Laser Polarization Control for Single-Point GaN Processing
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Solution Overview
Problem
When laser light is focused in a semiconductor object made of a birefringent material, such as a gallium nitride (GAN) ingot, the different refractive indexes for P-polarized and S-polarized light components result in multiple focal points, leading to unintended dents and inappropriate cracks, which degrade the quality of processing like slicing.
Innovation Solution
A laser processing device that includes a spatial light modulator to control the polarized light components of the laser light, ensuring it is focused on a single point within the semiconductor object. This is achieved by either blocking one of the polarized light components or converting the linearly polarized light into radially or azimuthally polarized light to unify the components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser light is focused in a birefringent semiconductor object, then the laser processing can be performed, but multiple focal points are formed due to different refractive indexes of P-polarized and S-polarized light components, resulting in multiple dents and inappropriate cracks
Solution Approach 1:
The patent changes the polarization state parameter of the laser light from linear polarization to circular polarization. This parameter change ensures that both P-polarized and S-polarized components are present equally, allowing them to focus at the same point and eliminate multiple focal points in birefringent materials
Solution Approach 2:
Instead of trying to eliminate one of the polarized components (which would require complex filtering), the patent inverts the approach by using circularly polarized light where both components are equally represented. This inversion of the polarization strategy allows both P and S components to contribute equally to a single focal point
2Productivity
If multiple focal points are formed in the semiconductor object, then the laser processing can proceed, but unintended dents and cracks are generated, degrading the quality of processing
Solution Approach 1:
By changing the polarization parameter to circular polarization, the patent ensures uniform energy distribution and single-point focusing, which maintains processing quality while preserving productivity. The circular polarization allows both P and S components to focus at the same location, preventing multiple dents and cracks
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 suppresses the generation of inappropriate cracks and improves the quality of laser processing by ensuring a single focal point is maintained, thereby enhancing the precision and quality of semiconductor processing.
Implementation Method 1
a spatial light modulator that modulates the laser light output from the laser output unit
Implementation Method 2
a focusing lens that focuses the laser light toward the semiconductor object
Implementation Method 3
a focusing lens that focuses the laser light toward the semiconductor object
Implementation Method 4
when laser light is focused in a semiconductor object made of a birefringent material, such as a gallium nitride (GAN) ingot, the refractive indexes of a P-polarized light component and an S-polarized light component of incident light are different from each other
Implementation Method 5
the incident light is divided into a normal light ray and an abnormal light ray, and the abnormal light ray does not follow the Snell's law and propagates at a refraction angle different from that of the normal light ray
Implementation Method 6
a polarized light component control unit that controls polarized light components of the laser light such that the laser light is focused on one point in the semiconductor object in an optical axis direction
Data Source
AI summary
There is provided a laser processing device that performs laser processing on an object made of a birefringent material, the device including: a light source that outputs laser light; a spatial light modulator that modulates the laser light output from the light source; a focusing lens that focuses the laser light toward the object; and a polarized light component control unit that is a function of the spatial light modulator to control polarized light components of the laser light such that the laser light is focused on one point in the object in a Z direction (optical axis direction).