Phase-Shift Film Nitrogen Control for ArF Light Fastness
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Solution Overview
Problem
Existing phase-shift masks face challenges in achieving uniformity and stability of composition and optical properties, particularly when using silicon-based materials without transition metals, which affect ArF light fastness and pattern line width stability during exposure to ArF excimer lasers.
Innovation Solution
A mask blank with a phase-shift film structure comprising laminated low and high transmission layers formed from silicon and nitrogen, where the low transmission layer has a relatively low nitrogen content and the high transmission layer has a higher nitrogen content, deposited using reactive sputtering with specific gas mixing ratios to ensure stable deposition and optimal optical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive film is formed on the surface of MoSi-based film pattern to improve ArF light fastness, then ArF light fastness is enhanced, but the internal structure of the MoSi-based film remains unchanged and passive films of uniform thickness are difficult to form on sidewalls due to large differences in in-plane coarseness and fineness of patterns
Solution Approach 1:
The invention changes the composition parameters of the phase-shift film by controlling nitrogen content (5-20 at%) and oxygen content (0-15 at%) to achieve both improved ArF light fastness and uniform film properties. This compositional parameter adjustment eliminates the need for post-deposition passive film formation while maintaining structural integrity and optical performance.
Solution Approach 2:
The invention uses composite material composition (transition metal, silicon, nitrogen, and oxygen) to create a phase-shift film that inherently possesses both the required optical properties and ArF light fastness. The composite structure allows simultaneous optimization of multiple properties through controlled element ratios during deposition.
2Reliability
If transition metal-silicon-based material film is used for phase-shift film, then ArF light fastness is improved, but pattern line width changes occur during long-term ArF exposure due to material instability
Solution Approach 1:
The invention optimizes the composition parameters by controlling nitrogen content (5-20 at%) and oxygen content (0-15 at%) to achieve a stable phase-shift film that resists line width changes during ArF exposure. This parameter optimization stabilizes the material composition while maintaining ArF light fastness properties.
Solution Approach 2:
The invention applies different element concentrations at different depths within the film structure, creating a gradient composition that provides both surface stability for ArF resistance and bulk stability for line width maintenance. The local composition varies to optimize both ArF light fastness and dimensional stability.
3Stability of the object's composition
If silicon-based material without transition metals is used for phase-shift film, then material stability is improved, but ArF light fastness and uniformity of composition and optical properties deteriorate
Solution Approach 1:
The invention creates a composite material system combining transition metal, silicon, nitrogen, and oxygen elements in specific ratios. This composite approach provides both the material stability of silicon-based materials and the ArF light fastness previously associated with transition metal-containing materials, while achieving uniform composition and optical properties throughout the film.
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 achieves high uniformity and low defectivity in the phase-shift film, maintaining optical properties and preventing pattern line width changes during ArF excimer laser exposure, thereby enhancing ArF light fastness and pattern stability.
Implementation Method 1
a phase-shift film provided on a transparent substrate, the phase-shift film having a function to transmit ArF exposure light therethrough at a predetermined transmittance and a function to generate a predetermined amount of phase shift in the ArF exposure light that is transmitted therethrough
Implementation Method 2
deposited using reactive sputtering with specific gas mixing ratios to ensure stable deposition and optimal optical characteristics
Data Source
AI summary
A mask blank is provided in which a phase-shift film is provided on a transparent substrate, the phase-shift film having a predetermined transmittance to ArF exposure light and being configured to shift a phase of ArF exposure light transmitted therethrough, wherein the phase-shift film comprises a nitrogen-containing layer that is formed from a material containing silicon and nitrogen and does not contain a transition metal, and wherein a content of oxygen in the nitrogen-containing layer, when measured by X-ray photoemission spectroscopy, is below a detection limit.