Laser Annealing Stripe Reduction via Beam Division
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Solution Overview
Problem
Laser annealing methods using linear beams often result in visible stripes on the irradiated surface due to scattered light on the lens surface, which deteriorates the uniformity of the beam and is difficult to improve with current machining accuracy limitations.
Innovation Solution
The method involves dividing the laser beam into multiple beams using long-axis or short-axis lens arrays, allowing them to overlap and reciprocate during irradiation, while adjusting the incident angle and intensity of the beam for each shot to reduce the impact of scattered light, thereby dispersing stripes effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a linear laser beam is used for annealing, then the processing efficiency is improved, but visible stripes appear on the irradiated surface due to scattered light on the lens surface
Solution Approach 1:
The patent divides the laser beam into multiple beams (e.g., 3-5 beams) using a beam dividing optical system consisting of cylindrical lenses. Each beam is then independently directed onto the substrate at different positions and angles. This segmentation of the single linear beam into multiple discrete beams eliminates the formation of continuous stripes while maintaining high processing efficiency, as each beam creates isolated irradiation patterns that do not form visible linear defects.
2Manufacturing precision
If the lens surface machining accuracy is improved, then the scattered light is reduced, but the machining cost and complexity increase due to current technology limitations
Solution Approach 1:
The patent introduces a beam dividing optical system as an intermediary component between the laser source and the substrate. This intermediate optical system, consisting of cylindrical lenses and beam splitting elements, divides the single laser beam into multiple beams before they reach the substrate. By placing this intermediary optical system, the patent reduces the demand for ultra-precise lens surface machining, as the beam division occurs upstream in the optical path. This approach lowers the machining complexity and cost while still achieving the goal of reducing scattered light and eliminating stripe formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the occurrence of irradiated stripes, achieving a high overlap ratio of 90% or more, resulting in a uniform surface that minimizes visible stripes and improves the quality of the annealed semiconductor films.
Implementation Method 1
visible stripes appear in a direction perpendicular to a long axial direction of the linear beam and in a direction parallel to the long axial direction... vertical stripes and the horizontal stripes are collectively called as 'irradiated stripes'... scattered light generated on the surface of a lens
Implementation Method 2
irradiates the amorphous silicon film, which is deposited on the glass substrate, with the linear beam; and melts and solidifies the silicon film in order to crystallize the silicon film
Implementation Method 3
melts and solidifies the silicon film in order to crystallize the silicon film
Implementation Method 4
melts and solidifies the silicon film in order to crystallize the silicon film
Data Source
AI summary
In the case of a lens array type homogenizer optical system, the incident angle and intensity of a laser beam 1 entering a large-sized lens (long-axis condenser lens 22) of a long-axis condensing optical system, which is provided on the rear side, are changed for every shot by performing laser irradiation while long-axis lens arrays 20a and 20b are reciprocated in a direction corresponding to a long axial direction of a linear beam (X-direction). Therefore, vertical stripes are significantly reduced. Further, the incident angle and intensity of a laser beam 1 entering a large-sized lens (projection lens 30) of a short-axis condensing optical system, which is provided on the rear side, are changed for every shot by performing laser irradiation while short-axis lens arrays 26a and 26b are reciprocated in a direction corresponding to a short axial direction of a linear beam (Y-direction). Therefore, horizontal stripes are significantly reduced.