Adhesion of Cu and low-k dielectric thin films with tungsten carbide
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K. Kershen, J. Bennett, and K. Pfeifer International Sematech, 2706 Montopolis Drive, Austin, Texas 78714
Y-M. Sun and J.M. White Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712
J.G. Ekerdta) Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712 (Received 31 May 2001; accepted 11 March 2002)
The adhesion of copper and various dielectric materials to tungsten carbide was studied using interfacial critical debond energies obtained by the four-point flexure method. Tungsten carbide (W2C), films 33.3 nm thick, were vapor deposited onto SiO2, spin-on carbon polymer resin (CPR), chemically vapor deposited organosilicate glass (OSG), and spin-on siloxane-organic polymer (SOP) surfaces using direct-current magnetron sputtering of a W metal target and a methane substrate plasma. Thick copper films (42.5 nm) were vapor deposited onto W2C. Some interfaces were modified by an Ar plasma, 1-nm W deposition, or O2 plasma treatment prior to Cu deposition. A W2C film deposited onto a CPR substrate was annealed for 2 h at 673 K in a 99% N2/1% H2 gas mixture. For the untreated dielectric surfaces, the debond energy ranged from 39.9 to 3.95 J/m2. In order of descending adhesion energy, the substrates are ranked CPR, SiO2, SOP, and OSG. Ar plasma treatment of the SiO2 surface increased the debond energy from 20.3 to 41.3 J/m2. The Cu/W2C debond energy was 20.4 J/m2. Ar plasma or 1-nm W deposition treatment to the carbide surface moved the point of delamination from the Cu/W2C interface to the W2C/CPR interface for a Cu/W2C/CPR multilayer structure.
I. INTRODUCTION
Adhesion between thin films within semiconductor devices is critical to successful device performance. New materials are being developed to increase device and integrated circuit performance such as high and low dielectric constant insulators, new contact metals, and diffusion barrier films. Metal diffusion barriers present interesting challenges since they should ideally react with neither the metal nor the dielectric and still have good adhesion with both. Transition metal carbides are currently being researched for the diffusion barrier in copper damascene metallization structures. In parallel, new low dielectric constant materials (to be further referred to as “low-k”) are under investigation for use as the insulating material. It is imperative in selecting the optimum copper/barrier/ a)
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J. Mater. Res., Vol. 17, No. 6, Jun 2002 Downloaded: 16 Mar 2015
low-k structure for future devices that adhesion be characterized at the two barrier layer interfaces. Of further importance is the efficacy of surface treatments, such as plasma exposure and the deposition of interlayers, which are commonly used to affect the properties of films in semiconductor device structures. Oftentimes, the goal of surface treatments is to promote adhesion. Quantitative evaluation of these treatments
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