Infrared Wafer Imaging Alignment for Precise Laser Dicing
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Solution Overview
Problem
Conventional laser machining devices face challenges in maintaining accurate machining positions due to environmental changes, such as temperature fluctuations, leading to positional deviations between the laser unit's optical axis and the infrared microscope's optical axis, which affects the precision of wafer machining, especially in narrow street processes where the width of intended dividing lines is less than 20 μm.
Innovation Solution
A laser machining device with a detection controller, laser machining controller, imaging controller, arithmetic operation unit, and correction unit that uses relative motion mechanisms to correct positional deviations by imaging alignment references, detecting intended dividing lines, and forming modified regions within the focusing range of the infrared imaging optical system, allowing for precise alignment and correction of the machining position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If periodic maintenance is performed to correct positional deviation, then machining precision can be restored, but productivity is reduced due to downtime and additional labor
Solution Approach 1:
The system performs preliminary action by automatically detecting and correcting positional deviation during the machining process itself, rather than waiting for periodic maintenance. The arithmetic operation unit continuously calculates correction values based on real-time imaging data, and the correction unit applies these corrections before they affect machining precision, thereby eliminating the need for separate maintenance downtime.
Solution Approach 2:
The system implements feedback by using the infrared imaging optical system to continuously monitor the actual machining position, comparing it with the intended position, and automatically adjusting the laser unit's position through the correction unit. This closed-loop feedback mechanism maintains machining precision without requiring external intervention or periodic maintenance stops.
2Measurement precision
If external test pieces are used for alignment correction, then positional deviation can be detected, but device complexity and labor requirements increase
Solution Approach 1:
The infrared imaging optical system serves multiple functions: it is used for both observing the wafer during laser machining and for detecting positional deviation of the laser unit. This multi-functionality eliminates the need for separate test pieces or dedicated measurement devices, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The system performs self-service by using its own infrared imaging optical system to detect and correct its positional deviation, rather than requiring external test pieces or separate measurement equipment. The arithmetic operation unit automatically calculates correction values based on images captured by the system's own imaging device, eliminating the need for external calibration tools.
3Ease of manufacture
If the laser unit and infrared microscope are positioned separately, then each component can be optimized independently, but alignment accuracy deteriorates due to environmental changes
Solution Approach 1:
The system merges the laser unit and infrared imaging optical system into a single integrated machining unit that moves together as one body. This combination ensures that both components experience identical environmental conditions and positional changes, maintaining their relative alignment accuracy while still allowing independent optimization of each component's design and performance characteristics.
Solution Approach 2:
The integrated machining unit acts as an intermediary that couples the laser unit and infrared imaging optical system together, ensuring they move in unison and maintain consistent relative positioning. This intermediary structure allows both components to be optimized independently while guaranteeing their alignment through the shared mounting mechanism that responds uniformly to environmental changes.
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 enables highly accurate laser machining by correcting positional relationships between the laser unit and infrared microscope optical axes, ensuring precise formation of modified regions along intended dividing lines, even under environmental changes, without the need for periodic maintenance or external test pieces, thus improving yield and reducing labor and costs.
Implementation Method 1
a laser optical system that emits laser light toward one surface of a wafer
Implementation Method 2
modified regions are formed inside the wafer along intended dividing lines on the wafer
Implementation Method 3
an infrared imaging optical system that is disposed at a position facing the one surface, has a second optical axis different from a first optical axis of the laser optical system and images the wafer
Data Source
AI summary
A laser machining device which condenses a laser light inside a wafer and forms modified regions in a plurality of layers in the wafer, includes an infrared imaging optical system configured to face one surface of the wafer. In a case where a modified region positioned on a side of another surface opposite to the one surface of the wafer is defined as a first modified region and another modified region is defined as a second modified region, among the modified regions in the plurality of layers, the infrared imaging optical system has a focusing range that includes the first modified region and the another surface, and simultaneously images the first modified region and the another surface, and the second modified region is positioned outside the focusing range.