Chemical etching
From Wikipedia, the free encyclopedia
This page discusses the industrial applications of the etching process. For etching in art or printing ,see etching
Chemical etching (sometimes called chemical milling or wet etching) is the process of using acids, bases or other chemicals to dissolve away unwanted materials such as metals, semiconductor materials or glass. It has applications in the printed circuit board and semiconductor fabrication industries.
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[edit] Etchants
There are two kinds of etching etchants, isotropic etchants and anisotropic etchants:
- Isotropic etchants attack the material being etched at the same rate in all directions.
- Anisotropic etchants attack the silicon wafer at different rates in different directions. On wafers the most used etchant is KOH. By doping silicon with high concentrations of boron it becomes unetchable. This technique is termed an etchstop. See footnote for further information.
Anisotropic etching does not cause undercutting, and is preferred in applications where straight side walls are essential. Anisotropic etching requires a substrate with a well defined crystalline structure such as silicon. The etch is directional and proceeds along the exposed plane in the crystal lattice. As atoms are removed from the crystal lattice, different planes are exposed to the etchant. Since the density of atoms on the planes varies, the etch rate varies significantly.
Footnote: http://www.techneglas.com/dopantpages/etch.htm
[edit] History of etching
The process is believed to have been invented by Daniel Hopfer (circa 1470-1536) of Augsburg, Germany, who decorated armour in this way, and applied the method to printmaking.
[edit] Explanation
Etching is used in the manufacturing of printed circuit boards and semiconductor devices and the preparation of metallic specimens for microscopic observation.
[edit] Etchants
Commonly used etchants for copper are:
- Iron (III) Chloride Ferric chloride
- Ammonium persulfate
- Ammonia
[edit] Etching of metals
[edit] Etching of glass
Hydrofluoric acid (HF) is a very efficient etchant for glass. It is however very dangerous if it comes into contact with the body.
[edit] Etching in the semiconductor industry
Semiconductor etching is divided into two major categories, isotropic and anisotropic.
[edit] Applications
[edit] See also
[edit] External links
- Precision Photo-Fab, based in Buffalo, NY, is a leader in the chemical etching industry.
- Example of a chemically-etched nameplate manufacturer who has won the Baldrige Award for quality twice, in 1998 and 2004
- Worldwide suppliers of Chemically etched parts Hi-Rel Lids Ltd.
ja:ウエットエッチング
