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Fabricating Patterns in Metal Oxide Zones by Electrochemical Reaction

IP.com Disclosure Number: IPCOM000081072D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Chang, IF: AUTHOR [+3]

Abstract

Considerable difficulty is often encountered in etching patterns in metal-oxide layers, such as tin oxide. Because tin oxide may be used as a transparent conductor, films of tin oxide have wide application in display devices, such as gas panels and liquid-crystal cells. The etching of tin oxide in such an environment is known to be quite difficult. Hydrofluoric acid may be used to etch the tin oxide, but it also attacks the glass substrate. The conventional process for etching tin oxide involves four basic steps.

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Fabricating Patterns in Metal Oxide Zones by Electrochemical Reaction

Considerable difficulty is often encountered in etching patterns in metal- oxide layers, such as tin oxide. Because tin oxide may be used as a transparent conductor, films of tin oxide have wide application in display devices, such as gas panels and liquid-crystal cells. The etching of tin oxide in such an environment is known to be quite difficult. Hydrofluoric acid may be used to etch the tin oxide, but it also attacks the glass substrate. The conventional process for etching tin oxide involves four basic steps.

The first step involves developing a photoresist pattern on the tin-oxide coated substrate, and the second step involves applying zinc powder thereto. Thereafter, hydrochloric acid is applied and finally, a brush is used to rub the zinc powder against the exposed tin oxide area. The tin oxide is reduced to tin and then etched off by the HCl solution. As can be seen, such a process is cumbersome and messy.

The present process involves an electrochemical reduction process whereby the tin oxide within selected patterns is reduced to tin according to the following equation:

(Image Omitted)

Basically, this process involves developing a photoresist pattern on the tin- oxide coated substrate. The tin-oxide pattern is then reduced by connecting the tin-oxide film to the negative terminal of power supply V, as shown in the figure, and connecting a further conducting electrode, such as a platinum electrode or the like, to the positive terminal of power supply V. With the electrodes immersed in an electrolyte, the exposed tin oxide is readily reduced. Various solutions (acetic, basic or neutral) can be used as the electrolyte. For example, a few drops of HCl or alkaline solution in water serves well as the electrolyte. With a voltage drop of 10 volts across the electrodes, approximately 30 mA flows through the electrolyte, and within a couple of minutes the tin oxide is reduced to tin. The reduced tin remaining within the exposed pattern is then easily etched off in a dilute solution of HCl in water. It is clear that resolution may be improved by prebaking and/or postbaking the photoresist.

In a further embodiment, the last-mentioned etching step is combined with the electrochemical reduction step such that the...