Study of the VHF Plasma Etching of Micro/Nano Patterned PMMA Coated on Ultra-Thin Flexible Glass Substrates

Flexible substrates are useful for roll to roll production of photovoltaic modules. In this study, we have demonstrated DVD (digital versatile disc) like pattern replication from a Nickel mold onto PMMA coated ultra-thin flexible Corning (R) Willow (R) Glass substrates (thickness 150 mu m) by thermal nanoimprint lithography (T-NIL) technique. These embossed PMMA coatings were subsequently etched in a capacitively coupled very high frequency (VHF) discharge of 40.68 MHz using Ar/O-2 gas mixture at a chamber pressure of 6.66 Pa for different periods of etching times in the range from 6 to 600 s. High plasma density under VHF together with low gas pressure promote ion directionality toward the substrate. Identification of the emitted species during the etching process was carried out by a quadrupole mass spectrometer. The temporal evolution of the etched patterns on PMMA was studied in detail by atomic force microscopy. The study may be helpful for understanding the plasma etching process of the micro/nano patterned PMMA under VHF leading to the surface structuring on the ultra-thin flexible glass substrates.