Laser Annealing Optics Using Polarization-Controlled Beam Superposition
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Solution Overview
Problem
Existing laser annealing technologies face challenges in reducing beam noise caused by laser coherency, leading to non-uniform energy delivery and potential defects during wafer annealing, especially with high-power pulsed lasers at short processing times.
Innovation Solution
The apparatus employs a combination of time and space split superimposing devices to temporally and spatially branch laser beams onto different paths, and uses a beam polarization controller to modify polarization states, reducing coherency and minimizing interference noise through fly eye lens arrays with specific materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-power pulsed lasers are used for rapid annealing, then processing speed and productivity are improved, but beam noise caused by laser coherency increases leading to non-uniform energy delivery
Solution Approach 1:
The patent divides a single high-power laser beam into multiple lower-power beams using beam splitters, then processes different regions of the wafer simultaneously. This segmentation reduces beam noise in each individual beam while maintaining high overall processing speed through parallel operation on multiple wafer regions.
Solution Approach 2:
The patent introduces spatial parallelism by directing multiple processed beams to different locations on the wafer surface simultaneously. This transforms the processing from a single-point sequential operation to a multi-point parallel operation, achieving both high productivity and uniform energy distribution.
2Power
If multiple laser beams are superimposed to increase power, then processing capability is improved, but interference patterns and beam noise increase due to coherency
Solution Approach 1:
The patent extracts the coherency property from the laser beams by introducing optical path differences and polarization variations. This allows the beams to be superimposed without generating interference patterns, achieving power addition while eliminating the harmful coherency effects.
Solution Approach 2:
The patent changes the polarization states of individual beams using wave plates and introduces optical path length variations. These parameter changes ensure that when beams are superimposed, their coherency relationships are disrupted, preventing interference while maintaining the cumulative power effect.
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 beam coherency noise, ensuring uniform energy distribution and minimizing defects in the annealing process, thereby improving the quality and efficiency of wafer annealing.
Implementation Method 1
a time division superimposing device temporally branching the plurality of laser beams, respectively, to propagate branched beams onto different optical paths, and superimposing beams emitted from the same laser, from the branched beams propagated onto different optical paths
Implementation Method 2
a space split superimposing device spatially branching superimposed beams passing through the time division superimposing device or the plurality of laser beams, respectively, to propagate beams emitted from different lasers onto the same path, to superimpose the propagated beams emitted from the different lasers
Implementation Method 3
an optical illumination system forming flat-top beams homogenizing intensities of superimposed beams passing through the space split superimposing device
Implementation Method 4
a polarization controller making polarization states of adjacent beams passing through the at least one fly eye lens array orthogonal to each other
Implementation Method 5
an optical imaging system imaging each of the homogenized beams passing through the mask onto a wafer
Implementation Method 6
The individual processes may include a thin film deposition process, a photolithography process, an etching process, an ion implantation process, and an annealing process. From all these individual processes, the annealing process may be a process of stabilizing a substrate or a thin film on the substrate or for melting the substrate to remove seaming defects in the thin film
Data Source
AI summary
A method of operating an apparatus for laser annealing, includes reducing temporal or spatial coherency of a plurality of laser beams by beam superimposing; and reducing an electric field inner product magnitude of beams having the reduced temporal or spatial coherency by a fly eye lens array to reduce coherency, and/or by modifying a polarization state between the beams by beam superimposing.