Laser processing method and chip
An object to be processed can be cut highly accurately along a line to cut. An object to be processed 1 is irradiated with laser light while locating a converging point within a silicon wafer 11 , and the converging point is relatively moved along a line to cut 5 , so as to form modified regions M 1 , M 2 positioned within the object 1 along the line to cut 5 , and then a modified region M 3 positioned between the modified regions M 1 , M 2 within the object 1.
1. A chip having a side face substantially parallel to a thickness direction;
wherein the side face is formed with:
first and second modified regions arranged in a row in the thickness direction;
a third modified region, positioned between the first and second modified regions, having a length in the thickness direction shorter than that of the first and second modified regions; and
a plurality of Wallner lines bridging successively at least the first and second modified regions and extending obliquely with respect to the thickness direction,
wherein at least one of said Wallner lines is configured so as to extend in a direction that crosses an advancing direction of fractures bridging the first and second modified regions by forming the third modified region, and
wherein the third modified region is formed after forming the first and second modified regions.
2. The chip according to claim 1 , wherein the chip is formed using a laser processing method of irradiating a planar object to be processed, wherein the planar object comprises a unilateral surface and an opposing lateral surface to the unilateral surface with laser light while locating a converging point within the object, so as to form a modified region to become a cutting start point within the object along a line to cut in the object, the method comprising the steps of:
the laser light is incident from the unilateral surface, forming first and second modified regions, arranged in a row in a thickness direction of the object, along the line to cut; and
irradiating the laser light from the unilateral surface to pass though either the first or second modified regions after the procedure of forming the first and second modified regions, forming a third modified region, positioned between the first and second modified regions, along the line to cut.
3. The chip according to claim 2 , wherein, in the step of forming the first and second modified regions of the laser processing method used to form the chip,
the first modified region is formed along the line to cut where the laser light is incident from the unilateral surface, and
the second modified region positioned between the first modified region and the unilateral surface where the laser light is incident from the unilateral surface along the line to cut after forming the first modified region.
4. The chip according to claim 2 , wherein, in the step of forming the first and second modified regions of the laser processing method used to form the chip,
the laser light is incident from the unilateral surface, forming first modified region along the line to cut,
the second modified region positioned between the first modified region and the unilateral surface where the laser light is incident from the unilateral surface along the line to cut after forming the first modified region.
5. The chip according to claim 3 , wherein the laser processing method used to form the chip comprises the step of forming a fourth modified region positioned between the second and third modified regions along the line to cut after forming the third modified region.
6. The chip according to claim 4 , wherein the laser processing method used to form the chip comprises further comprising the step of forming a fourth modified region positioned between the second and third modified regions along the line to cut after forming the third modified region.
7. The chip according to claim 3 , wherein the object comprises a semiconductor substrate, and wherein the modified region includes a molten processed region.
8. The chip according to claim 4 , wherein the object comprises a semiconductor substrate, and wherein the modified region includes a molten processed region.
9. The chip according to claim 5 , wherein the object comprises a semiconductor substrate, and wherein the modified region includes a molten processed region.
10. The chip according to claim 6 , wherein the object comprises a semiconductor substrate, and wherein the modified region includes a molten processed region.
11. The chip according to claim 3 , wherein the laser processing method used to form the chip comprises the step of cutting the object along the line to cut from the modified region acting as a cutting start point.
12. The chip according to claim 4 , wherein the laser processing method used to form the chip comprises the step of cutting the object along the line to cut from the modified region acting as a cutting start point.
13. The chip according to claim 2 , wherein, in the step of forming the third modified region of the laser processing method used to form the chip, a fracture bridging at least the first and second modified regions is generated.
14. The chip according to claim 13 , wherein, in the laser processing method used to form the chip, the third modified region is formed along substantially the whole line to cut.
15. The chip according to claim 13 , wherein, in the laser processing method used to form the chip, the third modified region is formed along one end part or the line to cut.
16. The chip according to claim 13 , wherein, in the laser processing method used to form the chip, the third modified region is formed such as to be biased toward one of the first and second modified regions closer to a laser entrance surface where the laser light is incident in the object.
17. The chip according to claim 13 , wherein the object comprises a semiconductor substrate, and wherein the modified region includes a molten processed region.