Resist Composition with Ammonium Salt for EUV Lithography
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Solution Overview
Problem
EUV lithography faces challenges with defects in mask blanks and low light intensity, leading to increased defect occurrence and risk of pattern collapse, especially at smaller feature sizes, due to the lack of effective defect control and high sensitivity in existing resist compositions.
Innovation Solution
A resist composition incorporating an ammonium salt and fluorine-containing polymer with specific repeat units, which segregates on the resist film surface to enhance light absorption, prevent acid diffusion, and improve solubility in alkaline developers, thereby reducing nano-bridging, pattern collapse, and residue formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If EUV lithography is used to achieve smaller feature sizes, then manufacturing precision is improved, but defect occurrence increases due to mask defects and particle deposition
Solution Approach 1:
The patent converts the harmful effect of iodine's low alkaline solubility (which causes residues) into a beneficial sensitizing effect by using iodine-containing compounds that generate acid upon exposure. The generated acid catalyzes the deprotection of the polymer, enabling pattern formation while the fluorinated components ensure proper dissolution. This transforms iodine from a harmful residue-causing element into a useful sensitizing agent.
Solution Approach 2:
The patent uses a composite polymer system combining fluorinated polymer components (for water repellency and surface segregation), iodine-containing compounds (for sensitizing effect), and alkaline-soluble polymer components (for pattern formation). This composite approach allows each component to contribute its strengths while mitigating individual weaknesses, achieving both high sensitivity and low defect occurrence.
2Use of energy by moving object
If iodine atoms are introduced to increase EUV absorption and sensitivity, then sensitivity is improved, but solubility in alkaline developer decreases causing residues
Solution Approach 1:
The patent converts the harmful effect of iodine's low alkaline solubility (which causes residues) into a beneficial sensitizing effect by using iodine-containing compounds that generate acid upon exposure. The generated acid catalyzes the deprotection of the polymer, enabling pattern formation while the fluorinated components ensure proper dissolution. This transforms iodine from a harmful residue-causing element into a useful sensitizing agent.
Solution Approach 2:
The patent introduces acid generators as intermediaries between the iodine-containing compounds and the alkaline developer. The iodine-containing compounds first generate acid upon EUV exposure, and this acid then catalyzes the deprotection of the polymer, making it soluble in the alkaline developer. This intermediary acid generation step bridges the gap between iodine's poor direct alkaline solubility and the need for pattern formation.
3Manufacturing precision
If fluorinated polymer is added to improve water repellency and solubility, then pattern rectangularity is improved, but acid diffusion increases
Solution Approach 1:
The patent applies local quality by having the fluorinated polymer segregate specifically at the resist film surface rather than being uniformly distributed throughout. This surface segregation provides water repellency and improves pattern rectangularity where needed, while the bulk polymer composition can be optimized to control acid diffusion. The localized presence of fluorinated groups at the surface does not significantly impact the bulk acid diffusion characteristics.
4Manufacturing precision
If double patterning is used to achieve 7-nm node devices, then manufacturing precision is improved, but process complexity increases
Solution Approach 1:
The patent changes the chemical parameters of the resist material to achieve higher sensitivity and better pattern definition, which allows for simpler processing conditions. The improved solubility characteristics and reduced acid diffusion enable better pattern formation with fewer processing steps, effectively reducing the complexity of double patterning processes while maintaining the required 7-nm node precision.
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, minimizes nano-bridging and pattern collapse, and improves the rectangularity and uniformity of resist patterns, ensuring reliable pattern formation even at small feature sizes.
Implementation Method 1
The additive polymer is effective for increasing the absorption of exposure light on the resist film surface due to iodine or bromine atoms whereby a sensitizing effect is exerted
Implementation Method 2
This is effective for suppressing acid diffusion on the resist film surface and improving the rectangularity of a resist pattern as developed
Implementation Method 3
This additive containing a 1,1,1,3,3,3-hexafluoro-2-propanol (HFA) group is effective for improving the solubility in alkaline developer at the resist film surface
Implementation Method 4
a fluorinated polymer additive which segregates on the surface of a resist film to improve water repellency
Data Source
AI summary
A resist composition comprising an ammonium salt and fluorine-containing polymer comprising repeat units AU having ammonium salt structure of a carboxylic acid having an iodized or brominated aromatic ring and repeat units FU-1 having a trifluoromethylalcohol group and/or repeat units FU-2 having a fluorinated hydrocarbyl group offers a high sensitivity and is unsusceptible to nano-bridging, pattern collapse or residue formation, independent of whether it is of positive or negative tone.