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Tapered Via Hole

IP.com Disclosure Number: IPCOM000042417D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Chen, MM: AUTHOR [+2]

Abstract

Desired sidewall tapers of etched via holes in silicon oxides can be achieved by controlling the wafer temperature (<_20 C) during reactive ion etching. Reactive ion etching of silicon oxides (SiO2 and SiO) may be used to define the via hole opening for intermetallic connections in integrated devices. The requirements for a successful etching process are high etching rate ratio of oxide to underlying films and tapered oxide sidewall edges. A typical process is reactive ion etching with hydrogen-containing fluorocarbon gases such as CF4+H2 and CHF3 . The process provides a reasonable etching selectivity of about 5 (CHF3) for oxide to niobium, but results in a vertical oxide sidewall profile which is undesirable. In addition, severe polymerization occurs inside the reactor chamber wall when these gases are used.

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Tapered Via Hole

Desired sidewall tapers of etched via holes in silicon oxides can be achieved by controlling the wafer temperature (<_20 C) during reactive ion etching. Reactive ion etching of silicon oxides (SiO2 and SiO) may be used to define the via hole opening for intermetallic connections in integrated devices. The requirements for a successful etching process are high etching rate ratio of oxide to underlying films and tapered oxide sidewall edges. A typical process is reactive ion etching with hydrogen-containing fluorocarbon gases such as CF4+H2 and CHF3 . The process provides a reasonable etching selectivity of about 5 (CHF3) for oxide to niobium, but results in a vertical oxide sidewall profile which is undesirable. In addition, severe polymerization occurs inside the reactor chamber wall when these gases are used. The reactive ion etching process using CF4+O2 was considered not suitable due to the resulting low etching selectivity (oxide to NbN NO.3) even though tapered oxide sidewalls have been demonstrated. (The other alternative is using a lift-off SiO technique, which results in SiO edge and angles of about 60-70OE. However, severe reduction in Nb critical current due to poor step coverage over lift-off SiO is still a problem.) This article describes a process to achieve the goals of high etching selectivity of oxide to Nb (N N5) and, in the meantime, to produce desired tapered oxide edge profiles, by using a CF4+O2 reactive ion etching technique...