EUV Lithography Pellicle Composite Structure
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Solution Overview
Problem
Current EUV lithography pellicles face challenges in achieving high transmittance and mechanical strength, particularly in vacuum environments and long-term exposure processes, while maintaining low extinction coefficients for EUV light.
Innovation Solution
A pellicle structure comprising a support layer pattern, a pellicle layer with a core layer and reinforcing layers on both surfaces, and an etching stop layer pattern, where the core layer includes materials like silicon and metal silicides, and the reinforcing layers include silicon compounds with nano-sized pores for enhanced mechanical and thermal characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single film pellicle using material with low extinction coefficient is used, then transmittance of EUV light is improved, but mechanical and thermal characteristics deteriorate
Solution Approach 1:
The pellicle is constructed as a multi-layered composite structure consisting of a core layer (100nm or less thickness) made of low extinction coefficient material for high EUV transmittance, and reinforcing layers (2-10nm thickness) made of materials with high mechanical strength such as silicon nitride or silicon oxide. This composite structure allows the pellicle to maintain high transmittance while gaining the mechanical and thermal reliability needed for vacuum environments and long-term exposure processes.
2Illumination intensity
If the pellicle layer is made extremely thin (100nm or less) for high transmittance, then transmittance of EUV exposure light is improved, but mechanical reliability deteriorates
Solution Approach 1:
Different regions of the pellicle structure are assigned different properties: the core layer is made extremely thin (100nm or less) with low extinction coefficient material to maximize EUV transmittance, while the reinforcing layers are strategically positioned on the surfaces with materials having high mechanical strength. This local differentiation allows each layer to perform its specific function optimally - the core layer for light transmission and the reinforcing layers for mechanical support.
3Reliability
If a multi-layered pellicle structure is used, then mechanical and thermal characteristics are improved, but device complexity increases
Solution Approach 1:
The pellicle is segmented into functionally distinct layers: a core layer for high EUV transmittance and reinforcing layers for mechanical strength. This segmentation allows each layer to be optimized for its specific function while maintaining overall simplicity through clear functional separation.
Solution Approach 2:
The core layer acts as an intermediary between the reinforcing layers, providing the essential function of high EUV transmittance while being mechanically supported by the outer reinforcing layers. This intermediary structure allows the system to achieve both high transmittance and mechanical reliability without excessive complexity.
4Strength
If reinforcing layers are added to the core layer, then mechanical strength is improved, but transmittance of EUV light deteriorates
Solution Approach 1:
The thickness of the reinforcing layers is precisely controlled at 2-10nm, which is thin enough to maintain high EUV transmittance while providing sufficient mechanical strength. This parameter optimization allows the reinforcing layers to contribute to mechanical reliability without significantly compromising the transmittance property of the pellicle.
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 pellicle achieves high transmittance and mechanical strength, with improved thermal dissipation and reduced risk of damage from impurities, enabling effective protection of photomasks during EUV lithography processes.
Implementation Method 1
the reinforcing layer comprises an outer porous surface having nano-sized pores
Data Source
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Figure 3A
AI summary
Disclosed is a pellicle for extreme ultraviolet (EUV) lithography. The pellicle may include: a support layer pattern which is formed by etching a support layer; a pellicle layer which is formed on the support layer pattern; and an etching stop layer pattern which is formed between the support layer pattern and the pellicle layer and formed by etching an etching stop layer of stopping etching when the support layer is etched. Thus, there is provided a pellicle for EUV photomask, which maintains high transmittance with the minimum thickness for EUV exposure light, and is excellent in mechanical strength and thermal characteristics.