1) thestress-to-rupture measured from the 4-lines tests is approximately four times inferior as the one obtained from thering-on-ring test which is due to a more complex stress field. (2) The edge defects are more important than the onesin the middle of the wafer. (3) The test methodology plays a role on the stress-to-rupture.