Laser Processing Apparatus for High-Precision Wafer Cutting
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Solution Overview
Problem
Conventional laser processing apparatuses face challenges in achieving high accuracy cutting due to the difficulty in connecting cracks formed from modified regions arranged in different timings in the thickness direction of a workpiece, leading to poor cutting precision.
Innovation Solution
A laser processing apparatus and method that utilizes a spatial light modulator, polarization beam splitter, and λ/2 wave plate to condense laser light at two positions differing in thickness direction but the same in relative movement direction, forming modified regions simultaneously and ensuring precise alignment of cracks for improved cutting accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser light is simultaneously condensed at two positions different in thickness direction and separated along relative movement direction, then two modified regions are formed simultaneously, but cracks from the two modified regions are difficult to connect, leading to poor cutting accuracy
Solution Approach 1:
The patent changes the spatial arrangement of condensing points from being separated along the relative movement direction (horizontal dimension) to being arranged in the thickness direction (vertical dimension). This dimensional change allows cracks to connect properly while maintaining simultaneous formation of modified regions, thus resolving the contradiction between productivity and cutting accuracy
Solution Approach 2:
The patent applies different hologram patterns to different regions of the spatial light modulator, creating locally optimized condensing conditions. By controlling the spatial light modulator to present specific hologram patterns, the system achieves precise control over where and how laser light condenses within the workpiece, enabling accurate crack formation and connection
2Productivity
If laser light is condensed at two positions separated along relative movement direction, then processing efficiency is improved, but the timing difference in forming modified regions causes poor crack connection
Solution Approach 1:
The patent transitions from separating condensing points along the movement direction to arranging them in the thickness direction. This ensures that both modified regions are formed at the same timing during relative movement, guaranteeing reliable crack connection while maintaining processing efficiency
Solution Approach 2:
The patent replaces traditional mechanical focusing methods with a spatial light modulator and hologram patterns to control laser condensing positions. This optical control mechanism enables precise timing-synchronized formation of modified regions at different depth positions, ensuring reliable crack connection
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 high-precision cutting along planned cutting lines by ensuring that cracks from modified regions are formed at the same timing, resulting in enhanced linearity and efficiency of crack extension within the workpiece.
Implementation Method 1
a spatial light modulator configured to modulate the laser light; a condenser lens configured to condense the laser light inside of the workpiece
Implementation Method 2
a light flux separating and combining device configured to polarize and separate the laser light emitted from the laser light source into two polarized light fluxes having polarization directions orthogonal to each other
Implementation Method 3
a λ/2 wave plate arranged between the total reflecting prism or mirror and the spatial light modulator, and configured to convert a polarization direction of the one polarized light flux reflected by the total reflecting prism or mirror into a polarization direction of the another polarized light flux
Implementation Method 4
a condenser lens configured to condense the laser light inside of the workpiece
Implementation Method 5
emit a laser light with a light condensing point set inside of a workpiece to form modified regions inside of the workpiece along a planned cutting line
Data Source
AI summary
A laser processing apparatus includes: a light flux separating-and-combining device configured to polarize and separate a laser light into two polarized light fluxes having polarization orthogonal to each other and emit the two light fluxes with their optical paths matching each other toward different regions of a spatial light modulator, and configured to combine the two polarized light fluxes modulated by the spatial light modulator and emit the two light fluxes toward a condenser lens; and a controller configured to control hologram patterns presented by the spatial light modulator for respective regions of the spatial light modulator irradiated with the two polarized light fluxes such that the laser light is condensed by the condenser lens at two positions different from each other in a thickness direction inside of the wafer and the same as each other in a relative movement direction of the laser light to form modified regions.