EUV Mask Inspection With Multi-Angle Diffraction Synthesis
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Solution Overview
Problem
Existing EUV mask inspection technologies face challenges in achieving high-resolution spatial domain imaging without expensive facet mirrors, and they struggle to implement various illumination systems effectively, leading to inconsistent mask inspection accuracy and high costs.
Innovation Solution
An EUV mask inspection apparatus using a light source, mirror, mirror stage, and detection array to control EUV light paths and irradiate the mask at different angles, synthesizing diffraction patterns to create various illumination systems, including dipole and annular configurations, without relying on expensive facet mirrors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-NA objective lens is used to achieve high-resolution mask imaging, then imaging performance is improved, but manufacturing difficulty and cost increase significantly
Solution Approach 1:
The patent uses a computational model to copy and simulate the optical system of the exposure machine, replacing the need for expensive high-NA objective lenses. The measurement light source and imaging lens combination with computational algorithms replicates the imaging characteristics of the exposure machine's optical system, achieving high-resolution mask imaging without requiring difficult-to-manufacture high-NA lenses.
2Measurement precision
If high-NA objective lens is used to improve resolution, then imaging performance is improved, but focus depth decreases
Solution Approach 1:
The computational optical system copying approach allows flexible adjustment of imaging parameters without being constrained by the physical limitations of high-NA lenses. The measurement system can simulate different NA values and illumination conditions computationally, maintaining both high resolution and adequate focus depth by optimizing the combination of imaging lens focal length and numerical aperture in the measurement system.
3Adaptability or versatility
If additional optical systems are installed to control illumination, then illumination control capability is improved, but light amount decreases due to EUV light characteristics
Solution Approach 1:
The patent copies the illumination system characteristics computationally rather than physically replicating complex optical components. By using a measurement light source that can be controlled to match the exposure machine's illumination conditions and processing the images computationally, the system achieves versatile illumination control without adding physical optical elements that would attenuate the already limited EUV light.
Solution Approach 2:
The patent replaces physical mechanical illumination control systems (such as facet mirrors with multiple adjustable mirrors) with a computational approach. The measurement system captures images under controlled illumination conditions and uses computational algorithms to analyze mask defects, substituting complex mechanical optical control with simpler optical components and software processing, thereby preserving light amount while maintaining illumination control capability.
4Adaptability or versatility
If facet mirror is used to control illumination system, then illumination control is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses computational copying of the exposure machine's illumination system characteristics rather than physically implementing a complex facet mirror system. The measurement system is configured to replicate the illumination conditions and optical path of the exposure machine, and computational algorithms process the images to achieve the same illumination control capability without the mechanical complexity of hundreds of independently adjustable mirrors.
Solution Approach 2:
The patent replaces the mechanical facet mirror system with a combination of a measurement light source, imaging lens, and computational processing. This substitution eliminates the need for complex mechanical illumination control while achieving the same functionality through controlled lighting and software-based image analysis, significantly reducing device complexity.
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 apparatus achieves high-resolution spatial domain imaging across different mask patterns, improving inspection accuracy and reducing costs by utilizing affordable components and flexible illumination systems.
Implementation Method 1
a light source for generating EUV light; a mirror for changing a path of light such that the EUV light generated from the light source is emitted to a mask
Implementation Method 2
a detection array for collecting the EUV light in diffracted through the mask to obtain a diffraction pattern of the diffracted EUV light
Data Source
AI summary
An EUV mask inspection apparatus is provided. The EUV mask inspection apparatus comprises: a light source for generating EUV light; a mirror for changing a path of light such that the EUV light generated from the light source is emitted to a mask; a mirror stage coupled to the mirror and controlling the position of the mirror such that an incident angle at which the EUV light is emitted to the mask is controlled; and a detection array for collecting the EUV light diffracted through the mask to obtain a diffraction pattern of the diffracted EUV light, wherein an illumination system is implemented by combining diffraction patterns of first EUV light and second EUV light emitted at different angles to the same region of the mask.