Method of processing wafer and processing apparatus for wafer

A method of processing a wafer including a plurality of devices formed in respective areas on a face side thereof that are demarcated by a plurality of projected dicing lines extending in a first direction and a plurality of projected dicing lines extending in a second direction across the projected dicing lines extending in the first direction, to divide the wafer into individual device chips, comprising:

• a first modified layer forming step of applying a laser beam having a wavelength transmittable through the wafer to the wafer while positioning a focused spot of the laser beam inside the wafer along the projected dicing lines extending in the first direction, thereby forming first modified layers in the wafer along the projected dicing lines extending in the first direction;
• and
• a second modified layer forming step of, after the first modified layer forming step is performed, applying a laser beam having a wavelength transmittable through the wafer to the wafer while positioning a focused spot of the laser beam inside the wafer along the projected dicing lines extending in the second direction intersecting with the first direction, thereby forming second modified layers in the wafer along the projected dicing lines extending in the second direction,
• wherein, in the second modified layer forming step, when the focused spot of the laser beam applied to the wafer along the projected dicing lines extending in the second direction reaches the first modified layers, the focused spot of the laser beam is shifted along the first modified layers to thereby undulate the laser beam in a staggered pattern to prevent the second modified layers from being formed straight in the wafer along the projected dicing lines extending in the second direction.