Wafer Laser Processing State Control via Plasma Light Monitoring
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Solution Overview
Problem
Current laser processing technologies for silicon wafers face challenges in real-time evaluation of processing states, leading to potential defects such as meandering cut lines, chipping, and residue on the lens, which can result in decreased yield in mass production due to inadequate crack extension and scattering of laser light at intersections, and the inability to detect processing abnormalities in real-time during the processing of product wafers.
Innovation Solution
A laser processing device equipped with a detection sensor to monitor plasma light generated during processing and an evaluation unit to assess the processing state, allowing for real-time correction of laser emission conditions to maintain a constant processing state, thereby ensuring proper crack extension and preventing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If laser processing conditions are not sufficient, then processing time can be reduced, but crack extension is weakened causing meandering cut lines and chipping
Solution Approach 1:
The patent implements real-time feedback control by detecting plasma light during laser processing and automatically adjusting laser emission conditions. The detection sensor monitors the processing state continuously, and the control unit modifies laser parameters based on detected plasma characteristics, ensuring optimal crack extension without requiring excessive processing time or manual intervention.
Solution Approach 2:
The system dynamically changes laser processing parameters (emission conditions) based on real-time plasma light detection. By adjusting laser power, pulse duration, or frequency according to detected plasma characteristics, the system optimizes crack formation quality while maintaining efficient processing speeds, resolving the trade-off between processing time and crack extension quality.
2Speed
If laser light intensity is increased to improve crack extension, then processing speed increases, but residue adheres to the objective lens causing lens stains
Solution Approach 1:
The detection sensor provides real-time feedback on plasma light characteristics, allowing the control unit to adjust laser intensity dynamically. This prevents excessive laser power that would generate harmful residue while maintaining sufficient power for effective crack extension, thus preventing lens contamination without sacrificing processing speed.
Solution Approach 2:
The system transitions from static laser parameters to dynamic adjustment based on real-time plasma detection. Laser emission conditions are continuously adapted during processing, enabling the system to maintain optimal processing speed while automatically reducing power when plasma characteristics indicate risk of residue generation, preventing lens stains.
3Manufacturing precision
If real-time detection is implemented to monitor processing state, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent introduces plasma light as an intermediary signal that naturally occurs during laser processing. By detecting this existing plasma emission rather than introducing complex sensing mechanisms into the processing zone, the system achieves real-time monitoring with minimal added complexity. The plasma acts as a natural indicator of processing state that can be detected using relatively simple optical sensors.
Solution Approach 2:
The system replaces complex mechanical monitoring methods (such as physical probes or multiple sensors) with optical detection of plasma light. This substitution uses light-based detection instead of mechanical measurement systems, achieving real-time processing state evaluation with simpler, non-contact sensing that adds minimal complexity to the overall system.
4Manufacturing precision
If conventional inspection methods are used after cutting, then manufacturing precision can be verified, but productivity decreases due to post-processing inspection time
Solution Approach 1:
The system performs verification of crack extension quality during the laser processing itself through real-time plasma light detection, rather than after cutting is complete. By evaluating processing state preliminarily during manufacturing, the system eliminates or reduces post-processing inspection steps, maintaining quality verification while improving overall productivity in mass production.
Solution Approach 2:
The detection and evaluation process runs continuously during laser processing without interrupting the manufacturing flow. Unlike discrete post-cutting inspections, the real-time plasma monitoring provides continuous verification of crack formation quality, ensuring manufacturing precision is maintained throughout production while keeping the process continuous and efficient for mass production.
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
Enables real-time evaluation and correction of laser processing, improving the yield of device mass production by preventing defects and ensuring accurate crack formation, reducing the need for post-processing inspections and minimizing lens contamination.
Implementation Method 1
a detection sensor that detects plasma light generated at a processing point of the laser light that is focused on the inside of the workpiece by the laser head
Data Source
AI summary
Provided are a laser processing device and a laser processing method capable of evaluating a processing state of laser processing for a workpiece in real time.A laser processing device 10 that irradiates a workpiece with laser light by aligning light-focusing points from a laser bead 16 to an inside of the workpiece while moving the laser head 16 relative to the workpiece (a wafer W) and executes laser processing of forming laser processing areas SP1 and SP2 inside the workpiece along a street of the workpiece, includes a detection sensor (photodiodes 20 and 36) configured to detect plasma light generated at a processing point of the laser light that is focused on the inside of the workpiece by the laser head during the laser processing, and an evaluation unit 48 configured to evaluate a processing state of the laser processing area on the basis of a detection signal of the detection sensor during the laser processing.