EUV Mirror Substrate with Thin Polishing Layer
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Solution Overview
Problem
In EUV lithography, existing mirror substrates suffer from high stray light and low reflectivity due to surface roughness and material limitations, which affect the performance of EUV projection exposure apparatuses.
Innovation Solution
A substrate with a main body made from high-strength aluminum alloys and a polishing layer with a thickness of less than 10 μm and root-mean-square roughness of less than 0.5 nm, optimized for EUV lithography, featuring an adhesion promoter layer to enhance surface smoothness and reflectivity, and a highly reflective coating for increased reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polishing layer is applied to improve surface smoothness, then reflectivity increases, but device complexity increases
Solution Approach 1:
The substrate is divided into two distinct layers: a main body made from aluminum alloy and a polishing layer with thickness less than 10 μm and RMS roughness less than 0.5 nm. This segmentation allows each layer to fulfill its specific function - the main body provides mechanical strength while the polishing layer provides optical smoothness, resolving the contradiction between surface quality and structural simplicity.
Solution Approach 2:
The invention uses a composite structure combining aluminum alloy main body with a specialized polishing layer. This composite approach enables the substrate to simultaneously achieve high mechanical strength from the aluminum alloy and superior surface smoothness from the polishing layer, thereby improving reflectivity without requiring the entire structure to be complex.
2Illumination intensity
If mirror substrates are used in EUV lithography, then reflectivity can be achieved, but stray light increases due to surface roughness
Solution Approach 1:
The polishing layer is applied in advance to the aluminum alloy main body before the highly reflective coating is deposited. This preliminary action of creating an ultra-smooth surface (RMS roughness < 0.5 nm) ensures that when the reflective coating is later applied, it achieves maximum reflectivity and minimum stray light generation, preventing optical degradation before it occurs.
Solution Approach 2:
The invention严格控制 the polishing layer thickness to less than 10 μm and RMS roughness to less than 0.5 nm. By precisely controlling these parameters, the substrate achieves optimal balance between surface smoothness (reducing stray light) and mechanical integrity, thereby improving EUV optical 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 proposed substrate significantly reduces stray light and increases reflectivity, enabling improved performance in EUV lithography by minimizing adverse optical effects and enhancing the mechanical properties of EUV mirrors.
Implementation Method 1
a polishing layer, wherein the polishing layer has a thickness of less than 10 μm and a root-mean-square roughness of less than 0.5 nm
Implementation Method 2
a highly reflective coating which are based on a multilayer system composed of alternate layers of material having different real parts of the complex refractive index, through which a crystal having lattice planes at which Bragg diffraction takes place for use with normal incidence is in a way simulated
Data Source
AI summary
Substrates suitable for mirrors which are used at wavelengths in the EUV wavelength range have a main body (2) and a polishing layer (3). The polishing layer (3) has a thickness of less than 10 μm and a root-mean-square roughness of less than 0.5 nm and the main body (2) is produced from an aluminum alloy. Moreover, a highly reflective layer (6) is provided on the polishing layer (3) of the substrate (1) of the EUV mirror (5).