A strategy to fabricate nanostructures with sub-nanometer line edge roughness

Area of Science:

• Nanofabrication
• Materials Science
• Surface Science

Background:

• Line edge roughness (LER) is a critical challenge in nanofabrication, particularly for integrated circuits, hindering the achievement of sub-nanometer precision.
• Existing methods struggle to deposit energy with the required sub-nanometer profile, limiting progress in reducing LER.

Purpose of the Study:

• To introduce a novel strategy for fabricating nanostructures with sub-nanometer line edge roughness.
• To systematically investigate the factors influencing LER in nanostructures using a unique experimental setup.

Main Methods:

• Utilizing a scanning helium ion beam to expose hydrogen silsesquioxane (HSQ) resist on a thin silicon nitride (SiNx) membrane (approximately 20 nm).
• Employing a suspended membrane as an energy filter to eliminate backscattering-induced secondary electrons.
• Characterizing nanostructures using scanning transmission electron microscopy (STEM) and atomic force microscopy (AFM).

Main Results:

• Achieved a spatial imaging resolution of 0.16 nm using the suspended membrane geometric construction.
• Determined a process window for fabricating lines with 0.2 nm LER by optimizing parameters like step size, designed exposure linewidth (DEL), dosage, and resist thickness with a high-contrast developer.
• AFM and simulations revealed that optimal LER is dependent on specific resist thickness and dosage at particular beam step sizes and DEL.

Conclusions:

• The developed scanning helium ion beam exposure strategy on HSQ-resist-coated suspended membranes effectively enables sub-nanometer LER fabrication.
• Understanding the interplay between beam parameters, resist properties, and developer choice is crucial for achieving minimal LER in nanostructure fabrication.
• This approach offers a pathway to overcome current limitations in achieving ultra-low LER for next-generation electronic devices.