EUV Collector Mirror with Blazed Grooves for Spectrum Purity
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Solution Overview
Problem
Existing EUV light source devices face issues with low efficiency and reliability due to the inefficiency of thin layer type spectrum purity filters (SPFs), which have low transmittivity and are prone to damage from debris and heat, and require numerous multi-layers for effective separation of EUV radiation, leading to significant energy loss and reduced output.
Innovation Solution
A mirror for extreme ultra violet is designed with a substrate and composite layers that incorporate blazed or undulating grooves, functioning as both a diffraction lattice and a spectrum purity filter, allowing EUV radiation to be focused and separated from other wavelengths without the need for a separate SPF, reducing the number of layers and enhancing diffraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a thin layer type spectrum purity filter is used to separate EUV radiation, then the device complexity is reduced, but the transmittivity is low and the reliability is poor due to damage from debris and heat
Solution Approach 1:
The patent combines the spectrum purity filter function with the collector mirror by forming a composite layer directly on the mirror surface. This integration eliminates the need for a separate thin layer filter, thereby maintaining low device complexity while significantly improving reliability as the integrated structure is more robust against debris and heat damage
Solution Approach 2:
The collector mirror is given multiple functions: it both collects/focuses the EUV radiation and acts as a spectrum purity filter through the composite layer. This multi-functionality reduces the need for separate components while enhancing the overall system reliability
2Measurement precision
If numerous multi-layers are used in the spectrum purity filter to achieve effective separation, then the purity of EUV radiation is improved, but the energy loss increases and output decreases
Solution Approach 1:
Instead of using numerous layers throughout the entire optical path, the patent applies a composite layer with specific properties (Mo/Si with controlled thickness and composition) only at the collector mirror surface where it is most effective. This localized approach achieves the required spectral purity while minimizing energy loss compared to using many layers throughout the system
Solution Approach 2:
The patent optimizes the parameters of the composite layer (thickness, material composition, layer structure) to achieve the desired spectral separation with minimal energy loss. By carefully controlling these parameters, the system achieves high EUV radiation purity without requiring numerous layers that would cause significant energy loss
3Measurement precision
If a separate spectrum purity filter is added to the EUV light source device, then the purity of EUV radiation is improved, but the device complexity and the risk of damage increase
Solution Approach 1:
The spectrum purity filter function is merged with the collector mirror by forming a composite layer directly on the mirror surface. This integration achieves high spectral purity while avoiding the addition of separate filter components, thereby preventing increased device complexity and reducing the risk of damage from additional parts
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 solution increases the efficiency of EUV radiation delivery to the exposure device by reducing energy loss and improving the purity of EUV radiation, while also enhancing the reliability and convenience of the EUV light source device by eliminating the need for a separate SPF and reducing the risk of debris and heat damage.
Implementation Method 1
a foundation portion formed from a first composite layer which is provided on one side of the substrate portion; and a reflecting portion made by forming grooves of predetermined shapes in a second composite layer which is integrally provided on the other side of the foundation portion from the substrate portion
Implementation Method 2
a reflecting portion made by forming grooves of predetermined shapes in a second composite layer which is integrally provided on the other side of the foundation portion from the substrate portion
Data Source
AI summary
An EUV light source is configured for generating an EUV light for an exposure device. The EUV light source includes a chamber, a target supply device configured for supplying a target into the chamber, an optical system for introducing laser light from a driver laser into the chamber and irradiating the target with the laser light to turn the target into plasma from which EUV light is emitted, and an EUV collector mirror in the chamber. The EUV collector mirror may include a multilayered reflecting surface with grooves and collect the EUV light from the plasma to a focal spot. The grooves can be arranged in a concentric fashion, and be configured for diffracting at least light at a wavelength which is the same as that of the laser light from the driver laser.