Laser working method, laser working apparatus, and its manufacturing method

A laser working method for irradiating a plate-shaped object to be processed with a laser light while locating a converging point within the object, to form modified regions in a plurality of lines serving as starting points for cutting along a line to cut the object so as to line up in the thickness direction of the object, wherein,

• a reflection spatial light modulator, which modulates the laser light, a converging optical system, which converges the laser light modulated by the reflection spatial light modulator inside the object, and an adjustment optical system, which has a first optical element and a second optical element functioning as lenses and located on the optical path between the reflection spatial light modulator and the converging optical system are prepared
• the first optical element and the second optical element are disposed such that a distance between the reflection spatial light modulator and the first optical element becomes a first focal distance of the first optical element, a distance between the converging optical system and the second optical element becomes a second focal distance of the second optical element, a distance between the first optical element and the second optical element becomes a sum of the first focal distance and the second focal distance, and the first optical element and the second optical element becomes a double telecentric optical system
• at the time of forming the modified regions in one line or a plurality of lines including a modified region farthest from a laser light entrance surface of the object among the modified regions in a plurality of lines, a distance between a converging optical system and the object is changed such that a distance between the converging optical system that converges the laser light inside the object and the object becomes a predetermined distance in accordance with the modified region to be formed, and the laser light is modulated by a reflection spatial light modulator such that aberration of the laser light occurs at a position on which a converging point of the laser light is located inside the object becomes a predetermined aberration or less.

A laser working apparatus that irradiates a plate-shaped object to be processed with a laser light while locating a converging point within the object, so as to form a modified region serving as a starting point for cutting along a line to cut the object, the laser working apparatus comprising:

• a supporting base supporting the object;
• a laser light source emitting the laser light;
• a reflection spatial light modulator modulating the laser light emitted from the laser light source;
• a converging optical system converging the laser light modulated by the reflection spatial light modulator, inside the object supported by the supporting base;
• an adjustment optical system, which has a first optical element and a second optical element functioning as lenses and located on the optical path between the reflection spatial light modulator and the converging optical system are prepared;
• and
• a controller that, at the time of forming the modified region, controls at least one of the supporting base and the converging optical system such that a converging point of the laser light is located at a predetermined distance from a laser light entrance surface of the object and the converging point of the laser light is relatively moved along the line, and controls the reflection spatial light modulator for modulating the laser light such that aberration of the laser light occurs at a position on which a converging point of the laser light is located inside the object becomes a predetermined aberration or less, wherein
• the first optical element and the second optical element are disposed such that a distance between the reflection spatial light modulator and the first optical element becomes a first focal distance of the first optical element, a distance between the converging optical system and the second optical element becomes a second focal distance of the second optical element, a distance between the first optical element and the second optical element becomes a sum of the first focal distance and the second focal distance, and the first optical element and the second optical element becomes a double telecentric optical system.