| 主权项 |
1. A wafer processing method of dividing a wafer into a plurality of individual optical devices along a plurality of crossing division lines, said wafer being composed of a substrate and a light emitting layer formed on a front side of said substrate, said optical devices being respectively formed in a plurality of regions partitioned by said division lines on said light emitting layer, said wafer processing method comprising:
a modified layer forming step of applying a laser beam having a transmission wavelength to said substrate from a back side of said substrate along said division lines in a condition where a focal point of said laser beam is set inside said substrate, thereby forming said modified layer inside said substrate along each division line; and a wafer dividing step of applying an external force to said wafer to break said wafer from said modified layer as a division start point along each division line after performing said modified layer forming step, thereby dividing said wafer into said individual optical devices; said modified layer forming step including the steps of
making a polarization plane of linearly polarized light of said laser beam parallel to a direction perpendicular to each division line,shifting a beam center of said laser beam from an optical axis of a focusing lens of focusing means for focusing said laser beam, in the direction perpendicular to each division line, andshifting the focal point of said laser beam by said focusing lens in a same direction as the direction where the beam center of said laser beam has been shifted, whereby a light intensity of through light not contributing to the formation of said modified layer, but acting on said light emitting layer is adjusted so that the light intensity of said through light is high in the area of each division line and low in the area of each optical device. |
