Substrate Edge Inspection via Optical Scanning
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Solution Overview
Problem
The existing methods for inspecting the edges of substrates for integrated circuits are inefficient due to the need for physically rotating inspection heads, which is time-consuming and limits the speed of the inspection process.
Innovation Solution
An apparatus using a light source, a two-dimensional beam deflector, and flared parabolic surfaces to create a semi-annular scanning beam that reflects off the substrate edge, allowing for defect detection without moving the inspection head, enabling the entire edge to be inspected in a single substrate rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a physical rotation of the inspection head is used to inspect the substrate edge, then the inspection can be performed, but the inspection process becomes time-consuming and reduces productivity
Solution Approach 1:
Instead of rotating the inspection head around the substrate edge, the patent inverts the approach by keeping the inspection head stationary and rotating the substrate itself. The light beam is directed along the circular path of the substrate edge through optical elements (parabolic cylinders and beam deflectors), allowing the entire edge to be inspected during a single substrate rotation without moving the inspection hardware.
Solution Approach 2:
The patent replaces the mechanical rotation of the inspection head with an optical scanning system. A light source, beam expander, quarter-wave plate, and two-dimensional beam deflector generate a beam that scans along the substrate edge through optical reflection and refraction. This eliminates the need for mechanical rotation while achieving complete edge inspection.
2Measurement precision
If the inspection head is repositioned during multiple rotations to inspect the entire edge, then complete inspection is achieved, but the complexity and time of the inspection process increases
Solution Approach 1:
The patent inverts the conventional approach by making the substrate rotate instead of repositioning the inspection head. The stationary inspection system uses optical elements to scan along the circular path of the substrate edge, achieving complete inspection during one substrate rotation without any mechanical repositioning of the inspection hardware.
Solution Approach 2:
The optical scanning system serves multiple functions: the light source provides illumination, the beam expander controls beam size, the quarter-wave plate manages polarization, and the beam deflector scans the beam along the edge. This multi-functional optical system replaces what would otherwise require multiple mechanical components for repositioning and scanning.
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 significantly increases the inspection speed by allowing the entire peripheral edge of the substrate to be inspected without repositioning the inspection head, enabling faster processing of multiple substrates compared to prior systems.
Implementation Method 1
a two-dimensional beam deflector, such as an acousto-optic beam deflector, receives the light beam and creates a semi-annular scanning beam
Implementation Method 2
A first flared parabolic surface receives the semi-annular scanning beam and directs the semi-annular scanning beam onto the edge of the substrate, thereby creating specularly reflected light from the edge of the substrate
Implementation Method 3
A second flared parabolic surface receives and directs the specularly reflected light to a detector
Implementation Method 4
a quarter-wave plate rotates the polarization of the specularly reflected light
Implementation Method 5
A Wollaston prism receives the rotated specularly reflected light and produces a first specularly reflected light component and a second specularly reflected light component
Data Source
AI summary
An apparatus for inspecting an edge of a substrate. A light source produces a light beam, and a two-dimensional beam deflector receives the light beam and creates a semi-annular scanning beam. A first flared parabolic surface receives the semi-annular scanning beam and directs the semi-annular scanning beam onto the edge of the substrate, thereby creating specularly reflected light from the edge of the substrate. A second flared parabolic surface receives and directs the specularly reflected light to a detector. The detector receives the directed specularly reflected light and produces signals. An analyzer analyzes the signals and detects defects at the edge of the substrate.