EUV Adhesion Layer Stack for Pattern Collapse and Etch Rate
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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 traditional hardmasks compromise etch rates due to high carbon content.
Innovation Solution
A method involving a carbon-rich layer, a hardmask layer, and an adhesion layer with specific thickness and low metal content is applied, followed by EUV radiation exposure and pattern transfer, using non-conductive adhesion layers with controlled stripping and high resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional trilayer stacks with carbon-containing layer and silicon-containing layer are used, then adhesion between photoresist and silicon underlayer is poor, but using spin-on-silicon hardmasks with high carbon content improves adhesion while decreasing CF4 etch rate
Solution Approach 1:
The patent introduces a methylsiloxane-based adhesion layer as an intermediary between the photoresist and the silicon-containing underlayer. This intermediate layer provides the necessary adhesion promotion without compromising the etch rate of the underlying silicon hardmask layer, thereby resolving the contradiction between adhesion and etch rate.
Solution Approach 2:
The patent segments the traditional trilayer stack into a multilayer structure by inserting a dedicated adhesion layer between the photoresist and the silicon hardmask. This segmentation allows each layer to perform its specific function independently: the silicon hardmask maintains high etch rate while the adhesion layer provides bonding interface, eliminating the need to compromise the hardmask composition for adhesion purposes.
2Manufacturing precision
If thinner films are used to achieve smaller feature sizes, then pattern collapse is prevented, but adhesion issues become more significant
Solution Approach 1:
The methylsiloxane adhesion layer serves as a mediator that enhances the bonding between the photoresist and the silicon underlayer, providing sufficient adhesion strength even when the overall film thickness is reduced to enable smaller critical dimensions.
Solution Approach 2:
The patent modifies the chemical composition parameters of the adhesion layer by using methylsiloxane-based materials with specific oxygen and silicon content ratios. This parameter optimization ensures strong adhesion while maintaining compatibility with EUV lithography processes and enabling thinner film structures.
3Reliability
If spin-on-silicon hardmasks with high carbon content are used, then adhesion to photoresist is improved, but silicon content decreases leading to lower etch rate
Solution Approach 1:
The patent separates the adhesion function from the hardmask function by introducing a dedicated adhesion layer. This allows the silicon hardmask layer to maintain high silicon content (90-100%) for optimal etch rate, while the adhesion layer independently provides the necessary bonding to photoresist.
Solution Approach 2:
The methylsiloxane adhesion layer acts as an intermediary that provides adhesion promotion without requiring the silicon hardmask layer to have high carbon content. This intermediary layer enables the hardmask to maintain its high silicon content and corresponding etch rate while still achieving good adhesion to photoresist.
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
Improves adhesion and reduces pattern collapse, achieving high resolution and etch rates suitable for microelectronic structures, particularly in EUV lithography.
Implementation Method 1
An adhesion layer is formed on the substrate, or on the one or more intermediate layers, if present
Implementation Method 2
A photoresist layer is formed on the adhesion layer and at least a portion of the photoresist layer is subjected to EUV radiation
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.