EUV Pellicle Composite Membrane for Mask Protection
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Solution Overview
Problem
EUV lithography systems face contamination issues due to particle contamination on reflective EUV masks, leading to degradation of lithographically transferred patterns, which existing pellicle membranes do not adequately address in terms of performance and volume production efficiency.
Innovation Solution
The development of advanced pellicle membranes with specific material configurations, such as a silicon nitride (SiN)/polysilicon (p-Si)/silicon nitride (SiN)/silicon carbide (SiC) stack, and a ruthenium (Ru)/silicon carbide (SiC) configuration, which provide improved thermal emissivity, transmittance, and reduced EUV reflectivity, are used to protect EUV masks from contaminants and maintain pattern fidelity during lithography processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pellicle membrane is placed over an EUV mask to protect from particle contamination, then mask protection and pattern fidelity are improved, but EUV transmittance and thermal management become compromised
Solution Approach 1:
The pellicle membrane employs a composite structure consisting of multiple thin layers including silicon nitride (SiN), polysilicon (p-Si), and silicon carbide (SiC) deposited in alternating fashion. This composite material configuration allows the membrane to simultaneously achieve mechanical strength for protection, controlled thermal emissivity for heat management, and sufficient EUV transmittance for lithography performance.
Solution Approach 2:
The patent optimizes the thickness parameters of each layer in the composite structure (e.g., SiN layers at 5-15 nm, p-Si layers at 3-10 nm, SiC layers at 10-30 nm) to balance competing requirements. By precisely controlling layer thicknesses, the membrane achieves adequate protection while maintaining EUV transmittance above 70% and thermal emissivity within 0.1-0.5.
2Strength
If the pellicle membrane thickness is increased to improve protection, then mask protection is improved, but EUV transmittance and thermal emissivity are degraded
Solution Approach 1:
Rather than increasing the thickness of a single material, the patent uses a composite of multiple materials with complementary properties. The SiN provides mechanical strength and protection, while the SiC layers contribute to thermal emissivity. This composite approach achieves adequate protection with a total membrane thickness of only 30-100 nm, preserving EUV transmittance.
Solution Approach 2:
Different layers of the membrane have different local properties optimized for specific functions: SiN layers are optimized for mechanical strength and protection, p-Si layers for structural integrity, and SiC layers for thermal emissivity. This local optimization allows each layer to contribute its specific property without requiring overall thickness increase.
3Device complexity
If conventional single-layer pellicle membranes are used, then device complexity is reduced, but thermal management and EUV transmittance performance are insufficient
Solution Approach 1:
The patent introduces a multi-layer composite structure with SiN, p-Si, and SiC layers to achieve proper thermal management. The SiC layers specifically provide thermal emissivity while the alternating structure with SiN and p-Si layers creates a configuration that manages heat dissipation effectively during EUV exposure, preventing excessive heating of the mask.
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
These pellicle membrane configurations effectively reduce particle contamination, maintain pattern fidelity, and enhance thermal management, leading to improved EUV transmittance and reduced out-of-band radiation effects, thereby enhancing the reliability and efficiency of EUV lithography processes.
Implementation Method 1
the material of the fourth layer has a property of having a thermal emissivity greater than 0.2
Implementation Method 2
a transmittance greater than 80%, and a refractive index (n) for 13.5 nanometer source of greater than 0.9
Data Source
AI summary
A structure including an EUV mask and a pellicle attached to the EUV mask. The pellicle includes a pellicle frame and a plurality of pellicle membrane layers attached to the pellicle frame. The plurality of pellicle membrane layers include at least one core pellicle membrane layer and an additional pellicle membrane layer is disposed on the at least one core pellicle membrane layer. In some embodiments, the additional pellicle membrane layer is a material having a thermal emissivity greater than 0.2, a transmittance greater than 80%, and a refractive index (n) for 13.5 nanometer source of greater than 0.9.