Laser irradiation method, method for manufacturing a semiconductor device, and a semiconductor device
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorKoichiro Tanaka
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Abstract
The present invention discloses the semiconductor device having the substrate that reflects the laser beam on a surface; that absorbs the laser beam therein; or that partially reflects the laser beam on the surface and partially absorbs the laser beam in the laser annealing. Moreover, the substrate has a poly-crystalline semiconductor film having a large grain size. The present invention suppresses the effect due to the reflected light from a rear surface of the substrate and therefore the uniform laser annealing can be performed.
Claims29
A semiconductor device comprising:
- a crystalline semiconductor film over a surface of a substrate,
- wherein an absorption coefficient α of the substrate to the light satisfies an inequality of α≧ln 10/2d where d is a thickness of the substrate, where the light is capable of being absorbed by the crystalline semiconductor film and partially transmitting through the crystalline semiconductor film to reach the surface of the substrate.
A semiconductor device comprising:
- a substrate having a first surface and a second surface;
- and
- a crystalline semiconductor film over the first surface of the substrate,
- wherein a light is partially reflected on the first surface of the substrate, and
- wherein a ratio of the light reflected on the second surface of the substrate is 0.4% or less.
A semiconductor device comprising:
- a crystalline semiconductor film over a surface of a substrate,
- wherein an absorption coefficient α of the substrate to the light satisfies an inequality of α≧ln 10/2d where d is a thickness of the substrate, where the light is capable of being absorbed by the crystalline semiconductor film and partially transmitting through the crystalline semiconductor film to reach the surface of the substrate.
A laser irradiation method comprising the steps of:
- homogenizing intensity distribution of a laser beam emitted from a laser oscillator using an optical system, and
- irradiating the laser beam vertically to a substrate with a semiconductor film over the substrate,
- wherein the substrate absorbs the laser beam, and an absorption coefficient α of the substrate to the light satisfies an inequality of α≧ln10/2d where d is a thickness of the substrate, and
- wherein the laser beam moves back and forth relative to the substrate.
A method for manufacturing a semiconductor device comprising the steps of:
- forming a semiconductor film over a substrate, and
- performing laser annealing in such a way that a laser beam emitted from a laser oscillator whose intensity distribution is homogenized by an optical system is irradiated vertically to the substrate,
- wherein the substrate absorbs the laser beam and an absorption coefficient α of the substrate to the light satisfies an inequality of α≧ln10/2d where d is a thickness of the substrate, and
- wherein the laser beam moves back and forth relative to the substrate.
Dependencies are inferred from the claim text.