Laser Processing Method for Silicon Substrate Crack Control
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Solution Overview
Problem
The existing laser processing method for cutting silicon substrates with functional devices suffers from inefficiencies in processing speed and surface quality, leading to damage on the front surface opposite the laser entrance and level differences on the cut surface, which degrades the characteristics of the functional devices.
Innovation Solution
A method involving the convergence of laser light at a silicon substrate with a back surface entrance, where the converging point is moved along a line to cut while maintaining specific distances and offsets to form modified regions, allowing for precise control of crack extension and surface smoothing by removing predetermined portions including the modified regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of scanning times of laser light for one line to cut is reduced to improve processing efficiency, then productivity is improved, but damage occurs on the front surface of the semiconductor substrate opposite to the laser light entrance surface
Solution Approach 1:
The patent introduces a new spatial dimension by offsetting the converging point position in the thickness direction of the substrate. Instead of forming the modified region directly on the line to cut, the converging point is positioned at a first distance from the front surface, creating a modified region that is spatially separated from both the entrance and exit surfaces, thereby preventing damage while maintaining cutting efficiency
Solution Approach 2:
The patent performs preliminary action by forming a modified region before the actual crack propagation occurs. The modified region is created at a controlled distance from the front surface, preparing the material structure in advance to guide crack propagation along the desired path without reaching the front surface, thus preventing damage before it can occur
2Manufacturing precision
If the laser light is converged at the semiconductor substrate to form modified regions, then the crack extension is controlled, but level differences appear on the cut surface
Solution Approach 1:
The patent applies local quality by creating a modified region with specific spatial characteristics - positioned at a first distance from the front surface and with a specific width. This localized modification ensures that the crack propagates along the intended path while the modified region itself is positioned such that it does not create level differences on the final cut surface, as it is removed along with the back surface portion
Solution Approach 2:
The patent extracts the problematic modified region from the final product by removing a predetermined portion including the back surface and at least the modified region. This extraction eliminates the source of level differences while maintaining the beneficial crack propagation control, as the modified region serves its purpose during cutting but is then removed
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 effectively suppresses damage on the front surface, improves the straightness and smoothness of the cut surface, and enhances the yield of semiconductor chips by accurately controlling the crack extension and surface level differences.
Implementation Method 1
converging laser light at an object to be processed including a semiconductor substrate formed with a plurality of functional devices on a front surface, with a back surface of the semiconductor substrate as a laser light entrance surface
Implementation Method 2
forming a first modified region along the line to cut
Implementation Method 3
converging the laser light at the object to be processed, with the back surface of the semiconductor substrate as the laser light entrance surface, and while maintaining a distance between the front surface of the semiconductor substrate and a second converging point at a second distance greater than the first distance
Implementation Method 4
forming a second modified region along the line to cut
Implementation Method 5
removing a predetermined portion including the back surface and at least the second modified region in the semiconductor substrate
Data Source
AI summary
Laser light is converged at an object including a semiconductor substrate formed with a plurality of functional devices on a front surface, from a back surface of the semiconductor substrate, and while a distance between the front surface and a first converging point of the laser light is maintained at a first distance, whereby a first modified region is formed along the line. The laser light is converged at the object from the back surface, and while a distance between the front surface and a second converging point is maintained at a second distance, and while the second converging point is offset with respect to a position at which the first converging point is converged, whereby a second modified region is formed along the line. A predetermined portion including the back surface and at least the second modified region is removed.