Semiconductors

Monday, October 16, 2006

Etching Process in Semiconductor Manufacturing

Etching processes are used to partly remove material in order to create patterns to obtain the desired device or interconnect geometry. Particles in the etching component (a liquid or gas) remove material by attacking the open surface.
The material may be isotropically removed, known as chemical or "wet" etching, or be etched in a plasma reactor ("dry"-etching). In the case of a dry-etching process, the total etch rate consists of an ion-assisted rate and a purely chemical etch rate due to etching by neutral radicals, which may still have a directional component. The total etch rate can depend on shadowing within the reactor and by the structure on the substrate itself, the angle-dependent flux distribution of particles from the reactor volume, the angle of incidence of the particles relative to the surface normal direction, reflection/re-emission of etching particles, and surface diffusion effects. Reactive ion etching (RIE) provides high anisotropy which is achieved by etching that is enhanced (via different mechanisms) by ions impinging onto the surface. The main advantage of RIE is enhanced directionality which becomes increasingly important as device sizes decrease substantially and etching must proceed in vertical direction without affecting adjacent features.

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