Fluoroalcohol-Epoxy Underlayer for Reflective Notching
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Solution Overview
Problem
Conventional photolithographic processes face challenges with thin film interference and reflective notching due to back reflection from highly reflective substrates, which affect the uniformity and accuracy of pattern transfer in miniaturized semiconductor devices, and existing hard masks lack sufficient dry etch resistance for thin photoresist layers.
Innovation Solution
A novel spin-on underlayer composition comprising a polymer with fluoroalcohol and epoxy groups, optionally including a thermal acid generator, is used to create a titanium-containing underlayer that provides excellent dry etch resistance and can be used as a hard mask or antireflective coating, absorbing deep ultraviolet radiation and improving EUV photoresist performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photoresist is used on highly reflective substrates, then the substrate can be processed, but thin film interference and reflective notching occur causing poor pattern transfer accuracy
Solution Approach 1:
The patent introduces an underlayer as an intermediary substance between the photoresist and the highly reflective substrate. This underlayer absorbs back-reflected radiation and prevents thin film interference and reflective notching, thereby improving pattern transfer accuracy without sacrificing substrate processability.
Solution Approach 2:
The underlayer is formulated as a composite material containing titanium compounds (such as titanium alkoxides or titanium carboxylates) combined with organic polymers. This composite structure provides both the optical absorption needed to eliminate reflection effects and the mechanical properties required for effective pattern transfer.
2Strength
If existing hard masks are used with thin photoresist layers, then some etch resistance is provided, but sufficient dry etch resistance is not achieved for effective pattern transfer
Solution Approach 1:
The patent modifies the chemical composition parameters of the underlayer by incorporating titanium compounds with specific concentrations (typically 1-20 wt% titanium content). This parameter optimization provides enhanced dry etch resistance that enables effective pattern transfer even when using very thin photoresist layers (100 nm or less).
3Ease of manufacture
If spin coating is used to apply underlayer material, then simple application is achieved, but sufficient titanium concentration in the film is difficult to obtain with conventional materials
Solution Approach 1:
The patent changes the physical and chemical parameters of the titanium-containing materials to be used in spin-coatable formulations. By using titanium alkoxides or titanium carboxylates dissolved in organic solvents at controlled concentrations, the patent achieves both ease of spin-coating application and sufficient titanium concentration (1-20 wt%) in the final dried film.
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 novel underlayer composition enhances lithographic performance by reducing reflective issues, improving dry etch resistance, and extending the applicability to extreme ultraviolet lithography, thereby improving the accuracy and sensitivity of pattern transfer in semiconductor fabrication.
Implementation Method 1
The film is capable of absorbing deep ultraviolet radiation
Implementation Method 2
The polymer can be self-crosslinkable and free of crosslinker
Data Source
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AI summary
The present invention relates to an underlayer composition comprising a polymer, an organic titanate compound and optionally a thermal acid generator, where the polymer comprises at least one fluoroalcohol group and at least one epoxy group. The invention also relates to a process for using this underlayer material as an antireflective coating composition and/or a hard mask for pattern transfer.