Wafer Backside Inspection Using Segmented Illumination
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Solution Overview
Problem
There is a growing need for an effective system to inspect the backside of semiconductor wafers for defects and quality monitoring, as existing methods are inadequate in providing comprehensive and efficient inspection solutions.
Innovation Solution
The system employs a combination of bright field and dark field light sources, a moving mechanism, and a camera to illuminate and capture images of the substrate's backside from different positions, allowing for the generation of detection signals that are processed to reconstruct images and detect defects, with the light sources configured to illuminate non-overlapping areas and the camera positioned to avoid self-reflection, enabling thorough inspection without wafer flipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single light source is used for illumination, then the device complexity is reduced, but the measurement precision and defect detection capability are insufficient
Solution Approach 1:
The illumination system is segmented into multiple independent light sources (first light source, second light source, third light source) positioned at different locations. Each light source illuminates a specific region or provides a specific illumination function, allowing comprehensive coverage of the substrate backside while maintaining independent control for optimized defect detection
Solution Approach 2:
Different light sources provide different illumination qualities tailored to specific inspection needs. The first light source provides illumination from a first location, the second from a second location, and the third from a third location, creating localized illumination zones that enhance detection of different defect types in different regions of the substrate
2Area of stationary object
If the camera optical axis passes through the substrate backside plane within the illuminated area, then the imaging coverage is maximized, but self-reflection artifacts are introduced
Solution Approach 1:
The camera optical axis is deliberately positioned asymmetrically relative to the substrate backside plane, crossing outside the substrate backside plane rather than through the center of the illuminated area. This asymmetric positioning eliminates self-reflection artifacts while the multiple light sources positioned at different locations ensure comprehensive illumination coverage of the entire substrate backside
3Ease of operation
If the substrate is inspected without flipping, then the ease of operation is improved, but the inspection completeness is reduced
Solution Approach 1:
Instead of flipping the substrate (one-dimensional solution), the system introduces multiple illumination dimensions by positioning light sources at different locations (first, second, and third locations) around the substrate. This multi-dimensional illumination approach enables comprehensive inspection of the substrate backside from various angles without requiring physical flipping, maintaining ease of operation while achieving complete inspection coverage
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 comprehensive inspection of the substrate's backside, detecting defects and evaluating quality effectively by capturing bright field and dark field images from multiple angles, ensuring high image quality and preventing self-reflection, thus addressing the inadequacies of existing inspection methods.
Implementation Method 1
a bright field light source that may be configured to illuminate different bright field illuminated parts of the surface of the substrate
Implementation Method 2
at least one dark field light source that may be configured to illuminate different dark field illuminated parts of the surface of the substrate
Implementation Method 3
a camera that may be configured to: (a) generate bright field detection signals in response to light that is detected by the camera as a result of the illumination of the different bright field illuminated parts
Data Source
AI summary
An inspection system for inspection a surface of a substrate, the inspection system may include an interface for holding the substrate; a movement mechanism for moving the interface, thereby moving the substrate between different positions; a bright field light source that is configured to illuminate different bright field illuminated parts of the surface of the substrate when the substrate is positioned at the different positions; at least one dark field light source that is configured to illuminate different dark field illuminated parts of the surface of the substrate when the substrate is positioned at the different positions; and a camera that is configured to: (a) generate bright field detection signals in response to light that is detected by the camera as a result of the illumination of the different bright field illuminated parts; and (b) generate dark field detection signals in response to light that is detected by the camera as a result of the illumination of the different dark field illuminated parts; and wherein light that is detected by the camera as the result of the illumination of the different bright field illuminated parts and as the result of the illumination of the different dark field illuminated parts does not include an image of the camera.