To provide a method for laser beam machining, by which the flatness of a cut face is improved when cutting a workpiece while making a modified area the starting point of cutting.
In the method for laser beam machining, a laser beam L has, at a focusing point P, a cross-sectional shape, in which the maximum length in a direction perpendicular to a predetermined cut line 5 is shorter than the maximum length in a direction parallel to the predetermined cut line 5. Thereby, a modified area 7 formed in a silicon wafer 11 has such a shape that the maximum length in a direction perpendicular to the predetermined cut line 5 is shorter than the maximum length in a direction parallel to the predetermined cut line 5, when seen in the incident direction of the laser beam L. By forming a modified area 7 having such a shape in a workpiece 1, appearance of twists and hackles on the cut face is suppressed when cutting the workpiece 1 while making the modified area 7 the starting point of cutting, so that the flatness of the cut face is improved.
SUGIURA RYUJI
ATSUMI KAZUHIRO
Shiro Terasaki
Satoru Ishida
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