Silicon three-dimensional structures fabricated by femtosecond laser modification with dry etching

Area of Science:

• Materials Science and Engineering
• Nanotechnology
• Microfabrication Technology

Background:

• Fabricating complex three-dimensional (3D) microstructures on silicon wafers is crucial for advancements in microelectromechanical systems (MEMS) and micro-optics.
• Existing methods often involve multiple steps, mask usage, or limitations in achievable complexity and surface finish.

Purpose of the Study:

• To develop a maskless, efficient, and flexible technology for fabricating diverse 3D microstructures on silicon wafers.
• To investigate the underlying mechanism of laser-induced modification and its interplay with dry etching for structure formation.
• To demonstrate the capability of the fabricated structures in MEMS and micro-optics applications.

Main Methods:

• A hybrid fabrication approach combining femtosecond laser surface modification with subsequent dry etching.
• Femtosecond laser irradiation was used to selectively alter silicon's oxidation state in 2D patterned areas.
• Dry etching was employed to remove unmodified silicon, revealing the 3D structures.

Main Results:

• Successfully fabricated complex 3D microstructures including micro gears, comb drive actuators, micro cantilevers, and micro Fresnel zone plates.
• Observed that silicon atoms in laser-modified areas were insufficiently oxidized, enabling selective etching.
• Demonstrated that increasing dry etching time improves the surface roughness of the fabricated microstructures.
• Achieved high efficiency and flexibility in the fabrication process.

Conclusions:

• The developed maskless technology offers a versatile and efficient route for creating intricate 3D microstructures on silicon.
• This technique is well-suited for producing components for microelectromechanical systems (MEMS) and micro-optics applications.
• The process allows for control over surface quality, making it adaptable for various demanding applications.