EUV Reticle Embedded Process Assistance Layer
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Solution Overview
Problem
The challenge in EUV photolithography is to maintain high reflectivity of the reflective multilayer while embedding a process assistance layer, such as an etch-stop layer, to control etching and reduce reticle-induced imaging aberrations.
Innovation Solution
The solution involves embedding a process assistance layer within the reflective multilayer of an EUV reticle, where the layer is selectively etchable with respect to the other layers, thereby allowing for precise etching without degrading the reflectivity of the multilayer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a process assistance layer is embedded in the reflective multilayer to control etching, then etching precision is improved, but reflectivity of the multilayer deteriorates
Solution Approach 1:
The patent applies local quality by making the process assistance layer selectively etchable compared to other layers in the reflective multilayer. This localized property difference allows the etching process to precisely stop at the process assistance layer without affecting adjacent layers, thereby achieving high etching precision while preserving the reflectivity of the surrounding reflective multilayer structure.
Solution Approach 2:
The process assistance layer acts as an intermediary element within the reflective multilayer stack. It serves as a mediator that enables controlled etching termination without compromising the optical properties of the overall structure. The layer is positioned strategically to provide etching control while its selective etchability ensures it can be removed or modified without damaging the reflective multilayer's integrity and reflectivity.
2Ease of manufacture
If traditional photolithography with longer wavelengths is used, then manufacturing simplicity is maintained, but feature size precision deteriorates
Solution Approach 1:
The patent employs parameter changes by transitioning from traditional photolithography using visible or ultraviolet light to EUV photolithography using extreme ultraviolet light with wavelengths around 13.5 nm. This fundamental change in the wavelength parameter enables the formation of much smaller and more precise features while maintaining manufacturing feasibility through the use of reflective multilayer optics and specialized process techniques.
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 enables the formation of absorption patterns in the EUV reticle while maintaining high reflectivity, leading to improved wafer yields and proper functioning of integrated circuits.
Implementation Method 1
EUV reticles may include a reflective multilayer and a pattern of absorption material
Implementation Method 2
EUV reticles may include a reflective multilayer and a pattern of absorption material
Data Source
AI summary
An extreme ultraviolet (EUV) photolithography reticle includes a substrate and a reflective multilayer on the substrate. The reflective multilayer includes a plurality of stacked first pairs of layers, each pair include a first layer of a first material and a second layer of a second material on the first layer. The reflective multilayer includes a second pair of layers between two of the first pairs and including a first process assistance layer and a third layer of the second material on the process assistance layer. The first material and the second material are selectively etchable with respect to the first process assistance layer. The reticle includes a plurality of first absorption structures extending from a top of the reflective multilayer to the first process assistance layer and configured to absorb extreme ultraviolet light.