Barium Salt Resist Composition for High-Resolution Lithography
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Solution Overview
Problem
Current resist compositions face challenges in achieving high resolution and sensitivity while minimizing line edge roughness (LER) and critical dimension uniformity (CDU) as feature sizes reduce below 100 nm, especially with the increased accelerating voltage in electron beam (EB) lithography, which affects pattern accuracy and throughput.
Innovation Solution
A resist composition incorporating a base resin with recurring units containing an acid labile group and a sodium, magnesium, potassium, calcium, rubidium, strontium, yttrium, cesium, or barium salt of fluorosulfonic acid with a benzene ring substituted with iodine or bromine atoms, enhancing sensitivity and pattern profile with minimal LER and CDU, and preventing electrostatic charges during EB image writing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the accelerating voltage in EB lithography is increased to improve resolution and reduce forward scattering, then the contrast of electron image writing energy is improved, but the sensitivity of the resist film lowers because electrons pass straightforward through the film
Solution Approach 1:
The patent introduces a metal salt compound (containing Ba, Sr, Pb, W, Mo, or Bi) as a sensitivity enhancer in the resist composition. This compound changes the physical-chemical parameters of the resist film to increase electron interaction, thereby improving sensitivity without sacrificing the resolution benefits of high accelerating voltage
Solution Approach 2:
The patent creates a composite resist composition by combining the base resin with a metal salt compound. This composite material allows the resist to benefit from both the high resolution capability (from high voltage electron beam) and high sensitivity (from metal salt-enhanced electron interaction) simultaneously
2Measurement precision
If chemically amplified resist materials are used to maintain sensitivity, then acid diffusion occurs which blurs the image, but reducing post-exposure bake temperature or time to control acid diffusion drastically reduces sensitivity and contrast
Solution Approach 1:
The patent introduces a metal salt compound as an intermediary substance in the resist composition. This compound acts as a mediator that enhances electron interaction and energy deposition, allowing the system to achieve high sensitivity without relying on aggressive post-exposure bake conditions that cause uncontrolled acid diffusion
Solution Approach 2:
The metal salt compound changes the energy deposition parameters in the resist film, creating a more efficient energy transfer mechanism that reduces dependence on thermal diffusion processes, thereby maintaining both resolution and sensitivity
3Length of moving object
If the thickness of the resist film is reduced below 100 nm to meet miniaturization requirements, then the pattern can be formed at smaller dimensions, but the line edge roughness is substantially exacerbated
Solution Approach 1:
The metal salt compound changes the physical parameters of the resist composition, including electron scattering characteristics and energy distribution, which helps maintain pattern fidelity and reduce line edge roughness even in ultrathin films below 100 nm
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 sensitivity, resolution, and controlled acid diffusion, resulting in improved pattern profiles and reduced LER and CDU, making it suitable for micropatterning in VLSIs and photomasks with enhanced exposure latitude and process adaptability.
Implementation Method 1
a sodium, magnesium, potassium, calcium, rubidium, strontium, yttrium, cesium, barium or cerium salt of fluorosulfonic acid
Implementation Method 2
a base resin comprising recurring units having an acid labile group
Implementation Method 3
control of acid diffusion is also important
Data Source
AI summary
A resist composition comprising a base resin comprising recurring units having an acid labile group, and a metal salt of sulfonic acid exhibits a high sensitivity and high resolution, and forms a pattern of satisfactory profile with minimal LWR or improved CDU when processed by lithography.