Microlens Array Homogenizer for Laser Energy Uniformity
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Solution Overview
Problem
Current laser thermal processing of semiconductor substrates faces challenges in achieving uniform energy distribution and adapting the shape of the laser energy field to match the desired processing geometry, particularly as semiconductor devices continue to miniaturize.
Innovation Solution
The use of a spatial homogenizer, such as a microlens array, followed by a refractive medium with varying thicknesses, to uniformize the laser energy and adjust its shape, ensuring a consistent energy field is applied to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high power laser is used for thermal processing, then processing effectiveness is improved, but energy distribution uniformity deteriorates
Solution Approach 1:
The laser beam is divided into multiple sub-beams by a microlens array, creating a segmented energy distribution pattern. Each microlens focuses a portion of the incident laser energy to a focal point, and the overlapping focal points create a uniform composite energy distribution on the substrate, resolving the non-uniformity issue while maintaining high power processing capability
Solution Approach 2:
The patent changes the optical parameters of the laser system by introducing a microlens array with specific focal lengths and a refractive medium with varying thickness. These parameter changes transform the original non-uniform laser energy distribution into a uniform distribution pattern, enabling high power processing with improved uniformity
2Device complexity
If conventional laser optics are used, then device complexity is minimized, but energy field shape adaptability deteriorates
Solution Approach 1:
The microlens array serves multiple functions simultaneously: it acts as a beam splitter, a focal point generator, and a uniformization element. The refractive medium with varying thickness provides both shape adaptation and additional uniformization. This multi-functional design achieves shape adaptability without proportionally increasing device complexity
Solution Approach 2:
The microlens array and refractive medium act as intermediary optical elements between the laser source and the substrate. These intermediaries transform the laser beam characteristics (shape and uniformity) without requiring direct modification of the laser source or complex positioning systems, simplifying the overall device architecture
3Productivity
If laser beam is used directly without homogenization, then processing speed is maintained, but processing uniformity deteriorates
Solution Approach 1:
The microlens array and refractive medium perform preliminary uniformization of the laser energy distribution before the energy reaches the substrate. This preliminary action ensures that the high power laser energy is already uniformly distributed when it contacts the substrate, achieving both high processing speed and uniform processing results without requiring post-processing adjustments
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 results in a highly uniform energy density distribution across the substrate, enhancing the uniformity of processing and aligning with the desired geometric shape, thereby improving the precision and effectiveness of thermal processing.
Implementation Method 1
A laser pulse or beam is directed to a spatial homogenizer, which may be a plurality of lenses arranged along a plane perpendicular to the optical path of the laser energy, an example being a microlens array.
Implementation Method 2
The spatially uniformized energy produced by the spatial homogenizer is then directed to a refractive medium that has a plurality of thicknesses.
Data Source
AI summary
Embodiments described herein provide apparatus and methods for processing semiconductor substrates with uniform laser energy. A laser pulse or beam is directed to a spatial homogenizer, which may be a plurality of lenses arranged along a plane perpendicular to the optical path of the laser energy, an example being a microlens array. The spatially uniformized energy produced by the spatial homogenizer is then directed to a refractive medium that has a plurality of thicknesses. Each thickness of the plurality of thicknesses is different from the other thicknesses by at least the coherence length of the laser energy.