Patent attributes
A laser processing apparatus for processing a wafer along projected dicing lines with a laser beam has a laser oscillator, a polygon mirror having a plurality of reflecting surfaces and rotatable about a central axis thereof, and an fθ lens for focusing the beam reflected by the reflecting surfaces of the polygon mirror and applying the focused beam to the wafer. The reflecting surfaces of the polygon mirror include a zero-gradient reflecting surface lying at a zero gradient parallel to the central axis, a positive-gradient reflecting surface that is inclined at a positive gradient from the zero gradient, and a negative-gradient reflecting surface that is inclined at a negative gradient from the zero gradient. The polygon mirror swings the laser beam in a direction perpendicular to a processing feed direction within the width of each of the projected dicing lines and in the processing feed direction.
