Resist Top Coat Composition for EUV Lithography
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Solution Overview
Problem
In EUV lithography, there is a trade-off between resist film sensitivity and edge roughness, and existing top coats either reduce sensitivity or cause film loss during development, while also being affected by out-of-band light and environmental contaminants.
Innovation Solution
A resist top coat composition with a polymer base containing a repeating unit of styrene with a 1,1,1,3,3,3-hexafluoro-2-propanol group and acenaphthylene, soluble in alkaline developers, which absorbs out-of-band light and reduces film loss by being simultaneously removable with the resist film during development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the resist sensitivity is increased to compensate for weak EUV light intensity, then the light sensitivity improves, but the resolution and edge roughness deteriorate
Solution Approach 1:
A top coat layer is introduced as an intermediary between the EUV light and the resist film. This top coat absorbs out-of-band light (140-300 nm) while allowing the primary EUV wavelength (13.5 nm) to pass through to the resist, thereby protecting the resist from environmental contaminants and OOB light effects without compromising sensitivity or resolution
Solution Approach 2:
The top coat is designed with specific local properties: it is transparent to the EUV wavelength (13.5 nm) to maintain light transmission to the resist, but absorbs out-of-band light (140-300 nm) to protect against environmental effects. This selective wavelength dependence allows simultaneous optimization of sensitivity and precision
2Object-affected harmful factors
If a top coat is formed on the resist film to protect against environmental effects and OOB light, then the environmental resistance improves, but the film loss and bridging between patterns increase
Solution Approach 1:
The top coat composition parameters are optimized to achieve the desired balance. The polymer structure includes specific repeating units (styrene with hexafluoroalcohol group and acenaphthylene) that provide the right optical properties (absorption of OOB light, transparency to EUV) and chemical properties (solubility in alkaline developer). The molecular weight and composition ratios are controlled to prevent excessive film loss while maintaining protective function
Solution Approach 2:
The top coat uses a composite polymer structure combining styrene units with hexafluoroalcohol groups and acenaphthylene units. This composite material provides multiple functions simultaneously: OOB light absorption, EUV transparency, and controlled solubility for removal during development, thereby reducing film loss while maintaining environmental protection
3Object-affected harmful factors
If a top coat is used to absorb out-of-band light, then the OOB light absorption improves, but the sensitivity to EUV light decreases
Solution Approach 1:
The top coat material is designed with wavelength-selective local quality: it strongly absorbs OOB light (140-300 nm) while remaining transparent to the EUV wavelength (13.5 nm). This is achieved through the specific molecular structure of the polymer, where certain functional groups absorb OOB light while the overall structure allows EUV transmission, thus protecting against harmful radiation without compromising the primary exposure process
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 top coat composition enhances resist film sensitivity, reduces edge roughness, and minimizes film loss and bridging between patterns, while protecting the resist film from environmental contaminants and out-of-band light.
Implementation Method 1
a top coat that absorbs light having a wavelength of 200 nm to 300 nm is applied on a resist film, the variation of pattern size within a shot can be reduced
Implementation Method 2
the resist top coat composition may be soluble in an alkaline developer
Data Source
AI summary
A resist top coat composition includes a polymer including a base resin having a repeating unit p of styrene having a 1,1,1,3,3,3-hexafluoro-2-propanol group and a repeating unit q of acenaphthylene having chemical formula 1. R is hydrogen, hydroxyl. R1 is hydrogen, hydroxyl, linear or branched C1-C10-alkyl, cycloalkyl, acyloxy, alkoxycarbonyl, carboxyl, —OC(═O)R2. R2 is linear or branched C1-C10-alkyl, cycloalkyl or fluorinated alkyl. m is 1 or 2. p and q are positive numbers satisfying the expressions 0<p<1.0 and 0<q<1.0, and 0<p+q≦̸1.0.