Laser Annealing Beam Instability Reduction via Thermal Feedback
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Solution Overview
Problem
Laser annealing processes face beam instability issues due to time-varying changes in the intensity profile of the line image, leading to non-uniform annealing results in semiconductor wafer processing.
Innovation Solution
A method and system that utilize a beam-redirecting element, a thermal emission detector, and a controller to detect and adjust the laser beam's path to eliminate or reduce the time-varying slope in the line-image intensity profile, ensuring consistent annealing by redirecting the conditioned laser beam based on real-time thermal emission data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a line-shaped intensity profile is scanned over the wafer to perform laser annealing, then the annealing process can be applied to select regions of the semiconductor wafer, but the intensity profile undergoes time-varying changes that manifest as beam wobble and reduce uniformity
Solution Approach 1:
The patent employs a feedback control system where a detector monitors the actual intensity profile of the laser beam in real-time, and a controller adjusts the beam shaping element (such as a spatial light modulator or deformable mirror) to compensate for detected deviations. This closed-loop feedback mechanism actively stabilizes the beam profile against time-varying changes, reducing beam wobble and maintaining uniformity during the scanning annealing process.
2Area of stationary object
If the line image is moved or the wafer is moved during scanning, then the laser annealing can be applied across different regions, but spatial variation in intensity along the scan direction is averaged out while cross-scan direction variation must be tightly controlled
Solution Approach 1:
The patent segments the laser beam into multiple independent controllable elements using a beam shaping device such as a spatial light modulator or an array of microlenses. Each segment can be individually adjusted to compensate for intensity variations. By controlling the shape and intensity distribution of each segment independently, the system maintains tight intensity uniformity control in the cross-scan direction while covering the required scan path area.
3Shape
If an aperture is used to define the line image length, then the beam profile can be controlled, but the intensity profile in the long direction undergoes time-varying changes with slope variations
Solution Approach 1:
The patent replaces static aperture-based beam shaping with a dynamic beam shaping element such as a spatial light modulator or deformable mirror that can actively adjust its configuration in real-time. This dynamic element allows the system to adapt the beam profile shape and compensate for time-varying changes, maintaining consistent intensity distribution and reducing slope variations in the long direction of the line image throughout the annealing process.
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
The solution effectively stabilizes the beam profile, improving the uniformity of the annealing temperature distribution, reducing variations from 2.75% to 1.56%, thereby enhancing the consistency and quality of semiconductor processing.
Implementation Method 1
forming a line image on the surface of the semiconductor wafer by imaging the aperture onto the surface, thereby locally heating the surface
Implementation Method 2
detecting a thermal emission from the locally heated wafer surface
Data Source
AI summary
Systems and methods for reducing beam instability in laser annealing are disclosed. The method includes: directing a conditioned laser beam through an opening in an aperture using a beam-redirecting element; forming a line image on the surface of the semiconductor wafer by imaging the aperture onto the surface, thereby locally heating the surface to form an annealing temperature distribution; detecting a thermal emission from the locally heated wafer surface; determining the annealing temperature distribution from the detected thermal emission; determining from the annealing temperature distribution a line-image intensity profile that includes a time-varying amount of slope; and adjusting the beam-redirecting element to redirect the laser beam to reduce or eliminate the time-varying amount of slope in the line-image intensity profile.