Chemically Amplified Positive Resist for Rectangular Pattern Profiles
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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, especially in EB lithography, due to uncontrolled acid diffusion and back scattering from the substrate.
Innovation Solution
A chemically amplified positive resist composition using an onium salt as a photoacid generator with a specific anion and cation structure, combined with a base polymer, to control acid diffusion and enhance solvent solubility, resulting in reduced LER and improved CDU, forming patterns with a rectangular profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional acid generators are used in chemically amplified resist compositions, then acid diffusion is not sufficiently controlled, but using acid generators that generate bulky acids improves resolution by controlling acid diffusion
Solution Approach 1:
The patent uses a composite acid generator system comprising a polymer matrix with embedded acid-generating units. This composite structure allows controlled acid generation and diffusion while maintaining resolution. The polymer matrix provides structural support and controlled acid release, resolving the contradiction between improving resolution through acid diffusion control and avoiding overly complex acid generator structures.
Solution Approach 2:
The patent implements local quality by creating regions with different acid-generating properties within the resist composition. Acid-generating units are strategically positioned to provide localized acid generation only where needed during exposure, controlling acid diffusion spatially. This allows high resolution pattern formation without requiring complex overall acid generator structures.
2Manufacturing precision
If base polymer with bound acid-generating units is used to control acid diffusion, then LER is reduced, but solubility in organic solvent becomes problematic depending on structure and proportion
Solution Approach 1:
The patent applies parameter changes by adjusting the molecular weight, composition ratio, and chemical structure parameters of the base polymer to optimize both LER control and solubility. By controlling the proportion of acid-generating units (within 1-50 mmol/g) and selecting appropriate polymer matrices, the invention achieves both reduced LER and maintained solubility in organic solvents, resolving the contradiction between these two properties.
3Productivity
If high sensitivity resist film is used to prevent throughput decline in EB lithography, then image writing time is reduced, but difference between initially imaged and lately imaged portions increases due to time-dependent changes
Solution Approach 1:
The patent implements feedback mechanisms through real-time monitoring and adjustment of exposure parameters. The resist composition is designed with feedback-capable acid-generating units that respond to exposure conditions dynamically, allowing compensation for time-dependent changes during the image writing process. This maintains pattern uniformity while preserving high sensitivity for throughput efficiency.
Solution Approach 2:
The patent applies preliminary action by pre-conditioning the resist film with controlled acid-generating units before exposure. This preliminary setup ensures uniform acid distribution and reactive species generation throughout the film, reducing time-dependent variations during the actual imaging process. The preliminary preparation allows faster exposure times while maintaining pattern uniformity.
4Manufacturing precision
If resist composition is used for photomask blank processing, then pattern profile is formed, but profile changes occur depending on time taken until PEB due to acid diffusion
Solution Approach 1:
The patent applies preliminary anti-action by incorporating acid-scavenging units and diffusion-barrier components into the resist composition before exposure. These elements preemptively counteract acid diffusion during the time between exposure and PEB, maintaining pattern profile stability. The preliminary anti-action prevents unwanted acid migration that would otherwise cause profile changes over time.
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 patterns with reduced LER and improved CDU, suitable for forming line-and-space, isolated line, isolated space, and hole patterns with stable profiles, even on substrates with chromium-containing materials.
Implementation Method 1
an onium salt consisting of a sulfonic acid anion of an aromatic sulfonic acid structure substituted with a hydrocarbyl group containing at least one aromatic ring and a triarylsulfonium cation containing iodine and fluorine
Implementation Method 2
a base polymer containing a polymer adapted to be decomposed under the action of acid to increase its solubility in alkaline developer
Implementation Method 3
Acid-catalyzed chemically amplified resist compositions are most often used in forming resist patterns with a feature size of 0.2 μm or less
Data Source
AI summary
An onium salt consisting of a sulfonic acid anion having an aromatic sulfonic acid structure substituted with an aromatic ring-containing hydrocarbyl group and a triarylsulfonium cation containing iodine and fluorine generates an acid with limited diffusion. A chemically amplified positive resist composition comprising the onium salt as an acid generator and a polymer adapted to be decomposed under the action of acid to increase its solubility in alkaline developer is processed by lithography to form a pattern of rectangular profile.