Laser irradiation apparatus with polarizing plate

1. A laser irradiation apparatus comprising:

a laser generation apparatus configured to generate first laser light for performing heat treatment of an object to be processed;

a measurement-laser emission unit configured to emit linearly-polarized second laser light toward an irradiation area on the object to be processed to which the first laser light is applied;

a first polarizing plate configured to let, of the whole reflected light of the linearly-polarized second laser light reflected by the object to be processed, a part of the reflected light that has a first polarization direction pass therethrough; and

a measurement-laser detection unit configured to detect the reflected light that has passed through the first polarizing plate, wherein

the first polarizing plate is positioned so that the first polarization direction is inclined with respect to an incident plane by about 45 degrees, the incident plane being a plane surface including an incident direction of the linearly-polarized second laser light onto the object to be processed and a reflecting direction of the linearly-polarized second laser light by the object to be processed, and

the measurement-laser emission unit is configured to emit the linearly-polarized second laser light in a second polarization direction corresponding to the first polarization direction.

2. The laser irradiation apparatus according to claim 1 , wherein the measurement-laser emission unit comprises:

a measurement-laser generation unit configured to generate randomly-polarized reference laser light; and

a second polarizing plate configured to let, of the randomly-polarized reference laser light generated by the measurement-laser generation unit, a part of the reference laser light having a second polarization direction corresponding to the first polarization direction pass therethrough as the linearly-polarized second laser light.

3. The laser irradiation apparatus according to claim 2 , wherein the second polarizing plate is configured to be rotatable.

4. The laser irradiation apparatus according to claim 1 , wherein the second polarization direction is inclined with respect to the incident plane by a predetermined angle.

5. The laser irradiation apparatus according to claim 4 , wherein the second polarization direction and the first polarization direction are symmetric with respect to the incident plane.

6. The laser irradiation apparatus according to claim 1 , wherein the object to be processed is a substrate having a bottom-gate structure in which a metal electrode and an amorphous film are laminated.

7. The laser irradiation apparatus according to claim 1 , wherein

the object to be processed is a substrate in which an amorphous semiconductor film is formed, and

the amorphous semiconductor film is transformed into a polycrystalline semiconductor film by irradiating it with the first laser light.