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STED-Inspired Cationic Photoinhibition Lithography
Sourav Islam1, Marco Sangermano2, Thomas A Klar1
1Institute of Applied Physics, Johannes Kepler University Linz, 4040 Linz, Austria.
The Journal of Physical Chemistry. C, Nanomaterials and Interfaces
|September 27, 2023
Summary
Researchers enhanced two-photon polymerization for cationic polymers using stimulated emission depletion (STED)-inspired techniques. This advancement allows for significantly smaller epoxy lines, crucial for semiconductor manufacturing.
Area of Science:
- Materials Science
- Nanotechnology
- Photochemistry
Background:
- Two-photon polymerization (TPP) is a high-resolution 3D printing technique.
- Stimulated emission depletion (STED) microscopy principles have enhanced TPP resolution.
- Previous STED-inspired TPP was limited to radical polymerization, excluding cationic polymers like epoxides.
Purpose of the Study:
- To extend STED-inspired TPP to cationic polymerization, specifically for epoxides.
- To investigate optical on/off switching capabilities in epoxide polymerization.
- To achieve sub-diffraction limit resolution in cationic TPP for microfabrication.
Main Methods:
- Utilized a thioxanthone sensitizer and sulfonium or iodonium salts as photoinitiators.
- Employed a second, depleting laser focus in the outer rim of the point spread function.
- Investigated the polymerization of epoxides using this modified TPP approach.
Main Results:
- Achieved partial optical on/off switching of two-photon polymerization.
- Demonstrated writing of epoxy lines with widths reduced by approximately two-thirds compared to conventional TPP.
- Successfully applied STED-inspired principles to cationic polymerization for the first time.
Conclusions:
- This study successfully adapted STED-inspired techniques for cationic polymerization, broadening the scope of high-resolution laser lithography.
- The developed method offers significant improvements in resolution for epoxide-based materials, relevant to semiconductor technology.
- The findings pave the way for advanced microfabrication using cationic photopolymerization with enhanced spatial control.
