VUV Optical Metrology Contamination Control via Photodesorption
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Solution Overview
Problem
Optical metrology instruments in the vacuum ultraviolet (VUV) range face challenges with contamination on optical surfaces, leading to performance degradation and inaccurate measurements, particularly due to the buildup of moisture and hydrocarbon compounds, which existing methods struggle to address without increasing system complexity and cost.
Innovation Solution
A technique that combines vacuum and purge methods to create a controlled environment within the VUV optical metrology instrument, using VUV irradiation with oxygen to non-destructively remove contaminants from optical surfaces, allowing for simultaneous monitoring and cleaning without additional components, thereby maintaining measurement accuracy and reducing system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate cleaning systems are coupled to existing measurement systems, then contamination removal capability is improved, but system cost and design complexity increase
Solution Approach 1:
The patent combines the cleaning function and measurement function into a single integrated system. The VUV light source serves dual purposes: it cleans optical surfaces by photodesorbing contaminants and simultaneously enables optical metrology measurements. This eliminates the need for separate cleaning systems and reduces overall system complexity.
Solution Approach 2:
The VUV light source is designed to perform multiple functions: cleaning optical surfaces through photodesorption and conducting optical measurements. This multi-functionality reduces the number of components needed and simplifies the overall system architecture while maintaining effective contamination removal capability.
2Measurement precision
If VUV irradiation is used to remove contaminants, then measurement accuracy is improved, but system complexity increases due to additional components
Solution Approach 1:
The cleaning irradiation and measurement irradiation are combined into a single VUV light source operation. The same VUV photons that clean the surface by removing contaminants also enable the optical measurements, eliminating the need for separate cleaning and measurement systems.
Solution Approach 2:
The VUV light source cleans the optical surfaces itself while performing measurements. The system uses its own measurement radiation to clean the surfaces, eliminating the need for external cleaning systems or additional components.
3Reliability
If microwave radiation and radiant heating are used for cleaning, then measurement repeatability is improved, but system cost and design complexity increase
Solution Approach 1:
The patent replaces mechanical/thermal cleaning methods (microwave radiation and radiant heating) with a photonic cleaning method using VUV light. This substitution eliminates the need for complex thermal management systems, microwave generators, and heating elements, significantly reducing system complexity and design challenges.
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 effectively minimizes surface contaminants, ensuring accurate and repeatable measurements in the VUV range by integrating cleaning and measurement processes within the instrument, reducing the need for separate cleaning systems and maintaining optical performance.
Implementation Method 1
VUV irradiation with oxygen to non-destructively remove contaminants from optical surfaces
Implementation Method 2
VUV irradiation with oxygen to non-destructively remove contaminants from optical surfaces
Data Source
AI summary
A technique is provided for monitoring and controlling surface contaminants on optical elements contained within the optical path (or sub-path) of an optical metrology instrument. The technique may be utilized in one embodiment in such a manner as to not require that additional components and/or instrumentation be coupled to, or integrated into, existing metrology equipment. Surface contaminants on optical elements within an optical metrology instrument are monitored so that cleaning procedures can be performed as deemed necessary. The cleaning procedures may include the use of exposing the optical elements to optical radiation. The optical metrology instrument may be an instrument which operates at wavelengths that include vacuum ultra-violet (VUV) wavelengths.