Nanoimprint Lithography Grating Edge Depth Gradient
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Solution Overview
Problem
Existing waveguide-based near-eye display systems face challenges in fabricating nanostructures with large gradual depth changes in small areas, leading to potential damage during demolding and affecting the performance of surface-relief gratings used in these systems.
Innovation Solution
The use of reactive ion etch (RIE) lag effect to etch nanostructures with large gradual depth changes in small areas near the edges, and modifying the etch mask to include a large gradual change in duty cycle, allowing for the production of soft stamps and surface-relief structures with varying depth and duty cycle, reducing stress during demolding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to fabricate nanostructures, then manufacturing process is simple, but large gradual depth changes in small areas cannot be achieved leading to demolding damage
Solution Approach 1:
The patent utilizes the RIE lag effect by modifying the etch mask duty cycle parameter to achieve gradual depth changes. The duty cycle varies continuously across the mask, causing corresponding gradual depth variations in the etched nanostructures without requiring complex multi-step etching processes
Solution Approach 2:
The RIE lag effect is a self-regulating phenomenon where the etching process automatically produces gradual depth changes in response to duty cycle variations in the mask. The system uses its own inherent lag characteristic to achieve the desired depth profile without external intervention or complex process control
2Reliability
If uniform depth nanostructures are used, then demolding stress is high causing damage, but varying depth increases stress distribution
Solution Approach 1:
The patent applies local quality by creating nanostructures with spatially varying depths. The duty cycle of the etch mask varies across different regions, producing local depth variations that reduce stress concentration at edges during demolding while maintaining the overall grating structure
Solution Approach 2:
The varying depth profile is designed in advance to cushion against demolding stresses. By creating gradual depth transitions before demolding occurs, the structure is pre-conditioned to distribute stresses evenly, preventing damage during the demolding process
3Manufacturing precision
If etch mask has uniform duty cycle, then etching process is simple, but cannot produce gradual depth changes
Solution Approach 1:
The etch mask duty cycle parameter is continuously varied across the mask area to produce gradual depth changes in the nanostructures. This single parameter modification enables precise depth control without complicating the overall etching process or requiring multiple etching steps
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 minimizes stress and damage during demolding, ensuring the integrity and performance of the imprinted nanostructures, such as slanted surface-relief gratings, used in near-eye display systems.
Implementation Method 1
The use of reactive ion etch (RIE) lag effect to etch nanostructures with large gradual depth changes in small areas near the edges
Data Source
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AI summary
A nano-structure includes an outer area at an edge of the nano-structure. A width of the outer area defined by a distance from the edge of the nano-structure is less than 100 µm. A depth of the nano-structure in the outer area changes gradually between 0% and at least 50% of a maximum depth of the nano-structure. A method includes forming an etch mask on a substrate and etching the substrate with the etch mask using an ion beam to form a nano-structure in the substrate. The etch mask includes an outer area near an edge of the etch mask. A width of the outer area defined by a distance from the edge of the etch mask is less than 100 µm. A duty cycle of the etch mask in the outer area changes gradually between at least 10% and at least 90%.