EUV Reflective Mask RuTi Buffer Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional reflective masks for EUV lithography suffer from stripping of the Ru protective film during repeated cleaning processes due to Si migration and oxidation, leading to reduced reflectance and pattern transfer inaccuracies.
Innovation Solution
Incorporating Ti into the Ru protective film to form a strong silicide with Si, preventing Si diffusion and oxidation, and optimizing the Ru content gradient within the film to enhance adhesion and cleaning resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ru protective film is formed on the multilayer reflective film to prevent damage during absorber pattern formation, then the multilayer reflective film is protected from etching damage, but Si migrates into the Ru protective film and forms SiO2 causing film stripping during repeated cleaning processes
Solution Approach 1:
A buffer layer comprising RuB2 (ruthenium boride) is introduced between the multilayer reflective film and the Ru protective film. This buffer layer acts as an intermediary that prevents Si migration from the multilayer reflective film into the protective film, thereby eliminating the formation of SiO2 and subsequent film stripping during cleaning processes.
Solution Approach 2:
The protective film structure is changed from a single-layer Ru film to a composite structure consisting of a RuB2 buffer layer and a Ru protective film. The RuB2 layer serves as a diffusion barrier while the Ru layer provides protection during etching, creating a composite material system that resolves the contradiction between protection and stability.
2Manufacturing precision
If over etching is applied to ensure complete absorber pattern formation, then the absorber pattern is fully formed, but the multilayer reflective film under the absorber film suffers damage
Solution Approach 1:
The RuB2 buffer layer is deposited beforehand on the multilayer reflective film before forming the absorber pattern. This buffer layer serves as a cushioning protective layer that absorbs the damage from over etching, allowing complete absorber pattern formation without damaging the underlying multilayer reflective film.
3Ease of operation
If the reflective mask is cleaned repeatedly to remove contaminants, then cleaning effectiveness is improved, but the Ru protective film strips due to Si oxidation
Solution Approach 1:
The RuB2 buffer layer acts as an intermediary barrier that prevents Si diffusion into the Ru protective film. By blocking Si migration, the buffer layer prevents the formation of SiO2 that would cause adhesion loss, thereby maintaining film integrity during repeated cleaning operations.
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 solution maintains high reflectance and cleaning resistance of the reflective mask even after repeated cleaning, preventing film stripping and ensuring accurate pattern transfer during semiconductor device manufacturing.
Implementation Method 1
Si migration and oxidation
Data Source
AI summary
A substrate with a multilayer reflective film that yields a reflective mask achieving high reflectance and exhibiting excellent cleaning resistance. The present invention is directed to a substrate with a multilayer reflective film, which has: a substrate; a multilayer reflective film, formed on a substrate, having a layer comprising Si as a high refractive-index material and a layer comprising a low refractive-index material, wherein the layers are periodically laminate; and a Ru protective film, formed on the multilayer reflective film, for protecting the multilayer reflective film, wherein the surface layer of the multilayer reflective film on the other side of the substrate is the layer comprising Si, and wherein the Ru protective film comprises a Ru compound comprising Ru and Ti, wherein the Ru compound contains Ru in an amount greater than that in the stoichiometric composition of RuTi.