CNT Pellicle Tensioning via Induced Current for EUV
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Solution Overview
Problem
In photolithography, carbon nanotube (CNT) pellicles used to protect photomasks from particles face challenges with sagging due to relaxation of CNT-CNT bonding, compromising mechanical and optical integrity, especially when exposed to extreme ultraviolet light.
Innovation Solution
A method involving the use of a border with deposited electrical contacts, where a current is induced through the CNT film by biasing the contacts or applying a changing magnetic field, thereby increasing tension and preventing sagging, allowing the CNT film to remain free-standing and transparent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a carbon nanotube film is made thin and transparent for EUV light, then optical transparency is improved, but mechanical strength decreases causing sagging
Solution Approach 1:
The patent applies electrical current to the CNT film to change its physical state, inducing tensile stress that counteracts sagging. This parameter change (electrical stimulation) transforms the film's mechanical properties without altering its thickness or material composition, resolving the contradiction between thinness for transparency and strength for structural integrity
Solution Approach 2:
The patent replaces traditional mechanical support structures with an electrical field-based solution. Instead of using thicker films or additional mechanical supports to prevent sagging, the invention uses applied electrical current to induce tensile stress, substituting a mechanical support system with an electromagnetic field-based tensioning mechanism
2Illumination intensity
If the pellicle film is made sufficiently thin for EUV transparency, then optical performance is improved, but the film becomes difficult to maintain as free-standing
Solution Approach 1:
The patent replaces mechanical support structures with electrical field-based tensioning. By applying current through electrodes, the CNT film maintains its free-standing nature through induced tensile stress, eliminating the need for mechanical supports that would compromise optical performance while ensuring stability
Solution Approach 2:
The invention changes the physical state of the CNT film through electrical stimulation. The applied current induces tensile stress that maintains the film's free-standing stability, allowing extremely thin films to be used without mechanical support while preserving both optical transparency and structural reliability
3Ease of manufacture
If no additional materials or complex tools are used, then manufacturing simplicity is improved, but the ability to prevent sagging is reduced
Solution Approach 1:
The patent replaces complex mechanical tensioning systems with simple electrical electrodes and current application. This substitution maintains manufacturing simplicity while effectively preventing sagging, as the electrical system is easier to implement than mechanical tensioning devices
Solution Approach 2:
The CNT film serves multiple functions simultaneously: it provides particle protection, maintains optical transparency for EUV light, and acts as an electrical conductor for tensioning. This multi-functionality eliminates the need for separate tensioning mechanisms, maintaining manufacturing simplicity while ensuring stability
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 induced tension in the CNT film reduces or eliminates sagging, maintaining mechanical and optical consistency, ensuring effective protection of the photomask without additional materials or complex tools, and can be applied outside the scanner or to already mounted pellicles.
Implementation Method 1
inducing a current through the free-standing part of the film by biasing at least one pair of the electrical contacts
Implementation Method 2
inducing a current through the free-standing part of the film by applying a changing magnetic field in the free-standing part of the film
Data Source
AI summary
A method for protecting a photomask comprises: (i) providing the photomask, (ii) providing a border, (iii) depositing at least two electrical contacts on the border, (iv) mounting a film comprising carbon nanotubes on the border such that the film comprises a free-standing part, wherein after the mounting and depositing steps, the electrical contacts are in contact with the film, (v) inducing a current through the free-standing part of the film by biasing at least one pair of the electrical contacts, and (vi) mounting the border on at least one side of the photomask with the free-standing part of the film above the photomask.