Chemically Amplified Resist Composition for EUV Lithography
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Solution Overview
Problem
Current chemically amplified resist compositions face challenges in achieving high resolution, reduced line edge roughness (LER), and minimizing develop loading effects, particularly in the formation of resist patterns for advanced lithography applications such as EUV and EB lithography, where acid diffusion and sensitivity control are critical.
Innovation Solution
A chemically amplified positive resist composition is developed, featuring a base polymer with specific structural units, including phenolic hydroxy groups and carboxy groups protected with acid labile groups, which are designed to enhance resolution, LER, and control acid diffusion, thereby minimizing develop loading effects. This composition includes aromatic ring-containing units that account for at least 65 mol% of the polymer, along with fluorinated polymer components and a photoacid generator with an anion having an acid strength pKa of −2.0 or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional acid generators are used to increase sensitivity, then exposure sensitivity is improved, but acid diffusion increases causing resolution degradation
Solution Approach 1:
The patent introduces a base polymer with specific functional groups (carboxyl, hydroxyl, amine) as an intermediary substance that mediates between the acid generator and the resist matrix. This base polymer interacts with the generated acid through acid-base reactions, controlling acid diffusion while maintaining high sensitivity. The base polymer acts as a buffer that captures excess acid without allowing it to diffuse uncontrollably, thus resolving the contradiction between sensitivity and resolution.
Solution Approach 2:
The patent changes the chemical parameters of the resist system by introducing a base polymer with specific pKa values and functional groups. This alters the acid-base equilibrium parameters in the resist, enabling controlled acid diffusion through pH buffering. The base polymer's functional groups are selected to have specific acid-base properties that optimize both sensitivity and resolution by controlling the ionization state and diffusion behavior of the generated acid.
2Reliability
If acid diffusion is increased to improve sensitivity, then exposure sensitivity is improved, but line edge roughness increases
Solution Approach 1:
The base polymer serves as an intermediary that buffers the acid generated during exposure. By controlling the acid-base interactions through carefully selected functional groups, the system achieves high sensitivity while the base polymer's buffering capacity prevents excessive acid diffusion that would cause line edge roughness. The intermediary base polymer thus enables both high sensitivity and smooth line edges.
3Manufacturing precision
If develop loading effects are minimized by controlling acid diffusion, then pattern uniformity is improved, but sensitivity may be reduced
Solution Approach 1:
The patent optimizes the pH buffering parameters by selecting base polymer functional groups with specific pKa values. This parameter optimization enables the system to maintain high sensitivity while achieving uniform pattern development. The acid-base equilibrium parameters are tuned so that the base polymer buffers acid effectively during development (improving uniformity) while not interfering with the exposure reaction (maintaining sensitivity).
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 resist patterns with reduced LER and controlled develop loading, ensuring improved etch resistance and sensitivity, making it suitable for micropatterning technologies like EUV and EB lithography.
Implementation Method 1
an acid generator capable of generating a sulfonic acid upon light exposure
Implementation Method 2
The major cause of such a change with time is diffusion of an acid generated upon exposure
Implementation Method 3
a base polymer protected with an acid labile group and adapted to turn alkali soluble under the action of acid
Data Source
AI summary
A chemically amplified positive resist composition is provided comprising a base polymer which contains a polymer comprising a phenolic hydroxy group-containing unit, a unit containing a phenolic hydroxy group protected with an acid labile group, and a unit containing a carboxy group protected with an acid labile group. The aromatic ring-containing repeat units account for at least 65 mol % of the overall repeat units of the polymer. A resist pattern with a very high resolution, reduced LER, improved rectangularity, and minimized influence of develop loading can be formed.