Polarized Rectangular Laser Annealing for Uniform Crystal Grains
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Solution Overview
Problem
Conventional laser annealing methods for transforming amorphous semiconductor films into polycrystalline or monocrystalline films result in non-uniform crystal grain sizes, affecting the performance of thin-film transistors due to varying energy distribution and temperature gradients, leading to inconsistent performance across different directions.
Innovation Solution
The method involves generating a linearly or elliptically polarized rectangular laser beam with a controlled wavelength and polarization direction, creating a standing wave on the semiconductor film to produce a uniform temperature gradient, which guides crystal growth and results in uniform crystal grain sizes in specific directions by adjusting the incident angle and energy density of the laser beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional rectangular laser beam is used for laser annealing, then the amorphous semiconductor film can be transformed into a polycrystalline or monocrystalline film, but the crystal grain sizes become non-uniform in different directions
Solution Approach 1:
The patent applies asymmetry by intentionally creating different energy distributions in the long-side and short-side directions of the rectangular laser beam. The polarization direction is set along the long-side direction, and the incident angle is specifically controlled to create asymmetric energy distribution that compensates for the natural tendency toward non-uniform crystal grain growth. This asymmetric energy distribution enables uniform crystal grain sizes in both directions by balancing the temperature gradients.
Solution Approach 2:
The patent changes key parameters including the polarization direction of the laser beam (set to long-side direction), the incident angle (controlled within specific ranges), and the energy density distribution. By adjusting these parameters, the energy distribution on the semiconductor film surface is optimized to produce uniform temperature gradients that guide crystal growth into uniform grains in both long-side and short-side directions.
2Reliability
If the laser beam energy distribution is adjusted to achieve uniform crystal grain size, then the performance consistency of thin-film transistors improves, but the control complexity of the laser annealing process increases
Solution Approach 1:
The patent applies local quality by creating direction-specific energy distribution characteristics. The laser beam is polarized along the long-side direction, and the incident angle is controlled to produce different energy distributions in the long-side versus short-side directions. This localized energy control ensures that crystal grains grow uniformly in each direction, leading to consistent thin-film transistor performance across the substrate.
Solution Approach 2:
The patent employs periodic pulsed laser irradiation to achieve uniform crystal grain formation. By using repeated laser pulses with controlled parameters (polarization direction, incident angle, energy density), the process builds up uniform crystal structure progressively. This periodic action allows precise control over crystal growth while maintaining process simplicity through standardized pulse parameters.
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 enables the formation of polycrystalline or monocrystalline semiconductor films with uniform crystal grain sizes in both the long-side and short-side directions, enhancing the performance consistency of thin-film transistors by controlling the crystal growth through precise energy distribution and temperature gradients.
Implementation Method 1
irradiating a rectangular laser beam onto the amorphous semiconductor film
Implementation Method 2
transforming amorphous silicon film into a polycrystalline or monocrystalline silicon film by laser annealing
Implementation Method 3
the direction of growth of crystal grains is greatly affected by temperature gradient or energy gradient of the laser beam
Implementation Method 4
when a polarized laser beam is irradiated onto a solid surface, a surface electromagnetic wave is excited on the solid surface
Implementation Method 5
interference of the surface electromagnetic wave with the incident laser beam generates a standing wave on the solid surface
Data Source
AI summary
A laser annealing method for executing laser annealing by irradiating a semiconductor film formed on a surface of a substrate with a laser beam, the method including the steps of, generating a linearly polarized rectangular laser beam whose cross section perpendicular to an advancing direction is a rectangle with an electric field directed toward a long-side direction of the rectangle or an elliptically polarized rectangular laser beam having a major axis directed toward a long-side direction, causing the rectangular laser beam to be introduced to the surface of the substrate, and setting a wavelength of the rectangular laser beam to a length which is about a desired size of a crystal grain in a standing wave direction.