EUV Pellicle Film Crystal Orientation for Crack-Resistant Transmission
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Solution Overview
Problem
Current pellicle films for extreme ultra violet (EUV) lithography face challenges in achieving high transmission, chemical stability, and fabrication yield due to amorphous silicon films with high absorption coefficients and stress issues, leading to cracks and defects during processing.
Innovation Solution
A pellicle film comprising a silicon single crystal film with a crystal plane inclined at 3 to 5° from {100} or {111} lattice planes, combined with a protection film made from materials like SiC, SiO2, or metals, and produced using a gas cluster ion beam evaporation method to enhance mechanical and chemical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon film is deposited by sputtering or CVD method, then the pellicle film can be formed, but the absorption coefficient in the EUV region becomes high and transmittance becomes low
Solution Approach 1:
The patent changes the crystal structure parameter of silicon from amorphous (deposited by sputtering or CVD) to single crystal orientation. Specifically, it uses silicon single crystal with <100> orientation which has lower absorption coefficient in EUV region compared to amorphous silicon, thereby improving transmittance while maintaining film formation
Solution Approach 2:
The patent employs a composite structure consisting of a silicon single crystal film layer and a protective film layer. The silicon single crystal provides low absorption and high transmittance, while the protective film (made of materials like SiO2, Si3N4, or metallic layers) provides mechanical strength and chemical stability, achieving both optical performance and structural reliability
2Reliability
If a silicon crystal film is made thin to improve transmission, then EUV light transmittance increases, but cracks and defects occur during stripping, etching, and handling
Solution Approach 1:
The patent uses a composite structure where a silicon single crystal film (thin layer for high transmission) is combined with a protective film (thicker layer for mechanical strength). The protective film serves as a mechanical reinforcement that prevents cracks and defects during handling, etching, and stripping processes, while the thin silicon single crystal layer maintains high EUV transmission
Solution Approach 2:
The patent applies different functional properties to different layers: the silicon single crystal film provides optical functionality (high transmission) while the protective film provides mechanical functionality (strength and crack resistance). This local differentiation of material properties allows the thin film to be both transparent and mechanically robust
3Reliability
If a (100) plane silicon single crystal film is used, then excellent optical properties are achieved, but cracks occur during processing when made into thin film
Solution Approach 1:
The patent combines silicon single crystal <100> orientation (which has excellent optical properties and low absorption) with a protective film structure. This composite approach allows the thin film to maintain its optical excellence while the protective film provides crack resistance and structural stability during processing
Solution Approach 2:
The protective film is applied beforehand to the silicon single crystal film to provide a cushioning effect that prevents cracks from forming during subsequent processing steps. This prior protection allows the thin film to be handled and processed without developing defects, while maintaining the excellent optical properties of the silicon crystal
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 solution provides a pellicle film with high EUV transmission, reduced crack occurrence, and improved fabrication yield, ensuring practicality and cost-effectiveness for EUV lithography applications.
Implementation Method 1
formed using a gas cluster ion beam evaporation method
Implementation Method 2
gas cluster ion beam evaporation method
Data Source
AI summary
A silicon single crystal film having a crystal plane as its principal plane, the crystal plane being inclined at 3 to 5° from any lattice plane belonging to {100} planes or {111} planes is used as a pellicle film. The silicon single crystal having such a crystal plane as its principal plane has effective bond density and Young's modulus thereof which are about 40% to about 50% higher than those of a silicon single crystal with <100> orientation, and therefore a cleavage and crack do not easily occur. Moreover, the silicon single crystal has a high chemical resistance such as hydrofluoric acid resistance, and hardly causes an etch pit and void. Accordingly, the present invention can provide a pellicle comprising a pellicle film for EUV having high transmission, and excellent mechanical and chemical stability, as well as having a high yield, and being practical also in cost.