Nanowire Net Pellicle for EUV Photomask Protection
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Solution Overview
Problem
The lithography process in IC device manufacturing is prone to defects due to contamination of photomasks by foreign materials, especially when using extreme ultraviolet (EUV) light, which has a short wavelength and high resolution, making it difficult to transfer patterns accurately without causing thermal damage or image errors.
Innovation Solution
A pellicle with a porous thin film comprising nanowires arranged in a net-like structure provides mechanical stability and high transmittance for EUV light, preventing contamination and thermal damage, and reducing out-of-band reflectance, thus enhancing the resolution and durability of the photomask during exposure processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional photomask is used without protection, then the manufacturing process is simple, but the photomask becomes contaminated with foreign materials and deformed by the ambient environment
Solution Approach 1:
A pellicle is introduced as an intermediary protective layer between the photomask and the ambient environment. This pellicle prevents direct contact between foreign materials and the photomask surface, thereby maintaining photomask cleanliness without requiring complex sealed enclosures or active protection systems.
Solution Approach 2:
The patent employs a thin-film pellicle structure that provides physical protection to the photomask. This flexible thin film acts as a barrier against contamination while allowing the photomask to maintain its operational characteristics, avoiding the need for rigid protective structures that would complicate the system.
2Manufacturing precision
If EUV light is used for high resolution patterning, then the pattern precision is improved, but thermal damage and image errors occur due to the short wavelength
Solution Approach 1:
The patent converts the harmful thermal effects of EUV light into a beneficial filtering mechanism. The pellicle structure is designed to selectively filter out harmful thermal radiation and out-of-band energy while allowing the useful EUV patterning light to pass through, thereby protecting the photomask from thermal damage while maintaining high resolution capability.
Solution Approach 2:
The pellicle employs a porous thin film structure that allows EUV light to pass through while blocking harmful thermal radiation and foreign materials. The porous configuration provides high transmittance for the required EUV wavelengths while simultaneously providing thermal and contamination protection.
3Reliability
If a protective structure is added to prevent contamination, then the photomask reliability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent uses a thin-film pellicle that can be easily integrated into the existing photomask assembly without requiring complex manufacturing processes. The thin film structure is simple to produce and can be applied without adding significant complexity to the manufacturing workflow, while still providing effective protection against contamination.
Solution Approach 2:
The porous thin film pellicle is designed to be manufacturable using standard thin-film deposition techniques. The porous structure is formed during the manufacturing process itself, eliminating the need for additional complex steps to create the protective pattern, thereby maintaining ease of manufacture while achieving reliable protection.
4Manufacturing precision
If the pellicle membrane is made thinner to reduce out-of-band reflectance, then the resolution is improved, but the mechanical stability decreases
Solution Approach 1:
The patent employs a porous thin film structure that achieves an optimal balance between thickness and mechanical strength. The porous configuration provides structural support through its three-dimensional network, allowing the pellicle to maintain mechanical stability even at reduced thickness levels that minimize out-of-band reflectance and maximize resolution.
Solution Approach 2:
The pellicle utilizes composite material structures that combine multiple properties to achieve both thinness and mechanical strength. By using composite thin-film constructions, the patent achieves the required mechanical stability for handling and operation while maintaining sufficient thinness to reduce out-of-band reflectance and improve patterning resolution.
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 ensures structural stability and high transmittance for EUV light, reducing errors and extending the photomask's lifespan by preventing contamination and thermal damage, while also simplifying the manufacturing process and improving pattern precision on wafers.
Implementation Method 1
reducing out-of-band reflectance
Implementation Method 2
high transmittance for EUV light
Implementation Method 3
mechanically stable structure
Implementation Method 4
structural stability
Implementation Method 5
protecting the photomask used for the lithography process from foreign materials
Implementation Method 6
preventing contamination and thermal damage
Data Source
AI summary
A pellicle includes a pellicle membrane, which includes a porous thin film. The porous thin film includes a plurality of nanowires, which are arranged across one another to form a net structure. A photomask assembly includes the pellicle and a photomask, wherein the pellicle is fixed to a surface of the photomask.