EUV Optical Member Ru Protective Layer Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of ruthenium (Ru) as a protective layer in EUV lithography leads to a decrease in EUV light reflectivity due to oxidation, resulting in reduced useful life and the need for frequent adjustments in exposure conditions during EUV exposure processes.
Innovation Solution
A reflective layer-equipped substrate is developed with a Mo/Si multilayer reflective film, a Ru protective layer, and an intermediate layer containing specific amounts of Si and O between the reflective layer and the protective layer to prevent oxidation and maintain high reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ru protective layer is formed on the Mo/Si multilayer reflective film, then the reflective layer is protected from etching damage, but the EUV light reflectivity deteriorates due to oxidation of the Ru layer
Solution Approach 1:
An intermediate layer made of SiO2 or SiOx is introduced between the Mo/Si multilayer reflective film and the Ru protective layer. This intermediate layer acts as a barrier that prevents oxygen from reaching and oxidizing the Ru layer, thereby maintaining high EUV light reflectivity while still allowing the Ru layer to provide etching protection.
Solution Approach 2:
The patent creates a composite structure consisting of multiple layers with different functions: the Mo/Si multilayer reflective film for high reflectivity, the SiO2/SiOx intermediate layer for oxidation prevention, and the Ru protective layer for etching resistance. This composite structure resolves the contradiction by combining materials that individually address different requirements.
2Ease of manufacture
If the Ru protective layer is used, then etching selectivity is improved, but the useful life of EUV masks and mirrors is reduced due to oxidation
Solution Approach 1:
The SiO2 or SiOx intermediate layer is formed in advance before the Ru protective layer is applied. This preliminary action creates a protective barrier that prevents future oxidation of the Ru layer, thereby extending the useful life of EUV masks and mirrors while maintaining the etching selectivity benefits of the Ru layer.
Solution Approach 2:
The intermediate layer serves as a mediator that isolates the Ru protective layer from oxygen exposure. This allows the Ru layer to maintain its etching protection function over extended periods without degradation from oxidation, thus extending the operational life of the optical components.
3Device complexity
If no intermediate layer is formed, then the structure is simpler, but oxidation occurs leading to frequent adjustments in exposure conditions
Solution Approach 1:
The SiO2/SiOx intermediate layer is a thin film that adds minimal structural complexity while providing crucial oxidation prevention. This thin intermediate layer prevents the need for frequent adjustments in exposure conditions, thereby maintaining high productivity in the EUV lithography process.
Solution Approach 2:
The patent optimizes the thickness and composition parameters of the intermediate layer (SiO2 or SiOx) to achieve the right balance between preventing oxidation and maintaining structural simplicity. By carefully controlling these parameters, the layer provides effective protection without significantly increasing device complexity.
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 intermediate layer effectively prevents deterioration of EUV light reflectivity, extending the useful life of EUV masks and mirrors by minimizing the need for mid-exposure condition changes and ensuring consistent performance over time.
Implementation Method 1
a reflective layer to reflect EUV light... a Mo/Si multilayer reflective film having a molybdenum (Mo) layer as a high refractive index layer and a silicon (Si) layer as a low refractive index layer alternately laminated to have the light reflectivity improved
Implementation Method 2
the refractive index of substances at such a wavelength is close to 1, whereby it is not possible to use a conventional refracting optical system
Implementation Method 3
an absorber layer to absorb EUV light... a material having a high absorption coefficient to EUV light
Implementation Method 4
the Ru protective layer and further, the uppermost layer of the multilayer reflective film (the Si layer in the case of the Mo/Si multilayer reflective film) are oxidized... deterioration of the EUV light reflectivity
Data Source
AI summary
There are provided an EUV optical member, in which deterioration in the reflectivity due to oxidation of the Ru protective layer is prevented, a functional film-equipped substrate to be employed for production of the EUV optical member, and a process for producing the functional film-equipped substrate. A reflective layer-equipped substrate for EUV lithography comprising a substrate, and a reflective layer for reflecting EUV light and a protective layer for protecting the reflective layer, formed in this order on the substrate, wherein the reflective layer is a Mo/Si multilayer reflective film, the protective layer is a Ru layer or a Ru compound layer, and an intermediate layer containing from 0.5 to 20 at % of oxygen and from 80 to 99.5 at % of Si is formed between the reflective layer and the protective layer.