Single Crystal Silicon EUV Pellicle with Porous Support
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Solution Overview
Problem
Current pellicle films for EUV lithography are not highly transmissive to extreme ultraviolet light and are chemically unstable, leading to decreased transmittance over time due to amorphous or polycrystalline silicon films with high absorptivity and oxidation issues.
Innovation Solution
A pellicle film made of single crystal silicon supported by a porous structure with an anti-oxidizing film and gas filters, manufactured using a SOI substrate with partial removal of the handle substrate by dry etching, ensuring mechanical strength and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous or polycrystalline silicon films are used as pellicle films, then the manufacturing process is simplified, but the transmittance to EUV light decreases due to high absorptivity
Solution Approach 1:
The invention changes the crystalline structure parameter of silicon from amorphous or polycrystalline to single crystal. This parameter change fundamentally reduces the absorption coefficient for EUV light while maintaining compatibility with existing semiconductor manufacturing processes through SOI substrate utilization.
Solution Approach 2:
The invention creates a composite structure combining single crystal silicon layer with handle substrate and porous layer. This composite approach leverages the high transmittance of single crystal silicon while using the handle substrate and porous structure to provide mechanical support and control stress.
2Ease of manufacture
If conventional silicon films are used, then the pellicle can be manufactured, but chemical stability deteriorates due to oxidation
Solution Approach 1:
The invention creates an inert environment by introducing a porous layer that prevents oxygen access to the single crystal silicon surface. This protective barrier maintains chemical stability by excluding oxidizing agents from the silicon material.
Solution Approach 2:
The porous layer acts as an intermediary barrier between the single crystal silicon and the external environment. This intermediate layer protects the silicon from direct contact with oxygen while allowing the pellicle to function in its intended application environment.
3Reliability
If the pellicle film is made ultrathin to improve transmittance, then EUV light transmission increases, but mechanical strength decreases making it difficult to maintain constant tension
Solution Approach 1:
The invention employs a nested structure where the ultrathin single crystal silicon layer is supported by the handle substrate and porous layer. This nested configuration allows the thin film to benefit from mechanical support from underlying structures while maintaining its high transmittance properties.
Solution Approach 2:
The invention utilizes the inherent flexibility and thin film characteristics of single crystal silicon to create an ultrathin pellicle that can conform to the photomask surface while maintaining structural integrity through the supported configuration.
4Ease of operation
If stress is applied to the silicon film during bonding to maintain tension, then the pellicle can function properly, but the film may be damaged due to excessive stress
Solution Approach 1:
The invention provides beforehand cushioning by incorporating the handle substrate and porous layer structure that can absorb and distribute bonding stresses. This pre-configured support system prevents excessive stress concentration on the silicon film during the bonding process.
Solution Approach 2:
The porous layer serves as an intermediary that mediates stress distribution during bonding. It allows controlled stress application to maintain film tension while preventing excessive stress that would cause damage to the ultrathin silicon layer.
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 single crystal silicon pellicle film exhibits significantly reduced absorption coefficients and improved chemical stability, maintaining high transmittance and mechanical integrity for EUV exposure.
Implementation Method 1
a pellicle film of single crystal silicon... which is a material that is highly transmissive to extreme ultraviolet light (EUV light)
Implementation Method 2
a support member including an outer frame portion and a porous portion that occupies an inner area surrounded by the outer frame portion
Implementation Method 3
manufacturing method thereof... manufactured using a SOI substrate with partial removal of the handle substrate by dry etching
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A pellicle for lithography according to the present invention comprises a pellicle film (10) of single crystal silicon, and the pellicle film (10) is supported by a support member (20) including an outer frame portion (20a) and a porous portion (mesh structure) (20b) that occupies an inner area surrounded by the outer frame portion (20a). In order to prevent oxidation of surfaces of the pellicle film 10, anti-oxidizing films 30a and 30b are provided to cover portions where the single crystal silicon film is exposed to the outside. The support member (20) can be obtained by processing a handle substrate of an SOI substrate, and the pellicle film (10) of single crystal silicon can be obtained from an SOI layer of the SOI substrate. Since the pellicle film (10) is tightly coupled to the support member (20), sufficient mechanical strength can be assured.