Fig. 30. Crack propagation profile from the fracture surface. (Contrast and brightness of the glass layer area has been adjusted to make the crack propagation profile more identifiable.)Figure optionsDownload full-size imageDownload as PowerPoint slide
Fig. 31. SEM image from the fracture surface at the bonding surface.Figure optionsDownload full-size imageDownload as PowerPoint slide
The double layer wafer cutting results show that there are regular ripple-like step lines on the fracture surfaces of both layers. These lines represent the crack fronts at different moments. The line shape and the distance between lines are completely
different from the LITP cutting result of single layer glass  and single layer silicon . Clearly, the two layer could affect each other greatly. This is mainly caused by the temperature-stress distribution and the differences between the physical properties of the materials, such as thermal expansion, fracture toughness, and elastic parameters. As Fig. 30 shows, the crack propagation profile is an S-shape curve. The width of the profile curve in the scanning direction is 0.981 mm, which is accordance with the tensile stress distribution and the XFEM status results gained by FE analysis.
The driver for this CID 2011756 study
was to analyze the mechanism of 1064 nm semiconductor laser cutting silicon-glass double layer wafer using LITP method. An effective three-dimensional computational model was proposed for calculating heat generation in the process of laser material interaction. This model was included in the DFLUX subroutine of the FE analysis model to simulate the temperature and stress distribution. A set of typical processing parameters (laser power is 53 W, spot diameter is 4 mm, and scanning speed is 4 mm/s) was adopted in the simulation and the experiments. The FE results show: the highest temperature occurs at the bonding interface; the temperature ranges from 400 °C to 500 °C for 85% of the time of the scanning process; the highest compressive stress occurs at the bonding interface; the stress ?yy is discontinued on the bonding interface; the bottom surface of the silicon layer has the highest tensile stress, the top surface of the glass layer has the lowest tensile stress; the crack tip is a curved line with the bottom surface of the silicon layer in the lead and then the interface and the top surface of the glass layer at last. The experimental results show the cutting quality is high. The crack propagation profile generally matches with the FE analysis results. The differences between the physical properties of the materials are the main reason for organ systems