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Texture of Sputtered Thin Copper Films on Amorphous SiO2 and Si3N4 substrates. Brando Okolo, Udo Welzel, Peter Lamparter, Thomas Wagner and Eric J. Mittemeijer. Max Planck Institute for Metals Research, Seestrasse 92, Stuttgart D-70174, Germany. ABSTRACT Cu films with thickness of 500nm and 5nm have been sputter deposited on amorphous SiO2 and Si3N4 substrates without and after sputter cleaning. The crystallographic texture has been characterized by x-ray diffraction techniques. Sputter cleaning of the substrates, by which the oxygen contaminants are removed from the Si3N4 substrates, leads to an increase in the {111} texture strength and sharpness of the Cu films on Si3N4. The texture is sharper in the 500nm thick Cu films than in the 5nm thick films. Roughness differences of the substrate surfaces have no obvious effect on the texture state.

INTRODUCTION A substantial amount of investigations has been focussed in recent times on Cu films due to their potential as a viable replacement for Al-based metallisation of substrates [1, 2, 3, 4]. Yet the role of substrates on the texture of Cu films is to be fully understood. Various influences of substrates have been reported, such as their amorphous or crystalline structure [4], roughness [5], surface contaminants and atomic density [4]. In the present study we report on the texture of Cu films on two different amorphous substrates, SiO2/Si and Si3N4/SiO2/Si and its dependence on different substrate sputter cleaning conditions. EXPERIMENTAL 500nm and 5nm thick Cu films were deposited on amorphous Si3N4 and SiO2 substrates in both as-received and sputter cleaned substrate conditions. Sputter cleaning was performed with Ar ions accelerated at 200V, 500V and 1000V for 3 min. Film deposition was carried out in UHV at 100 oC, at a working gas pressure of 4.6 x 10-1 Pa and a base pressure of 4 x 10-8 Pa. The deposition rate was 1.2 nm/s with the sample holder rotating at 100 rpm. The Cu films and a thick powdered Cu sample were investigated by x-ray diffraction (XRD). θ/2θ scans were carried-out in Bragg-Brentano geometry using a PHILIPS MPD diffractometer with Cu Kα1 radiation, while pole figure analyses of the Cu 111 reflection were performed on a PHILIPS MRD diffractometer with Cu Kα radiation. The θ/2θ scan data were fitted by Pseudo-Voigt functions and the extracted intensities were corrected for absorption. The pole figure data were corrected for background, absorption, thickness and intensity loss due to geometric effects [6]. Auger Electron Spectroscopy of the as-received and sputter cleaned substrates was conducted in the sputter deposition chamber without breaking the vacuum using a double-pass cylindrical mirror analyzer (Perkin-Elmer, 15-255G) at 3 keV. The roughness of the substrates was determined by AFM using a Digital Instruments AFM device operating in the tapping mode. A scan area of 10µm x 10µm, being representative of the specimens, was adopted.

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RESULTS AND DISCUSSION Texture characterization by XRD Figure 1 depicts the θ/2θ scans for 500nm thick