Wafer processing method

A wafer processing method for dividing a wafer of glass substrate into individual chips along a plurality of division lines formed intersecting one another, comprising:

• a first step of forming a plurality of shield tunnels by irradiating the water with a first pulsed laser beam of a first wavelength, which transmits through the wafer, with its focal point positioned inside the wafer at a region corresponding to each division line so that the plurality of shield tunnels, which are each formed of perforations and affected regions surrounding the perforations, are formed along the division lines, respectively,
• a second step of forming a plurality of modified layers, subsequent to the first step of forming the shield tunnels, by irradiating the wafer with a second pulsed laser beam of a second wavelength, which transmits through the wafer, with its focal point positioned inside the wafer at the region corresponding to each division line so that modified layers are formed in addition to the shield tunnels along the division lines, respectively, and
• a dividing step of applying an external force to the wafer to divide the wafer into individual chips.