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This process is now largely outdated but was used up until the late 1980s when it was superseded by dry plasma etching.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.
Dry etching is used in conjunction with photolithographic techniques to attack certain areas of a semiconductor surface in order to form recesses in material.. Applications include contact holes (which are contacts to the underlying semiconductor substrate), via holes (which are holes that are formed to provide an interconnect path between conductive layers in the layered semiconductor device ...
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 .
Bulk micromachining starts with a silicon wafer or other substrates which is selectively etched, using photolithography to transfer a pattern from a mask to the surface. Like surface micromachining, bulk micromachining can be performed with wet or dry etches, although the most common etch in silicon is the anisotropic wet etch.
The first attempts of MACE consisted of a silicon wafer that was partially covered with aluminum and then immersed in an etching solution. [2] This material combination led to an increased etching rate compared to bare silicon. Often this very first attempt is also called galvanic etching instead of metal assisted chemical etching. [citation ...
Micro-machining starts with a silicon wafer or other substrate upon which new layers are grown. These layers are selectively etched by photo-lithography; either a wet etch involving an acid, or a dry etch involving an ionized gas (or plasma). Dry etching can combine chemical etching with physical etching or ion bombardment. Surface micro ...