Positive Resist Composition Acid Diffusion Control
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Solution Overview
Problem
Current positive resist compositions face challenges in achieving high resolution and minimal edge roughness while maintaining sensitivity, particularly as feature sizes reduce, due to issues with acid diffusion and sensitivity trade-offs in electron beam and extreme ultraviolet lithography.
Innovation Solution
A chemically amplified positive resist composition incorporating a polymer with recurring units derived from hydroxypyridine, featuring carboxyl and phenolic hydroxyl groups substituted with acid labile groups, which suppresses acid diffusion and enhances resolution and pattern profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the accelerating voltage of the electron gun is increased to enable further size reduction, then the resolution and dimensional control are improved, but the sensitivity of the resist film is reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the resist film by incorporating specific polymers (poly-4-hydroxystyrene, poly-3-methoxystyrene) and acid generators with different properties. This allows optimization of the resist's response to high-energy radiation, improving sensitivity without sacrificing the resolution gains from higher accelerating voltages.
Solution Approach 2:
The patent uses composite resist formulations combining multiple polymer components and acid generator types. This composite approach enables the resist film to simultaneously achieve high sensitivity for throughput and maintain the dimensional control required for high-resolution patterning at increased accelerating voltages.
2Productivity
If chemically amplified resist compositions are used to enhance sensitivity and contrast, then the sensitivity is improved, but acid diffusion causes image blur that degrades resolution
Solution Approach 1:
The patent introduces basic compounds (amines) as intermediaries that neutralize excess acid and prevent diffusion. These basic compounds act as mediators between the acid generator and the polymer matrix, confining the acid generation to the exposure region and preventing the image blur that would otherwise degrade resolution while maintaining the sensitivity benefits of chemical amplification.
3Manufacturing precision
If the temperature and/or time of post-exposure baking is reduced to minimize acid diffusion, then the resolution is improved, but the sensitivity and contrast are drastically reduced
Solution Approach 1:
The basic compounds serve as intermediaries that enable reduced post-exposure baking conditions. By neutralizing acid diffusion, they allow shorter baking times and lower temperatures while maintaining both resolution and sensitivity, effectively decoupling the trade-off between these parameters.
Solution Approach 2:
The patent changes the chemical environment within the resist film by adding basic compounds, which alters the acid-base equilibrium. This parameter change allows the system to achieve acid confinement without relying solely on thermal parameters (temperature and time), enabling reduced PEB conditions while 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 resist composition achieves high resolution and minimal edge roughness, suitable for micropatterning in VLSI and photomask fabrication, with improved sensitivity and reduced acid diffusion, effectively addressing the limitations of prior art.
Implementation Method 1
image blurs due to acid diffusion become a problem
Implementation Method 2
chemically amplified resist compositions are contemplated
Implementation Method 3
the EB exposure system
Implementation Method 4
an improvement in dissolution contrast is important
Data Source
AI summary
A polymer obtained from copolymerization of a recurring unit having a carboxyl group and/or phenolic hydroxyl group substituted with an acid labile group with a methacrylate having a phenolic hydroxyl-bearing pyridine is useful as a base resin in a positive resist composition. The resist composition comprising the polymer is improved in contrast of alkali dissolution rate before and after exposure, acid diffusion control, resolution, and profile and edge roughness of a pattern after exposure.