Determination of the impact of the wire velocity on the surface damage of diamond wire sawn silicon wafers

Abstract

The sawing of silicon wafers with diamond coated wires still requires further development for a widespread application in the photovoltaic industry. The technique has the potential for a cost reduction due to higher cutting rates and the use of water as a low-cost cooling fluid, but it is also necessary to integrate the technique into the established processing chains particularly for sawing multicrystalline silicon (mc-Si). One of the requirements is an increasing industrial demand on the wafer surface quality, such as the optical appearance, the total thickness variations (TTV), the etching behavior and the sub-surface and surface damage, which determines the mechanical wafer stability.The goal of this work is to analyze the impact of different wire velocities on the surface damage of multicrystalline silicon wafers. First, the distribution of amorphous regions was measured using Raman microscopy. The results reveal slightly higher local fractions of the amorphous phase with increasing wire velocity. This also correlates with more scattering and higher inhomogeneity in the surface roughness values. Furthermore, the microcrack depths were analyzed on polished and etched bevel cut samples of wafers using confocal laser scanning microscopy (CLSM). Additionally, the present study investigates the impact of cleaning procedures and different grain orientations on the sawing damage characteristics.