Wire Grid Polarizer Hard Mask Structure for High Extinction Ratio
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Solution Overview
Problem
Fabricating wire grid polarizers with a period shorter than the wavelength of incident light is challenging due to the difficulty in achieving high polarization extinction ratios and preventing irregularities in the top surface, such as hillock formation, which affects the optical properties.
Innovation Solution
A wire grid polarizer is fabricated using a substrate with conductive wire patterns and multiple hard mask layers, where the second hard mask patterns have a taper angle greater than 90 degrees and a ratio of bottom to top width less than 1, and a protective layer is applied to prevent hillock formation and enhance processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional fabrication methods are used for wire grid polarizers with period shorter than wavelength of incident light, then manufacturing complexity increases, but polarization extinction ratio and surface quality deteriorate
Solution Approach 1:
The fabrication process is segmented into multiple sequential steps with distinct functions: forming resist patterns with first taper angle, depositing first hard mask layer, forming second hard mask patterns with second taper angle, and selective removal. This segmentation allows each step to be optimized independently, achieving high manufacturing precision without overwhelming complexity
Solution Approach 2:
Resist patterns are formed with a preliminary taper angle less than 90 degrees before hard mask deposition. This preliminary action creates a foundation that guides the subsequent formation of hard mask patterns with greater than 90 degree taper angles, ensuring precise wire pattern formation while maintaining processability
2Ease of manufacture
If conventional fabrication methods are used, then process simplicity is maintained, but surface irregularities such as hillock formation occur, deteriorating optical quality
Solution Approach 1:
Multiple hard mask layers with different taper angles act as intermediaries between the resist pattern and the final wire grid structure. The first hard mask layer with taper angle greater than 90 degrees prevents direct contact between subsequent processing steps and the resist pattern, eliminating hillock formation while maintaining ease of manufacture through systematic process design
Solution Approach 2:
The taper angle parameter is changed from less than 90 degrees in resist patterns to greater than 90 degrees in hard mask patterns. This parameter change is critical for preventing surface irregularities while maintaining processability, as the greater than 90 degree taper angle prevents material accumulation and hillock formation during deposition and etching processes
3Manufacturing precision
If single hard mask layer is used, then device structure is simplified, but manufacturing precision and processability deteriorate
Solution Approach 1:
The hard mask system is segmented into multiple layers with different taper angles and functions. The first hard mask layer provides the primary pattern definition with greater than 90 degree taper angle, while the second hard mask layer provides additional protection and precision. This segmentation achieves high pattern formation precision without excessive overall complexity
Solution Approach 2:
Different regions of the hard mask structure have different taper angles optimized for their specific functions. The first hard mask layer has taper angle greater than 90 degrees for preventing hillocks, while the second hard mask layer has taper angle less than 90 degrees for precise pattern transfer. This local quality optimization achieves high manufacturing precision with manageable device complexity
Data Source
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AI summary
Provided is a wire grid polarizer comprising a substrate, a plurality of conductive wire patterns formed in parallel to protrude from a top surface of the substrate and first hard mask patterns disposed on the conductive wire patterns and second hard mask patterns disposed on the first hard mask patterns, wherein a ratio of a taper angle of the second hard mask patterns to a taper angle of the first hard mask patterns is 1 or greater.