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Deposit and Etch Technique for Making Smooth, Low Resistivity Tungsten Films

IP.com Disclosure Number: IPCOM000037942D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Cronin, JE: AUTHOR

Abstract

By means of an alternating deposition and etching process, tungsten (W) films are created which are much less rough than those films created by conventional continuous chemical vapor deposition (CVD) techniques. The process is performed in situ by programming the tool controller to provide several deposition- and-etch cycles during the formation of a tungsten film. The film exhibits the low resistivity properties of conventionally deposited CVD W films.

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Deposit and Etch Technique for Making Smooth, Low Resistivity Tungsten Films

By means of an alternating deposition and etching process, tungsten (W) films are created which are much less rough than those films created by conventional continuous chemical vapor deposition (CVD) techniques. The process is performed in situ by programming the tool controller to provide several deposition- and-etch cycles during the formation of a tungsten film. The film exhibits the low resistivity properties of conventionally deposited CVD W films.

CVD W films, having no more than twice the bulk resistivity, are usually comprised of large, columnar W grains. The surface topography of such films is defined by projections of the tops of these grains. About 20% of the total film thickness lies above the point at which the grains are joined laterally. This topography creates difficulty in photo processing and in etching to form high density, very narrow lines. The unjoined, projecting tops of the grains also contribute little to the conductivity of the lines.

By interrupting the CVD process early in the deposition and performing a radio frequency (RF) etch with Nitrogen Trifluoride (NF3) gas in an isotropic etch mode, the grain projections can be removed. Upon resuming deposition, new grains are nucleated and, although the columnar structure again begins to form, the surface topography is much less rough than had the deposition been continued without interruption. It has been found that...