EUV Mask Substrate Multilayer Film Ru Protection
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Solution Overview
Problem
EUV mask blanks face challenges with maintaining high reflectance and etching resistance due to oxidation and peeling issues with conventional protection layers, especially when exposed to air or during etching processes.
Innovation Solution
A multilayer reflection film structure for EUV mask blanks is developed, featuring a Si/Mo laminated portion with a protection layer composed of Ru and additional metals or metalloids, where the upper layer is formed at the side remotest from the substrate, and a layer containing Si and N is introduced between Si and Mo layers to prevent oxidation and enhance etching resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a thin protection layer is used to increase reflectance, then reflectance is improved, but oxygen diffusion occurs causing oxidation and peeling
Solution Approach 1:
The protection layer is divided into multiple layers: a first protection layer (Ru) in contact with the Si/Mo laminated portion, and a second protection layer (Ru-Nb or Ru-Zr) formed on the first protection layer. This segmentation allows the first layer to provide oxygen barrier function while the second layer provides etching resistance, achieving both high reflectance and oxidation resistance.
Solution Approach 2:
The protection layer uses composite material structure combining Ru with Nb or Zr elements. The Ru-based composite material provides both oxygen diffusion barrier properties and etching resistance, resolving the contradiction between thin layer requirement for reflectance and thick layer requirement for oxidation protection.
2Reliability
If Ru is used as protection layer to prevent oxidation, then oxidation resistance is improved, but etching resistance deteriorates
Solution Approach 1:
The protection function is segmented between two layers: the first Ru layer provides oxidation resistance, while the second Ru-Nb or Ru-Zr layer provides etching resistance. This segmentation allows each layer to specialize in one function without compromising the other.
Solution Approach 2:
Different regions of the protection layer have different compositions optimized for different functions: the Ru-rich first layer near the Si/Mo interface provides oxidation resistance, while the Ru-Nb or Ru-Zr second layer at the outer surface provides etching resistance.
3Strength
If Nb or Zr is added to Ru to improve etching resistance, then etching resistance is improved, but oxygen diffusion increases causing oxidation
Solution Approach 1:
The protection layer is segmented into two functional layers: the first Ru layer serves as oxygen barrier, and the second Ru-Nb or Ru-Zr layer serves as etching resistance layer. This segmentation allows Nb or Zr to be added for etching resistance without compromising oxidation resistance.
Solution Approach 2:
The first Ru layer acts as an intermediary barrier between the Si/Mo laminated portion and the Ru-Nb or Ru-Zr second layer. It prevents oxygen from reaching the Si/Mo interface while allowing the second layer to provide etching resistance.
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 provides a substrate with a multilayer reflection film that maintains high reflectance and etching resistance, even when heated, by preventing oxygen diffusion and oxidation, thus ensuring stable performance in EUV lithography processes.
Implementation Method 1
a multilayer reflection film which is formed on a substrate and reflects EUV light
Implementation Method 2
a Mo/Si multilayer reflection film which is obtained a necessary reflectance for EUV light by alternately laminating molybdenum (Mo) films and silicon (Si) films
Implementation Method 3
oxygen in the air diffuses into the protection layer and reaches to the Si/Mo laminated portion
Implementation Method 4
silicon oxide is formed by the oxygen when the uppermost layer of the Si/Mo laminated portion is a Si layer
Implementation Method 5
an absorber film that is formed thereon and absorbs EUV light
Implementation Method 6
a material containing tantalum (Ta) or chromium (Cr) as a main component, which has a relatively large extinction coefficient with respect to EUV light
Implementation Method 7
when the multilayer reflection film is heated during mask processing or exposure with EUV light
Implementation Method 8
the protection layer may be peeled off by expansion due to the oxidation
Data Source
AI summary
A substrate with a multilayer reflection film for an EUV mask blank including a substrate, and a multilayer reflection film formed on the substrate is provided. The multilayer reflection film includes a Si/Mo laminated portion and a protection layer containing Ru and including a lower layer composed of Ru, and an upper layer composed of a material containing Ru and at least one selected from the group consisting of metals other than Ru, and metalloids.