Peripheral Illumination Crack Detection for Transparent SAW Wafer Processing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for laser processing of transparent materials like lithium tantalate and lithium niobate do not effectively detect or prevent the extension of pre-existing cracks during the processing of wafers into SAW devices.
Innovation Solution
An inspecting apparatus and laser processing apparatus are designed with illuminating and imaging means to detect cracks in transparent members by illuminating from the periphery and imaging the transparent member, allowing for the detection and display of cracks, and optionally storing their positions for comparison before and after laser processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a pulsed laser beam is applied to form laser processed grooves on a wafer, then the wafer can be divided into separate regions for SAW devices, but pre-existing minute cracks may be extended to affect devices that were previously crack-free
Solution Approach 1:
The inspection apparatus performs crack detection on the wafer before laser processing is applied. By identifying minute cracks in advance using the illuminating means and imaging means, the system can prevent laser processing on regions with pre-existing cracks, thereby avoiding crack extension while maintaining productive processing on crack-free regions
Solution Approach 2:
The system uses imaging means to capture images of the wafer surface, processes these images to detect cracks, and provides feedback information about crack locations. This feedback enables selective laser processing or rejection of affected regions, resolving the contradiction between maintaining productivity and preventing crack extension
2Device complexity
If the wafer is illuminated from the front side to detect cracks, then the lighting setup becomes simple, but cracks in transparent materials are difficult to detect due to light transmission
Solution Approach 1:
Instead of illuminating the wafer from the front side (where cracks are located), the system illuminates from the back side (opposite side) of the transparent wafer. Light passes through the wafer and cracks create visible shadows or refraction patterns when viewed from the front, enabling crack detection while maintaining a simple illuminating setup
Solution Approach 2:
The transparent wafer itself acts as an optical intermediary. By illuminating from the back side, the wafer transmits light while cracks in the material create optical disturbances (shadows, refraction) that can be detected by the imaging means from the front side, solving both the simplicity and detection accuracy requirements
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 efficient detection and monitoring of cracks in transparent materials before and after laser processing, improving the screening process by verifying the effect of laser beam application on crack extension and enhancing the separation of SAW devices without generating new cracks.
Implementation Method 1
illuminating means adapted to be positioned in the periphery of a transparent member for illuminating the transparent member from the outside of the circumference thereof
Implementation Method 2
imaging means adapted to be opposed to the transparent member for imaging the transparent member illuminated by the illuminating means
Data Source
AI summary
Disclosed herein is an inspecting apparatus including an illuminating unit adapted to be positioned in the periphery of a transparent member for illuminating the transparent member from the outside of the circumference thereof, an imaging unit adapted to be opposed to the transparent member for imaging the transparent member illuminated by the illuminating unit, and a displaying monitor for displaying an image obtained by the imaging unit.