Multilayer Photomask Blank for Low-Roughness EUV Defect Inspection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing photomask blanks face issues with surface roughness leading to pseudo defects, inadequate inspection sensitivity, and inability to adsorb foreign matter, particularly in EUV lithography, which affects defect detection and apparatus management.
Innovation Solution
A photomask blank with a multilayer film structure comprising a first layer of chromium, oxygen, nitrogen, and carbon, a second layer of chromium and nitrogen, and a third layer of chromium and oxygen, with specific atomic percentages and thicknesses, to achieve a surface roughness of 0.65 nm or less and a resistance value of 20Ω/□ or less, allowing for improved defect detection and foreign matter adsorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a chromium-containing film is used as a light shielding film on a photomask blank, then the optical density and light shielding performance are improved, but the surface roughness increases leading to pseudo defects that reduce inspection sensitivity
Solution Approach 1:
The chromium-containing film is divided into multiple layers (first chromium-containing film, second chromium-containing film) with different compositions and functions. The first layer provides light shielding with controlled optical density, while the second layer provides smooth surface for defect inspection, separating the conflicting requirements of light shielding performance and surface quality.
Solution Approach 2:
Different layers of the chromium-containing film have different local properties: the first layer has higher chromium content (5-20 nm thickness) for light shielding, while the second layer has lower chromium content and higher oxygen/nitrogen content (10-30 nm thickness) for surface smoothness. This local differentiation resolves the contradiction between light shielding performance and inspection sensitivity.
2Measurement precision
If the surface roughness of the chromium-containing film is reduced to improve inspection sensitivity, then defect detection capability is improved, but the film cannot adsorb foreign matter effectively
Solution Approach 1:
The film structure is segmented into two layers where the first layer provides smooth surface for inspection, and the second layer provides foreign matter adsorption capability. This segmentation allows each layer to optimize for its specific function without compromising the other.
Solution Approach 2:
The first chromium-containing film acts as an intermediary layer between the substrate and the second chromium-containing film. It provides the smooth surface needed for defect inspection while allowing the second layer to maintain its foreign matter adsorption function, mediating between the conflicting requirements.
3Ease of manufacture
If a single-layer chromium-containing film is used, then the manufacturing process is simplified, but it is impossible to simultaneously achieve low surface roughness, appropriate optical density, and foreign matter adsorption
Solution Approach 1:
The single-layer film is segmented into two layers with distinct compositions and functions. The first layer optimizes for light shielding and surface smoothness, while the second layer optimizes for foreign matter adsorption. This segmentation enables multifunctional performance that cannot be achieved with a single layer.
Solution Approach 2:
The chromium-containing film uses composite material structure with two layers having different compositions (different ratios of chromium, oxygen, and nitrogen). This composite approach allows simultaneous optimization of optical properties, surface quality, and chemical reactivity for foreign matter adsorption.
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 multilayer film structure enables sensitive defect detection of 50 nm or smaller defects and effective foreign matter adsorption, enhancing photomask manufacturing and apparatus management, particularly in EUV lithography.
Implementation Method 1
a surface roughness Rq of the multilayer film is 0.65 nm or less
Implementation Method 2
effective foreign matter adsorption
Data Source
AI summary
A photomask blank having a substrate; and a multilayer film including a first layer, a second layer, and a third layer. The first layer contains 43 at % or less chromium, 32 at % or more oxygen, 25 at % or less nitrogen and 5 at % or more and 18 at % or less carbon and has a thickness of 8 nm or more and 16 nm or less. The second layer contains 66 at % or more and 92 at % or less chromium and 8 at % or more and 30 at % or less nitrogen and has a thickness of 50 nm or more and 75 nm or less. The third layer contains 44 at % or less chromium, 30 at % or more oxygen and 28 at % or less nitrogen and has a thickness of 10 nm or less. A surface roughness Rq of the multilayer film is 0.65 nm or less.