Tantalum-Based EUV Absorber Film for High Selectivity Etching
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Solution Overview
Problem
Conventional photolithography methods face limitations in achieving fine patterns below 45 nm, particularly with the use of EUV lithography, where the refractive optical systems are ineffective due to high absorption and low refractive index of materials at EUV wavelengths, necessitating the development of reflective mask blanks with improved etching selectivity for pattern formation.
Innovation Solution
A reflective mask blank structure featuring a multilayer reflective film and a tantalum-based absorber film with specific nitrogen and krypton content, along with a ruthenium-based protective film, optimized for EUV light absorption and etching processes, enhancing etching selectivity and reducing damage to the reflective film during patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional absorber film is used in EUV lithography, then the pattern formation can be achieved, but the etching rate is insufficient and etching selectivity is poor
Solution Approach 1:
The absorber film material composition is changed from conventional tantalum-based materials to a specific compound with controlled stoichiometry (Ta1-xNyOz where x=0.05-0.5, y=0.1-2.0, z=0.1-1.0), which fundamentally alters the etching characteristics to achieve both high etching rate and high etching selectivity simultaneously
Solution Approach 2:
The invention uses a composite absorber film material comprising multiple elements (Ta, N, O) in specific ratios, combining the advantages of different elements to achieve superior etching performance while maintaining EUV absorption capability
2Ease of manufacture
If dry etching process is used to form patterns in absorber film, then pattern formation is achieved, but damage to the multilayer reflective film occurs due to poor etching selectivity
Solution Approach 1:
By changing the chemical composition parameters of the absorber film (specific element ratios of Ta, N, O), the etching selectivity is improved, allowing the dry etching process to selectively remove absorber material while protecting the reflective film from damage
Solution Approach 2:
The absorber film is designed as a sacrificial layer that can be selectively removed by dry etching without damaging the underlying reflective film, enabling clean pattern transfer
3Device complexity
If conventional photolithography method is used, then manufacturing process is simple, but resolution limit is about 45 nm
Solution Approach 1:
The invention changes the exposure wavelength parameter from conventional visible/UV light to EUV light (13.5 nm), which enables sub-45 nm resolution while using a reflective optical system instead of refractive
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 proposed structure achieves a sufficient etching rate and improved etching selectivity during dry etching, reducing processing time and minimizing damage to the multilayer reflective film, thereby enhancing productivity and pattern accuracy in EUV lithography.
Implementation Method 1
a multilayer reflective film which reflects EUV light
Implementation Method 2
an absorber film which absorbs EUV light
Data Source
AI summary
A reflective mask blank includes, on/above a substrate in the following order from the substrate side a multilayer reflective film which reflects EUV light and an absorber film which absorbs EUV light. The absorber film is a tantalum-based material film containing a tantalum-based material. The absorber film provides a peak derived from the tantalum-based material in an X-ray diffraction pattern, the peak having a peak diffraction angle (2θ) of 36.8 degrees or more and a full width at half maximum of 1.5 degrees or more.