Mask Inspection Microscope Diaphragm Pixel Segmentation
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Solution Overview
Problem
Current mask inspection microscopes are limited in their ability to accurately adapt illumination settings to scanners, as they can only achieve 'top hat' intensity profiles with steep gradients between maximum and minimum intensities, failing to realize finer gradations and complex illumination settings required for advanced imaging.
Innovation Solution
A diaphragm with light-transmissive and light-opaque pixels is used to create a resultant intensity distribution with additional intensity values between minimum and maximum, allowing for more precise simulation of scanner illumination settings by varying pixel size, distance, and arrangement, enabling softer transitions and higher resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional diaphragms with light-transmissive and light-opaque regions are used, then the illumination setting can be varied within wide ranges, but the intensity distribution can only achieve 'top hat' profiles with steep gradients between maximum and minimum intensities
Solution Approach 1:
The diaphragm is divided into multiple pixels of different sizes (large pixels, medium pixels, small pixels) that can be independently controlled. This segmentation allows each pixel to contribute differently to the overall intensity distribution, enabling fine gradations between maximum and minimum intensities while maintaining the ability to vary illumination settings within wide ranges
Solution Approach 2:
Different regions of the diaphragm (different pixels) are given different properties (different sizes and transmission characteristics). This local differentiation allows precise control of intensity at specific locations in the pupil plane, achieving both versatile illumination settings and precise intensity distribution control with softer transitions
2Device complexity
If simple diaphragms are used in mask inspection microscopes, then the device complexity is reduced, but the ability to realize complex illumination settings with finer gradations is limited
Solution Approach 1:
The diaphragm structure is made dynamically controllable through the independent control of multiple pixel regions. This allows the system to adapt to complex illumination settings requirements while maintaining a relatively simple physical structure that can be configured for different illumination patterns as needed
3Adaptability or versatility
If axicons and zoom lenses are used to achieve annular and multipolar illumination, then the illumination settings can be varied, but the intensity distribution still cannot achieve finer gradations between maximum and minimum values
Solution Approach 1:
Instead of using continuous optical elements like axicons that produce limited intensity profiles, the diaphragm is segmented into multiple discrete pixels of varying sizes. This segmentation enables precise control over the intensity distribution with fine gradations, while still achieving annular, multipolar, and other complex illumination patterns through appropriate pixel configuration
Solution Approach 2:
The invention changes the parameters of the diaphragm structure (pixel size, pixel distribution, pixel transmission) to achieve different illumination settings. By varying these parameters, the system can produce both the required illumination patterns and the fine intensity gradations that continuous optical elements cannot achieve
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 solution enables the mask inspection microscope to achieve more accurate and varied illumination settings, improving imaging capabilities by allowing for finer gradations and more precise adaptation to scanner requirements, enhancing defect detection and registration accuracy.
Implementation Method 1
the diaphragm (51) has a transmission that varies in a location-dependent manner for the projection light, such that the at least one further intensity value is formed
Data Source
AI summary
During mask inspection it is necessary to identify defects which also occur during wafer exposure. Therefore, the aerial images generated in the resist and on the detector have to be as far as possible identical. In order to achieve an equivalent image generation, during mask inspection the illumination and, on the object side, the numerical aperture are adapted to the scanner used. The invention relates to a mask inspection microscope for variably setting the illumination. It serves for generating an image of the structure (150) of a reticle (145) arranged in an object plane in a field plane of the mask inspection microscope. It comprises a light source (5) that emits projection light, at least one illumination beam path (3, 87, 88), and a diaphragm for generating a resultant intensity distribution of the projection light in a pupil plane (135) of the illumination beam path (3, 87, 88) that is optically conjugate with respect to the object plane. According to the invention, the diaphragm is embodied in such a way that the resultant intensity distribution of the projection light has at least one further intensity value between a minimum and a maximum intensity value.