EUV Blankmask Ru Barrier Layer Interdiffusion
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Solution Overview
Problem
The existing reflective type photomasks for EUV lithography face issues with interdiffusion between Mo and Si layers, leading to a decrease in reflectance over time, which shortens the mask's lifespan and affects the accuracy of semiconductor circuit patterns.
Innovation Solution
A multilayered reflection film structure using Ru or Ru compounds with added Mo, Nb, and Zr, and Si layers, along with an intermediate layer of B, B4C, or C, and a capping film, is employed to suppress interdiffusion, maintaining high reflectance and surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If Mo and Si layers are stacked in the reflection film to achieve high reflectance, then reflectance is improved, but interdiffusion occurs between layers leading to reflectance degradation over time
Solution Approach 1:
A barrier layer made of Ru (ruthenium) or Ru compound is introduced between the Mo layer and Si layer in the reflection film. This intermediary layer prevents direct contact and interdiffusion between Mo and Si atoms, while maintaining the optical properties needed for high reflectance at 13.5nm EUV wavelength. The barrier layer acts as a mediator that preserves the functional benefits of the Mo-Si structure without suffering from its interdiffusion problem.
Solution Approach 2:
The reflection film is designed as a composite multilayer structure combining Mo, Si, and Ru/Ru compound layers. This composite material approach leverages the high reflectance properties of Mo-Si while adding Ru to provide diffusion barrier functionality. The composite structure integrates multiple material properties: Mo for reflectance, Si for structural stability, and Ru for interdiffusion prevention.
2Ease of manufacture
If heat is applied during formation and coating processes, then layers are formed and coated, but interdiffusion is accelerated reducing mask lifespan
Solution Approach 1:
The Ru or Ru compound barrier layer is formed preliminarily between the Mo and Si layers before subsequent heating processes during resist film coating and other manufacturing steps. This preliminary protective structure is in place to prevent interdiffusion that would otherwise be accelerated by the necessary heat application during manufacturing processes.
3Productivity
If exposure light is applied for prolonged use, then manufacturing process continues, but reflectance decreases due to heat energy from exposure light
Solution Approach 1:
The Ru/Ru compound barrier layer provides beforehand protection against reflectance degradation caused by prolonged exposure to EUV light during manufacturing use. By preventing interdiffusion at the interface between Mo and Si layers, the barrier layer cushions against the cumulative thermal damage that would otherwise occur during extended exposure light application, maintaining stable reflectance over the mask's operational life.
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 effectively prevents interdiffusion, maintaining high reflectance and extending the photomask's lifespan by reducing thermal and exposure-induced degradation, ensuring precise pattern formation in semiconductor manufacturing.
Implementation Method 1
a pair including a first layer made of Ru or a Ru compound in which one or more of Mo, Nb, and Zr are added to Ru, and a second layer made of Si is stacked plural times
Implementation Method 2
The reflection film 104 is formed in a structure in which, for example, a molybdenum (Mo) layer made of a Mo material and a silicone (Si) layer made of a Si material are alternately stacked tens of times, and serves to reflect incident exposure light
Implementation Method 3
The absorbing film 106 generally has a two-layer structure of a lower layer 106a made of a TaBN material and an upper layer 106b made of a TaBON material, and serves to absorb incident exposure light
Data Source
AI summary
Disclosed is a blankmask for EUV includes a substrate, a reflection film that is stacked on the substrate; and an absorbing film that is stacked on the reflection film. The reflection film has a structure in which a pair including a first layer made of Ru or a Ru compound in which one or more of Mo, Nb, and Zr are added to Ru, and a second layer made of Si is stacked plural times. Interdiffusion between the respective layers constituting the reflection film is suppressed.