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A Metal Fill Process

IP.com Disclosure Number: IPCOM000020344D
Original Publication Date: 2003-Nov-14
Included in the Prior Art Database: 2003-Nov-14
Document File: 3 page(s) / 209K

Publishing Venue

Motorola

Related People

Olubunmi O. Adetutu: AUTHOR [+4]

Abstract

Rationale: Future CMOS require contact via/plug aspect ratio to decrease with increasing technology generation. For contact fill, the metal of choice has been and remains CVD tungsten from tungsten hexafluoride (WF6) for a variety of reasons. Due to the poor adhesion of CVD W on most dielectrics a glue (adhesion) layer with low contact resistance properties such as titanium is required. In addition, since the flourine from the W will attack titanium to form titanium flouride, a layer of diffusion barrier such as TiN is required. Thus, 3 films namely: titanium, titanium nitride and tungsten are required to fill the contact plugs. As the contact aspect ratio become aggressive, problems such as poor step coverage, "bread-loafing" and voids in the plug(coring) become apparent. Both the Ti and TiN film thicknesses have been reduced drastically in order to fill the plugs void-free. There is therefore a great need for a contact fill process with low defectivity and coring.

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A Metal Fill Process

Olubunmi O. Adetutu, Elsie D. Banks, Donald Arugu and Yolanda Musgrove


A Metal Fill Process

Rationale: Future CMOS require contact via/plug aspect ratio to decrease with increasing technology generation. For contact fill, the metal of choice has been and remains CVD tungsten from tungsten hexafluoride (WF6) for a variety of reasons. Due to the poor adhesion of CVD W on most dielectrics a glue (adhesion) layer with low contact resistance properties such as titanium is required. In addition, since the flourine from the W will attack titanium to form titanium flouride, a layer of diffusion barrier such as TiN is required. Thus, 3 films namely: titanium, titanium nitride and tungsten are required to fill the contact plugs. As the contact aspect ratio become aggressive, problems such as poor step coverage, "bread-loafing" and voids in the plug(coring) become apparent. Both the Ti and TiN film thicknesses have been reduced drastically in order to fill the plugs void-free. There is therefore a great need for a contact fill process with low defectivity and coring.

Proposal: We propose using a deposition-etch process for the tungsten fill. Typically, after the glue layers have been deposited, a tungsten nucleation layer is deposited from WF6 and SiH4 with or without hydrogen. This, is then followed by a via fill process formed from WF6 and H2.

We propose the following:

1) Deposit a the via fill process and interrupt this process before the contact opening is clos...