Metal oxide multilayer hard mask system for 3D nanofabrication

Area of Science:

• Materials Science
• Nanotechnology
• Lithography

Background:

• Focused ion beam (FIB) milling often introduces defects in microfabrication.
• Developing precise patterning methods is crucial for advanced nanofabrication.

Purpose of the Study:

• To demonstrate multilayer metal oxide hard masks for lithography and 3D nanofabrication.
• To combine Atomic Layer Deposition (ALD) and FIB for improved mask patterning.
• To overcome common FIB-induced defects in microfabrication.

Main Methods:

• Fabrication of Al2O3/Ta2O5/Al2O3 thin film stacks using ALD.
• Patterning of the multilayer stacks using FIB milling with gallium ions.
• Chemical etching using tetramethylammonium hydroxide.
• 2D lift-off processing for metal line fabrication.
• Fabrication of 3D structures using self-supporting masks.

Main Results:

• Successful patterning of multilayer metal oxide masks, avoiding FIB defects.
• Tailored masks for 2D lift-off processing, enabling sub-100 nm metal lines and multilevel contacts.
• Demonstration of self-supporting 3D masks for 3D nanofabrication.
• Fabrication of thin film resistors using controlled stiction of suspended structures.

Conclusions:

• The combined ALD and FIB approach provides a robust method for creating high-resolution hard masks.
• This technique is versatile for both 2D and 3D nanofabrication applications.
• The developed masks facilitate advanced microelectronic and nanodevice fabrication.