High-resolution wafer surface topology measurement and vibration analysis in modern wiresaw manufacturing

Wiresaw manufacturing is an emerging technology for silicon wafer production because of its ability to cut large ingot into thick or very thin wafers with small kerf loss and high yield.; First, we investigate the vibration behaviors of wire in wiresaw. The vibration of wire subject to excitations due to contact is modeled and analyzed with both closed-form and numerical solutions. The results of frequency response reveal that the amplitude of vibration is more sensitive to the variations of wire tension than the variations of the wire speed. This discovery is very significant in the design of wiresaw because it suggests that increasing the speed of wire will not cause more vibration nor kerf loss. On the other hand, increasing the tension of wire will reduce the amplitude of vibration, hence the kerf loss, and increase the stiffness of the system. The damping effect of abrasive slurry on the damped vibration of wire is also studied. The results will facilitate the analysis and prediction of the vibration and kerf loss in the wiresaw manufacturing process.; In wiresaw manufacturing, the wire is constrained by the two wafer walls as it slices into the ingot. The model for wire vibration with impact to wafer walls is developed. Numerical method using the Galerkin's method and the principle of balance of momentum is utilized to solve the impact problem. The results of simulation show that the wire vibration behavior is affected significantly by the wafer wall constraints.; After an ingot is sliced into wafers, the wafer surface needs to be measured to ensure the consistency of quality. We developed an innovative alternative for full-field, whole-wafer measurement using the modified shadow moire technique. In addition, the Talbot effect is utilized to obtain a fringe pattern of good quality. The results show that not only the full view of whole wafer surface can be obtained, but also enhanced surface resolution and accuracy can be realized. In addition, warpage due to excessive residual stresses can be observed distinctly with fringe patterns. Later, we applied phase shifting technique which takes advantage of the gray level information to enhance the resolution of the measurement by two orders of magnitude.