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Ion Oxide Mask Fabrication

IP.com Disclosure Number: IPCOM000076755D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Laming, FP: AUTHOR [+2]

Abstract

Etching of sputtered iron oxide films for the formation of semitransparent semiconductor masks has been found to be very difficult. The only suitable etchant known has been hot phosphoric acid, which often results in unwanted peeling of the film that may possibly be due to thermal stress.

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Ion Oxide Mask Fabrication

Etching of sputtered iron oxide films for the formation of semitransparent semiconductor masks has been found to be very difficult. The only suitable etchant known has been hot phosphoric acid, which often results in unwanted peeling of the film that may possibly be due to thermal stress.

The procedure set out below has been developed to minimize the disadvantages of such processing. As shown, the procedure consists of passing a stream of hydrogen chloride gas over the iron oxide film to be stripped. Pattern formation can be achieved by suitably coating the oxide film with a protective resist in the conventional photolithographic techniques. The reaction also can be represented as follows: Fe(2)O(3) + 6HCl 2FeCl(3) + 3H(2)O.

The excess HCl gas and water vapor can be exhausted from the system in any suitable manner, and the residual FeCl(3) on the substrate can be removed by a water wash.

In a typical operation using positive AZ-1350* resist as the protective layer, the hydrochloric gas was passed over a substrate between room temperature and 100 degrees C. Excellent results were obtained with substrate temperatures maintained at 35 degrees C. The process provided sharp line definition with no evidence of stress "lift-off", normally exhibited by phosphoric acid etching.

Solutions of concentrated hydrochloric acid can not be used for etching sputtered ferric oxide films because the reaction is far too slow, and the resist does not hold up...