A Study Of The Surface Characteristics Of Diamond Wire Sawn Multicrystalline Silicon Wafers And The Texturization

Diamond wire sawing is a new cutting technology，which used fixed diamondparticles instead of the wires and slurry. Compared with the conventionalslurry-cutting technology, its advantages include faster cutting speed, lessenvironmental impact and easier recycle of silicon kerf loss. Diamond wire sawing isexpected to become the mainstream wafer cutting technology for photovoltaicindustry. But it is reported that the current acid-texturization process fails todiamond-cutting multicrystalline silicon wafers. The antireflection effect is poor andthe cutting marks cannot be removed. The study is carried out to solve this problem.The results showed that, the surface morphology of diamond-cuttingmulticrystalline silicon wafers were quite different from the slurry-cutting siliconwafers’, including smooth areas, rough borders, brittle crackers and parallel cuttingmarks; Among these, smooth areas account for about38%. The surface of smoothareas exists an amorphous silicon layer, which is created by strong plasticdeformation induced silicon when scribed by diamond particles. Because of thesmooth areas, the reflectance of diamond cutting wafers is higher than the reflectanceof slurry cutting wafers in the visible range.Using HNO3-HF-H2O mixed acid system for the diamond cutting silicon wafers’texturing studies, with the HNO3-rich system and the HF-rich system. The resultsshowed that, both the HNO3-rich system and the HF-rich system failed to effectivelyeliminate the cutting marks on silicon wafer and reduce reflection, which couldn’tmeet production requirements. The effect of cutting marks for both acid etchingsystems is opposite. HNO3-rich system makes the cutting marks fading, while theHF-rich system make it deeper. Therefore, we think that we couldn’t solve the acidtexturing problem and cutting marks of diamond cutting silicon wafers only bysimply adjusting the recipes.We tried alkaline pretreatment, surface mask layer and vapor etching threemethods to form surface texture of diamond cutting multicrystalline silicon wafers.The alkaline pretreatment can completely eliminate the cutting patterns, but texturing effect needs to be improved. Surface mask layer could improve the appearance ofsurface texturization of diamond cutting wafers and decrease the reflectivity of thewafers. Vapor etching method can completely eliminate the cutting marks on thesilicon wafer, and along with a fine texturization which reflectance is down to12%.