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Ion Etch Lift Off Process

IP.com Disclosure Number: IPCOM000087544D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Chiu, GT: AUTHOR [+3]

Abstract

Lift-off patterns which can withstand high temperature metal deposition are formed using oxides, metals, or metal oxides in the pattern defining layer which are ion-etched at energies of less than about 10/4/ eV, to form a suitable lift-off profile.

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Ion Etch Lift Off Process

Lift-off patterns which can withstand high temperature metal deposition are formed using oxides, metals, or metal oxides in the pattern defining layer which are ion-etched at energies of less than about 10/4/ eV, to form a suitable lift-off profile.

As shown in Figs. 1(a)-(d), a layer of thermal oxide is formed on a silicon substrate. The oxide layer is coated with a polymer resist, for example, polymethyl methacrylate, which is patterned by electron-beam exposure and solvent developed to remove the exposed areas. The thermal oxide layer is then ion-etched through to the silicon to obtain a straight or concave angle wall. The resist is removed and a metal layer, such as, chromium, is deposited over the oxide and silicon. Lift-off of the oxide layer and overlying chromium is achieved with buffered HF to leave a pattern of chromium on the silicon surface.

Alternatively, a layer of ferrous oxide could be formed on the substrate and a layer of photoresist, such as Shipley AZ positive resist, coated on the ferrous oxide. The resist is then patterned and developed using e-beam or actinic radiation. The exposed portions of the oxide are removed by ion milling and a layer of a metal, such as gold, is deposited over the oxide and the substrate surface. Lift-off is accomplished by an acid etch, which attacks the ferrous oxide but leaves the gold in contact with the substrate intact.

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