Atmospheric pressure plasma directed assembly during photoresist removal: A new route to micro and nano pattern formation

We propose a new route for pattern formation based on atmospheric pressure plasma directed assembly during photoresist removal. Atmospheric plasma etching of AZ5214E resist coated on Silicon leads to the formation of periodic, oxygen-plasma resistant residuals on the underlying substrate. The O-2 content in the He/O-2 gas feed was found to play significant role on the size and density of the formed structures. Fourier analysis of the spatial morphology of surfaces confirmed quantitatively the approximate periodicity and its dependence on O-2 content. XPS analysis revealed the formation of sulfur-containing compounds coming from DNQ molecules of AZ5214E, which organize to etching-resistant molecules due to the synergistic effect of etching and radiation from the radio frequency (RF) discharge. Finally, we applied anisotropic plasma etching based on a pulsed-gas alternating plasma process in low pressure to transfer the atmospheric plasma induced pattern on the underlying Silicon substrate fabricating quasi-ordered Si pillars. The results show the potential of atmospheric plasma directed assembly for uniform, large-area and open-air pattern definition for application in modern nanofabrication.