Nanotube EUV Pellicle Structure for Strength and Contamination Resistance
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Solution Overview
Problem
EUV lithography faces challenges in maintaining high EUV transmittance and mechanical strength of pellicles due to environmental adsorption and contamination, particularly in hydrogen radical-rich environments, which affect the performance and longevity of EUV photomasks.
Innovation Solution
A pellicle structure for EUV lithography utilizing a network membrane of carbon nanotubes or non-carbon based nanotubes, treated to enhance mechanical strength and transparency, with conductive electrodes for Joule heating to remove contaminants and prevent wrinkling, thereby maintaining high EUV radiation transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional transparent film is used as pellicle, then EUV transmittance is maintained, but mechanical strength is insufficient and contamination occurs
Solution Approach 1:
The patent employs a composite structure combining carbon nanotubes (or non-carbon based nanotubes) with a porous substrate. The nanotubes form a network layer that provides both mechanical reinforcement and EUV transparency, while the porous substrate supports the nanotube network and enables controlled contamination resistance. This composite approach resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The patent uses a thin film structure where carbon nanotubes (or non-carbon based nanotubes) form a flexible network membrane stretched over a frame. This thin film maintains EUV transparency while providing mechanical strength through the nanotube network, eliminating the need for thicker conventional films that would compromise transparency or increase contamination risk.
2Object-generated harmful factors
If hydrogen radical-rich environment is used for cleaning, then contamination is removed, but mechanical strength of pellicle deteriorates
Solution Approach 1:
The patent converts the harmful effect of hydrogen radicals into a beneficial cleaning mechanism. Hydrogen radicals are used to remove contaminants from the pellicle surface, and the resulting hydrogen plasma treatment actually strengthens the nanotube network by removing organic contaminants that would otherwise weaken the structure. The harmful hydrogen radical environment becomes a beneficial cleaning and strengthening process.
Solution Approach 2:
The patent changes the chemical environment parameters by exposing the pellicle to hydrogen plasma treatment. This parameter change transforms the surface properties of the nanotube network, removing contaminants and modifying the chemical composition to enhance mechanical strength. The parameter change from ambient conditions to hydrogen-rich plasma environment achieves both cleaning and strengthening.
3Strength
If conventional materials are used for pellicle, then manufacturing is simple, but EUV transmittance and mechanical strength cannot be simultaneously achieved
Solution Approach 1:
The patent segments the pellicle structure into distinct functional layers: a porous substrate providing mechanical support, a nanotube network layer providing EUV transparency and contamination resistance, and a frame structure providing structural integrity. This segmentation allows each layer to be optimized independently and simplifies the manufacturing process by enabling separate fabrication and assembly of components.
Solution Approach 2:
The patent introduces a porous substrate as an intermediary between the nanotube network and the frame structure. This intermediary component provides mechanical support for the fragile nanotube network while maintaining EUV transparency, and serves as a platform for attaching the nanotubes to the frame. The intermediary simplifies manufacturing by providing a stable base for further processing.
4Strength
If pellicle thickness is increased to improve mechanical strength, then strength is improved, but EUV transmittance decreases
Solution Approach 1:
The patent uses an extremely thin film structure where carbon nanotubes (or non-carbon based nanotubes) form a sparse network membrane. This thin film maintains mechanical strength through the nanotube network while allowing maximum EUV radiation to pass through, eliminating the transmittance loss that would occur with conventional thicker films.
Solution Approach 2:
The patent employs a porous substrate structure that allows EUV radiation to pass through while providing mechanical support. The porous configuration maintains open pathways for radiation transmission while the nanotube network embedded in the porous structure provides the necessary mechanical strength, resolving the contradiction between thickness and transmittance.
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 nanotube-based pellicle structure improves EUV radiation transmission, mechanical strength, and resistance to hydrogen plasma etching, extending the pellicle's lifespan and reducing contamination, thus enhancing photolithographic performance.
Implementation Method 1
with conductive electrodes for Joule heating to remove contaminants and prevent wrinkling
Implementation Method 2
improves EUV radiation transmission
Data Source
AI summary
A method of manufacturing a semiconductor device includes heating a pellicle disposed over a photomask. Actinic radiation is passed through the pellicle to selectively expose a photoresist layer on a substrate. The selectively exposed photoresist layer is developed to form a pattern in the photoresist layer.