Pulsed Laser Substrate Processing to Suppress Cracks in GaN
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Solution Overview
Problem
Existing methods for forming modified regions in gallium nitride substrates using pulsed laser irradiation often result in unintended cracks and surface roughness due to high energy application, which can lead to large energy being applied at a single irradiation point.
Innovation Solution
A substrate manufacturing apparatus that uses a pulsed laser with multiple converging points arranged in a straight line, where the stage moves at a predetermined speed to ensure each point is irradiated multiple times, reducing the energy per irradiation while maintaining a total energy level, and allowing for adjustable pulse energy, width, and wavelength of the converging points to control the formation of modified regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laser output is increased to apply large energy to the irradiation point with single irradiation, then the modified region can be reliably formed, but unintended cracks may occur and surface roughness increases
Solution Approach 1:
The patent divides a single high-energy laser irradiation into multiple lower-energy irradiations by generating multiple converging points from a single laser beam. The beam is split into several beams that converge at different points along the scanning path, allowing the total energy to be distributed across multiple irradiation events rather than concentrated in one, thereby preventing cracks while still achieving reliable modified region formation
Solution Approach 2:
The patent employs periodic laser irradiation with a predetermined pulse period, where multiple converging points are generated in sequence as the laser beam scans through the substrate. This periodic action allows controlled energy delivery at regular intervals, ensuring cumulative energy reaches the required threshold for reliable modified region formation without exceeding damage thresholds at any single moment
2Object-affected harmful factors
If multiple converging points are used to divide energy application, then cracks are suppressed, but the complexity of the irradiation system increases
Solution Approach 1:
The patent makes a single laser beam perform multiple functions by generating multiple converging points from one beam source. Instead of requiring multiple separate laser sources, the system uses optical elements to split and redirect one laser beam to create several convergence points, making the single laser source multi-functional and reducing overall system complexity while still achieving crack suppression
Solution Approach 2:
The patent introduces optical intermediaries such as beam splitting elements and scanning mirrors that mediate between the single laser source and multiple converging points. These intermediary components enable the transformation of one beam into multiple beams without requiring multiple laser sources, managing the complexity through standardized optical intermediaries rather than complex multi-source coordination
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 effectively suppresses the occurrence of unintended cracks and surface roughness, allowing for precise control of modified region formation and improved substrate quality by distributing energy application over multiple irradiations.
Implementation Method 1
an irradiation unit that irradiates a semiconductor substrate disposed on the stage with a pulsed laser of a predetermined pulse period
Implementation Method 2
energy can be applied to the same irradiation point by the plurality of converging points in a state of being divided into a plurality of times
Implementation Method 3
The predetermined speed is a speed at which a moving distance of the plurality of converging points in one period of the predetermined pulse period is the same as the predetermined pitch
Implementation Method 4
The irradiation unit generates a plurality of converging points arranged on a straight line at a predetermined pitch
Data Source
AI summary
A substrate manufacturing apparatus includes a stage on which a semiconductor substrate is disposed. The substrate manufacturing apparatus includes an irradiation unit that irradiates the semiconductor substrate disposed on the stage with a pulsed laser of a predetermined pulse period. The substrate manufacturing apparatus includes a controller that controls a relative position between the stage and the irradiation unit. The irradiation unit generates a plurality of converging points arranged on a straight line at a predetermined pitch. The controller moves the relative position between the stage and the irradiation unit at a predetermined speed in parallel to the straight line on which the plurality of converging points are arranged. The predetermined speed is a speed at which a moving distance of the plurality of converging points in one period of the predetermined pulse period is the same as the predetermined pitch.