Rectangular Pixel Photodetector for Anamorphic Mask Inspection
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Solution Overview
Problem
In semiconductor inspection using anamorphic masks, reducing pixel size to enhance resolution leads to a decrease in light reception area per pixel, resulting in a deteriorated signal-to-noise ratio and difficulty in maintaining contrast.
Innovation Solution
A mask inspection method and apparatus utilizing a photodetector with rectangular pixels, where the ratio of pixel dimensions in the longitudinal direction to the lateral direction matches the inverse ratio of the reduction rates in those directions, allowing for improved resolution in the required direction while maintaining contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel size of the TDI sensor is reduced to increase resolution, then the resolution is improved, but the light receiving area per pixel is reduced and the signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies local quality by making the pixel shape asymmetric (rectangular rather than square) to match the anamorphic reduction rates in different directions. The pixel dimensions are specifically configured so that the ratio of the dimension in the longitudinal direction to the dimension in the lateral direction equals the inverse ratio of the reduction rates, optimizing light collection in each direction according to the specific inspection requirements
Solution Approach 2:
The patent changes the geometric parameters of the pixels from square to rectangular with specific aspect ratios. By adjusting the pixel dimensions to match the inverse ratio of reduction rates, the system maintains adequate light receiving area while achieving the required resolution in both longitudinal and lateral directions for anamorphic mask inspection
2Measurement precision
If the pixel size is reduced to detect smaller defects, then the detection capability is improved, but the amount of light received is reduced and contrast is difficult to maintain
Solution Approach 1:
The rectangular pixel configuration optimizes light collection efficiency in specific directions by matching the anamorphic reduction characteristics. This directional optimization ensures sufficient light receiving area is maintained even when pixel dimensions are reduced, thereby preserving image contrast while enhancing defect detection capability
Solution Approach 2:
The patent introduces asymmetry in pixel geometry (rectangular shape with specific aspect ratio) to match the asymmetric anamorphic reduction rates. This asymmetric design allows the pixel array to efficiently capture light in both longitudinal and lateral directions according to the specific inspection requirements, maintaining contrast while improving resolution
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-resolution inspection of anamorphic masks by maintaining the light reception area, preventing deterioration of the signal-to-noise ratio and contrast, thus facilitating precise defect detection.
Implementation Method 1
capturing an image of the mask using a photodetector including a rectangular pixel
Data Source
AI summary
Resolution is improved in a required direction while maintaining contrast in inspection of an anamorphic mask. A method for inspecting a mask with a reduction rate at the time of exposure in a longitudinal direction different from a reduction rate at the time of exposure in a lateral direction according to the present disclosure includes capturing an image of the mask using a photodetector including a rectangular pixel, a ratio of a dimension of the rectangular pixel in the longitudinal direction to a dimension of the rectangular pixel in the lateral direction being equal to an inverse ratio of the reduction rate in the longitudinal direction to the reduction rate in the lateral direction.