Optical Wafer Division via Laser-Induced Crack Growth
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Solution Overview
Problem
Existing methods for dividing optical device wafers using laser beams often result in residual melted or modified layers on the side walls, which reduce the luminance of individual optical devices.
Innovation Solution
A method involving the formation of modified dots or ablated holes at the intersections of division lines using a laser beam, followed by the application of a CO2 laser beam to grow cracks inside the substrate, thereby minimizing residual layers and improving luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a laser beam is applied to form ablated grooves along division lines, then the wafer can be divided into individual optical devices, but melted layers remain on the side walls causing reduction in luminance
Solution Approach 1:
The division process is segmented into two distinct stages: first forming modified layers at intersection points, then growing cracks along division lines. This segmentation allows each stage to be optimized independently, preventing melted layer formation on side walls while maintaining division efficiency.
Solution Approach 2:
Modified layers are formed in advance at the intersection points of division lines before the crack growing step. This preliminary action creates predetermined stress concentration points that guide crack propagation, eliminating the need for direct ablation along the entire division line and thus preventing melted layer contamination on side walls.
2Productivity
If a laser beam is applied to form modified layers inside the substrate, then the wafer can be divided into individual optical devices, but modified layers remain on the side walls causing reduction in luminance
Solution Approach 1:
The laser processing is applied locally only at the intersection points of division lines rather than along the entire division line. This localized modification creates stress concentration points that guide crack propagation along the division lines without depositing modified layers on the side walls, thus maintaining optical device luminance.
Solution Approach 2:
Modified layers are formed in advance at the intersection points of division lines before the crack growing step. This preliminary action creates predetermined stress concentration points that guide crack propagation, eliminating the need for direct ablation along the entire division line and thus preventing melted layer contamination on side walls.
3Productivity
If external force is applied to division lines after laser processing, then the wafer is divided into individual optical devices, but residual layers remain on side walls
Solution Approach 1:
The division process is segmented into two distinct stages: first forming modified layers at intersection points, then growing cracks along division lines. This segmentation allows each stage to be optimized independently, preventing melted layer formation on side walls while maintaining division efficiency.
Solution Approach 2:
The laser processing is applied locally only at the intersection points of division lines rather than along the entire division line. This localized modification creates stress concentration points that guide crack propagation along the division lines without depositing modified layers on the side walls, thus maintaining optical device luminance.
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 method effectively suppresses the reduction in luminance by minimizing the presence of residual layers on the side walls, enhancing the performance of individual optical devices.
Implementation Method 1
applying a laser beam having a transmission wavelength to the substrate to the intersections of the crossing division lines in the condition where the focal point of the laser beam is set inside the substrate in an area corresponding to the intersections of the crossing division lines, thereby forming a plurality of modified dots as division start points inside the substrate
Implementation Method 2
applying a laser beam having an absorption wavelength to the substrate to the intersections of the crossing division lines, thereby forming a plurality of ablated holes as division start points at the intersections of the crossing division lines
Implementation Method 3
applying a CO2 laser beam along the division lines to grow cracks inside the substrate from the division start points
Implementation Method 4
applying an external force to the division lines after performing the crack growing step, thereby dividing the optical device wafer into the individual optical devices
Data Source
AI summary
An optical device wafer processing method for dividing an optical device wafer into a plurality of individual optical devices. The optical device wafer is composed of a substrate and a semiconductor layer formed on the front side of the substrate. The optical devices are partitioned by a plurality of crossing division lines formed on the semiconductor layer. The optical device wafer processing method includes a division start point forming step of applying a laser beam having a transmission wavelength to the substrate to the intersections of the crossing division lines in the condition where the focal point of the laser beam is set inside the substrate in an area corresponding to the intersections of the crossing division lines, thereby forming a plurality of modified dots as division start points inside the substrate at the intersections of the crossing division lines; and a crack growing step of applying a CO2 laser beam along the division lines to grow cracks inside the substrate from the division start points.