Photoluminescence Defect Positioning on Semiconductor Substrates
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Solution Overview
Problem
Current methods for detecting defects on semiconductor substrates, such as silicon wafers, struggle to accurately identify the position of defects, especially when they are located under passivation layers or on specific faces of the substrate, due to low charge carrier lifetimes and limited penetration depth of photoluminescence techniques, which complicates industrial manufacturing processes.
Innovation Solution
A method that modulates the wavelength and charge carrier lifetime during photoluminescence characterization to differentiate defect signals based on their location on either face of the substrate, using a control substrate with a low charge carrier lifetime to enhance measurement contrast and accurately determine defect positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photoluminescence techniques are used with standard charge carrier lifetimes, then defect detection can be performed, but the measurement contrast between defects on different faces is insufficient to accurately identify defect positions
Solution Approach 1:
The patent changes the parameter of charge carrier lifetime by introducing a control substrate with modified lifetime characteristics. This allows the photogenerated carriers to recombine preferentially at defects on the illuminated face, creating sufficient contrast to distinguish front-face defects from back-face defects in photoluminescence images.
Solution Approach 2:
The patent introduces a control substrate as an intermediary element with known defect positions and modified charge carrier lifetime. This control substrate serves as a reference to interpret photoluminescence signals from the actual substrate, enabling accurate defect position identification through comparative analysis.
2Length of stationary object
If the penetration depth of photoluminescence is increased to detect deeper defects, then more defects become visible, but the ability to differentiate between front and back face defects is lost
Solution Approach 1:
The patent modifies the charge carrier lifetime parameter to create a balance where photoluminescence can penetrate sufficiently to detect defects while maintaining face-specific signal differentiation. The controlled lifetime ensures carriers recombine at illuminated-face defects before reaching back-face defects, preserving localization accuracy.
3Measurement precision
If additional manipulations are performed on substrates to enhance defect detection, then detection sensitivity improves, but additional defectivity is introduced
Solution Approach 1:
The control substrate acts as a mediator that undergoes lifetime modification without affecting the actual substrates being inspected. This separates the enhancement process from the sample preparation, avoiding introduction of additional defects to the substrates of interest.
Solution Approach 2:
The control substrate serves as a copy or reference model with known defect positions. By analyzing the control substrate's photoluminescence response, the system can interpret signals from actual substrates without performing manipulations on them, thus avoiding additional defectivity.
4Measurement precision
If existing defect characterization methods are implemented in industrial production lines, then defect identification capability is achieved, but significant investment is required
Solution Approach 1:
The patent makes the photoluminescence inspection system multi-functional by enabling it to perform both conventional defect detection and face-specific defect localization using the same hardware. The control substrate approach allows existing equipment to achieve enhanced capabilities without requiring additional specialized devices or significant investment.
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 allows for precise identification of defect positions on both faces of the substrate, improving defectivity detection and enabling better quality control in industrial manufacturing by increasing the measurement contrast beyond a threshold value, facilitating the differentiation of defects on the illuminated versus unlit faces.
Implementation Method 1
characterization step by photoluminescence of each face of the control substrate
Data Source
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Figure 5A
AI summary
One aspect of the invention relates to a method for determining the location of at least one defect on semiconductor substrates in a production line. The method is implemented using at least one test substrate having a first face and a second face, and includes, for each test substrate, a step of characterizing each face of the test substrate by photoluminescence at at least one point in the production line. The method also includes a step of determining the position and the face of the test substrate on which each defect considered during the characterization step is located.