Chemically Amplified Resist Composition for EUV Lithography
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Solution Overview
Problem
Current chemically amplified resist compositions face challenges in achieving high-resolution resist patterns with reduced line edge roughness (LER) and improved rectangularity, while also minimizing develop loading effects and development residue defects, especially in the processing of photomasks and semiconductor substrates.
Innovation Solution
A chemically amplified positive resist composition is developed, featuring a base polymer with phenolic hydroxy groups and carboxy groups protected by specific acid labile groups, which are blended to control acid diffusion and enhance the resist pattern's resolution, LER, and rectangularity, along with a photoacid generator generating acids with sufficient acid strength for deprotection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional acid generators are used, then resist sensitivity is achieved, but acid diffusion cannot be sufficiently controlled leading to increased LER and reduced resolution
Solution Approach 1:
The patent modifies the chemical structure of the acid generator by introducing specific substituents (such as fluorinated groups, bulky groups, or electron-withdrawing groups) to alter the acid diffusion characteristics. This changes the physical-chemical parameters of the acid generator to achieve controlled acid diffusion while maintaining sufficient sensitivity for high-resolution patterning
Solution Approach 2:
The patent employs composite acid generator systems combining multiple acid generator components with different diffusion characteristics. This composite approach allows balancing between sensitivity and acid diffusion control, achieving both high resolution and reduced LER through synergistic effects of different acid generator materials
2Productivity
If high-sensitivity resist is used for EB lithography, then throughput is improved, but pattern profile rectangularity and LER worsen
Solution Approach 1:
The patent introduces functional groups with different properties at specific positions within the polymer structure. For example, aromatic rings provide etching resistance and structural stability for rectangular profiles, while other regions provide sensitivity. This local differentiation of material properties enables simultaneous achievement of high throughput and good pattern fidelity
Solution Approach 2:
The patent adjusts the glass transition temperature (Tg) and molecular weight of the base polymer to optimize the balance between sensitivity and pattern profile. By controlling these parameters, the resist achieves high sensitivity for fast exposure (improving throughput) while maintaining structural integrity for rectangular pattern profiles with low LER
3Manufacturing precision
If base polymer with acid-generating repeat units is used, then LER is reduced, but solubility in organic solvent deteriorates
Solution Approach 1:
The patent separates the acid-generating function from the solubility-providing function by using a copolymer structure. One polymer component contains acid-generating repeat units for LER control, while another component provides solubility in organic solvents. This segmentation allows each function to be optimized independently without compromising the other
Solution Approach 2:
The patent creates a composite polymer system combining acid-generating polymers with solvent-soluble polymers. This composite approach maintains the LER-reducing effect of acid-generating units while the solvent-soluble component ensures proper resist formulation and processing
4Strength
If photomask blank with chromium oxide layer is used, then etching resistance is improved, but resist pattern profile changes with time due to acid diffusion
Solution Approach 1:
The patent modifies the acid diffusion coefficient by selecting acid generators with appropriate molecular weight, glass transition temperature, and chemical structure. This parameter optimization reduces acid diffusion during the time between exposure and development, stabilizing the resist pattern profile while maintaining etching resistance through the chromium oxide layer
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 effectively forms high-resolution resist patterns with reduced LER and improved rectangularity, minimizing develop loading effects and development residue defects, and is suitable for high-energy radiation such as EUV and EB lithography.
Implementation Method 1
a base polymer protected with an acid labile group and adapted to turn alkali soluble under the action of acid, wherein the base polymer contains a polymer comprising repeat units containing a phenolic hydroxy group... capable of generating a sulfonic acid upon light exposure
Implementation Method 2
The major cause of such a resist pattern profile change with time is diffusion of an acid generated upon exposure
Data Source
AI summary
A chemically amplified positive resist composition is provided comprising a polymer comprising units containing a phenolic hydroxy group and units containing a phenolic hydroxy group protected with an acid labile group, in which a carbon atom neighboring the carbon atom to which the phenolic hydroxy group protected with an acid labile group is attached is substituted with a specific group. A resist pattern with a high resolution, reduced LER, rectangularity, minimized influence of develop loading, and few development residue defects can be formed.