Reflective Mask Blank Niobium Etching Mask Film
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Solution Overview
Problem
The existing reflective mask blanks used in EUV lithography face challenges in forming fine patterns of the absorption film due to the high aspect ratio of the resist pattern, which leads to pattern collapse during dry etching.
Innovation Solution
Incorporating an etching mask film containing niobium (Nb) on the absorption film, which can be dry-etched using a gas containing oxygen (O), particularly chlorine (Cl) and oxygen (O), to facilitate the formation of a fine pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the absorption film is thinned to improve pattern transfer accuracy, then the shadowing effect is reduced, but the film becomes more difficult to pattern using conventional dry etching methods
Solution Approach 1:
An etching mask film containing niobium (Nb) is introduced as an intermediary layer between the absorption film and the resist pattern. This Nb-containing film serves as a protective mask during dry etching, allowing the thin absorption film to be patterned accurately without direct exposure to etching gases that would cause collapse or excessive etching. The intermediary film enables precise pattern transfer while protecting the delicate thin absorption film structure.
2Stability of the object's composition
If a thick resist pattern is formed to avoid collapse during dry etching, then the resist pattern stability is improved, but the aspect ratio increases making fine pattern formation difficult
Solution Approach 1:
The niobium-containing etching mask film acts as a mediator that protects the thin absorption film during dry etching. By placing this protective layer between the resist pattern and the absorption film, the system can use thinner resist patterns (lower aspect ratios) while still maintaining stability during the etching process. The intermediary film prevents direct etching of the absorption film, allowing finer patterns to be formed without collapse.
3Manufacturing precision
If chromium (Cr)-based absorption films are used instead of tantalum (Ta) to reduce shadowing effect, then the film thickness can be reduced, but the film becomes more susceptible to damage during dry etching
Solution Approach 1:
A niobium-containing etching mask film is introduced as a protective intermediary layer over the chromium-based absorption film. This intermediary film protects the Cr-based absorption film from damage during dry etching while allowing the thin film structure to maintain its low shadowing effect. The Nb-containing film serves as a sacrificial protective layer that enables the use of thinner, more susceptible Cr-based absorption films without compromising their durability during the patterning process.
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 allows for the successful formation of a fine and preferable pattern of the absorption film, improving the accuracy of pattern transfer to the wafer by reducing the shadowing effect during exposure.
Implementation Method 1
a multilayer reflection film that is formed on one main surface of the substrate, and reflects the exposure light
Implementation Method 2
an absorption film that is formed on the multilayer reflection film, and absorbs the exposure light
Implementation Method 3
the absorption film consists of a material that can be dry-etched by a gas containing oxygen (O), and the reflective mask blank includes an etching mask film containing niobium (Nb) on the absorption film
Data Source
AI summary
A fine and preferable pattern of an absorption film can be formed from the absorption film that can be patterned by dry etching using a gas containing oxygen (O) by a reflective mask blank including a substrate, a multilayer reflection film that is formed on one main surface of the substrate, and reflects exposure light, an absorption film that is formed on the multilayer reflection film, and absorbs the exposure light, and an etching mask film containing niobium (Nb) on the absorption film.