Patent Number: 
Section: claims

1. A laser crystallization apparatus comprising an crystallization optical system which irradiates laser light to a thin film disposed on a substrate to form an image of the laser light thereon through an imaging optical system to melt and crystallize an irradiated region of the thin film, the apparatus comprising:a measurement light source which is disposed outside a light path of the laser light, and which emits imaging position measurement light to illuminate the irradiated region of the thin film;an imaging position measurement light illumination optical system which illuminates the imaging position measurement light on the irradiated region of the thin film through the imaging optical system to form an image of the imaging position measurement light on the thin film to detect a surface level thereof;a detecting unit which determines an imaging position shift between the surface level of the irradiated region of the thin film and an imaging plane of the imaging optical system based on the formed image of the imaging position measurement light on the irradiated region of the thin film;an imaging position correcting unit which corrects the surface level of the irradiated position of the thin film to a level with the imaging position shift being within a desired range, if the imaging position shift is out of predetermined range; anda control unit which controls an emission of the laser light from a laser light source, if the imaging position shift is within the predetermined range. 2. A laser crystallization apparatus comprising a crystallization optical system which comprises a laser light source which emits laser light; a phase modulating element which is disposed on a light path of the laser light and modulates the laser light to have a light intensity distribution of an inverse peak pattern to form crystallization laser light; and an imaging optical system which irradiates the crystallization laser light to a thin film disposed on a substrate to be crystallized to melt and crystallize an irradiated region of the thin film, the apparatus comprising:a measurement light source which is disposed outside a light path of the crystallization laser light, and which emits imaging position measurement light to illuminate the irradiated region of the thin film to form an image of the imaging position measurement light thereon;an imaging position measurement light illumination optical system which illuminates the imaging position measurement light on the irradiated region of the thin film through the imaging optical system to form an image of the imaging position measurement light on the thin film to detect a surface level thereof;a detecting unit which determines an imaging position shift between the surface level of the irradiated region of the thin film and an imaging plane of the imaging optical system based on the formed image of the imaging position measurement light on the irradiated region of the thin film;an imaging position correcting unit which corrects the surface level of the irradiated position of the thin film to a level with the imaging position shift being within a desired range, if the imaging position shift is out of predetermined range; anda control unit which controls an emission of the laser light from a laser light source, if the imaging position shift is within the predetermined range. 3. The laser crystallization apparatus according to claim 2, wherein the imaging position shift is detected based on light intensity of reflected imaging position measurement light, or distortion, defocusing, or enlargement of the image of the imaging position measurement light. 4. The laser crystallization apparatus according to claim 2, wherein the imaging position shift is determined by detecting a reflected image of the imaging position measurement light through a pinhole, the reflected image being from the image formed on the irradiated region of the thin film. 5. The laser crystallization apparatus according to claim 2, wherein the crystallization laser light is ultraviolet excimer laser light, wherein the imaging optical system is an optical system designed for the excimer laser light, and wherein the imaging position measurement light is visible laser light and enters to the imaging optical system through a visible light correction optical system to correct aberration of the visible light by the imaging optical system. 6. The laser crystallization apparatus according to claim 2, wherein an imaging position correcting unit corrects a surface level of the irradiated region of the thin film by moving a substrate holding stage mounting the substrate in a height direction.