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Etching System

IP.com Disclosure Number: IPCOM000087312D
Original Publication Date: 1977-Jan-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Kranefuss, LC: AUTHOR

Abstract

In general, the oxidizing gases, such as fluorine, either have more negative or approximately the same oxidation potential as the commonly used persulfate ion. The equilibrium expression for the oxidation of a metal with a gas, such as fluorine, is as follows: Cu+F(2)->(CuF(2). In the equilibrium condition, the equilibrium constant (K/(p)) is equal to the reciprocal of the partial pressure of the oxidizing gas. By increasing the partial pressure of the oxidizing gas (F(2) in this case), it is possible to move the equilibrium of the system to the right, that is, to force the reaction to the right.

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Etching System

In general, the oxidizing gases, such as fluorine, either have more negative or approximately the same oxidation potential as the commonly used persulfate ion. The equilibrium expression for the oxidation of a metal with a gas, such as fluorine, is as follows: Cu+F(2)->(CuF(2). In the equilibrium condition, the equilibrium constant (K/(p)) is equal to the reciprocal of the partial pressure of the oxidizing gas. By increasing the partial pressure of the oxidizing gas (F(2) in this case), it is possible to move the equilibrium of the system to the right, that is, to force the reaction to the right. Fluorine is the preferred oxidizing gas, although bromine, chlorine or oxygen can be used, but with fluorine the reaction can be increased with less pressure than is required for the other commonly used oxidizing gases.

In operation, the work to be etched is suspended in an air-tight pressure vessel that is equipped with high pressure water sprays. As the metal is etched, the high pressure water spray washes off the metal fluoride salt, thereby exposing a fresh layer of the metal, which is in turn etched off to the salt. The liquid spray removes the salt layer from the material being etched and the process continues until sufficient etching has occurred. Then the oxidizing gas is pumped out from the air-tight enclosure, and the work removed.

This type of an oxidizing system has a number of advantages. The gaseous etching system can have its partial pressur...