Laser Processing Apparatus Polygon Mirror Beam Guidance
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Solution Overview
Problem
The existing methods for cutting semiconductor wafers with low-k films using laser processing suffer from poor productivity due to the refilling of laser-processed grooves with melt, leading to inefficient processing and damage to the devices.
Innovation Solution
A laser processing apparatus with a pulsed laser oscillator, condenser, and a polygon mirror system that includes an optical switching element and polarization beam splitter to guide the pulsed laser beam, preventing it from falling on angular portions of the mirrors and allowing for overlapping ablation processing to form desired grooves without refilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ablation processing is performed by applying the laser beam along the division line to form laser-processed grooves, then the laminate including the low-k film is removed and grooves are formed, but the grooves are refilled with melt scattered from the laminate, requiring multiple applications of the laser beam and reducing productivity
Solution Approach 1:
The patent applies preliminary cooling to the workpiece surface using a cooling device before and during laser beam irradiation. This pre-cooling prevents the scattered laminate material from melting and refilling the grooves, allowing groove formation to be completed in a single laser application pass, thereby resolving the contradiction between groove formation precision and processing productivity
Solution Approach 2:
The cooling device creates a preliminary counteracting effect by removing heat from the workpiece surface before the laser processing occurs. This preliminary cooling action counteracts the heat generation from the laser beam that would cause melt refilling, enabling single-pass groove formation and improving productivity without sacrificing precision
2Device complexity
If the pulsed laser beam is applied to the angular portion of mirrors in the polygon mirror, then the beam path is simplified, but processing loss occurs and the beam scattering causes degradation in workpiece quality
Solution Approach 1:
The patent employs a rotation position detecting device that continuously monitors the angular position of the polygon mirror and provides feedback to the control device. The control device uses this feedback information to dynamically adjust the laser beam irradiation timing, ensuring the beam never strikes the angular portions of the mirrors. This feedback mechanism maintains processing quality while managing optical path complexity through intelligent control
Solution Approach 2:
The patent replaces a purely mechanical optical path design with an intelligent control system that uses rotation position detection and conditional beam irradiation. Instead of mechanically avoiding the angular portions through complex mirror positioning, the system uses electronic control to substitute the mechanical constraint with a smart irradiation strategy, maintaining reliability while managing device complexity
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 prevents processing losses and degradation by ensuring the pulsed laser beam is accurately applied, allowing for efficient formation of laser-processed grooves with desired widths in low-k films and substrates, enhancing productivity and quality.
Implementation Method 1
a pulsed laser oscillator (51) that oscillates a pulsed laser beam (LB)
Implementation Method 2
a condenser (53) that condenses the laser beam (LB) oscillated from the pulsed laser oscillator (51)
Implementation Method 3
a polygon mirror (54) that disperses the pulsed laser beam (LB) oscillated from the pulsed laser oscillator (51)
Implementation Method 4
perform laser processing on the workpiece held by the chuck table
Implementation Method 5
ablation processing is performed by applying the laser beam along the division line, and thereby the laminate including the low-k film is removed
Data Source
AI summary
A laser beam irradiating mechanism of a laser processing apparatus includes: a pulsed laser oscillator configured to oscillate a pulsed laser beam; a condenser configured to condense the laser beam oscillated from the pulsed laser oscillator, and irradiate a workpiece held on a chuck table with the condensed laser beam; a polygon mirror disposed between the pulsed laser oscillator and the condenser, and having a plurality of mirrors arranged concentrically with respect to a rotating shaft, the plurality of mirrors dispersing the pulsed laser beam oscillated from the pulsed laser oscillator; and a guiding unit disposed between the pulsed laser oscillator and the polygon mirror, the guiding unit guiding the pulsed laser beam such that the pulsed laser beam is not applied to an angular portion of mirrors adjacent to each other.