Patent ID: 8536486

Claim:
A method of dividing a workpiece along a dividing line, the workpiece including an irregularly shaped portion at a location on the dividing line, comprising: an irregularly shaped portion detecting step of detecting the location of said irregularly shaped portion, wherein the location includes a leading edge and a trailing edge; after performing said irregularly shaped portion detecting step, performing a surface height detecting step of applying a detecting laser beam to an area of the workpiece, except for the location which was detected in said irregularly shaped portion detecting step, along the dividing line to detect a height of a surface of the workpiece except for said location, whereby the detecting laser beam is stopped in a vicinity of the leading edge of said location and the detecting laser beam is re-started in a vicinity of the trailing edge of said location of the irregularly shaped portion; a modified layer forming step of applying and focusing a machining laser beam having a wavelength which permeates the workpiece within the workpiece while moving a focused spot of the machining laser beam based on the height of the surface of the workpiece which is detected in said surface height detecting step to form a modified layer in an area of the workpiece except for at least said location of said irregularly shaped portion along the dividing line; and a dividing step of applying an external force to said modified layer to divide the workpiece along the dividing line.