EUV Multilayer Reflective Film for Stable Diffusion Layer Thickness
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Solution Overview
Problem
The thickness of the diffusion layer in multilayer reflective films used in EUV lithography changes due to heating during the mask forming process, affecting the reflection properties of the multilayer reflective film.
Innovation Solution
The multilayer reflective film is structured such that low refractive index layers and high refractive index layers are alternately stacked, with a crystallite size of the low refractive index layers exceeding 3.1 nm, and specific intensity ratios and half-widths are maintained to minimize diffusion layer thickness changes during heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the multilayer reflective film is heated during mask forming process, then the mask forming process can be completed, but the thickness of the diffusion layer changes and reflection properties deteriorate
Solution Approach 1:
The patent applies parameter changes by controlling the crystallite size of the low refractive index layer to be within 3.0-6.0 nm and adjusting the thickness ratio of low to high refractive index layers to be within 0.3-0.7. These parameter optimizations suppress diffusion layer thickness changes when heating occurs during mask forming, thereby maintaining reflection properties while enabling complete mask forming process
Solution Approach 2:
The patent uses composite materials by stacking alternating low refractive index layers (e.g., molybdenum) and high refractive index layers (e.g., silicon) to form a multilayer reflective film. This composite structure with specific thickness ratios and crystallite size controls provides thermal stability that suppresses diffusion layer changes during heating while maintaining EUV light reflection capability
2Stability of the object's composition
If the crystallite size of low refractive index layers is increased, then the diffusion layer thickness change is suppressed, but the layer formation complexity increases
Solution Approach 1:
The patent optimizes the crystallite size parameter to be within 3.0-6.0 nm and the thickness ratio parameter to be within 0.3-0.7, which suppresses diffusion layer thickness changes during heating. These parameter ranges balance stability improvement with acceptable formation complexity
Solution Approach 2:
The patent uses X-ray diffraction measurement to non-destructively measure crystallite size and layer properties, replacing complex mechanical/physical measurement methods. This enables precise control and verification of crystallite size and thickness ratios without adding complex formation steps
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 solution stabilizes the thickness of the diffusion layer, ensuring consistent reflection properties of the multilayer reflective film even under heating conditions.
Implementation Method 1
a multilayer reflective film to reflect EUV light
Implementation Method 2
in a diffraction chart obtained by X-ray diffraction measurement
Implementation Method 3
in a diffraction chart obtained by X-ray diffraction measurement, a crystallite size calculated from a diffraction peak
Implementation Method 4
between adjacent low refractive index layer and high refractive index layer in contact with each other in the multilayer reflective film, elements of materials constituting the respective layers may diffuse into each other
Data Source
AI summary
To provide a multilayer reflective film-provided substrate in which the thickness of a diffusion layer in the multilayer reflective film when heated is less likely to change. A multilayer reflective film-provided substrate for reflective mask blank, comprising a substrate, and a multilayer reflective film to reflect EUV light, wherein the multilayer reflective film has a structure such that low refractive index layers and high refractive index layers are alternately stacked; and in a diffraction chart obtained by X-ray diffraction measurement, a crystallite size calculated from a diffraction peak with a maximum intensity attributable to the low refractive index layers is more than 3.1 nm.