Wire Grid Polarization Element Manufacturing via Nanoimprint Resist Control
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Solution Overview
Problem
Existing methods for manufacturing wire grid polarization elements face challenges in maintaining consistent polarization properties due to variations in residual film thickness across the mother substrate, leading to issues with the width of wire-shaped metal layers and optical properties.
Innovation Solution
A method involving sequential film formation of a metal film and an inorganic material film on a mother substrate, followed by nanoimprinting to create a resist mask with controlled thickness variation, ensuring the resist mask remains intact during etching and division into multiple polarization elements, with specific conditions on Δt/P to stabilize the contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the etching time is extended to remove thick residual film, then the residual film thickness is reduced, but the wire-shaped metal layer width is narrowed and optical properties deteriorate
Solution Approach 1:
The patent applies local quality by differentiating the treatment of residual film at different locations. The resist mask is designed to remain at the bottom portion of concave portions between convex portions, creating localized residual film regions that do not interfere with wire-shaped metal layer formation. This allows selective removal of residual film in specific areas while preserving it where needed to define metal layer boundaries.
Solution Approach 2:
The patent employs preliminary action by forming the resist mask pattern before etching the metal film. The resist mask with its specific convex and concave structure is created in advance, and the etching process is then performed with control to remove residual film only in predetermined regions. This sequence prevents premature metal layer formation that would be compromised by varying residual film thickness.
2Reliability
If the etching time is shortened to preserve wire-shaped metal layer width, then the optical properties are maintained, but thick residual film remains and interferes with subsequent processing
Solution Approach 1:
The resist mask structure creates localized regions where residual film is intentionally preserved (bottom of concave portions) versus regions where it is removed (top surfaces). This local differentiation allows the etching process to proceed for sufficient time to remove harmful residual film while preserving the metal layer width, as the resist mask physically protects certain areas from over-etching.
3Productivity
If a mother substrate division method is used to produce multiple polarization elements, then productivity is improved, but variation in residual film thickness across the substrate leads to inconsistent wire grid properties
Solution Approach 1:
The patent applies segmentation by dividing the mother substrate into multiple smaller substrates after forming the complete resist mask and metal film patterns. This allows batch processing of multiple polarization elements simultaneously, improving productivity. The key is that the resist mask and metal film are formed on the entire mother substrate first, ensuring uniform patterns across all segments before division occurs.
Solution Approach 2:
The patent employs preliminary action by forming the complete resist mask and metal film patterns on the entire mother substrate before division into smaller substrates. This ensures that all patterns are established uniformly across the large substrate area, and any residual film variations are addressed during the etching process before the substrate is divided, thereby maintaining consistency across all produced polarization elements.
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 ensures the production of wire grid polarization elements with consistent polarization properties and a contrast ratio of 100 or greater, by controlling the thickness variation of the resist mask to maintain uniform wire-shaped metal layer widths and optical performance.
Implementation Method 1
a mold material for nanoimprinting is pressed against the resist layer to form, to the resist layer, a plurality of convex portions arranged in parallel to each other at a pitch equivalent to a pitch of the plurality of wire-shaped metal layers
Implementation Method 2
thereafter the resist layer is cured to form the resist mask
Implementation Method 3
performing dry etching with the resist mask formed, and thus performing a patterning of the metal film to form the plurality of wire-shaped metal layers
Data Source
AI summary
In a manufacturing process of a wire grid polarization element, a metal film, a light absorption film, and an inorganic material film for hard mask are sequentially formed, and then a resist mask is formed using nanoimprinting. Next, the metal film is patterned into a plurality of wire-shaped metal layers by dry etching. The resist mask is remaining at the bottom portion of the concave portion interposed between the adjacent convex portions. Δt/P (%), which is obtained by dividing, by the pitch P (nm), the difference Δt (nm) between the maximum value and the minimum value of the thickness t (nm) of the residual film of the resist mask remaining at the bottom portion of the concave portion, is rendered to be 13.4% or less.