Pupil Transmittance Measurement Using Phase Diffraction Grating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring pupil transmittance distribution in projection optical systems, used in photolithography for semiconductor and liquid crystal display device manufacturing, are inefficient and lack precision, affecting the quality of pattern images formed.
Innovation Solution
A method involving a phase diffraction grating that imparts different phase values to light passing through specific regions, generating +first-order and -first-order diffracted beams which are measured to calculate the transmittance ratio across pupil partial regions, allowing for accurate determination of pupil transmittance distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used for pupil transmittance distribution, then measurement can be performed, but measurement precision and efficiency are insufficient
Solution Approach 1:
The measurement method divides the pupil into multiple partial regions and measures the transmittance of each region separately using diffracted beams. By segmenting the measurement into discrete regions that can be measured independently and then combined, the method achieves both high precision for each region and complete coverage of the entire pupil, resolving the contradiction between measurement precision and efficiency.
Solution Approach 2:
A phase diffraction grating is introduced as an intermediary element to generate multiple diffracted beams that correspond to different pupil partial regions. This intermediary device enables simultaneous measurement of multiple regions without requiring sequential scanning, thereby improving measurement efficiency while maintaining precision through the use of phase modulation.
2Measurement precision
If multiple measurement points are measured to improve accuracy, then measurement precision improves, but measurement time and system load increase
Solution Approach 1:
The method uses periodic phase modulation through the diffraction grating to generate a series of diffracted beams that sequentially illuminate different pupil regions. This periodic action allows multiple measurement points to be captured in a structured, time-efficient manner, reducing total measurement time while maintaining the precision required for accurate transmittance distribution mapping.
Solution Approach 2:
Multiple measurements from different pupil regions are merged into a single comprehensive transmittance distribution map. By combining the information from multiple diffracted beams and their corresponding pupil regions simultaneously, the method achieves high accuracy without requiring prolonged sequential measurement of each point individually.
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 enables high-accuracy, quick measurement of pupil transmittance distribution with minimal load, improving the contrast and quality of pattern images formed through the projection optical system.
Implementation Method 1
a beam diffracting step is provided which imparts a first phase value to light passing through a first phase region on the first surface and imparts a second phase value different from the first phase value to light passing through a second phase region adjacent to the first phase region, thereby diffracting the first beam
Data Source
AI summary
A measuring apparatus for measuring a pupil transmittance distribution of an optical system to be examined has a diffraction grating mounted on a first surface in an optical Fourier transform relation with a pupil of the optical system, an illumination optical system which makes a beam inclined relative to the optical axis, incident to a predetermined position on the first surface so that a +first-order diffracted beam, generated through the diffraction grating, passes through a first pupil partial region in an effective region of the pupil and so that a −first-order diffracted beam, generated through the diffraction grating, passes through a second pupil partial region, and a measuring unit which measures an intensity of the +first-order diffracted beam, and an intensity of the −first-order diffracted beam, and determines a ratio of a pupil transmittance in the first and second pupil partial region regions.