Laser Processing Silicon Holes via Depression Refraction
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Solution Overview
Problem
In laser processing methods for forming holes in silicon substrates, the straightness of fractures on the laser light entrance surface is often compromised due to thermal shock, leading to meandering fractures and unpredictable hole sizes and shapes, making it difficult to control the opening width of the holes.
Innovation Solution
A laser processing method that forms a depression on the laser light entrance surface with a sloped inner face, exposing the modified region to the depression, allowing the laser light to refract and converge at a specific point, reducing the need for precise positional control of the laser source and enhancing the controllability of the hole opening width by inhibiting etching along fractures with low straightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser light is used to form modified regions in silicon substrate, then holes can be formed through anisotropic etching, but the straightness of fractures on the laser light entrance surface deteriorates due to thermal shock, causing meandering fractures and making it difficult to control the opening width of holes
Solution Approach 1:
The patent applies preliminary action by forming a depression structure on the laser light entrance surface before laser irradiation. This depression pre-defines the opening shape and position, so that during subsequent anisotropic etching, the opening is formed in conformity to the depression shape rather than following meandering fractures. The depression is created through preliminary mechanical or chemical processing, establishing a template that guides the final hole formation and ensures straight, controlled openings despite thermal shock effects during laser processing.
2Measurement precision
If laser light is converged directly onto the silicon substrate, then modified regions can be formed for hole creation, but the position of the converging point shifts due to positional deviations of the laser light source, requiring complex positional control
Solution Approach 1:
The patent introduces the depression structure as an intermediary element between the laser light source and the silicon substrate. The depression acts as a passive optical guide that automatically directs and converges laser light to a specific point based on its geometric configuration, rather than relying on active positional control of the laser source. This intermediary structure simplifies the system by replacing complex laser positioning mechanisms with a static geometric feature that inherently guides light convergence, reducing device complexity while maintaining precision.
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 method improves the controllability of the opening width of holes by forming them in conformity to the depression shape, reducing the impact of fractures with low straightness and achieving a more consistent and controlled hole formation process.
Implementation Method 1
the modified region forming step may irradiate the sloped surface with the laser light, so as to refract the laser light by the sloped surface and converge the laser light at a part corresponding to the hole in the object
Data Source
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AI summary
A laser processing method for forming a hole in a sheet-like object to be processed made of silicon comprises a depression forming step of forming a depression in a part corresponding to the hole on a laser light entrance surface side of the object, the depression opening to the laser light entrance surface; a modified region forming step of forming a modified region along a part corresponding to the hole in the object by converging a laser light at the object after the depression forming step; and an etching step of anisotropically etching the object after the modified region forming step so as to advance the etching selectively along the modified region and form the hole in the object; wherein the modified region forming step exposes the modified region or a fracture extending from the modified region to an inner face of the depression.