Rotating Lens Array Illumination for Semiconductor Inspection
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Solution Overview
Problem
Conventional illumination systems for semiconductor inspection face challenges in reducing speckle noise, which limits their ability to detect small pattern defects efficiently due to coherence-related interference fringes, and this hampers the resolution and throughput in inspecting smaller semiconductor elements and large-area LCDs.
Innovation Solution
The system employs a lens array with element lenses of equal or greater diameter than the laser beam, arranged to rotate around the optical axis, generating a single point light source that scans the sample, preventing interference fringes and ensuring even illumination, thus reducing speckle noise without degrading throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser beam is used as the light source to shorten the wavelength and enhance resolution capability, then the resolution capability is improved, but coherence-related interference fringes (speckle noise) are generated
Solution Approach 1:
The patent divides the laser beam into multiple separate beam paths by passing it through a lens array with multiple element lenses. Each element lens creates a separate sub-beam that illuminates different portions of the sample. This segmentation prevents the coherent interference fringes from forming across the entire sample area, thereby reducing speckle noise while maintaining the short wavelength benefits for high resolution.
Solution Approach 2:
The patent introduces a spatial dimension by using a lens array to create multiple beam paths in different spatial locations. Instead of a single beam illuminating the entire sample, the light is distributed across multiple spatial positions through the lens array, effectively adding a spatial dimension to the illumination and preventing coherent interference.
2Area of stationary object
If the illumination area is increased to inspect large-area LCDs, then the inspection coverage is improved, but the inspection time increases and throughput decreases
Solution Approach 1:
The lens array divides the illumination into multiple separate beam paths that simultaneously cover different areas of the large-sample. Each element lens creates a sub-beam that illuminates a specific region, allowing parallel inspection across multiple areas. This segmentation enables the entire large sample to be inspected in a single exposure time, maintaining high throughput while covering large areas.
Solution Approach 2:
The patent ensures continuous and uniform illumination across the entire sample area by using the lens array to distribute light continuously across all regions simultaneously. The multiple element lenses work in parallel to maintain continuous illumination without gaps or delays, allowing the entire large-area sample to be inspected in one continuous operation without increasing total inspection time.
3Object-affected harmful factors
If the illumination is made uniform to eliminate interference fringes, then the speckle noise is reduced, but the complexity of the illumination system increases
Solution Approach 1:
The lens array serves multiple functions simultaneously: it segments the laser beam into multiple paths, distributes light uniformly across the sample area, and prevents coherent interference fringes. By making the illumination system multi-functional, the patent reduces the need for additional separate components to address each issue individually, thereby limiting the increase in overall system complexity.
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 configuration enhances the resolution capability and efficiency of defect detection in semiconductor inspection, allowing for the identification of fine defects in semiconductor elements and large-area LCDs with improved throughput and reduced speckle noise.
Implementation Method 1
a lens array 1001 dividing a light beam from a light source (not illustrated) to generate a point light source group. The light becoming the point light source group is shaped into parallel light by a condenser lens 1002
Implementation Method 2
the light emitted from the laser beam source becomes coherent light, and unfortunately a given interference fringe (speckle) is generated due to coherence
Implementation Method 3
the light transmitted through the element lenses 1001a, 1001b, and 1001c constituting the lens array 1001 overlap one another on the object 1003 with different angles. For this reason, the interference fringe is generated on the object 1003
Data Source
AI summary
An illumination apparatus comprising, a light source that emits a laser beam, a lens array on which the laser beam is illuminated, a plurality of element lenses having a diameter greater than or equal to the laser beam are arranged in the lens array, the lens array being rotatable around an optical axis of the laser beam, wherein the two lens arrays are arrayed in an optical axis direction of the laser beam, andthe element lenses in each lens array are arranged such that a boundary between the element lenses adjacent to each other radiates from a rotation center of the lens array and a direction in which the element lens of one of the lens arrays traverses the optical axis of the laser beam is orthogonal to a direction in which the element lens of the other lens array traverses the optical axis of the laser beam.