Optical EUV Pellicle Inspection for Lifetime Prediction
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Solution Overview
Problem
Carbon nanotube (CNT) pellicles used in EUV lithography are susceptible to damage from intense EUV radiation, leading to contamination of the lithography machine and potential downtime due to pellicle rupture, which can cause defects in semiconductor wafers and increase production costs.
Innovation Solution
Implement non-destructive methods to predict pellicle lifetime by correlating pellicle thickness and density with measured transmittance of non-EUV radiation, allowing for timely replacement or maintenance to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If CNT pellicles are used in EUV lithography, then particle blocking capability is improved, but susceptibility to EUV radiation damage increases
Solution Approach 1:
The patent applies preliminary action by implementing non-destructive inspection methods (optical coherence tomography, reflectometry, interferometry) to assess pellicle condition before EUV radiation causes damage. These inspection techniques detect changes in pellicle thickness, density, and optical properties in advance, allowing timely replacement before rupture occurs, thus preventing contamination while maintaining the benefits of CNT pellicles.
2Reliability
If non-destructive inspection methods are implemented, then pellicle lifetime prediction is improved, but system complexity increases
Solution Approach 1:
The patent replaces complex mechanical inspection systems with optical-based non-destructive inspection methods. Techniques such as optical coherence tomography, reflectometry, and interferometry use light interactions to assess pellicle condition without physical contact or complex mechanical components, thereby improving prediction accuracy while minimizing added system complexity.
Solution Approach 2:
The patent introduces optical properties (reflectivity, transmittance, optical path length) as intermediary parameters that correlate with pellicle thickness and density. These optical intermediaries provide indirect but accurate measurement of pellicle condition, simplifying the inspection process while maintaining high prediction accuracy for pellicle lifetime.
3Object-affected harmful factors
If pellicle inspection and timely replacement is performed, then contamination prevention is improved, but production downtime increases
Solution Approach 1:
The patent enables preliminary detection of pellicle degradation through non-destructive inspection methods, allowing planning of pellicle replacement during scheduled maintenance windows rather than responding to emergency failures. This proactive approach prevents contamination while minimizing unplanned downtime by coordinating replacements with existing production schedules.
Solution Approach 2:
The patent implements feedback mechanisms where inspection results (changes in optical properties, thickness, density) are continuously monitored and fed back to production scheduling systems. This feedback loop optimizes replacement timing to balance contamination prevention with production continuity, replacing pellicles just before predicted failure points rather than using fixed conservative intervals.
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
Early detection of pellicle damage prevents contamination and downtime by ensuring timely replacement, maintaining the integrity of the EUV lithography system and reducing production defects.
Implementation Method 1
causing the pellicle to generate radiation when a source of first radiation causes the first radiation to impinge on the reticle
Implementation Method 2
measuring an intensity of the radiation generated by the pellicle
Data Source
AI summary
An embodiment method of inspecting an EUV pellicle includes generating a plurality of intensity measurements by causing first radiation to impinge on the EUV pellicle, which causes the EUV pellicle to generate second radiation, and measuring an intensity of the second radiation. The method further includes determining, from a plurality of such intensity measurements, a time-dependent intensity increase and predicting a pellicle lifetime based on the time-dependent intensity increase. The first radiation includes wavelengths from 150 nm to 350 nm, from 495 nm to 570 nm, or a white light spectrum. Measuring the intensity of the second radiation further includes measuring a first intensity component of a first wavelength and measuring a second intensity component of a second wavelength, with measured wavelengths chosen from 402 nm, 425 nm, 450 nm, 475 nm, 515 nm, 550 nm, 555 nm, 600 nm, 640 nm, 690 nm, 745 nm, and 855 nm.