The impact of subsurface damage on the fracture strength of diamond-wire-sawn monocrystalline silicon wafers
We describe a multi-diamond-wire saw for cutting monocrystalline silicon bricks into thin (120 µm) and thick (200 µm) wafers and label as fresh- and worn-wire sides. While almost no difference was found in the fracture stress of the thick wafers(200 µm)cut from either side, the thin (120 µm) wafers showed a lower fracture stress in those from the fresh-wire side compared to the worn-wire side. This is a remarkable result when wafers are sawn with conventional diamond wire. On the contrary, wafers sawn with improved diamond wire (100d-M6/12) showed a higher fracture stress compared to those cut with conventional diamond wire (100d-M8/16), for both the fresh- and worn-wire sides. Observing the subsurface areas of wafers by micro-Raman spectroscopy, we succeeded in quantifying the defective silicon fraction as the Raman crystallinity factor (Φc). We found that wafers having a higher fracture strength had a larger Φc.