Fluorinated Ester Resist for ArF Immersion Lithography
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Solution Overview
Problem
In ArF immersion lithography, existing resist compositions face challenges with water penetration leading to development defects and require enhanced water repellency without compromising substrate adhesion, which is difficult to achieve with increased fluorine content.
Innovation Solution
A polymerizable ester compound containing a fluorinated alkyl group, a lactone ring, and an acid-eliminatable unit is developed, which can be polymerized into a resin that improves water repellency, transparency, and dry etching resistance while maintaining good substrate adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If fluorine content is increased to enhance water repellency, then water repellency is improved, but substrate adhesion deteriorates
Solution Approach 1:
The patent applies local quality by incorporating fluorinated alkyl groups at specific positions (R1, R4, R5) of the polymer backbone rather than uniformly throughout. This localized fluorine placement provides water repellency at the surface while maintaining adhesion through the non-fluorinated polymer backbone and carboxyl groups that bond to the substrate.
Solution Approach 2:
The patent creates a composite polymer structure combining fluorinated alkyl groups (for water repellency) with carboxyl groups (for adhesion) and lactone rings (for transparency and etching resistance) within the same polymer chain. This composite approach allows multiple functional properties to coexist without compromising each other.
2Ease of manufacture
If conventional base resins are used in ArF lithography, then ease of manufacture is improved, but transparency at 193 nm deteriorates due to strong absorption
Solution Approach 1:
The patent changes the chemical composition parameters of the base resin by using poly(meth)acrylate structures with specific side chains (fluorinated alkyl groups, lactone rings, carboxyl groups) instead of conventional novolac or polyhydroxystyrene. This parameter change maintains ease of polymerization while achieving the required transparency at 193 nm wavelength.
3Manufacturing precision
If water is used for immersion lithography, then resolution is improved by increased NA, but development defects occur due to water penetration into the resist film
Solution Approach 1:
The patent applies preliminary anti-action by incorporating fluorinated alkyl groups and carboxyl groups into the polymer structure before the lithography process. These groups create a hydrophobic barrier that prevents water penetration during immersion lithography, thereby preventing development defects before they can occur.
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 resulting resist composition exhibits improved resolution, minimal line edge roughness, and surface roughness, effectively addressing water penetration issues in ArF immersion lithography while maintaining adhesion.
Implementation Method 1
acid-catalyzed chemical amplification positive working resist materials are used
Implementation Method 2
A polymerizable ester compound containing a fluorinated alkyl group, a lactone ring, and an acid-eliminatable unit is developed, which can be polymerized into a resin
Data Source
AI summary
A polymer comprising recurring units (2) obtained through polymerization of an ester compound of formula (1) is used to form a resist composition. R1 is F or C1-C6 fluoroalkyl, R2 is H or C1-C8 alkyl, R3 is O or C1-C6 alkylene, R4 and R5 each are H or C1-C10 alkyl or fluoroalkyl, and R6 is H or an acid labile group. The resist composition, when processed by ArF lithography, has advantages including improved resolution, transparency, minimal line edge roughness, and etch resistance. The resist composition exhibits better performance when processed by ArF immersion lithography with liquid interposed between a projection lens and a wafer.