2013 年 79 巻 805 号 p. 3285-3289
Sapphire wafer with pre-groove is cleaved by the irradiation of continuous CO2 laser. The width of groove is 5 μm and the depth is 15 μm. The groove is made by the irradiation of third harmonic wave of Nd:YAG laser whose wavelength is 322 μm. The pre-groove plays the initial crack which is conventionally introduced by pressing the diamond indenter in laser cleaving. The crack is induced from the pre-groove by the irradiation of laser beam and propagates along the pre-groove and as a result the wafer is divided. The surface roughness of the cleaved surface is very smooth and the surface roughness is smaller than 0.1 μm. Using the pre-groove makes possible to propagate the crack cross the cleaved surface of the wafer.