Low-voltage-exposure-enabled hydrogen silsesquioxane bilayer-like process for three-dimensional nanofabrication

Area of Science:

• Nanotechnology
• Materials Science
• Lithography

Background:

• Fabricating three-dimensional (3D) nanostructures often requires complex multi-step processes.
• Existing methods can be limited in achieving precise undercut profiles necessary for advanced applications.

Purpose of the Study:

• To develop a simplified, single-layer electron-beam lithography process for creating 3D nanostructures.
• To demonstrate the fabrication of metallic 3D nanostructures with high fidelity and unique optical properties.

Main Methods:

• Utilized a bilayer-like process with a single hydrogen silsesquioxane (HSQ) resist layer.
• Employed low-energy (1.5 keV) electron irradiation for partial cross-linking of the top layer.
• Used high-voltage (30 keV) electron beam to define self-aligned undercut and freestanding HSQ nanostructures.

Main Results:

• Successfully fabricated freestanding and mushroom-shaped HSQ nanostructures.
• Achieved direct, high-fidelity fabrication of 3D metallic nanostructures (e.g., Ag-coated) by depositing a metallic layer onto the resist patterns.
• Demonstrated lower plasmon resonance damping in Ag-coated 3D nanostructures compared to planar ones.
• Enabled reliable lift-off for fabricating high-quality silver nanohole arrays with distinct optical transmission.

Conclusions:

• The developed single-layer process offers an efficient route to 3D nanostructure fabrication.
• The resulting 3D metallic nanostructures exhibit improved optical performance and processing advantages.
• This method holds potential for advanced optical devices and nano-fabrication.