EUV Polarization Splitter Multilayer Structure
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Solution Overview
Problem
In extreme ultraviolet (EUV) lithography, it is challenging to achieve high-contrast image printing due to the difficulty in filtering and polarizing EUV light, as traditional methods like metal gratings are ineffective for blocking EUV wavelengths, and materials with uniform structure/composition do not provide sufficient refractive index contrast for splitting EUV light into transverse electric (TE) and transverse magnetic (TM) waves.
Innovation Solution
A multilayer structure comprising alternating film pairs, such as molybdenum-silicon (Mo/Si), is used to split unpolarized EUV light into TE and TM waves by varying the thickness of the layers and the angle of incidence, allowing for improved polarization and refractive index contrast, thereby enhancing image contrast during EUV exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional metal grating methods are used to filter EUV light, then the filtering mechanism is simple and well-established, but the method is ineffective for blocking EUV wavelengths and achieving polarization
Solution Approach 1:
The patent employs a multilayer composite structure consisting of alternating high-refractive-index and low-refractive-index layers (e.g., Mo/Si, Mo/Be) deposited on a substrate. This composite material approach enables effective EUV light polarization by creating sufficient refractive index contrast, which single materials cannot achieve at EUV wavelengths. The alternating layers work together to separate TE and TM waves through differential reflection and transmission.
Solution Approach 2:
The invention transitions from traditional single-layer or simple grating structures to a multidimensional multilayer architecture. By stacking multiple thin layers with varying refractive indices in the vertical dimension and controlling their thicknesses, the system achieves polarization functionality that cannot be obtained with conventional single-plane filtering methods.
2Reliability
If materials with uniform structure and composition are used, then the material structure is simple and easy to fabricate, but they do not provide sufficient refractive index contrast for splitting EUV light into TE and TM waves
Solution Approach 1:
The polarizing material is segmented into multiple discrete thin layers with alternating refractive indices. Instead of using a single uniform material, the structure divides the functional requirement across many individual layers (e.g., 20-50 pairs of Mo/Si layers), each contributing to the overall polarization effect through cumulative differential interference of TE and TM waves.
Solution Approach 2:
The invention systematically varies critical parameters including layer thickness (typically 2-10 nm per layer), material composition (Mo/Si, Mo/Be, W/Si), and angle of incidence (optimized near Brewster's angle) to maximize refractive index contrast effects. These parameter optimizations enable effective EUV polarization while maintaining fabrication feasibility through controlled deposition processes.
3Reliability
If a multilayer structure with alternating film pairs is used to achieve polarization, then effective separation of TE and TM waves is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent replaces mechanical or physical assembly of complex polarizing components with a streamlined deposition-based manufacturing process. The entire multilayer polarizing structure is created in-situ through sequential atomic layer deposition (ALD) or sputtering processes, eliminating the need for separate assembly steps and reducing manufacturing complexity despite the high number of layers.
Solution Approach 2:
The multilayer deposition process serves multiple functions simultaneously: it creates the refractive index contrast needed for polarization, controls layer thickness precision, ensures uniform coverage, and integrates the polarizing function directly into the existing lithography tool architecture. This multi-functionality reduces the need for additional specialized manufacturing equipment.
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 solution effectively polarizes EUV light, directing TE waves for exposure and improving image contrast, enabling better pattern transfer in EUV lithography by maximizing the separation of TE and TM waves at the Brewster's angle, thus overcoming the limitations of traditional methods.
Implementation Method 1
A polarization splitter for splitting unpolarized extreme ultraviolet (EUV) light into transverse electric (TE) waves and transverse magnetic (TM) waves
Implementation Method 2
allowing for improved polarization and refractive index contrast
Implementation Method 3
directing TE waves for exposure and improving image contrast, enabling better pattern transfer
Data Source
AI summary
A polarization filter includes a multilayer structure including a first plurality of elements and a second plurality of elements alternating between each other. The first plurality of elements and the second plurality of elements have different thicknesses, and the multilayer structure is configured to interact with unpolarized light incident on the multilayer structure and separate transverse electric (TE) waves and transverse magnetic (TM) waves of the unpolarized light.