Reflective Photomask Laser Annealing for Narrow Border Edge Slopes
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Solution Overview
Problem
Conventional laser annealing methods for reflective photomasks result in an unnecessarily wide forbidden area due to a gentle slope in the edge area, potentially damaging the reflection and absorption layers with steep slopes, especially when using short pulsed lasers.
Innovation Solution
A method and apparatus utilizing a laser annealing technique that split-irradiates laser beam spots onto the border area of a reflective photomask, with each spot having a center portion and an edge portion, where the edge portion has an inclined energy profile to adjust the slope and reduce the width of the edge area, thereby minimizing layer damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a very short pulsed laser is used to create a steep slope in the edge area, then the reflectance is reduced, but the reflection layer and absorption layer are physically damaged (cracked)
Solution Approach 1:
The laser beam is divided into multiple separate beams that irradiate different regions of the border area. Each laser beam processes a specific zone (e.g., first border area, second border area) with appropriate energy levels, avoiding the need for a single high-energy beam that would cause layer damage while still achieving the desired slope profile.
Solution Approach 2:
Different regions of the border area are treated with different laser energy levels and beam configurations. The first border area receives laser irradiation with energy levels optimized for its specific requirements, while the second border area receives different energy levels suited to its characteristics, allowing precise control over slope formation without causing damage.
2Manufacturing precision
If a conventional laser annealing method is used, then the border area reflectance is reduced, but a very gentle slope occurs in the edge area causing the forbidden area to be unnecessarily widened
Solution Approach 1:
The laser processing is segmented into multiple beams with different characteristics. Some beams are configured to create steep slopes in specific regions, while others handle different zones, allowing the forbidden area to be minimized without compromising the slope profile.
Solution Approach 2:
The laser beam parameters (energy level, pulse duration, beam shape) are changed and optimized for different regions of the border area. By adjusting these parameters, the edge slope can be controlled to be sufficiently steep, thereby reducing the forbidden area width to the minimum necessary.
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 effectively reduces the width of the edge area to less than 1/20 of the border area, preventing physical damage to the layers and ensuring low reflectance in the border area without widening the forbidden region.
Implementation Method 1
irradiating a laser beam onto the border area of the reflective photomask to recess the border area
Implementation Method 2
Method of annealing reflective photomask by using laser
Data Source
AI summary
A laser annealing method performed on a reflective photomask may include preparing a reflective photomask including a pattern area and a border area surrounding the pattern area and irradiating a laser beam onto the border area of the reflective photomask. The irradiating of the laser beam may include split-irradiating a plurality of laser beam spots onto the border area. Each of the plurality of laser beam spots may be shaped using a beam shaper. The beam shaper may include a blind area, a transparent area at a center of the blind area, and a semitransparent area between the blind area and the transparent area. Each of the plurality of laser beam spots may include a center portion passing through the transparent area and having a uniform energy profile and an edge portion passing through the semitransparent area and having an inclined energy profile.