Negative Resist Composition for High-Voltage Electron Beam Lithography
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Solution Overview
Problem
High-energy electron beam lithography requires resist materials with improved sensitivity and dry etch resistance to maintain resolution and throughput as accelerating voltage increases, and existing resist films become less sensitive due to reduced forward scattering, necessitating a chemically amplified negative resist composition with enhanced properties.
Innovation Solution
A negative resist composition comprising a polymer with recurring units of styrene having an ester group bonded to 1,1,1,3,3,3-hexafluoro-2-propanol (HFA) and hydroxyl-containing units, which provides high sensitivity, resolution, and etch resistance, along with an acid generator and other additives to enhance alkaline dissolution contrast and prevent acid diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the accelerating voltage of the electron gun is increased to reduce pattern rule, then the resolution is improved, but the sensitivity of the resist film is reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the resist film by incorporating specific polymers with carboxylic acid groups and hydroxyl groups in controlled ratios. This chemical parameter modification enables the resist to maintain high sensitivity even at increased electron beam accelerating voltages (50-100 kV), resolving the contradiction between resolution improvement and sensitivity loss.
Solution Approach 2:
The patent creates a composite resist system combining multiple polymer components (polymer with carboxylic acid groups, polymer with hydroxyl groups) and chemically amplifiable components. This composite structure provides both the sensitivity needed for high-voltage electron beam exposure and the resolution required for fine pattern formation, simultaneously addressing both contradictory requirements.
2Manufacturing precision
If the resist film thickness is reduced to improve resolution, then the resolution is improved, but the dry etch resistance is reduced
Solution Approach 1:
The patent modifies the chemical composition parameters of the resist film by incorporating specific polymers with carboxylic acid groups and hydroxyl groups in controlled ratios. This chemical parameter modification enables the resist to maintain high sensitivity even at increased electron beam accelerating voltages (50-100 kV), resolving the contradiction between resolution improvement and sensitivity loss.
Solution Approach 2:
The patent modifies the molecular structure of the polymer components, particularly using cycloolefin-based structures with curved/ring formations instead of linear chains. This structural curvature increases the carbon density and robustness of the polymer backbone, thereby enhancing dry etch resistance even when the film thickness is reduced to improve 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 achieves high sensitivity, resolution, and minimal pattern collapse with improved etch resistance, making it suitable for fine pattern formation in VLSIs and photomasks, while maintaining high alkaline dissolution contrast and suppressing acid diffusion.
Implementation Method 1
chemically amplified negative resist composition
Implementation Method 2
exposing the chemically amplified negative resist composition to high-energy radiation
Implementation Method 3
developing the exposed film in a developer to form a negative pattern wherein the unexposed region of resist film is dissolved away
Data Source
AI summary
A polymer comprising recurring units (a) of styrene having an HFA group and an ester group adjacent thereto and recurring units (b) having a hydroxyl group is used as base resin to formulate a negative resist composition. The negative resist composition has a high dissolution contrast in alkaline developer, high sensitivity, high resolution, good pattern profile after exposure, and a suppressed acid diffusion rate.