WAFER CUTTING OFF PROCESS

摘要

PURPOSE:To cut off a wafer without producing any evaporated particles at all by a method wherein the wafer surface is irradiated with laser beams focussed by an optical system such as a lens and then the wafer is scanned along a prospected cutting line in the proper mean power density and at the scanning rate to produce no surface evaporation nor removal so that the cracking may be induced and propagated by thermal stress to cut off the wafer. CONSTITUTION:The continuously oscillating YAG laser beams are focussed by a quartz glass lens. When a wafer is scanned in the (011) direction and the (011) direction (a direction making 45 deg. with the (011) direction), in the relation between a sliceable irradiating laser power and the scanning rate, both factors shall be on the lower side of the curves respectively displayed by solid lines preferably on the curves. That is, the wafer can be cut off without evaporating the material meeting the requirements that in the (011) direction, the laser power exceeds 40W but not exceeding 70W, while in the (011) direction, the laser power exceeds 50W but not exceeding 70W, and the scanning rate not exceeding 8mm/s. At this time, cutting crack is generated at the position slightly deviated out of the central position of the laser spot but in the deviated amount not exceeding 0.2mm in the (011) direction also not exceeding 0.3mm in the (011) direction. Accordingly, the optimum requirements of the irradiation laser power exceeding 40W but not exceeding 70W as well as the laser scanning rate not exceeding 15mm/s can be selected.