Dry Etching (RIE and DRIE)
Reactive Ion Etching
Reactive Ion Etching (RIE) is an ion-assisted reactive etching method used in the semiconductor fabrication process. Because of its excellent process control (homogeneity, etch-rate, etch-profile, selectivity), which is critical for high-fidelity pattern-transfer, RIE is used in the manufacturing of topographical structures in micro- and nano-system technologies. RIE is based on a combination of chemical and physical etching which allows isotropic and anisotropic (uni-directional) material removal. The etching process is carried out in a chemically reactive plasma containing positively and negatively charged ions generated from the gas that is pumped into the reaction chamber. A mask on top of the substrate is used to protect certain areas from etching, exposing only the areas to be etched. The ions are accelerated into the etching region, where they attack the substrate surface and react with it. RIE primarily employs ion-assisted processes, where heavy ion bombardment damages chemical bonds and the radicals chemically react with exposed surface atoms producing a volatile product. RIE provides excellent pattern-transfer results even for very fine structures significantly under 100nm.
Deep Reactive Ion Etching
DRIE (Deep Reactive Ion Etching) is a RIE modification for silicon deep etching using alternating etch and passivation cycles (gas chopping, time-multiplexed etching, ASE - Advanced Silicon Etching). It is used for high anisotropy and etch rates to obtain patterns with maximal aspect ratios and resolution.
- Selectivity, anisotropy and etch rates can be controlled through the process chemistry (gases) and process parameters (RF-power, pressure, gas flow, substrate cooling etc.). High anisotropy of etched structures is guaranteed by applying side-wall polymer passivation.
- Fabrication of micro- and nano-structures and components based on silicon, dielectrics or polymers
- Plasma-cleaning of wafer surfaces
- Deep etching down to 1 mm
- Aspect ratios (width/height) from 1:10 to 1:100 (material dependent)
- Resolution below 100 nm (mask dependent)
Fields of application
- Semiconductor technology
- Micro-reactors, micro-flow sensors, micro-switches, optocouplers, micro-motors, biosensors
- Small-sized components for movable and unmovable microstructures