Surface formation, morphology, integrity and wire marks in diamond wire slicing of mono-crystalline silicon in the photovoltaic industry

Abstract

The diamond wire sawing is superior for the wafers manufacturing in the photovoltaic and semiconductor industry. In this research, analytical models were emphasized and experiments were designed to describe the surface formation, wire marks formation and crack generation in diamond wire sawing (DWS). It was found that wire marks are mainly caused by the wire bow and the wire lateral motion. The width of the wire marks are alternately difference due to the reciprocating sawing and wire bow. The twisting effect of wire was introduced as a composition of surface formation. Chips are removed by abrasive grains, and residual material left forms sawn surface. Surface roughness was investigated regarding the combination of wire marks and sawn surface. It was found that roughness changes with the feeding position and wire motion. Wire number that forming the wire web has influence on the sawing quality. It was found that increasing of wire number was useful for improving roughness as the stiffness of wire web is enhanced. The wafer surface was observed by Scanning Electron Microscope (SEM) and 3D profiler to analysis the geometric characteristics of wire mark and wafer deformation. It was found the wire mark in the contact zone was related to the sawing direction and action force. Furthermore, the surface defects was analyzed on the aspect of bearing rate. Wafer surface profile of long-term deformation after stress relief was observed.