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Molybdenum Etchant

IP.com Disclosure Number: IPCOM000074858D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Sybalsky, J: AUTHOR

Abstract

A conventional etchant for molybdenum is a solution of potassium ferricyanide and sodium hydroxide. In the formation of printed circuits and microelectronic components, the patterns may be etched by applying this solution preferably in the spray form. It has been found that there is a critical relationship between concentration of the ferricyanide ion and sodium hydroxide ion. If the ratio of ferricyanide to hydroxyl concentration is low, the result is a dissolution of the metallic film which is too rapid and produces ragged edges in the etched pattern. On the other hand, if the ratio is too high, because of a lower than normal hydroxyl ion concentration, the etching rate is so slow that it is impractical.

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Molybdenum Etchant

A conventional etchant for molybdenum is a solution of potassium ferricyanide and sodium hydroxide. In the formation of printed circuits and microelectronic components, the patterns may be etched by applying this solution preferably in the spray form. It has been found that there is a critical relationship between concentration of the ferricyanide ion and sodium hydroxide ion. If the ratio of ferricyanide to hydroxyl concentration is low, the result is a dissolution of the metallic film which is too rapid and produces ragged edges in the etched pattern. On the other hand, if the ratio is too high, because of a lower than normal hydroxyl ion concentration, the etching rate is so slow that it is impractical. The following formula of etchant appears to produce excellent etching, with a good etch rate and superior edge definition. An aqueous solution in deionized water of Potassium Ferricyanide 125 g/liter Sodium Hydroxide 6.8 g/liter Wetting Agent 0.67 g/liter.

When the ferricyanide to hydroxide ratio is not high, e.g., the proportions set forth in the formula, it appears a molybdenum oxide film first appears on the molybdenum being etched during the process. It is the presence of this film during etching that insures good edge definition with no ragged edges.

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