Micro-structuring of epoxy resists containing nanoparticles by proton beam writing

Proton beam writing (PBW) on SU-8 composites with nanoparticles (size: 14-750 nm) of silver, silica, alumina, and carbon with concentration of 5.0 wt% was studied aiming for high-aspect-ratio micro-structuring. Results of SRIM simulation suggest that deep micromachining of more than 100 μm is possible by 3.0 MeV PBW with increase in lateral straggling of less than 5.0%. Sensitivity loss of 150% was observed by introduction of 5.0 wt% nanoparticles to SU-8. There is a correlation between the sensitivity loss and volume concentration of nanoparticles. We fabricated pillar arrays of SU-8/silver nanocomposites with 10 μm in diameter and 80 μm in height by PBW at 3.0 MeV. Cross-sectional observation of the SU-8/silver pillar arrays shows that silver nanoparticles are homogeneously dispersed in SU-8, while aggregation was observed at the side surface.