Aperture Structure for Semiconductor Measurement Resolution
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Solution Overview
Problem
Current measuring systems for semiconductor manufacturing lack sufficient resolution for accurately inspecting periodic structures on substrates, particularly due to inadequate light distribution and capture of diffraction orders, leading to blurred edges and reduced resolution.
Innovation Solution
Incorporating an aperture structure with a condenser having an entrance pupil, such as an annular aperture, in the illumination beam path to modify the intensity distribution of diffraction orders, enhancing the resolution by adjusting the transmission characteristics of the aperture, which can be dynamically configured using LCD arrays or mechanical slides to optimize imaging for specific periodic structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional condenser without aperture structure is used, then the device complexity is low, but the measurement precision is insufficient due to inadequate resolution
Solution Approach 1:
The patent applies local quality by introducing an aperture structure with spatially varying transmission characteristics into the condenser. The aperture structure contains regions with different transmission properties (e.g., transparent and opaque areas) that are strategically positioned to modify the illumination beam path. This creates localized intensity distribution patterns in the pupil plane that enhance resolution for specific diffraction orders while maintaining device simplicity
Solution Approach 2:
The patent employs parameter changes by varying the transmission characteristics of the aperture structure. The aperture structure includes areas with different transmission values (from fully transparent to fully opaque), and these transmission parameters are optimized to enhance the intensity of specific diffraction orders. By adjusting the transmission parameters of different aperture regions, the system achieves enhanced resolution without requiring complex mechanical adjustments
2Measurement precision
If the aperture of the condenser is increased to capture more diffraction orders, then the resolution is enhanced, but the intensity distribution becomes unbalanced with insufficient light in higher diffraction orders
Solution Approach 1:
The aperture structure creates local quality variations in the illumination beam by introducing regions with different transmission characteristics. These localized transmission variations are designed to specifically enhance the intensity of higher diffraction orders that would otherwise be insufficient, while maintaining overall balance in the intensity distribution across all diffraction orders
Solution Approach 2:
The aperture structure acts as an intermediary element between the illumination source and the periodic structure. It mediates the intensity distribution by selectively transmitting or blocking specific portions of the illumination beam, thereby balancing the intensity across different diffraction orders and enabling enhanced resolution without overwhelming the system with unbalanced light distribution
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 solution significantly enhances the resolution and depth of focus for periodic structures, improving the accuracy and reproducibility of measurements, particularly in critical dimension measurements and optical inspections, by optimizing the capture of diffraction orders and phase relationships.
Implementation Method 1
The diffraction of light on the periodic structure generates an intensity distribution of the diffraction orders in the pupil of the imaging optics
Implementation Method 2
aperture structures provided in an illumination beam path, for changing the distribution of the intensities of the orders of diffraction in an imaging beam path
Data Source
AI summary
A measuring system is disclosed with enhanced resolution for periodic structures on a substrate for semiconductor manufacture. Aperture structures of varying geometries are provided in the illumination beam path. The aperture structures differ regarding the transmission characteristics of light, and which adjust the intensity distribution of the diffraction orders in the imaging pupil of the optical system.