Elliptical Laser Beam Splitting for Narrow Groove Formation
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Solution Overview
Problem
Existing laser processing methods face challenges in forming narrow, high-speed laser grooves on wafers due to reduced peak energy intensity with elliptical beam spots and increased groove width when using high-powered pulsed laser beams.
Innovation Solution
A laser processing apparatus and method that generates a pulsed laser beam with an elliptical spot, branches it into multiple beams with partially overlapping major axes, and applies these as a single elongated beam spot to the workpiece, maintaining high power and intensity distribution for efficient groove formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a pulsed laser beam with an elliptical beam spot is used to process a narrow division line, then the processing area is widened, but the peak energy intensity is reduced causing insufficient groove formation
Solution Approach 1:
The single high-power laser beam is segmented into multiple lower-power beams through a beam splitter. Each beam is then focused to create an elongated beam spot that maintains high peak energy intensity while covering a larger processing area along the division line. This segmentation allows the system to process narrow division lines effectively without sacrificing groove formation quality.
2Manufacturing precision
If the power of the pulsed laser beam is increased to sufficiently form the laser processed groove, then the groove formation is improved, but the width of the laser processed groove is increased
Solution Approach 1:
The invention creates a non-uniform intensity distribution within the beam spot by using a cylindrical lens to generate an elongated beam profile. This local quality variation ensures that the intensity is concentrated along the narrow division line direction while extending along the feeding direction, thereby achieving sufficient groove formation without increasing groove width.
Solution Approach 2:
The beam spot is transformed from a circular cross-section to an elongated elliptical shape by introducing a cylindrical lens. This dimensional change allows the beam to cover a larger area along the division line while maintaining narrow width in the groove formation direction, effectively resolving the contradiction between groove quality and groove width.
3Manufacturing precision
If multiple pulsed laser beams are applied along the same division line to form a groove of desired depth, then the groove depth is achieved, but the processing efficiency is reduced due to multiple passes
Solution Approach 1:
The invention uses multiple beams that operate simultaneously along the division line rather than requiring sequential passes. The beam splitter divides the laser beam into multiple parallel beams that process different segments of the division line at the same time, achieving the desired groove depth in a single continuous pass and significantly improving processing efficiency.
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 narrow laser grooves at high processing speeds while preventing increased groove width, enhancing the efficiency and precision of the laser processing method.
Implementation Method 1
a diffractive optical element for branching the pulsed laser beam having the elliptical beam spot obtained by the elliptical spot forming means, into a plurality of pulsed laser beams
Implementation Method 2
a condensing lens for condensing each of the pulsed laser beams branched by the diffractive optical element to the workpiece
Implementation Method 3
applying a laser beam to a workpiece such as a semiconductor wafer and an optical device wafer to perform ablation to the workpiece
Data Source
AI summary
A laser processing apparatus has a laser beam applying unit for applying a laser beam to a workpiece held on a chuck table. The laser beam applying unit includes an elliptical spot forming member for changing the spot shape of a pulsed laser beam into an elliptical shape and making the major axis of the elliptical beam spot parallel to a feeding direction, a diffractive optical element for branching the pulsed laser beam having the elliptical beam spot obtained by the elliptical spot forming member, into a plurality of pulsed laser beams each having an elliptical beam spot whose major axis extends in the feeding direction, and a condensing lens for condensing each of the pulsed laser beams branched by the diffractive optical element to the workpiece in such a manner that the major axes of the elliptical beam spots of the pulsed laser beams branched are partially overlapped.