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Drypoint is a printmaking technique of the intaglio family, in which an image is incised into a plate (or "matrix") with a hard-pointed "needle" of sharp metal or diamond point. In principle, the method is practically identical to engraving .
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.
The plate's ground side is then dipped into acid, or the acid poured onto it. The acid bites into the surface of the plate where it was exposed. Biting is a printmaking term to describe the acid's etching, or incising, of the image; its duration depends on the acid strength, metal's reactivity, temperature, air pressure and the depth desired. [8]
Etching is a critically important process module in fabrication, and every wafer undergoes many etching steps before it is complete. For many etch steps, part of the wafer is protected from the etchant by a "masking" material which resists etching. In some cases, the masking material is a photoresist which has been patterned using photolithography.
This process is called aquatint, and allows for the creation of tones, shadows, and solid areas of color. The design is then drawn (in reverse) with an etching-needle or échoppe. An "echoppe" point can be made from an ordinary tempered steel etching needle, by grinding the point back on a carborundum stone, at a 45–60 degree angle.
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 .
Simplified illustration of dry etching using positive photoresist during a photolithography process in semiconductor microfabrication (not to scale). A single iteration of photolithography combines several steps in sequence. Modern cleanrooms use automated, robotic wafer track systems to coordinate the process. [12]
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 ...