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MATERIALS RESEARCH

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Textures of thin copper films W-M. Kuschke, A. Kretschmann, and R-M. Keller Max-Planck-Institut f¨ur Metallforschung and Institut f¨ur Metallkunde der Universit¨at Stuttgart, Seestr. 71, 70174 Stuttgart, Germany

R. P. Vinci Department of Materials Science and Engineering, Stanford University, Stanford, California 94305-2205

C. Kaufmann TU Chemnitz-Zwickau, Fakult¨at f¨ur Elektrotechnik und Informationstechnik, Zentrum f¨ur Mikrotechnologien, Reichenhainer Str. 70, 09126 Chemnitz, Germany

E. Arzt Max-Planck-Institut f¨ur Metallforschung and Institut f¨ur Metallkunde der Universit¨at Stuttgart, Seestr. 71, 70174 Stuttgart, Germany (Received 27 July 1997; accepted 3 December 1997)

The textures of thin copper films were determined quantitatively by measuring (111) pole figures with x-ray diffraction. Measurements were performed on a variety of samples, differing in copper film thickness and deposition technique, diffusion barrier material, and the presence or absence of a cap layer. Texture changes due to an annealing treatment were also recorded and correlated with stress measurements by the wafer-curvature technique. It is found that the deposition method (PVD vs CVD) has a strong effect on texture, barrier layer effects range from negligible to significant depending on the barrier material, and the effect of a cap layer is insignificant.

I. INTRODUCTION

II. EXPERIMENTAL

The primary interconnect metallizations used in integrated circuits are based on Al alloys. Because of the continuing trend toward miniaturization and the resulting increase in current density, electromigration may become a major failure mechanism for conductor lines. Consequently, much research is in progress, including the development of alternative materials to replace the aluminum-based metallizations. Copper is a potential substitute (e.g., Refs. 1 and 2) because of its high electromigration resistance (e.g., Ref. 3), high thermal conductivity, and low electrical resistivity. Besides other microstructural attributes, texture affects the mechanical and physical properties of thin films. Electromigration resistance of Al-based interconnects correlates with the volume fraction of (111) fiber oriented grains.4–8 Assuming that this is also true for Cu, the texture of copper films is of particular interest. In the present study, pole figure x-ray diffraction was used to investigate the texture of copper films deposited on oxidized silicon wafers, differing in thickness, diffusion barrier material, presence of a cap layer, and deposition technique. Quantitative texture data were determined from fiber texture plots in the as-deposited state and after an annealing treatment. Some samples were further investigated with regard to the texture evolution as a function of the annealing temperature.

A. Samples

2962

http://journals.cambridge.org

J. Mater. Res., Vol. 13, No. 10, Oct 1998

Downloaded: 03 Dec 2014

A variety of sample systems were deposited on (100) oxidized silicon wafers, differing in diffus