Laser Beam Micro-Smoothing for Annealing Inhomogeneity
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Solution Overview
Problem
Conventional laser annealing systems fail to completely eliminate small-scale inhomogeneities in laser beams, resulting in stripes on substrates during processing, as prior art homogenization techniques are inadequate for this purpose.
Innovation Solution
The laser beam is shifted perpendicular to the scanning direction between individual pulses, using micro-smoothing mirrors or rotating wedges to average out inhomogeneities without altering the beam profile in the scanning direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional beam homogenization techniques (diffusers, light tunnels, lenses, DOE, holographs) are used, then the homogeneity of the laser beam is improved, but small-scale inhomogeneities cannot be completely removed, resulting in stripes on the substrate
Solution Approach 1:
The patent introduces dynamic movement of the laser beam perpendicular to the scanning direction during pulse delivery. A rotating wedge or oscillating mirror shifts the beam position between pulses, creating a dynamic averaging effect that eliminates small-scale inhomogeneities and prevents stripe formation on the substrate.
Solution Approach 2:
The patent adds movement in a new dimension (perpendicular to the scanning direction) to address inhomogeneities. By shifting the beam in the y-direction between pulses while scanning in the x-direction, the system averages out inhomogeneities across an additional spatial dimension, effectively eliminating stripes.
2Manufacturing precision
If rotating wedges are used to move the laser beam in circular motion, then small-scale inhomogeneities are averaged out, but the system becomes unsuitable for laser annealing applications
Solution Approach 1:
The patent applies local quality by making the beam shifting action selective and localized. The rotating wedge or oscillating mirror is positioned to affect only the beam path, allowing precise control of beam position in the y-direction while maintaining the overall laser annealing process integrity. This localized approach preserves suitability for annealing while achieving inhomogeneity averaging.
Solution Approach 2:
The patent changes the operational parameters of the beam delivery system by introducing controlled positional variations perpendicular to the scanning direction. By adjusting the wedge rotation speed, oscillation amplitude, or mirror frequency to match the pulse repetition rate, the system achieves optimal averaging effect while maintaining compatibility with laser annealing requirements.
3Manufacturing precision
If the laser beam is shifted perpendicular to the scanning direction between pulses, then small-scale inhomogeneities are smoothed out, but additional optical components (micro-smoothing mirrors, rotating wedges) are required
Solution Approach 1:
The patent achieves multi-functionality by using the rotating wedge or oscillating mirror to simultaneously perform beam shifting for inhomogeneity averaging and maintaining proper beam positioning on the substrate. This single component addresses both the homogeneity problem and the scanning requirement, reducing the need for separate dedicated smoothing optics.
Solution Approach 2:
The rotating wedge or oscillating mirror acts as an intermediary element between the laser source and the substrate. It mediates the beam path by introducing controlled positional variations that average out inhomogeneities, while allowing the beam to still reach and process the substrate effectively, thus adding minimal complexity to the overall system.
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 method effectively smooths out small-scale inhomogeneities, preventing the formation of stripes on substrates and improving the homogeneity of the laser beam profile during the annealing process.
Implementation Method 1
Laser beam micro-smoothing comprises shifting a laser beam in the direction perpendicular to the scanning direction of the laser annealing system, while holding the laser beam substantially fixed in the scanning direction.
Implementation Method 2
laser annealing system scans a substrate in a scanning direction by applying a series of laser beam pulses to contiguous positions on a surface of the substrate
Data Source
AI summary
The present invention provides laser beam micro-smoothing for laser annealing systems. Laser beam micro-smoothing comprises shifting a laser beam in the direction perpendicular to the scanning direction (y) of a laser annealing system, while holding the laser beam fixed in the direction of scanning (x). The shifting may be accomplished, for example, with a pair of micro-smoothing mirrors. The shifting smoothes out small-scale inhomogeneities in the profile of the laser beam and prevents microscopic stripes associated with prior art laser annealing systems. Because the shifting occurs only in the direction perpendicular to the scanning direction (y), the laser annealing process in not adversely affected.