Laser-Induced Subcritical Cracks for Precise Solid Body Separation
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Solution Overview
Problem
Existing methods for producing wafers from solid bodies, such as silicon carbide ingots, result in uncontrollable material transformation and extensive crack propagation due to close focal point choices, leading to increased absorption and compressive stresses, which damage the surrounding structure and require significant reworking.
Innovation Solution
A method involving laser radiation to introduce modifications in the interior of a solid body, with precise control of focal point spacing and polarization, producing subcritical cracks that limit crack propagation and allow for controlled material separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If focal points are chosen close together during laser irradiation, then material transformation efficiency is improved, but uncontrolled crack propagation and material damage occur
Solution Approach 1:
The patent applies parameter changes by precisely controlling the spacing between focal points during laser irradiation. By optimizing this spatial parameter, the method achieves efficient material transformation while preventing uncontrolled crack propagation. The focal point spacing is set to a specific range that balances transformation efficiency with crack control, resolving the technical contradiction between productivity and harmful effects.
2Speed
If laser absorption is increased to enhance material transformation, then processing speed is improved, but compressive stresses increase causing extensive damage
Solution Approach 1:
The patent applies local quality by creating modifications at predetermined locations rather than uniform irradiation. The laser radiation produces localized modifications that generate subcritical cracks only where needed, concentrating the material transformation effect in specific regions. This localized approach increases processing speed while limiting compressive stress generation to controlled areas, preventing extensive damage.
3Ease of manufacture
If extensive crack propagation occurs to separate solid body layers, then separation is achieved, but surrounding structure is damaged requiring reworking
Solution Approach 1:
The patent applies segmentation by producing discrete modifications at predetermined locations that generate subcritical cracks. These segmented, controlled cracks propagate in a limited manner to achieve layer separation without causing extensive damage to the surrounding structure. The segmentation principle allows separation to be achieved while maintaining manufacturing precision and reducing reworking requirements.
4Object-affected harmful factors
If focal point spacing is reduced to control crack propagation, then material damage is minimized, but processing time increases
Solution Approach 1:
The patent applies partial action by irradiating only specific predetermined locations rather than the entire material volume. This selective approach controls crack propagation and minimizes material damage while avoiding the need to process every point, thus preventing excessive processing time. The partial action principle optimizes the balance between damage control and 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
Reduces material damage and reworking effort by minimizing absorption and controlling crack propagation, enabling precise and efficient separation of solid body layers.
Implementation Method 1
laser radiation of a laser is introduced into the interior of a solid body via a first surface of the solid body
Implementation Method 2
The solid body cracks subcritically in the region of the respective modification
Data Source
AI summary
A method includes: providing a solid body having opposite and substantially parallel first and second surfaces; and introducing laser radiation into an interior of the solid body via the first surface, the laser radiation producing modifications in the solid body. Linear shapes are produced by the modifications. The solid body cracks in a region of each respective modification. The cracks have orthogonality to a direction of longitudinal extent of the respective linear shape and an average crack length of less than 150 μm. The modifications that belong to a same linear shape and successively produced are spaced at a distance from one another which is defined by: x>d, d being the diameter of a focal point of the laser radiation and x the distance between adjacent focal points of the laser radiation. The distance between two directly adjacent linear shapes in each case is less than 50 μm.