Wafer Inspection Objective Lens Layout for Wide-Field Aberration Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing objectives for wafer inspection face challenges in achieving high resolution with a wide field of view and long working distance while effectively correcting aberrations, particularly spherical aberration and coma aberration, due to the limitations of existing lens configurations.
Innovation Solution
The objective design includes a first lens group with a meniscus lens having positive refractive power and a second lens group with negative refractive power, featuring a pair of meniscus lens components and multiple cemented lenses, configured to satisfy specific conditional expressions to correct aberrations and ensure a high numerical aperture and long working distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the numerical aperture is increased to achieve high resolution, then the resolution is improved, but the working distance becomes short and the risk of collision increases
Solution Approach 1:
The objective lens is divided into multiple lens groups (first lens group with positive refractive power, second lens group with negative refractive power, and additional lens groups) that work together to achieve both high numerical aperture and long working distance. Each lens group is optimized for specific functions: the first lens group (including meniscus lens L1) corrects spherical and coma aberrations, while subsequent groups contribute to overall aberration correction and focal length control, enabling the contradiction to be resolved through functional segmentation.
Solution Approach 2:
The patent employs composite lens structures including cemented lenses (multiple lenses cemented together) and a combination of positive and negative meniscus lens components. These composite optical structures allow for sophisticated aberration correction while maintaining the required numerical aperture and working distance characteristics, resolving the contradiction between resolution and working distance.
2Productivity
If the field of view is widened to improve throughput, then the throughput is improved, but the aberration correction becomes difficult particularly for spherical aberration and coma aberration
Solution Approach 1:
The objective lens is divided into multiple lens groups (first lens group with positive refractive power, second lens group with negative refractive power, and additional lens groups) that work together to achieve both high numerical aperture and long working distance. Each lens group is optimized for specific functions: the first lens group (including meniscus lens L1) corrects spherical and coma aberrations, while subsequent groups contribute to overall aberration correction and focal length control, enabling the contradiction to be resolved through functional segmentation.
Solution Approach 2:
Different lens groups are assigned different optical properties and positions to correct specific types of aberrations in different regions of the optical path. The first lens group with positive refractive power is positioned to correct spherical and coma aberrations from the object side, while the second lens group with negative refractive power addresses other aberration components, allowing effective aberration correction across the wide field of view.
3Device complexity
If a compact configuration is achieved to reduce size, then the device complexity is reduced, but the aberration correction capability deteriorates
Solution Approach 1:
Multiple lens elements are cemented together to form cemented lenses, merging several optical functions into compact units. This reduces the overall size and complexity of the objective lens while maintaining the aberration correction capabilities that would otherwise require separate, larger optical components.
Solution Approach 2:
The patent employs composite lens structures including cemented lenses (multiple lenses cemented together) and a combination of positive and negative meniscus lens components. These composite optical structures allow for sophisticated aberration correction while maintaining the required numerical aperture and working distance characteristics, resolving the contradiction between resolution and working distance.
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
The design achieves favorable correction of aberrations across a wide field of view, enabling high resolution and throughput with a compact configuration, while maintaining a high numerical aperture and long working distance.
Implementation Method 1
a first lens group G1 that has positive refractive power and converts divergent light from an object point to convergent light
Implementation Method 2
The second lens group G2 includes a pair of meniscus lens components L4, L5 whose concave surfaces face each other. The meniscus lens components L4, L5 have negative refractive power
Data Source
AI summary
The objective includes a first lens group having positive power and a second lens group having negative power and including a pair of meniscus lens components having concave surfaces facing each other. The first lens group includes a first lens situated closest to an object side and has positive power with a concave surface facing the object side. The objective includes three or more cemented lenses arranged closer to the object side than the pair of meniscus lens components, and satisfies the following conditional expressions.2.6≤φL1/DL1≤16 (1)0.1≤|R212|/f≤3.5 (2)Here, φL1 and DL1 are an outer diameter and a thickness of the first lens. R212 is a radius of curvature of a surface closest to the image side in a first meniscus lens component among the pair of meniscus lens components. f is a focal length of the objective.