EUV Photomask Particle Detection via Real-Time Optical Monitoring
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Solution Overview
Problem
In extreme ultraviolet (EUV) lithography, maintaining reticle quality is challenging due to the high sensitivity of defects on photomasks, which can lead to yield, quality, and reliability issues in semiconductor devices, as conventional methods like pellicle films are not effective in reducing particles and may cause heat-related problems.
Innovation Solution
A real-time particle monitoring system is implemented in the lithography process to detect and classify particles on or near the photomask using a light source and optical sensors, allowing for their removal before exposure, and generating a reticle map to track particle positions and sizes, thereby preventing defects from being transferred to the target substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pellicle films are used in DUV processes, then particle reduction on the mask is achieved, but heat-related problems occur and particle reduction becomes insufficient for EUV wavelength requirements
Solution Approach 1:
The patent removes the pellicle film from the system entirely and replaces it with an in-situ particle detection and removal system that uses a sensor array and gas jet mechanism to detect and eliminate particles directly at the photomask surface during the lithography process
Solution Approach 2:
The patent introduces a gas jet as an intermediary mechanism that delivers particles to a collection point away from the photomask, enabling particle removal without direct contact with the photomask and avoiding heat-related problems associated with pellicle films
2Measurement precision
If real-time particle monitoring is implemented, then particle detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent divides the particle detection function into multiple discrete sensor elements arranged in an array, where each sensor independently monitors a specific region of the photomask, enabling precise particle localization while maintaining manageable system complexity through modular architecture
Solution Approach 2:
The sensor array serves multiple functions simultaneously: particle detection, particle localization, and real-time monitoring coverage of the entire photomask surface, reducing the need for separate detection systems and simplifying the overall device architecture
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 enhances the accuracy of pattern reproduction on the target substrate by identifying and removing particles in real-time, improving yield and reducing the need for manual inspection, while also eliminating the use of pellicles that can absorb EUV radiation and cause heat issues.
Implementation Method 1
determine an energy loss of the light beam... The determination of the particle may be based on a decrease in intensity or energy of the light
Data Source
AI summary
The method includes performing a photolithography process which includes using a photomask to pattern a radiation beam. The photolithography process also includes exposing a target substrate to the patterned radiation beam. During the exposing of the target surface, there is a real-time monitoring for particles incident or approximate the photomask.