Flexible Polymer Foil Intermediate Stamp for Nanoimprint Lithography
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Solution Overview
Problem
The existing nanoimprint lithography techniques face challenges in achieving high replication fidelity due to differences in thermal expansion coefficients between templates and substrates, air inclusion between inflexible stamps and substrates, and damage from demolding, especially when using hard and inflexible materials.
Innovation Solution
A two-step imprint process using a flexible polymer foil as an intermediate stamp, where the pattern is first imprinted on the foil from a template and then transferred to a substrate, minimizing wear and damage by using a soft material for the initial imprint and avoiding direct contact between hard materials, and employing a combined radiation and heat-assisted imprint process to manage thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If an inflexible stamp or substrate material is used, then the structural stability is improved, but air inclusion occurs between the stamp and moldable layer, reducing replication fidelity
Solution Approach 1:
The patent employs a flexible polymer foil as the stamp material instead of traditional inflexible materials. This flexible foil can conform to the substrate surface and accommodate minor irregularities, preventing air inclusion while maintaining structural integrity. The flexibility allows the stamp to adapt during the imprinting process, ensuring complete contact between the stamp and moldable layer.
2Strength
If hard and inflexible materials are used for stamp and substrate, then the mechanical strength is improved, but physical damage occurs during demolding, especially for high aspect ratio patterns
Solution Approach 1:
The flexible polymer foil serves as a compliant intermediate layer between the hard template and the substrate. During demolding, the flexible nature of the foil allows it to deform and release patterns with high aspect ratios without causing physical damage to either the template or the substrate. The foil absorbs the mechanical stress of demolding through elastic deformation.
Solution Approach 2:
The flexible polymer foil acts as an intermediary material that mediates between the rigid template and the substrate. It transfers the pattern while accommodating differential thermal expansion and mechanical stresses, preventing direct contact between hard materials that would cause damage during demolding.
3Adaptability or versatility
If the template and substrate are made of different materials, then the application versatility is improved, but different thermal expansion coefficients cause reduced replication fidelity
Solution Approach 1:
The patent utilizes the flexible polymer foil's ability to undergo thermal expansion and contraction to accommodate different thermal expansion coefficients between template and substrate. The foil's elastic properties allow it to expand and contract with the substrate during thermal cycles without causing pattern distortion, effectively decoupling the thermal mismatch between dissimilar materials.
Solution Approach 2:
The flexible polymer foil serves as a thermal accommodation layer that can dynamically adjust its dimensions in response to temperature changes. This flexibility allows the system to tolerate different thermal expansion coefficients between the template and substrate while maintaining pattern fidelity throughout the imprinting process.
4Manufacturing precision
If a flexible polymer foil is used as intermediate stamp, then the replication fidelity is improved and material wear is reduced, but the device complexity increases with additional transfer steps
Solution Approach 1:
The patent divides the imprinting process into two sequential steps: first, imprinting the template pattern onto the flexible polymer foil; second, transferring the pattern from the foil to the substrate. This segmentation allows each step to be optimized independently, with the foil serving as a disposable intermediate carrier that simplifies the overall process despite adding a transfer operation.
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
This approach enhances replication fidelity, reduces material wear and damage, and allows for the use of expensive templates less frequently, while maintaining high precision and accuracy in pattern transfer, even with substrates and templates having different thermal expansion coefficients.
Implementation Method 1
If the template and the substrate are not made of the same material, which they generally are not, they will typically have different thermal expansion coefficients. This means that during heating and cooling of the template and the substrate, the extent of expansion and contraction will be different.
Implementation Method 2
the stamp is pressed towards the film followed by cooling and release—often called demolding—of the stamp, after the desired pattern depth has been transferred into the film
Implementation Method 3
After heating the object to a suitable temperature above the glass transition temperature of the polymer film the stamp is pressed towards the film
Implementation Method 4
This requires that either the substrate or the stamp is transparent to the applied radiation. In a subsequently performed process after the achieved imprint, the object—comprising the substrate and the patterned polymer film—can be post-processed e.g. by etching of the substrate within the imprinted regions
Data Source
AI summary
The invention relates to an imprint apparatus for carrying out a two-step process for transferring a pattern from a template to a target surface of a substrate. The apparatus works by creating an intermediate disc, e.g. from a flexible polymer stamp, by imprint from the template in a first imprint unit. A feeder device is then operated to feed the intermediate stamp to a second imprint unit, where it is used to make an imprint in a target surface of a substrate.