Laser processing method, semiconductor device manufacturing method, and examination device
An inspecting device includes a stage configured to support a wafer in which a plurality of rows of modified regions are formed in a semiconductor substrate, a light source configured to output, an objective lens configured to pass light propagated through the semiconductor substrate, a light detection part configured to detect light passing through the objective lens, and an inspection part configured to inspect a tip position of a fracture in an inspection region between a back surface and the modified region closest to the back surface of the semiconductor substrate. The objective lens aligns a focus from the back surface side in an inspection region. The light detection part detects light propagating from the front surface side of the semiconductor substrate to the back surface side.
1. A laser processing method comprising:
a first step of preparing a wafer including a semiconductor substrate having a front surface and a back surface and a functional element layer formed on the front surface, and forming a plurality of rows of modified regions in the semiconductor substrate along each of a plurality of lines by irradiating the wafer with laser light from the back surface side along each of the plurality of lines;
a second step of inspecting a tip position of a fracture in an inspection region with inspection light, the tip position of the fracture being in the thickness direction of the semiconductor substrate, the tip position being within the semiconductor substrate between the back surface and the modified region closest to the back surface among the plurality of rows of modified regions, the fracture extending to the back surface side from the modified region closest to the back surface, in the second step, by passing the inspection light through an objective lens having a numerical aperture of 0.45 or more, to inspect the tip position of the fracture having a width smaller than a wavelength of the inspection light; and
a step of notifying an operator of a result of the inspecting the tip position, wherein
in the first step, the wafer is irradiated with the laser light from the back surface side along each of the plurality of lines under a condition that a fracture extending through the plurality of rows of modified regions is formed, and
in the second step, the tip position is inspected by aligning a focus of the objective lens from the back surface side in the inspection region and detecting, through the objective lens, the inspection light propagating in the semiconductor substrate from the front surface side to the back surface side.
2. The laser processing method according to claim 1 , wherein
in the first step, the wafer is irradiated with the laser light from the back surface side along each of the plurality of lines under a condition that the fracture extending through the plurality of rows of modified regions reaches the front surface.
3. The laser processing method according to claim 2 , further comprising:
a third step of evaluating a processing result in the first step based on an inspection result in the second step, wherein
in the third step,
it is evaluated that the fracture extending through the plurality of rows of modified regions reaches the front surface, in a case where the tip position is located on the back surface side with respect to a reference position between the back surface and the modified region closest to the back surface, and
it is evaluated that the fracture extending through the plurality of rows of modified regions does not reach the front surface, in a case where the tip position is located on the front surface side with respect to the reference position.
4. The laser processing method according to claim 3 , wherein
the inspection region is a region extending from the reference position to the back surface side and not reaching the back surface, and
in the third step, it is evaluated that the fracture extending through the plurality of rows of modified regions reaches the front surface, in a case where the tip position is located in the inspection region, and it is evaluated that fracture extending through the plurality of rows of modified regions does not reach the front surface, in a case where the tip position is not located in the inspection region.
5. The laser processing method according to claim 1 , wherein
the plurality of rows of modified regions are two rows of modified regions.
6. A method for manufacturing a semiconductor device, the method comprising:
a first step of preparing a wafer including a semiconductor substrate having a front surface and a back surface and a functional element layer formed on the front surface, and forming a plurality of rows of modified regions in the semiconductor substrate along each of a plurality of lines by irradiating the wafer with laser light from the back surface side along each of the plurality of lines;
a second step of inspecting a tip position of a fracture in an inspection region with inspection light, the tip position of the fracture being in the thickness direction of the semiconductor substrate, the tip position being within the semiconductor substrate between the back surface and the modified region closest to the back surface among the plurality of rows of modified regions, the fracture extending to the back surface side from the modified region closest to the back surface, in the second step, by passing the inspection light through an objective lens having a numerical aperture of 0.45 or more, to inspect the tip position of the fracture having a width smaller than a wavelength of the inspection light; and
a step of notifying an operator of a result of the inspecting the tip position,
wherein in the first step, the wafer is irradiated with the laser light from the back surface side along each of the plurality of lines under a condition that a fracture extending through the plurality of rows of modified regions is formed,
wherein in the second step, the tip position is inspected by aligning a focus of the objective lens from the back surface side in the inspection region and detecting, through the objective lens, the inspection light propagating in the semiconductor substrate from the front surface side to the back surface side, and
wherein in the first step, the wafer is irradiated with the laser light from the back surface side along each of the plurality of lines under a condition that the fracture extending through the plurality of rows of modified regions reaches the front surface;
a third step of evaluating a processing result in the first step based on an inspection result in the second step, wherein
in the third step, it is evaluated that the fracture extending through the plurality of rows of modified regions reaches the front surface, in a case where the tip position is located on the back surface side with respect to a reference position between the back surface and the modified region closest to the back surface, and it is evaluated that the fracture extending through the plurality of rows of modified regions does not reach the front surface, in a case where the tip position is located on the front surface side with respect to the reference position; and
a fourth step of, in a case where it is evaluated that the fracture extending through the plurality of rows of modified regions reaches the front surface in the third step, exposing the fracture extending through the plurality of rows of modified regions to the back surface by grinding the back surface, and cutting the wafer into a plurality of semiconductor devices along each of the plurality of lines.
7. The method for manufacturing a semiconductor device according to claim 6 , wherein
in the fourth step, the back surface is ground up to at least the reference position.
8. An inspecting device comprising:
a stage configured to support a wafer including a semiconductor substrate having a front surface and a back surface and a functional element layer formed on the front surface, the wafer in which a plurality of rows of modified regions are formed in the semiconductor substrate along each of a plurality of lines;
a light source configured to output inspection light having transparency to the semiconductor substrate;
an objective lens configured to pass the inspection light output from the light source and propagated through the semiconductor substrate;
a light detection part configured to detect the inspection light passing through the objective lens; and
an inspection part configured to inspect a tip position of a fracture having a width smaller than a wavelength of the inspection light in an inspection region, the tip position of the fracture being in the thickness direction of the semiconductor substrate, the tip position being within the semiconductor substrate between the back surface and the modified region closest to the back surface among the plurality of rows of modified regions, based on a signal output from the light detection part, the fracture extending to the back surface side from the modified region closest to the back surface side; and
a notification unit configured to notify an operator of a result of the inspecting the tip position, wherein
the objective lens has a numerical aperture of 0.45 or more, and aligns a focus of the objective lens light from the back surface side in the inspection region, and
the detection part detects, through the objective lens, the inspection light propagating in the semiconductor substrate from the front surface side to the back surface side.
9. The inspecting device according to claim 8 , wherein
the objective lens includes a correction ring.