Dianion Onium Salt Resist for Acid Diffusion Control
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Solution Overview
Problem
Existing chemically amplified resist compositions face challenges in achieving high sensitivity, resolution, and lithography properties such as exposure latitude (EL), line width roughness (LWR), critical dimension uniformity (CDU), and depth of focus (DOF) while minimizing acid diffusion and preventing pattern collapse during the formation of small-size patterns.
Innovation Solution
A chemically amplified resist composition incorporating an onium salt with a dianion structure containing a carboxylate anion and sulfonate anion on one aromatic ring, along with a hydroxy group or an acid labile group, acts as a quencher to enhance sensitivity, resolution, and improve lithography properties, including EL, LWR, CDU, and DOF, while preventing pattern collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acid diffusion is suppressed by reducing temperature and/or time of post exposure bake (PEB), then resolution is improved, but sensitivity and contrast drastically reduce
Solution Approach 1:
The patent introduces a novel onium salt structure with specific molecular weight range (500-2000) and structural parameters (n1, n2, n3, R1, RAL, LA, Z+) to optimize acid diffusion characteristics. By changing the chemical structure parameters of the onium salt, the patent achieves suppressed acid diffusion while maintaining sensitivity and contrast, resolving the contradiction between resolution improvement and sensitivity/contrast maintenance.
Solution Approach 2:
The patent creates a composite resist composition containing the onium salt in specific proportions (0.1-10 wt% based on total resist composition). This composite approach combines the onium salt with other resist components to achieve synergistic effects, where the onium salt suppresses acid diffusion while the overall composition maintains high sensitivity and contrast, thereby resolving the contradiction between resolution and sensitivity/contradiction.
2Manufacturing precision
If acid diffusion distance is reduced to improve resolution, then manufacturing precision improves, but sensitivity declines
Solution Approach 1:
The patent optimizes the molecular weight of the onium salt (500-2000) and its structural parameters to control acid diffusion distance. By precisely adjusting these parameters, the patent achieves the optimal balance where acid diffusion is sufficiently suppressed to improve resolution while maintaining adequate sensitivity for pattern formation.
Solution Approach 2:
The onium salt provides localized acid diffusion control at the exposure interface, creating a gradient effect where acid diffusion is suppressed in critical regions while maintaining overall sensitivity. This local quality approach allows resolution improvement without sacrificing global sensitivity.
3Reliability
If conventional onium salts are used, then sensitivity is maintained, but acid diffusion cannot be sufficiently suppressed and lithography properties degrade
Solution Approach 1:
The patent introduces specific structural parameters for the onium salt (n1, n2, n3, R1, RAL, LA, Z+) that are optimized to simultaneously maintain sensitivity and improve lithography properties. These parameter changes enable the onium salt to provide both high sensitivity and suppressed acid diffusion, resolving the contradiction between sensitivity maintenance and lithography property improvement.
Solution Approach 2:
The patent uses onium salts with specific cation structures (sulfonium, iodonium, ammonium, phosphonium) that replicate and enhance the beneficial effects of known acid diffusion suppressors while maintaining compatibility with existing resist systems. This copying approach allows sensitivity maintenance while achieving improved lithography properties.
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 resist composition achieves high contrast, high sensitivity, and improved lithography properties, including EL, LWR, CDU, and DOF, with enhanced resistance to pattern collapse during small-size pattern formation.
Implementation Method 1
the sulfonium or iodonium salt capable of generating α-non-fluorinated sulfonic acid undergoes ion exchange with the α-fluorinated sulfonic acid. Through the ion exchange, the α-fluorinated sulfonic acid once generated upon light exposure is converted back to the sulfonium or iodonium salt.
Implementation Method 2
The addition of an acid generator capable of generating a bulky acid is an effective means for suppressing acid diffusion.
Implementation Method 3
an acid generator capable of generating a sulfonic acid which is substituted at α-position with fluorine (referred to as 'α-fluorinated sulfonic acid,' hereinafter)
Data Source
AI summary
Provided are an onium salt, a chemically amplified resist composition comprising the onium salt, and a pattern forming process using the chemically amplified resist composition, the chemically amplified resist composition exhibiting a high sensitivity, high resolution, improved lithography properties including EL, LWR, CDU and DOF, and resist pattern collapse resistance, when processed by photolithography using high-energy radiation independent of whether it is of positive or negative tone. An onium salt has the formula (1):