Study On The Performance Of Diamond Wire Saw Cutting Of Crystalline Silicon

The diamond wire saw is made of a special steel wire, the surface of which is coated with diamond grains by plated. Compared to conventional slurry wire saw, the fixed abrasive diamond wire saw has high cutting efficiency, easy recycling of cutting silicon and low cost, and it has broad prospects for large-scale application, but the industry have the remaining questions about silicon surface quality and mechanical damage. According to the problem, the cutting performance of the diamond wire saw slicing of silicon was studied.Experiments of single diamond scoring of crystalline silicon and diamond wire saw slicing of crystalline silicon have been carried out. The micro-morphologies of the cut surfaces were examined. The results show that, under higher pressure, crystalline silicon is cut by diamond wire saw in brittle model, with broken pits on cut surfaces, and brittle cleavage stripes in the case of single diamond scoring test; under lower pressure, crystalline silicon is cut by diamond in plastic model, with relatively flat and smooth scratches. On silicon wafers sliced by diamond wire saw, there are lots of irregular pits, along with extended smooth scratches on top of them, indicating a mixture of the brittle cutting mode and the plastic cutting mode. The reason may be that the pressure underneath the cutting wire is high, where the crystalline silicon is cut in brittle mode, while the exposed surface would inevitably be scratched by the diamonds on lateral sides of the wire saw, under a much lower pressure, which would cut the surface in plastic mode. Therefore, a cut surface characterized by a mixture of brittle and plastic cutting mode is generated by diamond wire saw slicing.The experiment of cutting monocrystalline silicon wafers was carried on a single line cutting machine. Force measurement device were designed, and as the change of the feeding rate, the performance of the cutting wire tension, the surface quality and damage of silicon wafers were researched. The results show that, the effect on diamond wire sawing of silicon of feeding rate was examined, with the feeding rate increasing, surface morphology and roughness were not discrepant, but fluctuation cycle of silicon surface increased. Silicon wafers were etched layer by layer, followed by minority carrier lifetimes measurement after each etching. According to the depth-profiles of the life times, the depths of sub-surface damage of differently cutting wafers are acquired. The sub-surface damage of silicon wafers sliced on different feeding rate is measured. The results show that, the damage depth of diamond wire slicing silicon wafer is about 12μm; with the feeding rate increasing, the thickness of damage layer increases to a certain extent, but don't change significantly.The micro-morphologies of the cut surfaces by diamond wire saws and wire-slurry saws were examined respectively. And the cutting mechanisms were analyzed. Silicon wafers cut by diamond wire saw showed a mixture of brittle and plastic cutting mode with relatively flat and smooth scratches and lots of irregular broken pits. While silicon wafers cut by wire-slurry saws showed a brittle cutting mode with lots of irregular broken pits. Silicon surface are relatively flat as a whole, while the surface roughness of the diamond wire sawing of silicon were greater. The depth of sub-surface damage of silicon wafers by wire-slurry saws is found to be about 10μm, and the depth by diamond wire saws is found to be about 6μm. It is shown that, sub-surface damage of the silicon wafers cutting by diamond wire saws is less than that by wire-slurry saws.