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Seedless Superfill: Copper Electrodeposition in Trenches with Ruthenium Barriers

IP.com Disclosure Number: IPCOM000125630D
Original Publication Date: 2003-Aug-04
Included in the Prior Art Database: 2005-Jun-09
Document File: 3 page(s) / 318K

Publishing Venue

National Institute of Standards and Technology

Related People

Daniel Josell: INVENTOR [+4]

Abstract

The successful application of copper electrodeposition in the synthesis of low resistivity interconnect metallization is due to the ability to achieve void and seam-free filling of submicrometer features. This is accomplished through the superconformal bottom-to-top filling process called "superfill" caused by the impact of area change on local coverage of a rate-enhancing heterogeneous catalyst. 1-4 The success of the superconformal portion of the feature filling process makes fabrication of copper seed layers the bottleneck for further increases of aspect ratio and decrease of feature size. Usually, the copper seed layers are deposited on the diffusion barriers, generally TiN or Ta, that prevent reactions between the conductor and the surrounding dielectric. In the optimized conventional process, the surface oxide on the copper seed is removed during immersion into the electrolyte and there is an insignificant barrier to nucleation during subsequent copper electrodeposition. The copper seed layer also improves wafer length scale current distribution during plating.

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Electrochemical and Solid-State Letters, 6 ~10! C143-C145 ~2003!

0013-4651/2003/6~10!/C143/3/$7.00 © The Electrochemical Society, Inc.

C143

Seedless Superfill: Copper Electrodeposition in Trenches with Ruthenium Barriers

D. Josell,a D. Wheeler,a C. Witt,b and T. P. Moffata,*,z

aNational Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA

           bInternational Sematech, Austin, Texas 78741, USA Superfilling of fine trenches by direct copper electrodeposition onto a ruthenium barrier is demonstrated. The ruthenium layer, as well as an adhesion promoting titanium or tantalum layer, was deposited by physical vapor deposition onto patterned silicon dioxide. Copper was deposited from an electrolyte previously shown to yield superconformal feature filling on copper seeded features. The single-step deposition process offers significant processing advantages over conventional damascene processing. © 2003 The Electrochemical Society. @DOI: 10.1149/1.1605271# All rights reserved.

Manuscript submitted April 23, 2003; revised manuscript received June 5, 2003. Available electronically August 4, 2003.

  The successful application of copper electrodeposition in the synthesis of low resistivity interconnect metallization is due to the ability to achieve void and seam-free filling of submicrometer fea- tures. This is accomplished through the superconformal bottom-to- top filling process called ''superfill'' caused by the impact of area change on local coverage of a rate-enhancing heterogeneous catalyst.1-4 The success of the superconformal portion of the feature filling process makes fabrication of copper seed layers the bottle- neck for further increases of aspect ratio and decrease of feature size. Usually, the copper seed layers are deposited on the diffusion barriers, generally TiN or Ta, that prevent reactions between the conductor and the surrounding dielectric. In the optimized conven- tional process, the surface oxide on the copper seed is removed during immersion into the electrolyte and there is an insignificant barrier to nucleation during subsequent copper electrodeposition. The copper seed layer also improves wafer length scale current dis- tribution during plating.

  Sputter deposition of copper seed layers is widespread in the current implementation of damascene processing. However, it pro- vides poor step coverage in high-aspect-ratio features, as is typical of line-of-sight, physical vapor deposition processes. For this reason other approaches have been tried for growing copper seed layers, including chemical vapor,5 ionized physical vapor,6 and electroless7,8 deposition as well as combinations of the above.9 Seeds fabricated by these processes have their own drawbacks ôr limitations!. These include surface roughness and selectivity for electroless processes and poor adhesion for chemical vapor deposi- tion processes. Significant effort is being expended on barrier modi- fication to promote adhesion and wettability10 as w...