Heated Collector Mirror for Stable EUV Mask Inspection Sources
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Solution Overview
Problem
The high development cost and long equipment delivery period of EUV optical systems for EUV mask inspection necessitate a more efficient and cost-effective EUV light source device that reduces the number of optical parts and shortens manufacturing time.
Innovation Solution
An EUV light source device utilizing a lithium liquid phase plasma (LPP)-based system with a collector mirror heated by heaters to evaporate contaminants, a debris shield, and a target feeder to maintain a stable liquid target, optimizing EUV light collection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an EUV optical system is used for EUV mask inspection, then inspection performance is improved, but equipment cost and delivery time increase
Solution Approach 1:
The inspection system is divided into separate functional modules: an EUV light source device that can be independently configured, and an inspection device that receives the EUV light. This segmentation allows the light source to be optimized separately from the inspection optics, reducing overall system complexity and cost while maintaining inspection performance
Solution Approach 2:
The EUV light source device is designed to serve dual purposes: it can provide EUV light for both mask inspection and potentially other EUV applications. The light source uses a collector mirror that can collect EUV light from a lithium liquid phase plasma source, creating a versatile platform that reduces the need for dedicated inspection-only optical systems
2Use of energy by moving object
If a collector mirror is used to collect EUV light, then light collection efficiency is improved, but liquid target contaminants deposit on the mirror surface
Solution Approach 1:
The heater periodically activates to evaporate deposited contaminants from the collector mirror surface. This periodic cleaning action maintains the mirror's reflectivity and light collection efficiency over time, counteracting the continuous deposition of liquid target contaminants during EUV light generation
Solution Approach 2:
The heater converts the harmful effect of contaminant deposition into a manageable process by actively evaporating the contaminants. The same thermal energy that could potentially damage the mirror is used beneficially to remove deposits, maintaining optical performance without requiring frequent mirror replacement or complex cleaning mechanisms
3Reliability
If heaters are added to the collector mirror to evaporate contaminants, then mirror performance is maintained, but device complexity increases
Solution Approach 1:
The heater is integrated directly into the collector mirror structure, merging the heating function with the optical component. This integration eliminates the need for separate heating devices and complex mounting mechanisms, reducing overall device complexity while maintaining the ability to evaporate contaminants and preserve mirror performance
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 device achieves high collection efficiency of EUV light, enabling stable and efficient EUV mask inspection with reduced equipment costs and shorter delivery times.
Implementation Method 1
the IR laser beam reacts with the liquid target to produce the EUV light
Implementation Method 2
a plurality of heaters located on the collector mirror to heat and evaporate liquid target contaminants deposited on the surface of the collector mirror
Data Source
AI summary
The present disclosure relates to an EUV light source device for EUV mask inspection, including: an IR laser source for emitting an IR laser beam; a condenser lens for collecting the IR laser beam emitted from the IR laser source; a collector mirror having a hole formed at the center thereof in such a way as to pass the IR laser beam collected onto the condenser lens therethrough, the collector mirror being adapted to collect EUV light reflected onto a liquid target if the IR laser beam reacts with the liquid target to produce the EUV light; a target feeder for continuously feeding the liquid target to allow the IR laser beam passing through the hole formed on the collector mirror to react with the liquid target; and a plurality of heaters located on the collector mirror.