Onium Salt Resist Composition for Controlled Acid Diffusion
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Solution Overview
Problem
Existing chemically amplified resist compositions face challenges in forming small-size patterns with controlled acid diffusion, leading to issues such as inversely tapered profiles and pattern collapse during development, particularly in EB lithography, due to uncontrolled acid diffusion and substrate reflection effects.
Innovation Solution
Incorporation of an onium salt with a fluorinated alkanesulfonic acid anion containing an alkyl or fluoroalkyl group and an iodized aromatic ring as a photoacid generator, which segregates in the resist film's upper layer to control acid diffusion, improving pattern profile and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional acid generators are used in chemically amplified resist compositions, then exposure and development can proceed, but acid diffusion occurs leading to poor resolution and pattern profile instability
Solution Approach 1:
The patent introduces a base polymer with basic functional groups as an intermediary substance between the acid generator and the resist matrix. This base polymer acts as a diffusion barrier and acid scavenger, capturing diffusing acid species and preventing them from reaching and degrading the patterned regions. The base polymer is specifically designed with pKa values and concentrations that optimize its acid-capturing capability while maintaining resist performance.
Solution Approach 2:
The resist composition is formulated as a composite material system comprising multiple components: the acid generator, the base polymer with basic functional groups, and the resist matrix polymer. This composite approach allows synergistic interaction between components, where the base polymer enhances acid control while the acid generator provides exposure functionality, and the matrix provides structural integrity, achieving both high resolution and pattern stability.
2Productivity
If the resist sensitivity is increased to reduce image writing time in EB lithography, then throughput improves, but acid diffusion increases leading to worse resolution
Solution Approach 1:
The base polymer serves as a mediator that decouples the relationship between exposure dose and acid diffusion. By providing a buffering capacity through its basic functional groups, it allows higher exposure doses to be used for improved throughput while the base polymer captures the additional acid generated, preventing the expected degradation in resolution. This enables sensitivity enhancement without sacrificing pattern fidelity.
3Manufacturing precision
If acid diffusion is controlled by binding acid-generating units to base polymer, then resolution improves, but solubility in organic solvent deteriorates
Solution Approach 1:
Instead of covalently binding acid-generating units to the polymer backbone, the patent segments the acid control function into a separate base polymer component that is physically mixed with the resist composition. This segmentation maintains the solubility and processability of each component individually while achieving acid diffusion control through the base polymer's acid-capturing capability, avoiding the solubility problems associated with bound acid generators.
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 onium salt-based resist composition achieves high-resolution patterns with reduced line edge roughness (LER) and improved critical dimension uniformity (CDU), forming rectangular profiles and preventing pattern collapse during development.
Implementation Method 1
acid-catalyzed chemically amplified resist compositions... High-energy radiation such as UV, deep-UV or EB is used as the energy source for exposure
Implementation Method 2
The major cause for time-dependent changes is the diffusion of acid generated upon exposure
Data Source
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AI summary
An onium salt containing a fluorinated alkanesulfonic acid anion having an alkyl or fluoroalkyl group and an iodized aromatic ring generates an acid with controlled diffusion. A chemically amplified positive resist composition comprising the onium salt is also provided.