The Fabrication of High Aspect Ratio Nanostructures on Quartz Substrate

Abstract

This work investigates the fabrication process to achieve high aspect ratio nanostructures on quartz substrates using electron beam lithography (EBL) patterning and fluorinated plasma etching processes. A PMMA bilayer resist was coated on a quartz substrate and then e-beam exposed with the designed pattern of sub-100 nm feature sizes, using the Raith-150 EBL patterning tool. Additive pattern transfer was employed by depositing a 40 nm nichrome layer on the resist pattern using a metal evaporator and later lifted off by soaking in the acetone. The etching was performed on quartz substrates with nichrome pattern masks using the conventional Oxford Plasmalab 80Plus reactive ion etcher. The etching process was carried out in a gas mixture of CHF3/Ar with a flow rate ratio of 50/30 sccm, pressure of 20 mTorr, RF power of 200 W and at room temperature. This etching process setting was found to achieve a 10 nm/min etch rate and tall vertical side walls profile. An aspect ratio of 10:1 has been achieved on a 60 nm feature size structures.