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Minimization of Electrical Shorting Between Adjacent Metal Layers in a Multilayer Integrated Circuit Conductor Structure

IP.com Disclosure Number: IPCOM000043956D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Barber, JR: AUTHOR [+4]

Abstract

A typical dual dielectric structure between two levels of metallization consists of 4000 angstroms of plasma-deposited silicon nitride followed by 1.1 microns of polyimide. These layers provide a protective layer (barrier) between the first (M1) and second (M2) metal lines. Vias are etched through this dielectric composite in the desired areas to provide electrical contact between M1 and M2. A serious problem arises when the M1 line has a so-called foot, as seen in Fig. 1. This foot will cause a crack or cusp in the nitride film. The result will be a conductive path connecting M1 and M2, producing a short. A thicker coat of nitride may help alleviate the shorts problem, but at the expense of an increase in the severity of the topography.

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Minimization of Electrical Shorting Between Adjacent Metal Layers in a Multilayer Integrated Circuit Conductor Structure

A typical dual dielectric structure between two levels of metallization consists of 4000 angstroms of plasma-deposited silicon nitride followed by 1.1 microns of polyimide. These layers provide a protective layer (barrier) between the first (M1) and second (M2) metal lines. Vias are etched through this dielectric composite in the desired areas to provide electrical contact between M1 and M2. A serious problem arises when the M1 line has a so-called foot, as seen in Fig. 1. This foot will cause a crack or cusp in the nitride film. The result will be a conductive path connecting M1 and M2, producing a short. A thicker coat of nitride may help alleviate the shorts problem, but at the expense of an increase in the severity of the topography. The authors have developed a process, utilizing spacer technology in a unique and new way, which eliminates the cusping of the nitride film due to the M1 foot and also provides a more gradual topography for M2. The process is outlined in Figs. 1-5. Following M1 lift-off (Fig. 1) a 1.2- micron thick nitride film is deposited. This thickness is equal to that of first metal. This structure is shown in Fig. 2. Next, the nitride film is blanket reactive ion etched (RIE) to produce Fig. 3. CF4-H2 is used as the gas mixture. The etch must be directional in order to produce the desired nitride spacer structure. The etching is stopped either before or at the PSG (Phosphosilicate...