Post-directed-self-assembly membrane fabrication for in situ analysis of block copolymer structures

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Science

Background:

• Characterizing three-dimensional block copolymer self-assembly structures is challenging.
• Transmission electron microscope (TEM) tomography and resonant soft X-ray scattering are key characterization techniques.
• These methods require specialized membrane substrates for sample preparation.

Purpose of the Study:

• To develop a generalizable process for block copolymer directed self-assembly (DSA) on silicon nitride membranes.
• To enable artifact-free characterization of DSA structures using advanced microscopy and scattering techniques.
• To identify and mitigate process variations when transitioning from silicon to silicon nitride substrates.

Main Methods:

• Implementation of block copolymer (BCP) DSA with density multiplication on silicon nitride membranes.
• Performing DSA prior to membrane fabrication to prevent damage to polymer assemblies.
• Fabrication of membranes with varied sizes and layouts on full wafers for diverse characterization needs.
• Utilizing TEM tomography and resonant soft X-ray scattering for structural analysis.

Main Results:

• A generalizable process for BCP DSA on silicon nitride membranes was successfully developed.
• The process avoids artifacts and damage to polymer assemblies by performing DSA before membrane etching.
• Process variations between silicon nitride/silicon stacks and silicon substrates were identified and addressed.
• Membranes suitable for both TEM and X-ray characterization were fabricated.

Conclusions:

• The developed method provides a robust platform for artifact-free characterization of BCP DSA structures.
• This approach expands the utility of silicon nitride membranes for advanced nanoscale material analysis.
• The findings facilitate a deeper understanding of three-dimensional self-assembled polymer structures.