In-situ Wavefront Aberration Measurement via PDI Plate
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Solution Overview
Problem
Existing optical inspection devices for semiconductor manufacturing lack the ability to precisely measure wavefront aberrations of objective and imaging lenses in real operating conditions, especially after installation and shipment, due to limitations in current wavefront aberration measuring equipment, and there is a need for in-situ measurement of combined lens aberrations during semiconductor production.
Innovation Solution
An inspection device and method utilizing a point light source, diffraction grating, and a point diffraction interferometry (PDI) plate with large and small holes, allowing for in-situ measurement of wavefront aberrations by diffracting and analyzing measurement light to form fringe images, enabling precise detection of aberrations in the objective and pupil relay lenses without affecting the optical path of the sample inspection system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated wavefront aberration measuring equipment such as an interferometer is used to measure the objective lens and imaging lens separately, then measurement precision can be achieved, but the lenses cannot be measured in their actual operating state after mounting and transportation, and combined lens aberrations cannot be measured
Solution Approach 1:
The patent merges the measurement function with the inspection device itself by integrating a point light source, diffraction grating, and PDI plate into the existing optical path. This allows the inspection device to measure wavefront aberrations of the objective lens and imaging lens in their actual mounted state, eliminating the need for separate dedicated measuring equipment and enabling measurement of combined lens aberrations.
Solution Approach 2:
The inspection device is designed to perform both inspection functions and wavefront aberration measurement functions using the same optical path and components. The point light source can be switched between sample illumination and measurement light emission, and the diffraction grating and PDI plate serve dual purposes in both measurement modes, achieving multi-functionality without requiring separate dedicated equipment.
2Measurement precision
If wavefront aberration measuring equipment is used before lenses are mounted, then separate lens aberrations can be measured, but combined lens aberrations after mounting and transportation cannot be quantitatively measured
Solution Approach 1:
The patent enables wavefront aberration measurement to be performed at any stage after lens mounting by integrating the measurement capability into the inspection device. This preliminary integration allows measurements to be conducted before, during, or after transportation and installation, providing temporal flexibility that was not available with separate dedicated measuring equipment.
3Device complexity
If conventional measurement methods are used, then equipment complexity is reduced, but the ability to measure combined lens aberrations in real operations is lost
Solution Approach 1:
The patent introduces a point diffraction interferometry plate with a specific hole pattern as an intermediary element in the optical path. This PDI plate, combined with a diffraction grating and point light source, acts as a mediator that enables wavefront aberration measurement without requiring complex dedicated interferometer equipment, thus achieving in-situ measurement capability while maintaining relatively simple device structure.
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
Enables high-precision in-situ measurement of wavefront aberrations, improving imaging performance and allowing for real-time management of semiconductor manufacturing processes without the need for expensive additional equipment, and simplifies the measurement of combined lens aberrations.
Implementation Method 1
a diffraction grating disposed between the first lens and the intermediate imaging plane and that diffracts the measurement light
Implementation Method 2
a point diffraction interferometry (PDI) plate disposed within a range of a depth of focus of the intermediate imaging plane... the PDI plate transmits light diffracted by the diffraction grating
Data Source
AI summary
An inspection device includes an objective lens that transmits inspection light reflected from a sample during inspection and measurement light from a point light source during aberration measurement, a first pupil relay lens that transmits the inspection light and the measurement light, a second pupil relay lens in which an intermediate imaging plane is formed between the second pupil relay lens and the first pupil relay lens, a diffraction grating disposed between the first pupil relay lens and the intermediate imaging plane and that diffracts the measurement light, a point diffraction interferometry plate disposed within a depth of focus of the intermediate imaging plane and that selectively transmits the diffracted light, a first detector that detects an image of the sample, and a second detector that detects a fringe image of the measurement light.