Fluorinated Copolymer Additive for Resist Underlayer Adhesion
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Solution Overview
Problem
In advanced lithography processes like ArF immersion and EUV lithography, resist patterns face collapse due to reduced contact area with the substrate, necessitating enhanced adhesion between the resist underlayer film and the resist pattern, which existing additives fail to adequately provide.
Innovation Solution
A copolymer additive with specific structural units is introduced into the resist underlayer film-forming composition, which cross-links with the resist material components upon baking, improving adhesion by forming chemical bonds and preventing pattern collapse, especially in ultra-thin film applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a resist underlayer film-forming composition containing only a lactone structure is used, then adhesion to the resist pattern is enhanced, but it cannot sufficiently prevent collapse of finer resist patterns in advanced lithography processes
Solution Approach 1:
The patent uses a composite material approach by combining a lactone structure (for adhesion enhancement) with a specific copolymer additive containing fluorinated groups and hydroxy groups. This composite composition provides both the adhesion benefits of the lactone structure and the collapse prevention capabilities of the copolymer additive, which modifies the surface state and reduces Laplace forces during development and rinsing.
2Length of moving object
If the contact area between resist pattern and substrate is reduced for finer patterns, then processing dimension is miniaturized, but the aspect ratio increases making the resist pattern more prone to collapse
Solution Approach 1:
The patent applies preliminary action by forming a resist underlayer film with modified surface properties before applying the resist pattern. The copolymer additive segregates near the surface of the underlayer film, creating a surface state that provides enhanced adhesion and mechanical support in advance, preventing pattern collapse during subsequent processing steps.
3Length of stationary object
If a resist underlayer film with small thickness (25 nm or less) is formed, then finer resist patterns can be achieved, but adhesion to the substrate becomes more critical and difficult to maintain
Solution Approach 1:
The patent changes the chemical composition parameters of the resist underlayer film-forming composition by incorporating a copolymer additive with specific fluorinated and hydroxy groups. This modifies the surface state and adhesion properties of the underlayer film, enabling it to maintain sufficient adhesion strength even when the film thickness is reduced to 25 nm or less.
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 additive significantly enhances the adhesion of the resist underlayer film to the resist pattern, effectively preventing pattern collapse and ensuring stable formation of fine resist patterns even in extreme ultraviolet lithography processes.
Implementation Method 1
cross-links with the resist material components upon baking, improving adhesion by forming chemical bonds
Implementation Method 2
segregate an additive component near a surface of a resist underlayer film
Data Source
AI summary
An additive for a resist underlayer film-forming composition, including a copolymer having structural units of the following Formulae (1) to (3):wherein R1s are each independently a hydrogen atom or a methyl group, R2 is a C1-3 alkylene group, A is a protecting group, R3 is an organic group having 4 to 7-membered ring lactone skeleton, adamantane skeleton, tricyclodecane skeleton, or norbornane skeleton, and R4 is a linear, branched, or cyclic organic group having a carbon atom number of 1 to 12, wherein at least one hydrogen atom is substituted with a fluoro group and that optionally has at least one hydroxy group as a substituent. A resist underlayer film-forming composition for lithography including additive, a resin that is different from copolymer, organic acid, crosslinker, and solvent, wherein the copolymer's content is 3 parts by mass to 40 parts by mass relative to 100 parts by mass of the resin.