US Patent 7341926 Wafer dividing method

A method of dividing a wafer having a plurality of first dividing lines and a plurality of second dividing lines perpendicular to the plurality of first dividing lines formed on the front surface, into individual chips along the plurality of first dividing lines and the plurality of second dividing lines, comprising the steps of a deteriorated layer forming step for applying a laser beam capable of passing through the wafer along the first and second dividing lines to form a deteriorated layer in the inside of the wafer; an expansion sheet affixing step for putting the wafer on the surface of an expandable expansion sheet having an adhesive which is cured by applying an external stimulus on the surface; a first sheet expanding step for dividing the wafer into a plurality of belt-like pieces along the first dividing lines by expanding the expansion sheet in direction perpendicular to the first dividing lines and forming a space between adjacent belt-like pieces; an adhesive curing step for curing the adhesive by applying an external stimulus to the adhesive laid on the expansion sheet; and a second sheet expanding step for dividing the wafer which has been divided into the plurality of belt-like pieces along the second dividing lines, by expanding the expansion sheet in direction perpendicular to the second dividing lines.