US Patent 8247311 Laser processing method

A laser processing method for preventing particles from occurring from cut sections of chips obtained by cutting a silicon wafer is provided. An irradiation condition of laser light L for forming modified regions 77 to 712 is made different from an irradiation condition of laser light L for forming the modified regions 713 to 719 such as to correct the spherical aberration of laser light L in areas where the depth from the front face 3 of a silicon wafer 11 is 335 μm to 525 μm. Therefore, even when the silicon wafer 11 and a functional device layer 16 are cut into semiconductor chips from modified regions 71 to 719 acting as a cutting start point, twist hackles do not appear remarkably in the areas where the depth is 335 μm to 525 μm, whereby particles are hard to occur.