Laser Scan Sequencing and Direction with Gas Flow
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Solution Overview
Problem
Conventional laser dicing processes for semiconductor wafers result in wide kerf widths due to mechanical cutting blades, limiting the number of rows and columns of die that can be fit on a wafer and hindering the reduction of street width, despite advancements in laser parameters and processing techniques.
Innovation Solution
A method involving a laser processing system that orients a laser processing field relative to a workpiece, establishing a cumulative gas flow direction using a gas input and outtake flow, and scanning a laser beam in directions oblique to the gas flow to enhance edge characteristics and reduce kerf width variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mechanical cutting blades are used for dicing, then cutting speed and throughput are improved, but kerf width increases and manufacturing precision deteriorates
Solution Approach 1:
The patent replaces mechanical cutting blades with a laser processing system that uses optical energy to ablate material. The laser beam scans across the workpiece to create scribe lines and separate die, eliminating the need for physical contact between cutting tool and workpiece. This substitution enables kerf widths determined by laser spot size rather than blade thickness, achieving significantly narrower cuts while maintaining high processing speeds through rapid laser scanning.
Solution Approach 2:
The patent employs dynamic adjustment of laser processing parameters including scan direction, pulse duration, and energy density to optimize the cutting process. By varying these parameters based on the specific material and desired kerf width, the system achieves precise control over cut quality and dimensions without the mechanical constraints of blade-based systems.
2Productivity
If laser scanning is performed perpendicular to gas flow direction, then processing speed is improved, but edge quality and manufacturing precision deteriorate due to increased waviness and wobble
Solution Approach 1:
The patent introduces asymmetric scanning patterns where laser scans are performed at oblique angles (e.g., 45 degrees) relative to the gas flow direction rather than perpendicular to it. This asymmetric orientation creates a more favorable interaction between the laser-induced plasma and the assisting gas flow, reducing turbulence and improving edge quality while maintaining processing efficiency.
Solution Approach 2:
The patent dynamically adjusts scan parameters including angle, speed, and direction based on real-time process conditions and material properties. The system can vary scan orientation between 0-90 degrees relative to gas flow to optimize the balance between processing speed and edge quality for different materials and feature geometries.
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 improves scribe line quality by reducing waviness and wobble, achieving more uniform kerf widths and position accuracy, allowing for greater circuit density on the workpiece with reduced noise and outliers.
Implementation Method 1
scanning a laser beam in a first laser scan direction of relative movement of a laser beam processing axis of the laser beam with respect to the workpiece, wherein the laser beam impinges the workpiece along the first laser scan direction affecting the material along the first laser scan direction
Implementation Method 2
establishing, from a gas supply, a gas input flow in a gas input direction across at least a portion of a major surface of the workpiece... establishing, from a vacuum source, a gas outtake flow in a gas outtake direction across at least the portion of the major surface of the workpiece
Data Source
AI summary
Employing laser scanning directions (20) that are oblique to and against a predominant gas flow direction (25) equalize the quality and waviness characteristics of orthogonal scribe lines (26) made by the laser scans. Positioning and sequence of multiple scan passes to form a feature wider than the width of a scribe line (26) can be controlled to enhance quality and waviness characteristics of the edges of the feature.