Sub-wavelength Grating Manufacturing via Sacrificial Layer Segmentation
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Solution Overview
Problem
Existing methods for manufacturing sub-wavelength gratings face challenges in achieving high density, high aspect ratio, and high mark-space ratio, limiting their application due to a 1:1 aspect ratio.
Innovation Solution
A manufacturing method involving a substrate with a patterned mask layer formed using photoresist films and nano-imprint lithography, followed by etching with a microwave plasma system using CF4, SF6, and Ar2 gases to create a grating with a high aspect ratio greater than or equal to 6:1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithography methods are used to manufacture sub-wavelength gratings, then the manufacturing process is simple, but the aspect ratio is limited to 1:1
Solution Approach 1:
The manufacturing process is divided into multiple distinct steps: forming a mandrel pattern, depositing a first sacrificial layer, forming a second sacrificial layer, performing selective etching, and removing sacrificial materials. This segmentation enables independent control of each parameter (depth, width, mark-space ratio) to achieve high aspect ratios greater than 1:1 while maintaining manufacturing feasibility through systematic process breakdown.
Solution Approach 2:
The patent employs preliminary actions by forming sacrificial layers and mandrel patterns before the actual grating structure is created. The first and second sacrificial layers are deposited and patterned in advance, allowing subsequent selective etching to achieve precise cavity depths and widths. This preliminary preparation enables the final grating to achieve aspect ratios exceeding 1:1 by establishing the necessary structural framework before main fabrication.
2Reliability
If the grating density is increased to achieve sub-wavelength performance, then the diffraction efficiency improves, but the manufacturing precision requirements become more stringent
Solution Approach 1:
The patent applies local quality by using different sacrificial materials with distinct etching characteristics in different regions. The first sacrificial layer and second sacrificial layer are selectively removed in specific patterns to create cavities with precise local dimensions. This localized differentiation enables tight control of cavity width and depth at high densities, achieving sub-wavelength grating performance with aspect ratios greater than 1:1 while meeting stringent manufacturing precision requirements.
3Object-affected harmful factors
If the mark-space ratio is increased to achieve high density, then the scattering is reduced, but the etching process becomes more difficult to control
Solution Approach 1:
The patent introduces sacrificial layers as intermediary materials that facilitate precise etching control. The first and second sacrificial layers serve as mediators between the mandrel pattern and the final cavity structure, enabling controlled removal of material to achieve precise mark-space ratios. These intermediary layers allow the etching process to proceed with high precision, creating cavities with controlled dimensions that reduce scattering while maintaining manufacturability through systematic process control.
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 method enables the production of sub-wavelength gratings with high density, high aspect ratio, high mark-space ratio, high diffraction efficiency, and low scattering, expanding their application potential.
Implementation Method 1
etching using a microwave plasma system with CF4, SF6, and Ar2 gases
Implementation Method 2
etching using a microwave plasma system with CF4, SF6, and Ar2 gases to create a grating
Data Source
AI summary
A method for making a grating includes the following steps. A first photoresist film is formed on a substrate. A second photoresist film is applied on the first photoresist film. A number of first cavities are formed in the second photoresist film, wherein part of the first photoresist film is exposed to form a first exposed part. A number of second cavities are formed, wherein part of the surface of the substrate is exposed to form an exposed surface. A mask layer is deposited on the second photoresist film and the exposed surface of the substrate. A patterned mask layer is formed, and part of the substrate is exposed to form a second exposed part. The second exposed part of the substrate is etched through the patterned mask layer. The patterned mask layer is removed.