Laser Condenser Aberration Control for SiC Processing
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Solution Overview
Problem
Existing laser processing apparatuses fail to consistently form excellent modified layers within workpieces, particularly when the condensing point of the laser beam has zero aberration in the atmosphere, leading to issues like peeling layers with cracks in SiC ingots during processing.
Innovation Solution
A laser processing apparatus with a chuck table and a laser irradiating unit that includes a concave lens, a convex lens, and an actuator, where the convex lens is positioned to create zero aberration in the atmosphere, allowing the actuator to adjust the distance to generate aberration within the workpiece, ensuring precise laser processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the condensing point of the laser beam is positioned within the workpiece with zero aberration in the atmosphere, then the laser beam can be focused precisely, but the aberration does not become completely zero within the workpiece due to refraction, resulting in poor processing quality
Solution Approach 1:
The patent changes the optical parameters by introducing a meniscus lens that creates positive aberration in the atmosphere, which compensates for the negative aberration caused by refraction within the workpiece. This parameter adjustment ensures that the total aberration within the workpiece becomes zero, achieving excellent processing quality.
Solution Approach 2:
The patent applies preliminary anti-action by pre-introducing positive aberration through the meniscus lens before the laser beam enters the workpiece. This pre-compensation counteracts the negative aberration that would otherwise occur due to refraction at the workpiece interface, ensuring zero total aberration within the workpiece.
2Ease of operation
If a condenser with zero aberration in the atmosphere is used, then the laser beam focusing is optimized for atmospheric conditions, but excellent processing cannot be achieved within the workpiece due to uncorrected aberration
Solution Approach 1:
The patent modifies the optical system parameters by adding a meniscus lens with specific positive aberration characteristics. This changes the overall aberration profile of the condenser system to compensate for refraction effects within the workpiece, achieving zero total aberration and excellent processing quality.
3Measurement precision
If the convex lens distance is fixed to achieve zero aberration in the atmosphere, then the atmospheric focusing is optimal, but the processing within the workpiece suffers from non-zero aberration
Solution Approach 1:
The patent introduces a movable meniscus lens that can be dynamically adjusted in position along the optical axis. This dynamic adjustment capability allows the system to optimize the balance between atmospheric focusing and workpiece processing, achieving zero total aberration within the workpiece by precisely controlling the meniscus lens position.
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 configuration enables excellent processing by maintaining zero aberration within the workpiece, resulting in high-quality modified layers and peeling layers without cracks, enhancing the division of device chips and ingots.
Implementation Method 1
the actuator is formed by a piezoelectric element
Data Source
AI summary
A laser beam oscillated by a laser oscillator is condensed by a condenser. The condenser includes: a concave lens; a convex lens disposed at a predetermined interval from the concave lens, and disposed at a position such that aberration of a condensing point in the atmosphere is zero; and an actuator that generates an aberration at the condensing point in the atmosphere by changing the distance of the convex lens with respect to the concave lens. The actuator generates the aberration in the atmosphere such that the aberration of the condensing point is zero within a workpiece.