Patent ID: 7549560

Claim:
A method of dividing a wafer having function elements formed in areas sectioned by a plurality of first dividing lines formed parallel to one another and a plurality of second dividing lines that intersect with the first dividing lines and are formed parallel to one another, on the front surface thereof, along the first dividing lines and the second dividing lines, comprising: an internal deteriorated layer forming step for forming internal deteriorated layers in the inside of the wafer along the first dividing lines and the second dividing lines by applying a pulse laser beam capable of passing through the wafer along the first dividing lines and the second dividing lines; an intersection deteriorated layer forming step for forming intersection deteriorated layers that are thicker than the internal deteriorated layers by applying a pulse laser beam capable of passing through the wafer to intersection areas formed between the first dividing lines and the second dividing lines, wherein the intersectional deteriorated layers are formed inside the wafer, between the front and back surfaces thereof, wherein the intersection deteriorated layers are formed above and below the internal deteriorated layers to thereby form a cross shape therewith, a dividing step for dividing the wafer into individual chips along the first dividing lines and the second dividing lines by exerting external force along the first dividing lines and the second dividing lines of the wafer having the internal and intersectional deteriorated layers, wherein the total thickness of the intersection deteriorated layers is set to 60% or more of the thickness of the wafer, and wherein the length of the intersection deteriorated layers is set to 10 to 30% of the interval of the first dividing lines and the interval of the second dividing lines.