Ga(+) beam lithography for nanoscale silicon reactive ion etching

Area of Science:

• Materials Science
• Nanotechnology
• Microfabrication

Background:

• Fabricating high aspect ratio nanostructures in silicon presents challenges.
• Existing methods often require multiple steps and resist materials.

Purpose of the Study:

• To develop a resist-free fabrication technique for precision silicon nanostructures.
• To investigate the use of focused ion beam (FIB) implanted gallium (Ga) as an etch mask.

Main Methods:

• Utilizing a focused ion beam (FIB) for gallium (Ga) ion implantation into silicon to create etch masks.
• Employing inductively coupled plasma reactive ion etching (ICP-RIE) with fluorinated chemistries for anisotropic silicon etching.
• Investigating two etch processes: Pseudo Bosch (SF(6)/C(4)F(8)) and cryogenic fluorine (SF(6)/O(2)).

Main Results:

• Demonstrated resist-free fabrication of nanostructures down to 30 nm.
• Achieved high aspect ratio structures with ratios up to 17:1.
• Established a linear relationship between implanted Ga density and etch depth, enabling grayscale lithography.
• Successfully created multilayer structures in silicon.

Conclusions:

• Gallium (Ga) implantation via FIB provides a versatile and effective method for patterning silicon etch masks.
• This technique offers high fidelity and resolution for micro- and nanostructure fabrication.
• The process is suitable for creating complex multilayer structures and grayscale patterns.