EUV Lithography Mirror Scattering DUV Radiation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lithographic systems face challenges in suppressing unwanted deep ultraviolet (DUV) radiation, which causes heating issues and contrast loss in EUV lithography, as existing filters and coatings either absorb significant EUV radiation or have limited effectiveness in reducing the DUV to EUV ratio.
Innovation Solution
An optical apparatus with a primary reflective element and an array of secondary reflective elements is used to scatter DUV radiation away from the target location, minimizing its impact on the EUV radiation path while maintaining high reflectivity for EUV wavelengths, utilizing a scattering layer with silicon particles or a phase grating structure to achieve this.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter or coating is used to suppress DUV radiation, then DUV suppression is improved, but EUV transmission is reduced
Solution Approach 1:
The optical element applies different surface properties to different wavelength ranges: a scattering layer is applied only to the portion of the surface that reflects DUV radiation, while the EUV-reflecting portion maintains high reflectivity without the scattering layer. This local differentiation allows DUV suppression without compromising EUV transmission.
Solution Approach 2:
The optical element combines multiple materials with different wavelength-dependent properties: a base material for EUV reflection (such as platinum or multilayer coating) and a scattering layer material (such as silicon oxide or silicon nitride) that selectively scatters DUV radiation. This composite structure achieves simultaneous DUV suppression and EUV transmission.
2Object-affected harmful factors
If a scattering layer is applied to suppress DUV radiation, then DUV scattering is improved, but EUV reflectivity is reduced
Solution Approach 1:
The optical element is divided into functionally distinct portions: a first portion dedicated to DUV reflection with a scattering layer applied, and a second portion dedicated to EUV reflection without the scattering layer. This segmentation allows each portion to optimize its function without compromising the other.
Solution Approach 2:
The scattering layer is applied selectively only to the DUV-reflecting portion of the optical element, leaving the EUV-reflecting portion with its native high-reflectivity surface intact. This local application ensures that DUV scattering is achieved without degrading EUV reflectivity.
3Object-affected harmful factors
If the entire optical element surface is treated to scatter DUV radiation, then DUV suppression is improved, but the optical element area is reduced
Solution Approach 1:
The optical element surface is segmented into a DUV-reflecting portion and an EUV-reflecting portion, with the scattering layer applied only to the DUV portion. This segmentation preserves the total surface area of the optical element while achieving DUV suppression only where needed.
Solution Approach 2:
The scattering layer is applied locally only to the portion of the surface that handles DUV radiation, rather than treating the entire surface. This local treatment maintains the overall surface area and optical collection efficiency while achieving DUV suppression.
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 reduces unwanted DUV radiation to the target location, minimizing EUV loss and achieving a significant suppression of DUV radiation while maintaining high EUV transmission, thus improving the precision and efficiency of EUV lithography.
Implementation Method 1
the primary reflective element is formed such that radiation in a second wavelength range will be subject to a degree of scattering
Implementation Method 2
the primary reflective element is arranged to reflect radiation in a first wavelength range to an associated secondary reflective element
Data Source
AI summary
In an EUV (extreme ultraviolet) lithography apparatus, an illumination system includes a multifaceted field mirror and a multifaceted pupil mirror. A field facet mirror within mirror focuses EUV radiation onto a particular associated pupil facet mirror, from where it is directed to a target area. Each field facet mirror is modified to scatter unwanted DUV (deep ultraviolet) radiation into a range of directions. The majority of DUV falls onto neighboring pupil facet mirrors within the pupil mirrors, so that the amount of DUV radiation reaching target E is suppressed in comparison to the wanted EUV radiation. Because the distance between mirrors is much greater than the width of an individual pupil facet mirror, good DUV suppression can be achieved with only a narrow scattering angle. Absorption of EUV radiation in the scattering layer can be minimized.