Laser Dicing Height Control With Switchable Displacement Meters
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Solution Overview
Problem
Existing laser processing devices face challenges in accurately controlling the vertical position of the processing laser beam on substrates with non-uniform film thickness and reflectivity, which affects the precision and efficiency of the laser dicing process.
Innovation Solution
The implementation of a laser processing device with a dual measurement system, utilizing both coaxial and separate-axis laser displacement meters, allows for the selection of the appropriate meter based on the reflectivity and film thickness, ensuring accurate vertical position control of the processing laser beam by switching between the two systems for each dividing target line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single laser displacement meter is used to measure substrate height, then the device structure is simple, but measurement precision deteriorates when substrate reflectivity or film thickness varies
Solution Approach 1:
The system dynamically switches between coaxial and separate-axis laser displacement meters based on substrate conditions. The controller selects which measurement system to use according to the specific dividing target line being processed, allowing the measurement system to adapt to varying substrate reflectivity and film thickness without requiring both systems to operate simultaneously, thus balancing precision with manageable complexity
Solution Approach 2:
The invention changes the measurement parameter (which laser displacement meter is active) based on substrate characteristics. By switching between two different measurement systems with different optical paths and sensitivities to reflectivity, the system optimizes measurement precision for different substrate conditions without permanently increasing device complexity
2Manufacturing precision
If the light condensing unit vertical position is not controlled, then the device structure is simple, but manufacturing precision deteriorates due to non-uniform modification layer depth
Solution Approach 1:
The controller receives real-time vertical position data from the selected laser displacement meter and uses this feedback to automatically adjust the light condensing unit's vertical position. This closed-loop control ensures the condensing point remains at the correct depth regardless of substrate height variations, achieving uniform modification layer depth without requiring complex manual intervention
Solution Approach 2:
The system uses the substrate's own reflected light from the measurement laser beam to generate height information, which then serves to control the processing laser beam position. The substrate effectively provides its own measurement signal, and the controller uses this self-generated information to maintain precise control, reducing the need for external reference systems
3Manufacturing precision
If laser processing is performed without accurate height measurement, then the processing speed is high, but processing precision deteriorates on substrates with varying film thickness
Solution Approach 1:
The system performs preliminary height measurement of the substrate surface using the laser displacement meter before executing the laser dicing process. This advance measurement allows the controller to pre-calculate the required light condensing unit position for each dividing target line, ensuring precise processing without requiring slow real-time adjustments during cutting, thus maintaining both precision and productivity
Solution Approach 2:
The system dynamically adjusts the light condensing unit position based on pre-measured substrate height data for each specific dividing target line. By preparing the control parameters in advance based on actual substrate topography, the system achieves precise dicing while maintaining efficient processing speed, as the adjustments are made before processing begins rather than during
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 enhances the precision and efficiency of the laser dicing process by securely measuring the vertical position of the processing laser beam, even on substrates with varying film thickness and reflectivity, thereby improving processing time and accuracy.
Implementation Method 1
a coaxial laser displacement meter configured to measure the vertical direction position of the irradiation point by radiating, to the upper surface of the substrate, a first measurement laser beam having a different wavelength from the processing laser beam and a path same as the processing laser beam from a dichroic mirror provided in a path of the processing laser beam to the upper surface of the substrate and by receiving a reflected light of the first measurement laser beam
Implementation Method 2
a separate-axis laser displacement meter configured to measure the vertical direction position of the irradiation point by radiating, to the upper surface of the substrate, a second measurement laser beam having a different wavelength and a different path from the processing laser beam and the first measurement laser beam and by receiving a reflected light of the second measurement laser beam
Implementation Method 3
The dichroic mirror allows a laser beam having a specific wavelength (for example, processing laser beam) to be transmitted therethrough and reflects a laser beam having another specific wavelength (for example, measurement laser beam)
Data Source
AI summary
A laser processing device includes a height measurement unit configured to measure a vertical direction position of an irradiation point of a processing laser beam on an upper surface of a substrate; and a controller configured to control a vertical direction position of a light condensing unit based on the vertical direction position of the irradiation point while moving the irradiation point along multiple dividing target lines. The height measurement unit includes a coaxial laser displacement meter and a separate-axis laser displacement meter. The controller controls the vertical direction position of the light condensing unit by using only one of the coaxial or the separate-axis laser displacement meter for each of the multiple dividing target lines while the substrate is processed and performs a switchover of a laser displacement meter for controlling the vertical direction position of the light condensing unit between the coaxial and the separate-axis laser displacement meters.