Resist Protective Film Composition for EUV Lithography
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Solution Overview
Problem
In EUV lithography, there is a need for a resist material that is sensitive to EUV light but not to out-of-band (OOB) light, while also minimizing film thickness loss and avoiding bridges between pattern features, and existing protective films either reduce sensitivity or are difficult to strip.
Innovation Solution
A resist protective film-forming composition comprising a copolymer with recurring units derived from styrene, indene, or benzothiophene with 1,1,1,3,3,3-hexafluoro-2-propanol, which is soluble in alkaline developers, allowing simultaneous stripping with the resist film and providing transparency to EUV light while absorbing OOB light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a protective film is formed on the resist film to prevent environmental impacts and OOB light absorption, then environmental resistance and OOB light protection are improved, but the sensitivity of the resist material to EUV light is reduced
Solution Approach 1:
The protective film uses a copolymer with specific repeating units that have different functional properties: some units provide environmental resistance and OOB light absorption, while other units maintain EUV light transparency and sensitivity. This local differentiation of material properties within the same film allows simultaneous protection and sensitivity maintenance.
Solution Approach 2:
The protective film is formed from a copolymer combining multiple functional units: styrene units with hexafluoro-2-propanol groups provide environmental resistance and OOB absorption, while indene and benzothiophene units contribute to EUV transparency and sensitivity. This composite material structure enables multiple functions to coexist without compromising sensitivity.
2Reliability
If a protective film is formed to prevent acid generator leaching and profile degradation, then film integrity is improved, but the film becomes difficult to strip after use
Solution Approach 1:
The protective film's solubility parameters are specifically designed to match the alkaline developer conditions. The copolymer structure includes units that remain stable during exposure and development but become soluble in the alkaline developer, enabling easy stripping. This parameter optimization allows the film to maintain integrity during use while being readily removable afterward.
3Productivity
If the resist material sensitivity is increased to compensate for low light quantity in EUV lithography, then throughput is improved, but resolution and edge roughness deteriorate
Solution Approach 1:
The protective film acts as an intermediary layer that selectively filters harmful OOB light while allowing EUV light to pass through to the resist material. This intermediary function enables the resist material to operate at optimal sensitivity levels without being exposed to damaging OOB radiation, thereby maintaining both throughput and resolution.
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 composition enhances resist film sensitivity, prevents film thickness loss, and minimizes bridge defects between pattern features by absorbing OOB light and being easily removable, thus improving the EUV lithography process efficiency.
Implementation Method 1
a copolymer comprising recurring units (p) derived from at least one monomer selected from the group consisting of a styrene, indene, benzofuran or benzothiophene having 1,1,1,3,3,3-hexafluoro-2-propanol... which is soluble in alkaline developers, allowing simultaneous stripping with the resist film and providing transparency to EUV light while absorbing OOB light
Data Source
AI summary
A pattern is printed by forming a photoresist layer on a wafer, forming a protective film thereon, exposure, and development. The protective film is formed from a composition comprising a copolymer comprising recurring units derived from a styrene, indene, benzofuran or benzothiophene monomer having 1,1,1,3,3,3-hexafluoro-2-propanol, and recurring units derived from a styrene, vinylnaphthalene, indene, benzofuran, benzothiophene, stilbene, styrylnaphthalene or dinaphthylethylene monomer and an ether solvent.