Reflective Photomask Blank With Ruthenium Absorber for Fine EUV Patterns
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing reflective photomask blanks face challenges in forming fine assist patterns without damaging the multilayer reflection film during etching, particularly in EUV lithography, due to the need for complex etching processes and the difficulty in controlling side etching, leading to pinhole defects and reduced pattern resolution.
Innovation Solution
A reflective photomask blank structure with a light absorbing film composed of ruthenium (Ru) and a hard mask film resistant to specific dry etching processes, allowing for the formation of fine assist patterns with a thickness of not more than 60 nm, while protecting the multilayer reflection film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a light absorbing film is etched to form fine assist patterns, then pattern resolution is improved, but the multilayer reflection film may be damaged due to side etching
Solution Approach 1:
A hard mask film is introduced as an intermediary layer between the light absorbing film and the multilayer reflection film. This hard mask film is resistant to oxygen-containing chlorine-based dry etching, allowing the light absorbing film to be etched without the etching gas reaching and damaging the multilayer reflection film. The hard mask film acts as a protective barrier that enables fine pattern formation while preventing side etching damage to underlying layers.
2Reliability
If a complex etching process is used to protect the multilayer reflection film, then film integrity is maintained, but productivity decreases
Solution Approach 1:
The hard mask film is formed in advance before the light absorbing film etching process. This preliminary action creates a protective barrier that remains during subsequent etching steps, eliminating the need for complex in-process protection measures. The hard mask film is designed to withstand the etching conditions, allowing straightforward single-step etching of the light absorbing film without worrying about damaging the multilayer reflection film, thereby simplifying the overall process and improving productivity.
3Manufacturing precision
If the light absorbing film is etched with oxygen-containing chlorine-based gas, then fine assist patterns are formed, but pinhole defects occur without adequate protection
Solution Approach 1:
The hard mask film serves as a protective intermediary that prevents oxygen-containing chlorine-based etching gas from directly contacting the light absorbing film in uncontrolled manner. By controlling the etching process through this intermediate layer, fine assist patterns can be formed with precise geometry while the hard mask film prevents pinhole defects by providing a stable, defect-free template for the pattern transfer.
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
Enables the formation of assist patterns with line widths of not more than 20 nm without damaging the multilayer reflection film, enhancing pattern resolution and productivity by simplifying the etching process.
Implementation Method 1
a multilayer reflection film which is formed on the substrate and reflects exposure light being light in extreme ultraviolet range
Implementation Method 2
a light absorbing film which is formed on the protection film and absorbs the exposure light
Implementation Method 3
patterning the light absorbing film to form a pattern of the light absorbing film by oxygen-containing chlorine-based dry etching
Data Source
AI summary
A reflective photomask blank including a substrate, a multilayer reflection film on the substrate that reflects exposure light being light in extreme ultraviolet range, a protection film on the multilayer reflection film, a light absorbing film in contact with the protection film that absorbs the exposure light, and a hard mask film in contact with the light absorbing film is provided. The protection film consists of a first layer provided at the substrate-side, and a second layer provided at the side remote from the substrate, the second layer is composed of a material resistant to dry etching capable of etching of the light absorbing film, the light absorbing film has a phase shift function and is formed of a single layer or multiple layers, and the single layer and each layer constituting the multiple layers are composed of a material containing ruthenium as a main component.