Improved mechanical strength and reflectance of diamond wire sawn multi-crystalline silicon wafers by inductively coupled plasma (ICP) etching

Abstract

In this work the standard wet chemical and plasma texturing processes for multi wire slurry abrasive sawn multi-crystalline silicon were applied to fixed diamond wire sawn (DW) multi-crystalline silicon. The plasma etch produced an effective anti-reflective layer without any changes to the process parameters. The achieved texture features a reflectance well below 5% in the visible range. Furthermore the mechanical strength of the wafers was investigated. 4-point bending tests revealed that anisotropic strength behavior is still present for the plasma textured wafer. In addition to their excellent optical properties, the plasma textured wafers show increase of 123% in characteristic fracture stress related to the as-cut batch for the critical loading with the saw marks parallel to the rollers. This can lead to a significantly reduced breakage rates during solar cell production. It is shown, that the characteristic fracture stress of the multi-crystalline plasma textured batch is equal to the strength of mono-crystalline industrial wet etched fixed diamond wire sawn wafer.