Onium-Salt Monomeric PAG for EUV Resist Sensitivity and Low LWR
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Solution Overview
Problem
Existing chemically-amplified resist compositions face challenges in achieving high sensitivity, improved lithography performance, reduced line width roughness (LWR), critical dimension uniformity (CDU), and etching resistance, particularly in the context of miniaturized photolithography processes such as EUV lithography, where acid diffusion and solvent solubility issues persist.
Innovation Solution
Development of an onium-salt-type monomer and monomeric photo-acid generator with specific structural features, including an aromatic ring substituted with a polymerizable group and iodine atom, combined with an aromatic sulfonate anion structure and acid-labile group, which enhances solvent solubility, sensitivity, and reduces acid diffusion, leading to improved LWR and CDU.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amount of acid generator is increased to enhance sensitivity, then sensitivity is improved, but the acid diffusion distance is increased leading to degraded LWR and CDU
Solution Approach 1:
The acid generator is segmented into two functional components: an onium salt portion that generates acid and an iodine-containing portion that absorbs EUV light and generates secondary electrons. This segmentation allows the acid generation function and the light absorption function to be spatially and functionally separated, enabling the acid to be generated at a controlled distance from the polymer chain, thus limiting acid diffusion while maintaining sensitivity.
Solution Approach 2:
The patent creates a composite acid generator by combining an onium salt structure with an iodine-containing aromatic ring structure. This composite structure integrates the acid-generating capability of onium salts with the high EUV absorption and secondary electron generation capability of iodine atoms, achieving both high sensitivity and controlled acid diffusion through the rigid polymer backbone that limits mobility.
2Manufacturing precision
If the PEB temperature is lowered to reduce LWR, then LWR is reduced, but sensitivity becomes lower
Solution Approach 1:
The patent changes the fundamental parameter of acid generation mechanism by introducing iodine atoms that generate secondary electrons upon EUV absorption. This alternative acid generation pathway is less dependent on thermal energy, allowing effective acid generation at lower PEB temperatures. The secondary electrons directly promote acid release from the onium salt without requiring high thermal activation energy, thus maintaining sensitivity at lower temperatures while reducing thermal diffusion that causes LWR.
3Measurement precision
If iodine atoms are introduced to enhance EUV absorption and secondary electron generation, then lithography performance is improved, but organic solvent solubility decreases causing precipitation
Solution Approach 1:
The iodine atoms are localized within the aromatic ring structure of the onium salt cation rather than being distributed throughout the entire molecule. This localized placement allows the iodine to perform its EUV absorption function while the rest of the molecule, particularly the aromatic rings and substituents, can be designed to provide solubility. The local concentration of iodine achieves the desired lithography enhancement without globally compromising solubility.
Solution Approach 2:
The patent modifies the chemical parameters of the onium salt by introducing fluorine atoms and aromatic substituents that enhance solubility in organic solvents. These parameter changes counterbalance the potential precipitation caused by iodine introduction, allowing the molecule to maintain both high EUV absorption capability and adequate solubility for resist formulation.
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 onium-salt-type monomer and monomeric photo-acid generator enhance the solvent solubility, sensitivity, and lithography performance, including LWR and CDU, while providing excellent etching resistance, particularly in EUV lithography, by efficiently generating acids and promoting deprotection reactions.
Implementation Method 1
Iodine atoms very greatly absorb EUV having a wavelength of 13.5 nm, and an effect that secondary electrons are generated from iodine atoms during exposure is observed.
Implementation Method 2
a polymer-bound photo-acid generator which is capable of generating a polymer-type sulfonic acid upon exposure
Data Source
AI summary
An onium-salt-type monomer is represented by the formula (a), where “n1” is 0 or 1, “n2” is 1 to 4, “n3” is 0 to 2, “n4” is 0 or 1, “n5” is 0 to 4, and “n6” is 0 to 2; RA is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group; RAL is an acid-labile group; R1 is a halogen atom, a nitro group, a cyano group; R2 is a halogen atom other than a fluorine atom, a nitro group, a cyano group; RF is a fluorine atom, a fluorinated saturated hydrocarbyl group, a fluorinated saturated hydrocarbyloxy group, or a fluorinated saturated hydrocarbylthio group having 1 to 6 carbon atoms; LA and LB are each a single bond, an ester bond; XL is a single bond or a hydrocarbylene group; and Z+ is an onium cation.