Onium Salt Resist Composition for Controlled Acid Diffusion
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Solution Overview
Problem
Existing chemically amplified resist compositions face challenges in controlling acid diffusion, leading to issues such as corner rounding in hole patterns, increased line edge roughness (LER), and reduced critical dimension uniformity (CDU) during the formation of small-sized patterns in semiconductor manufacturing, particularly in EB and EUV lithography.
Innovation Solution
Incorporation of an onium salt with specific substituent groups on the carbon atom adjoining the sulfo group, forming a photoacid generator that generates benzene sulfonic acid with controlled diffusion, resulting in improved resolution and reduced LER, enabling the formation of rectangular profiles in resist patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional acid generators are used in chemically amplified resist compositions, then the resist can be exposed and developed to form patterns, but acid diffusion occurs leading to corner rounding, increased LER, and reduced CDU
Solution Approach 1:
The patent modifies the molecular weight and structure of the acid generator (changing from conventional smaller acid generators to larger onium salts with specific substituent groups) to control acid diffusion. This parameter change in the acid generator's physical properties directly reduces acid migration while maintaining deprotection efficiency, thereby preventing corner rounding and LER
Solution Approach 2:
The patent uses composite onium salt structures combining specific cationic groups with large anionic groups containing substituent groups. This composite structure creates a bulky acid generator that physically restricts acid diffusion pathways while maintaining the necessary acid-generating functionality upon exposure
2Manufacturing precision
If the acid generator structure is modified to control acid diffusion, then pattern profile is improved, but the complexity of the resist composition increases
Solution Approach 1:
The patent systematically varies parameters of the onium salt structure (substituent group types, positions, and sizes) to optimize acid diffusion control. By changing these molecular parameters rather than fundamentally redesigning the entire resist system, the patent achieves profile control while managing composition complexity
3Manufacturing precision
If high-energy radiation exposure is used for EB lithography, then fine patterns can be formed, but the image writing time increases and stability of exposed portions deteriorates
Solution Approach 1:
The patent modifies the acid generator's molecular weight and structure to enhance exposure sensitivity. The specific onium salt structure with defined substituent groups optimizes the acid-generating efficiency per unit energy input, allowing finer patterns to be formed with reduced exposure doses and shorter writing times
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 use of the onium salt in chemically amplified resist compositions enhances pattern resolution and reduces LER, ensuring high-resolution, rectangular profile patterns are achieved, particularly in EB and EUV lithography processes.
Implementation Method 1
Incorporation of an onium salt with specific substituent groups on the carbon atom adjoining the sulfo group, forming a photoacid generator that generates benzene sulfonic acid with controlled diffusion
Implementation Method 2
The major cause for time-dependent changes is the diffusion of acid generated upon exposure
Data Source
AI summary
An onium salt having a substituent group on the carbon atom adjoining the sulfo group in the anion and containing a triarylbenzene or diarylbenzene structure generates an acid with adequate strength and controlled diffusion. A chemically amplified positive resist composition comprising the onium salt has a high resolution and forms a pattern with reduced LER.