Wafer Crack Inspection Using Infrared Feedback Control
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Solution Overview
Problem
In laser processing devices, the length of cracks formed across modified regions in semiconductor substrates may not reach the desired length, leading to unreliable cutting of wafers along intended lines due to issues with the processing device.
Innovation Solution
An inspection device and method that includes a stage for supporting wafers, a laser irradiation portion for forming modified regions, an image capturing portion to detect light penetrating the substrate, and a control portion to determine the crack length and adjust irradiation conditions based on captured images, ensuring the crack reaches the desired front surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser light is irradiated to form modified regions in the semiconductor substrate, then the wafer can be cut along lines, but the crack length may not reach the desired length due to device problems
Solution Approach 1:
The patent implements a feedback mechanism where the infrared camera captures images of the semiconductor substrate after laser irradiation, the image processing unit analyzes the crack length from captured images, and the control unit adjusts laser irradiation conditions based on the analysis results to achieve the desired crack length, thereby resolving the contradiction between manufacturing precision and reliability
Solution Approach 2:
The patent performs preliminary inspection of crack length immediately after laser irradiation using infrared imaging before proceeding to the cutting process. This preliminary action allows detection and correction of insufficient crack length before actual cutting, ensuring both precision and reliability
2Reliability
If the crack length is not sufficient to reach the front surface, then the wafer cannot be reliably cut, but increasing laser energy may cause processing damage
Solution Approach 1:
The control unit uses feedback from image analysis to precisely control laser irradiation parameters. By measuring actual crack length and comparing it with the target length, the system adjusts laser energy to achieve sufficient crack length without excessive energy that would cause processing damage
Solution Approach 2:
The patent dynamically adjusts laser irradiation parameters (energy, pulse duration, frequency) based on real-time crack length measurement. This parameter optimization ensures the crack reaches the front surface for reliable cutting while avoiding excessive energy input that would cause processing damage to the functional element layer
3Measurement precision
If an infrared camera is used to observe modified regions and cracks, then the crack length can be detected, but the system complexity increases
Solution Approach 1:
The patent introduces an infrared camera as an intermediary device that non-invasively observes the semiconductor substrate from the rear surface. This intermediary enables precise crack length measurement without physical contact or additional processing steps, achieving high measurement precision while adding minimal system complexity
Solution Approach 2:
The infrared camera system serves multiple functions: it observes modified regions, detects crack formation, measures crack length, and provides feedback for control. This multi-functionality reduces the need for separate inspection devices, thereby limiting the increase in system complexity while maintaining high measurement precision
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
The solution allows for precise adjustment of crack length, ensuring reliable cutting of wafers by accurately determining and adjusting the crack length, improving the accuracy and reliability of the laser processing device.
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... one or a plurality of modified regions are formed inside the semiconductor substrate when the wafer is irradiated with the laser light
Data Source
AI summary
A laser processing device includes a stage; a laser irradiation unit; an image capturing unit; 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, determining whether or not a crack extending from the modified region is in a crack reaching state where the crack has reached a front surface side of the semiconductor substrate on the basis of a signal output from the image capturing unit, and deriving information related to adjustment of irradiation conditions of the laser irradiation unit on the basis of determination results.