Wafer Crack Inspection Using Light Transmission Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In laser processing devices, there is a concern that cracks formed in semiconductor substrates may not sufficiently extend to the front surface, hindering the reliable cutting of wafers along intended lines due to issues with the processing device.
Innovation Solution
An inspection device and method that uses a stage, laser irradiation, and image capturing to form modified regions inside the semiconductor substrate, detect light penetration, and determine the position of crack tips on the front and rear surfaces, assessing whether cracks have reached the front surface by analyzing differences in crack tip positions across lines with varying formation depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser light is irradiated from the rear surface side to form modified regions, then cutting along plurality of lines can be achieved, but cracks may not sufficiently extend to the front surface side
Solution Approach 1:
The patent performs preliminary inspection of crack extension depth using light transmission detection before completing the cutting process. This allows early detection of insufficient crack extension and enables adjustment of laser irradiation conditions to ensure adequate crack propagation to the front surface.
Solution Approach 2:
The patent implements a feedback mechanism where the inspection results (crack extension status) are used to control subsequent laser irradiation processes. The control portion adjusts irradiation conditions based on whether cracks have sufficiently extended, ensuring reliable cutting while preventing defects from insufficient crack propagation.
2Productivity
If crack extension is not sufficiently verified, then processing can be completed quickly, but reliable cutting cannot be ensured
Solution Approach 1:
The inspection process is performed as a preliminary step before final cutting completion. By detecting crack extension status early through light transmission inspection, the system can quickly identify insufficient cracks and trigger re-processing only where needed, maintaining high overall productivity while ensuring cutting reliability.
Solution Approach 2:
The system uses feedback from inspection results to control the cutting process. When cracks are found to be insufficient, the control portion triggers additional laser irradiation. This closed-loop control ensures reliable cutting while minimizing re-processing needs, thereby maintaining high productivity.
3Reliability
If inspection of crack extension is performed, then cutting reliability can be improved, but device complexity increases
Solution Approach 1:
The patent uses light as an intermediary to detect crack extension. Light transmission through the semiconductor substrate provides information about crack depth without requiring complex direct measurement equipment. This simple optical inspection method achieves reliable crack detection while minimizing device complexity.
Solution Approach 2:
The patent replaces complex mechanical measurement systems with an optical inspection method. Instead of using mechanical probes or complex imaging systems to measure crack depth, the system uses light transmission properties to indirectly detect crack extension status, thereby reducing device complexity while maintaining reliability.
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 accurate checking of crack extension to the front surface, allowing for precise adjustment of irradiation conditions to ensure cracks reach the desired length, thereby facilitating reliable wafer cutting.
Implementation Method 1
an image capturing portion (4) configured to output light able to penetrate the semiconductor substrate and detect the light propagated through the semiconductor substrate
Implementation Method 2
a laser irradiation portion (3) configured to irradiate the wafer with laser light... controlling the laser irradiation portion (3) such that one or a plurality of modified regions are formed inside the semiconductor substrate
Data Source
AI summary
A laser processing device includes a stage; a laser irradiation unit configured to irradiate the wafer with laser light; an image capturing unit configured to detect light propagated through a semiconductor substrate; and a control portion configured to execute controlling the laser irradiation unit such that one or a plurality of modified regions are formed inside the semiconductor substrate when the wafer is irradiated with the laser light, deriving a position of a tip of an upper crack on a rear surface side, which is a crack extending from the modified region to the rear surface side of the semiconductor substrate, on the basis of a signal output from the image capturing unit having detected the light, and determining whether or not a crack reaching state has been realized on the basis of the position of the tip of the upper crack on the rear surface side.