EUV Adhesion Layer Composition for Pattern Collapse Control
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Solution Overview
Problem
EUV lithography faces challenges with poor adhesion between photoresist and silicon underlayers, leading to pattern collapse, especially at lower critical dimensions, and compromises etch rates due to high carbon content in hardmasks.
Innovation Solution
A method involving the formation of a non-conductive adhesion layer with a thickness greater than a monolayer but less than 9 nm and low metal content, applied between the substrate and photoresist, enhancing adhesion and etch rates while maintaining high carbon content for improved EUV lithography performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon-containing layer is used in traditional trilayer stacks to improve adhesion, then adhesion between photoresist and silicon underlayer improves, but etch rate decreases significantly
Solution Approach 1:
The patent applies local quality by creating a gradient in carbon content across different layers. The adhesion layer has high carbon content (50-90 at%) to provide excellent adhesion, while the hardmask layer has lower carbon content (10-40 at%) to maintain high etch rate. This spatial variation in composition allows each layer to optimize its function without compromising the other.
Solution Approach 2:
The patent uses composite materials by combining carbon-containing adhesion layer with silicon-containing hardmask layer. Each layer is composed of specific elements in controlled ratios (carbon 50-90 at%, silicon 10-40 at%, oxygen 0-30 at%) to achieve the desired balance between adhesion and etch performance, rather than using a single uniform material.
2Reliability
If spin-on-silicon hardmasks with high carbon content are used to improve adhesion, then adhesion to photoresist improves, but silicon content decreases leading to lower etch rate
Solution Approach 1:
The patent segments the mask stack into functionally distinct layers: an adhesion layer optimized for bonding to photoresist (high carbon content) and a hardmask layer optimized for etching (higher silicon content). This segmentation allows each layer to have the ideal composition for its specific function, avoiding the compromise required in unified spin-on-silicon hardmasks.
Solution Approach 2:
The patent changes the compositional parameters between layers. The adhesion layer contains carbon 50-90 at% and silicon 10-40 at%, while the hardmask layer contains carbon 10-40 at% and silicon 40-80 at%. This parameter variation optimizes adhesion in the first layer and etch rate in the second layer.
3Length of moving object
If feature size is decreased to follow Moore's law, then device density increases, but pattern collapse becomes more significant due to poor adhesion
Solution Approach 1:
The patent applies preliminary action by forming an adhesion layer before depositing the photoresist and pattern transfer layers. This adhesion layer is prepared in advance with optimal carbon content to ensure strong bonding, preventing pattern collapse during subsequent processing steps when working at reduced feature sizes.
Data Source
AI summary
New lithographic compositions for use as EUV adhesion layers are provided. The present invention provides methods of fabricating microelectronics structures using those compositions as well as structures formed by those methods. The method involves utilizing an adhesion layer immediately below the photoresist layer. The adhesion layer can either be directly applied to the substrate, or it can be applied to any intermediate layer(s) that may be applied to the substrate, such as an alpha-carbon, spin-on carbon, spin-on silicon hardmask, metal hardmask, or deposited silicon layer. The preferred adhesion layers are formed from spin-coatable, polymeric compositions. The inventive method improves adhesion and reduces or eliminates pattern collapse issues.