EUV Reflective Mask Blank Radial Thickness Correction
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Solution Overview
Problem
In EUV lithography, the in-plane distribution of peak reflectivity and center wavelength at the surface of multilayer reflective films leads to fluctuations in pattern dimensions, impairing high precision patterning due to non-uniform thickness distributions of layers, particularly when sputtering is done with particles entering at an oblique angle.
Innovation Solution
A process where at least one layer in the multilayer reflective film or protective layer is made a reflectivity distribution correction layer with a thickness distribution in a radial direction to suppress and reduce in-plane distribution of peak reflectivity, adjusting thickness to achieve uniformity within specific limits, such as a difference of 0.3% between maximum and minimum peak reflectivity values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sputtering is done with particles entering at an oblique angle to form multilayer reflective film, then the film formation process is efficient, but in-plane distribution of peak reflectivity and center wavelength occurs leading to pattern dimension fluctuations
Solution Approach 1:
The patent applies local quality by creating a thickness distribution correction layer with specific thickness variations in the radial direction. This correction layer has different thicknesses at different locations (center vs. periphery) to compensate for the oblique angle sputtering effects, thereby achieving uniform peak reflectivity and center wavelength across the entire substrate surface while maintaining efficient oblique angle deposition.
2Manufacturing precision
If uniform thickness distribution is maintained in multilayer reflective film, then in-plane uniformity of peak reflectivity is achieved, but radial variations in thickness occur due to sputtering geometry
Solution Approach 1:
The patent applies preliminary anti-action by intentionally designing the thickness distribution correction layer with predetermined thickness variations that counteract the expected radial thickness variations from oblique angle sputtering. By pre-compensating for the geometric effects of oblique deposition, the final multilayer reflective film achieves uniform peak reflectivity and center wavelength across the substrate.
3Productivity
If oblique angle sputtering is used for multilayer film deposition, then deposition rate is improved, but in-plane distribution of center wavelength results impairing pattern precision
Solution Approach 1:
The patent applies local quality by creating a thickness distribution correction layer with specific thickness variations in the radial direction. This correction layer has different thicknesses at different locations (center vs. periphery) to compensate for the oblique angle sputtering effects, thereby achieving uniform peak reflectivity and center wavelength across the entire substrate surface while maintaining efficient oblique angle deposition.
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 results in a mask blank for EUVL with improved in-plane uniformity of peak reflectivity and center wavelength, enhancing the precision and consistency of pattern formation by controlling the thickness distribution of layers to minimize radial variations.
Implementation Method 1
a reflective layer to reflect EUV light
Implementation Method 2
a multilayer reflective film having a low refractive index layer with a low refractive index to EUV light and a high refractive index layer with a high refractive index to EUV light, alternately stacked to have the light reflectivity improved
Implementation Method 3
the reflective layer is a multilayer reflective film having a low refractive index layer and a high refractive index layer alternately stacked plural times by a sputtering method
Data Source
AI summary
Process for producing a substrate with reflective layer for EUVL, which comprises forming a reflective layer for reflecting EUV light on a substrate, wherein the reflective layer is a multilayer reflective film having a low refractive index layer and a high refractive index layer alternately stacked plural times by a sputtering method, and depending upon the in-plane distribution of the peak reflectivity of light in the EUV wavelength region in a radial direction from the center of the substrate at the surface of the multilayer reflective film, at least one layer among the respective layers constituting the multilayer reflective film is made to be a reflectivity distribution correction layer having a thickness distribution provided in a radial direction from the center of the substrate, to suppress the in-plane distribution of the peak reflectivity of light in the EUV wavelength region in a radial direction from the center of the substrate.