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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. Other situations require a more durable mask, such as silicon nitride.
Buffered oxide etch (BOE), also known as buffered HF or BHF, is a wet etchant used in microfabrication. It is a mixture of a buffering agent, such as ammonium fluoride NH 4 F, and hydrofluoric acid (HF). Its primary use is in etching thin films of silicon nitride (Si 3 N 4) or silicon dioxide (SiO 2), by the reaction: SiO 2 + 4HF + 2NH 4 F → ...
Silicon nitride is a chemical compound of the elements silicon and nitrogen. Si 3 N 4 ... to electrically isolate different structures or as an etch mask in bulk ...
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 ...
Hardmask materials can be metal or dielectric. Silicon based masks such as silicon dioxide or silicon carbide are usually used for etching low-κ dielectrics. [3] However, SiOCH (carbon doped hydrogenated silicon oxide), a material used to insulate copper interconnects, [4] requires an etchant that
The key steps of the STI process involve etching a pattern of trenches in the silicon, depositing one or more dielectric materials (such as silicon dioxide) to fill the trenches, and removing the excess dielectric using a technique such as chemical-mechanical planarization. [2]
A photo mask, composed of silicon nitride, is patterned on the top of this sacrificial oxide. A second layer is added to the wafer to create a planar surface. After that, the silicon is thermally oxidized, so the oxide grows in regions where there is no Si 3 N 4 and the growth is between 0.5 and 1.0 μm thick. Since the oxidizing species such ...
Left: Spacer (blue) is deposited on mandrel (gray) and etched, leaving only the portion covering the sidewall. Center: Mandrel is removed. Right: Spacer is trimmed by etching to smaller width. Spacer patterning is a technique employed for patterning features with linewidths smaller than can be achieved by conventional lithography.