Stealth Dicing Laser Positioning for Semiconductor Wafer Defect Reduction
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Solution Overview
Problem
Stealth dicing methods face challenges such as the formation of beard-like conductor lines, cracks, and meandering cutting lines due to the mechanical weakness of insulating layers and the brittleness of Low-k films, which affect the precision and yield of semiconductor chip production.
Innovation Solution
Irradiating a laser to the side of a test pad in a separation region on a semiconductor wafer to form a modified region as a division starting point, allowing for precise bending or groove formation to avoid these issues, and removing test pads to prevent defects in the cutting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If blade dicing method is used to cut thin semiconductor wafers, then individual chips can be obtained, but chipping occurs and bending strength decreases
Solution Approach 1:
The patent replaces the mechanical blade dicing system with a laser-based system. The laser beam irradiates the semiconductor wafer to form a modified layer internally, which then guides crack propagation for clean separation. This substitution eliminates mechanical contact with the chip edges, preventing chipping and maintaining bending strength while achieving high-speed cutting.
2Speed
If Low-k film is used for insulating film to improve operation speed, then signal transmission improves, but the film becomes brittle and peels off during dicing
Solution Approach 1:
The laser-based internal modification method replaces mechanical stress during dicing. The laser forms a modified layer within the Low-k film that guides crack propagation along the desired cutting line, eliminating the need for mechanical force that would cause the brittle film to peel or crack unpredictably.
Solution Approach 2:
The laser pre-modifies the material structure along the cutting path before actual separation occurs. This preliminary action creates a controlled weakness line that directs where the crack will propagate, preventing random peeling of the Low-k film that would occur with conventional mechanical dicing.
3Strength
If stealth dicing with laser irradiation is used to avoid chipping, then bending strength is maintained, but beard-like conductor lines and cracks form due to mechanical weakness of insulating layers
Solution Approach 1:
The patent applies local quality by creating a modified layer with different properties than the surrounding material. The laser irradiation selectively modifies the material structure along the cutting path, creating a region with altered mechanical and optical properties that guides crack propagation precisely along the intended line while maintaining high-quality separation without beard-like conductor lines.
Solution Approach 2:
The laser irradiation changes the physical and chemical parameters of the material along the cutting path. By controlling laser parameters such as power, speed, and pulse duration, the modified layer creates optimal conditions for clean crack propagation, eliminating defects while maintaining precision cutting.
4Productivity
If laser beam is irradiated to form modified layer for stealth dicing, then cutting speed increases beyond 300 mm per second, but defects form in brittle Low-k films
Solution Approach 1:
The patent optimizes laser parameters including power density, irradiation speed, and pulse characteristics to match the specific properties of Low-k films. By carefully controlling these parameters, the modified layer forms without excessive heat accumulation or stress that would cause cracking or peeling, enabling high-speed cutting while maintaining quality.
Solution Approach 2:
The laser creates a localized modified layer with precisely controlled properties along the cutting path. This local modification ensures that the thermal and mechanical effects are confined to the immediate cutting zone, preventing damage to the surrounding brittle Low-k film while enabling high-speed processing.
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 reduces defects in the cutting shape of semiconductor wafers, increases the reliability and yield of thin semiconductor devices, and enables high-speed cutting without compromising bending strength or chip quality.
Implementation Method 1
the inside of a semiconductor wafer is radiated with laser beam to selectively form a modified layer
Implementation Method 2
a melting-processing region is formed through multiphoton absorption by placing a focal point of the laser beam at the inside of the semiconductor wafer
Implementation Method 3
the semiconductor wafer is cut with taking this modified layer as a division starting point
Data Source
AI summary
To divide a semiconductor wafer by stealth dicing, a test pad in a cutting region and an alignment target are collectively arranged along one side in a width direction of the cutting region, and a laser beam for forming a modified region is irradiated to a position away in plane from the test pad and the alignment target Am. In this manner, defects in cutting shape in a cutting process of a semiconductor wafer using stealth dicing can be reduced or prevented.