title: High aspect ratio nano-fabrication of photonic crystal structures on glass wafers using chrome as hard mask.
abstract: Wafer-scale nano-fabrication of silicon nitride (Si x N y ) photonic crystal (PhC) structures on glass (quartz) substrates is demonstrated using a thin (30 nm) chromium (Cr) layer as the hard mask for transferring the electron beam lithography (EBL) defined resist patterns. The use of the thin Cr layer not only solves the charging effect during the EBL on the insulating substrate, but also facilitates high aspect ratio PhCs by acting as a hard mask while deep etching into the Si x N y . A very high aspect ratio of 10:1 on a 60 nm wide grating structure has been achieved while preserving the quality of the flat top of the narrow lines. The presented nano-fabrication method provides PhC structures necessary for a high quality optical response. Finally, we fabricated a refractive index based PhC sensor which shows a sensitivity of 185 nm per RIU.
authors.affiliation: Tyndall National Institute, University College Cork, Lee Maltings, Cork, Ireland.
authors.forename: Md Nazmul
authors.initials: MN
authors.lastname: Hossain
authors.forename: John
authors.initials: J
authors.lastname: Justice
authors.forename: Pierre
authors.initials: P
authors.lastname: Lovera
authors.forename: Brendan
authors.initials: B
authors.lastname: McCarthy
authors.forename: Alan
authors.initials: A
authors.lastname: O'Riordan
authors.forename: Brian
authors.initials: B
authors.lastname: Corbett