Talbot Mask Demagnified EUV Nanostructure Patterning
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Solution Overview
Problem
Current methods for printing nano-scale structures are inefficient and require feature sizes on the mask to be as small as the desired sizes on the target, leading to high costs and defects in the printing process.
Innovation Solution
The use of a Talbot mask illuminated with a convergent coherent light beam, allowing for demagnification of the Talbot image and enabling the printing of arrays of nanostructures with dimensions smaller than those on the mask, using extreme ultraviolet light and a photosensitive surface, which reduces the need for precise feature sizes on the mask and minimizes defect transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional printing methods are used to print nano-scale structures, then the desired feature sizes can be achieved on the target, but the mask features must be as small as the target features, leading to high manufacturing costs and defects
Solution Approach 1:
The patent uses optical copying through the Talbot effect to transfer patterns from mask to target. By illuminating the mask with coherent light and positioning the target at the Talbot distance, a self-image of the mask pattern is formed on the target plane. This optical copying mechanism allows the target features to be smaller than mask features through the demagnification inherent in the Talbot imaging geometry, eliminating the need to manufacture masks with extremely small features.
Solution Approach 2:
The patent introduces the dimensional parameter of propagation distance (Talbot distance) between mask and target. By utilizing the longitudinal dimension (distance along the optical axis) rather than only the transverse dimension (lateral scaling), the system achieves demagnification. The Talbot distance z_T = 2p²/λ provides a specific propagation distance where the self-image forms, and by controlling this distance and the mask periodicity p, the target feature size can be reduced relative to mask feature size.
2Productivity
If conventional printing methods are used, then direct pattern transfer is achieved, but the process is slow and costly
Solution Approach 1:
The Talbot self-imaging effect creates an optical copy of the mask pattern directly on the target plane without requiring physical contact or complex multi-step processes. This single-step optical copying method rapidly transfers patterns across the entire target area simultaneously, dramatically increasing printing speed compared to sequential or contact-based methods while reducing manufacturing complexity and cost.
Solution Approach 2:
The patent replaces mechanical contact-based printing or step-by-step lithographic processes with an optical field-based method. The coherent light field carries the pattern information from mask to target through diffraction and interference, eliminating the need for mechanical mask alignment, physical contact, or multiple exposure steps, thereby improving productivity and reducing costs.
3Reliability
If conventional printing methods are used, then patterns are transferred directly, but defects on the mask are transferred to the target
Solution Approach 1:
The mask pattern is segmented into periodic units with period p. The Talbot effect exploits this periodicity to create self-images at specific propagation distances. By designing the mask as a periodic array rather than a single complex pattern, the system can tolerate defects in individual units because the periodic structure allows the Talbot imaging to reconstruct the overall pattern, averaging out local defects and preventing their transfer to the target.
Solution Approach 2:
The patent changes the parameter of mask feature size relative to target feature size. Instead of requiring mask features to be equal to or smaller than target features, the Talbot demagnification allows mask features to be larger. This parameter change means that defects in mask features do not directly translate to equivalent defects in target features, as the optical imaging process with periodic structures filters and averages defect effects, improving reliability.
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 enables rapid, cost-effective printing of large arrays of nanostructures with sub-100 nm spatial resolution, continuously adjustable demagnification, error resistance due to unit cell averaging, non-contact processing, and reduced mask wear, resulting in defect-free patterns on the target substrate.
Implementation Method 1
illuminating a mask with a coherent beam of extreme ultraviolet light, such that the Talbot image is demagnified
Implementation Method 2
a focusing optic into which the light beam from the light source is directed, for causing the light beam emerging therefrom to converge
Implementation Method 3
the sample being disposed at a second chosen distance from the Talbot mask, and having a photosensitive surface thereon responsive to the light beam passing through the Talbot mask
Data Source
AI summary
An apparatus and method for nanopatterning of substrates using the demagnified Talbot effect, wherein: (a) large arrays of nanostructures can rapidly be printed; (b) short extreme ultraviolet wavelengths permits sub-100 nm spatial resolution; (c) the de-magnification factor can be continuously adjusted, that is, continuously scaled; (d) the patterning is the effect of the collective diffraction of numerous tiled units that constitute the periodic array, giving rise to error resistance such that a defect in one unit is averaged over the area of the mask and the print does not show any defects; (e) the Talbot mask does not wear out since the method is non-contact; and (f) the feature sizes on the mask do not have to be as small as the feature sizes desired on the target, are described. The apparatus includes a source of coherent radiation having a chosen wavelength directed onto a focusing optic, the reflected converging light passing through a Talbot mask and impinging on a target substrate.