Transparent Substrate Inspection via Spatial Light Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
It is challenging to inspect the polished upper surface of transparent substrates like silicon carbide and sapphire for defects due to overwhelming scattered light from the unpolished bottom surface, which interferes with the detection of defects on the top surface and transparent films formed thereon.
Innovation Solution
A system is developed that includes an illumination subsystem, an objective to collect scattered light, and an optical element to direct light from patterned features into one direction and other scattered light into another, allowing a detector to generate output responsive only to the light in the second direction, enabling the processor to detect defects on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is directed to inspect the polished upper surface, then defect detection capability is improved, but scattered light from the unpolished bottom surface overwhelms the defect signal
Solution Approach 1:
The patent introduces a new dimension by using a mirror to redirect scattered light from the bottom surface away from the detector. The mirror is positioned at a specific angle to reflect the harmful scattered light into a different spatial direction, while allowing the useful defect signal to reach the detector directly. This spatial separation resolves the contradiction by adding a dimensional component to the optical path management.
Solution Approach 2:
The mirror acts as an intermediary element between the substrate and the detector. It selectively interacts with the scattered light from the bottom surface, redirecting it away from the detection path, while being transparent to the useful defect signals. This intermediary component enables the system to distinguish between harmful and useful signals by manipulating their spatial trajectories.
2Measurement precision
If light is directed to inspect the patterned upper surface, then defect detection capability is improved, but scattered light from patterned structures superimposes on the defect signal
Solution Approach 1:
The patent applies dimensional separation by using a mirror to create a spatial distinction between the scattering patterns from the patterned structures and the defect signals. By redirecting the scattered light from patterned features into a different spatial dimension, the system can filter out these interfering signals while maintaining the defect detection capability through proper optical path design.
3Ease of manufacture
If the substrate is transparent and unpolished on the bottom surface, then manufacturing simplicity is improved, but inspection difficulty increases due to overwhelming scattered light
Solution Approach 1:
The mirror serves as an intermediary device that compensates for the unpolished bottom surface without requiring any changes to the substrate manufacturing process. It selectively manages the scattered light from the unpolished surface, redirecting harmful signals away from the detector while preserving the ability to detect defects on the polished upper surface. This approach maintains manufacturing simplicity while resolving the inspection difficulty.
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 system effectively separates and detects defects on the top surface of transparent substrates by isolating the scattered light from the patterned features from the bottom surface, improving the detection capability of defects on substrates with patterned features.
Implementation Method 1
light scattered from the patterned features into a first direction and other scattered light into a second direction
Implementation Method 2
an optical element positioned in a path of the light collected by the objective. The optical element is configured to direct light scattered from the patterned features into a first direction and other scattered light into a second direction
Data Source
AI summary
Various embodiments for substrate inspection are provided.