Etching

Reactive Ion Etching (RIE) combines chemical and physical etching to remove material deposited on wafers. Deep reactive-ion etching (DRIE) is a highly anisotropic etch process used to create high aspect ratio structures on substrates.

The process

Reactive Ion Etching (RIE) is a method that combines both chemical and physical etching to allow isotropic and anisotropic material removal. The etching process is carried out in a chemically reactive plasma containing positively and negatively charged ions generated from gases that are pumped into the reaction chamber. A mask on top of the substrate is used to protect designated areas from etching, exposing only the areas to be etched. Dry etching offers excellent process control for cleanliness, homogeneity, etch-rate, etch-profile, selectivity and run-to-run consistency, which is critical for high-fidelity pattern-transfer in micro- and nano-system technologies.

The uses

RIE is extensively used in the field of displays & lighting (LEDs), semiconductors, electronics, MEMS, communication technology, microfluidics, optoelectronics and photovoltaics.

The instruments

MCN houses two RIE systems, both of which are Oxford Instruments PLASMALAB100 ICP380. One is dedicated for deep silicon etching called DRIE (Deep Reactive Ion Etching). The system uses alternating etch (SF6) and passivation (C4F8) cycles to achieve high aspect ratio structures (~1:10). The other is used as a general etch, wherein other materials including silicon dioxide, silicon nitride, germanium, aluminium, aluminium oxide, and numerous other dielectrics and metals can be etched using chlorine and fluorine chemistries. Substrate temperatures range from 10^oC to 40^oC, with the possibility for cryogenic silicon etching. Substrate sizes range from 1mm chips to 8 inch wafers and it can achieve a variety of side-wall profiles, feature sizes and high-aspect ratio silicon structures.

Ashers

Ashing is a surface cleaning process used to descum and remove materials, mainly photoresist, from a substrate. The cleaning process involves exposing photoresist to plasma, in a vacuum environment, creating ash which is easily removed from the substrate surface.

MCN has two ashers, the Plasma Asher: Harrick Plasma and the Barrel Asher: PVA TePla IoN Wave 10.