TOWARDS AN INTEGRATED APPROACH FOR ANALYSIS AND DESIGN OF WAFER SLICING BY A WIRE SAW

Crystalline and polycrystalline ingots of silicon and other materials need to be cut into thin wafers for microelectronics, photovoltaics, a nd many other applications. For slicing process to be cost-effective, the kerf loss should be minimum and the surface finish should be of a high quality. Wire saw can meet these demands and is considered to be a potentially better technology than the inner diameter (ID) saw. An i nitial study of the current technology shows that the wire saw cutting is a poorly understood process and no model exists for simulation, de sign, and control of this process. The wire saw slicing process can be well modeled as a cutting process, where the initial fracture occurs because of the stress distribution between the two surfaces subjected to compressive loading and sliding friction. A preliminary analysis is carried out using a standard finite element method to develop a bette r understanding of this process and to determine possible ways of impr oving the process design. The results of vibration (modal) and thermal stress analyses show that an accurate prediction of the effects of pr ocess parameters would help in improving the wire saw design. Similarl y, a proper feedback control algorithm would enable a better control o f the process by using on-line information on wire tension and stiffne ss, temperature, and other relevant quantities. A methodology for syst ematic approach to analysis and design of an advanced wire saw process is also outlined.