By Karlsruhe Nano Micro Facility (KNMF)
Dry Etching Cluster (DRIE) KNMFi Laboratory for Micro- and Nanostructuring Our Dry Etching Cluster consists of the Oxford RIE Plasmalab System 100 with ICP 380 source and the Oxford RIBE Ionfab 300. (RIE: Reactive Ion Etching, ICP: Inductively Coupled Plasma, RIBE: Reactive Ion Beam Etching). The Dry Etching Cluster is an advanced tool for micro- and nanomachining of various materials. The basic feature is a high frequency generator (RF) working at 13.56 Mhz, combined with a high vacuum chamber for wafers with a diameter of 4”. The power varies in the range of 1-2500 W. Available process gases are SF 6 and O 2 for silicon etching; Cl 2, He, Ar and O 2 for chromium and other metals. Features - Silicon etching via the cryo process (process temperatures are between -80 and -150 °C) - Production of highly vertical, highly parallel and smooth sidewalls - Critical lateral dimensions down to the range of 100 nm - Aspect ratios (ARs) up to 6 are possible. - Laser end point detection - Metal etching via RIBE Limitations/constraints Silicon: - Min. lateral dimensions: 100 nm - Min. depth: 50 nm - Max. aspect ratio at critical dimensions: 4 - Total max. depth: 40 µm Chromium: - Min. dimensions in lateral: 100 nm - Selectivity over resist: 1:1 - Etch rate: 25…35 nm/min Materials - Mask material: PMMA, SiO 2, ma-N 2401 - Structures on Si fragments or complete 4” Si wafers Notice: Only silicon and chromium substrates can be processed reproducibly with standard processes at the moment. Design rules - Explicit and unambiguous layout according to the mentioned limitations. - Markers for the better localization of the structures, e.g. in the SEM - If the micro/nano structure is already written onto the substrate, the mask material has to be PMMA, SiO 2 or ma-N 2401 - If combined with the KNMF e-beam, specific limitations concerning the e-beam design rules have to be considered Typical structures and designs Fig. 1: Deep etched silicon gratings Fig. 2: Silicon nanopillars with high aspect ratio Fig. 3: Freestanding cantilevers in silicon Fig. 4: Cantilever structures in chromium
