Abstract: Currently, free abrasive multi-wire sawing (FAMS) is adopted as the primary wafering technique in China. However, its main drawbacks are generating deep saw marks and thick damage layer as well, which cannot meet the further demand of large scale and ultra thin wafers. Free abrasive electrochemical multi-wire sawing (FAEMS) is a new grinding method of which combines with electrochemical machining, i.e., the silicon ingot and the cutting wire are served as anode and cathode, respectively, and the anodic passivation (or erosion) on silicon can be controlled by applying an anodic potential during the mechanical sawing process. Hereby, cutting load can be effectively reduced. And cutting efficiency as well as surface quality of wafers will be significantly improved. In this work, 156 mm×156 mm (8″) p-type (boron-doped) polycrystalline silicon ingots with a resistivity of 1-3Ω∙cm are selected as raw materials, and in order to explore the difference of surface integrity between FAMS and FAEMS methods, all machining parameters are fixed with no change. The experimental results show that the profile bending rate (BOW) of FAEMS is 3 μm lower than that of FAMS, and is quite centered on narrow size distribution ranging from 0 to 9 μm. Further, hidden cracks and deep grooves on the sub-surface of FAEMS wafer are relatively rare to be observed after being etched by 20% NaOH solution, which indicates that surface damage is less than that of FAMS, and the thickness reduction of wafer for subsequent texturing process will be thinner too. For free abrasive and fixed abrasive multi-wire sawing techniques, this new method is totally compatible to be adopted with low cost of equipment improvement, which has a bright future for industry applications.

Key words: free abrasive multi-wire sawing, hybrid electrochemical machining, solar wafer, surface integrity