Patent ID: 7232741

Claim:
A method of dividing a wafer along predetermined dividing lines, comprising the steps of: a deteriorated layer forming step for applying a pulse laser beam capable of passing through the wafer along the dividing lines to form deteriorated layers in the inside of the wafer along the dividing lines; an extensible protective tape affixing step for affixing an extensible protective tape to one side of the wafer before or after the deteriorated layer forming step; and a dividing step for dividing the wafer along the deteriorated layers by expanding the protective tape affixed to the wafer after the deteriorated layer forming step, wherein processing conditions are set to satisfy 1.0≦V/(Y×D)≦2.5 in which Y is a repetition frequency (Hz) of the pulse laser beam, D is a focusing spot diameter (mm) of the pulse laser beam, and V is a processing-feed speed which is a relative moving speed of the wafer and the pulse laser beam (mm/sec) in the deteriorated layer forming step.