EUV Mask Pellicle Inspection for Contaminant and Angle Analysis
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Solution Overview
Problem
EUVL technology faces challenges with pellicle materials that are not suitable for extreme ultraviolet light, and contaminants affect mask imaging, necessitating a device to study the impact of contaminants and optimize pellicle-mask distance and material properties.
Innovation Solution
An extreme ultraviolet lithography mask pellicle inspection device with adjustable distance and angle settings to analyze contaminants and pellicle properties, including a hydrogen production module for chemical reaction studies, and modules for measuring transmissivity, reflectivity, and reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a pellicle is introduced to prevent particles from falling onto the mask pattern, then particle contamination is reduced, but larger-sized contaminants can still significantly affect pattern formation
Solution Approach 1:
The patent replaces physical particle filtering with optical property measurement and chemical analysis. Instead of relying solely on the mechanical barrier of the pellicle, the system uses spectroscopic methods to detect and characterize contaminants, enabling identification of both particle and stain contaminants through their optical signatures.
Solution Approach 2:
The patent introduces an intermediary measurement system between the pellicle and mask that characterizes contaminants without physical contact. This intermediary layer of analysis allows for detection of contaminant properties (size, type, chemical composition) that would otherwise require direct interaction with the mask pattern.
2Ease of manufacture
If traditional transmissive Deep Ultraviolet mask technology is used, then manufacturing is simpler, but EUVL process requirements cannot be met
Solution Approach 1:
The patent changes the operating parameters from traditional transmissive DUV to reflective EUV, measuring optical properties at EUV wavelengths (13.5 nm). This parameter change enables compatibility with EUVL processes while maintaining measurement capabilities through adaptation of the inspection system to the new wavelength regime.
Solution Approach 2:
The patent employs composite measurement approaches that combine multiple characterization techniques (transmissivity measurement, transmission uniformity measurement, reflectivity measurement) to assess pellicle performance. This composite methodology provides comprehensive evaluation needed for EUVL applications.
3Strength
If nanometer-thick graphite films are used for pellicle material, then light transmissivity and mechanical strength are excellent, but reactivity with hydrogen poses a challenge
Solution Approach 1:
The patent uses extreme ultraviolet light as a high-energy radiation source that accelerates chemical reaction detection. The EUV irradiation promotes hydrogen radical generation and accelerates the reaction between hydrogen and graphite film, enabling faster and more sensitive detection of chemical changes through real-time monitoring of transmissivity and reflectivity variations.
Solution Approach 2:
The patent implements real-time feedback monitoring of pellicle optical properties during hydrogen exposure. By continuously measuring transmissivity, transmission uniformity, and reflectivity, the system provides feedback on chemical changes occurring in the graphite film, enabling detection of degradation mechanisms and assessment of chemical stability.
4Productivity
If oblique incidence with high numerical aperture is used, then lithography resolution is improved, but incidence angle increases affecting optical properties measurement
Solution Approach 1:
The patent employs dynamic measurement capabilities that can adjust to different incidence angles. The system is designed to measure optical properties at the specific oblique incidence angles used in high-NA EUVL (e.g., 6° chief ray angle), adapting the measurement geometry to match the actual lithography conditions rather than requiring normal incidence measurements.
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 precise analysis of contaminant impact and pellicle performance under EUV irradiation, determining optimal pellicle-mask distance and material properties for improved imaging quality.
Implementation Method 1
an extreme ultraviolet light source with a wavelength in a range of 10 to 20 nm
Implementation Method 2
a hydrogen production module to control a hydrogen partial pressure in the vacuum chamber, wherein the adjustable range is 0 to 10 Pa
Data Source
AI summary
Pellicle inspection device for extreme ultraviolet lithography masks comprises inspection light source module to generate light source with wavelength in extreme ultraviolet band and equipped with extreme ultraviolet irradiation time control electronic shutter and light source transmission system; sample platform module in vacuum chamber to fix, move and rotate sample to switch between different performance tests of pellicle and achieve irradiation of extreme ultraviolet light source at different positions and angles of incidence on pellicle; module for detecting impact of contaminants on mask imaging to study impact of different types and sizes of contaminants below 50 μm and distance between pellicle and mask on mask imaging and determine optimal distance; module for measuring transmissivity, transmittance uniformity, and reflectivity of pellicle to measure optical properties of pellicle at different angles of incidence and study impact of chemical changes of pellicle on optical properties.