Chemically Amplified Resist Composition for EB Lithography
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Solution Overview
Problem
In electron beam (EB) lithography, the existing chemically amplified positive resist compositions face challenges in achieving high resolution and reduced line edge roughness (LER) while minimizing temperature dependence and line width variation, especially when processing photomask blanks which require long exposure times and are sensitive to baking temperature.
Innovation Solution
A chemically amplified positive resist composition is developed, featuring a polymer with recurring units that include a basic compound with a secondary or tertiary amine structure, which acts as an acid activity inhibitor, reducing temperature dependence and improving resolution and LER by controlling acid reactivity and diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If chemically amplified positive resist compositions are used in EB lithography to achieve high sensitivity, then exposure sensitivity is improved, but line edge roughness and temperature dependence increase
Solution Approach 1:
A basic compound acts as an intermediary between the acid generator and the polymer to control acid diffusion and activity. The basic compound moderates the acid-catalyzed deprotection reaction, reducing excessive acid activity that causes line edge roughness while maintaining the sensitivity benefits of chemically amplified resists.
Solution Approach 2:
The patent modifies the chemical parameters of the resist system by introducing a basic compound with specific pKa values and stoichiometric ratios. This changes the acid-base equilibrium parameters to control the spatial distribution and activity of generated acid, thereby reducing line edge roughness while preserving exposure sensitivity.
2Manufacturing precision
If chemically amplified positive resist compositions are used to achieve high resolution, then pattern resolution is improved, but line width variation with temperature increases
Solution Approach 1:
The basic compound serves as a buffer that stabilizes the acid activity during the post-exposure bake process. By controlling the rate and extent of acid-catalyzed reactions, the basic compound reduces the sensitivity of line width to temperature variations, thereby improving compositional stability.
Solution Approach 2:
The introduction of the basic compound changes the thermal parameters of the resist system. The acid-base buffering capacity modifies the temperature dependence of the deprotection reaction, reducing line width variation across different baking temperatures while maintaining high resolution.
3Manufacturing precision
If photomask blanks are processed with long exposure times to achieve fine patterns, then pattern fineness is improved, but temperature sensitivity and line width variation increase
Solution Approach 1:
The basic compound acts as a thermal buffer during the extended exposure and bake processes required for photomask fabrication. It stabilizes the chemical reactions against temperature fluctuations, allowing long exposure times to produce fine patterns without excessive temperature sensitivity.
4Use of energy by moving object
If acid generator activity is increased to improve sensitivity, then exposure sensitivity is improved, but resolution and line edge control deteriorate
Solution Approach 1:
The basic compound intermediates the acid generation process by neutralizing excess acid activity. This allows the use of high-activity acid generators for sensitivity while the basic compound controls the effective acid concentration to maintain resolution and line edge control.
Solution Approach 2:
The basic compound changes the effective acid activity parameter in the resist system. By adjusting the acid-base stoichiometry and pKa matching, the system achieves high sensitivity through efficient acid generation while maintaining resolution through controlled acid activity during the deprotection reaction.
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 composition achieves high resolution, reduced LER, and minimized line width variation, even under varying temperature conditions, making it suitable for forming ultrafine patterns in EB lithography and photomask processing.
Implementation Method 1
an acid generator capable of generating an acid upon exposure to high-energy radiation
Implementation Method 2
a basic compound must be added as an additional component... a polymer having a basic compound bound thereto in order to prevent the basic compound from migrating and diffusing
Implementation Method 3
a polymer having acidic functional groups to render the polymer soluble in alkaline developer wherein some or all acidic functional groups are protected with acid labile protective groups so that the polymer is insoluble in alkaline developer
Data Source
AI summary
A chemically amplified positive resist composition for EB or EUV lithography is provided comprising (A) a polymer or a blend of polymers wherein a film of the polymer or polymer blend is insoluble in alkaline developer, but turns soluble under the action of acid, (B) an acid generator, (C) a basic compound, and (D) a solvent. The basic compound (C) is a polymer comprising recurring units bearing a side chain having a secondary or tertiary amine structure as a basic active site and constitutes a part or the entirety of the polymer or polymers as component (A).