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Dry etching refers to the removal of material, typically a masked pattern of semiconductor material, by exposing the material to a bombardment of ions (usually a plasma of reactive gases such as fluorocarbons, oxygen, chlorine, boron trichloride; sometimes with addition of nitrogen, argon, helium and other gases) that dislodge portions of the material from the exposed surface.
This process is now largely outdated but was used up until the late 1980s when it was superseded by dry plasma etching. [1]: 147 The wafer can be immersed in a bath of etchant, which must be agitated to achieve good process control. For instance, buffered hydrofluoric acid (BHF) is used commonly to etch silicon dioxide over a silicon substrate.
To etch through a 0.5 mm silicon wafer, for example, 100–1000 etch/deposit steps are needed. The two-phase process causes the sidewalls to undulate with an amplitude of about 100–500 nm . The cycle time can be adjusted: short cycles yield smoother walls, and long cycles yield a higher etch rate.
Wet etching was widely used in the 1960s and 1970s, [144] [145] but it was replaced by dry etching/plasma etching starting at the 10 micron to 3 micron nodes. [146] [147] This is because wet etching makes undercuts (etching under mask layers or resist layers with patterns). [148] [149] [150] Dry etching has become the dominant etching technique ...
Reactive-ion etching (RIE) is an etching technology used in microfabrication. RIE is a type of dry etching which has different characteristics than wet etching . RIE uses chemically reactive plasma to remove material deposited on wafers .
The dry etch is then performed so that structured etching is achieved. After the process, the remaining photoresist has to be removed. This is also done in a special plasma etcher, called an asher. [14] Dry etching allows a reproducible, uniform etching of all materials used in silicon and III-V semiconductor technology. By using inductively ...
It was particularly dry in the city throughout 1910, New York's driest year until 1964, in fact, w hen water reservoirs dropped to a low of 26 percent capacity.
In etching, a liquid ("wet") or plasma ("dry") chemical agent removes the uppermost layer of the substrate in the areas that are not protected by photoresist. In semiconductor fabrication, dry etching techniques are generally used, as they can be made anisotropic, in order to avoid significant undercutting of the photoresist pattern. This is ...