Diffusion of TiN into aluminum films measured by soft x-ray spectroscopy and Rutherford backscattering spectroscopy

Abstract

Understanding the atomic bonding properties at the interface between thin films is crucial to a number of key modern technical devices, including semiconductor integrated circuits, magnetic recording media, batteries, and even solar cells. Semiconducting materials such as titanium nitride (TiNx) are widely used in the manufacturing of modern electronic devices, requiring a wealth of information about its electronic structure. We present data from soft x-ray emission, soft x-ray absorption, and Rutherford backscattering spectroscopy experiments involving a sample consisting of a 40 nm TiN layer on top of an aluminum film 600 nm thick. Soft x-ray emission spectroscopy and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy are tools that provide a nondestructive, atomic site-specific probe of the interface, where the electronic structure of the material can be mapped out element by element. Rutherford backscattering spectroscopy (RBS) measurements supply data on the elemental composition and depth profiling of the sample. From these measurements, we show that the Ti and the N diffuse into the Al film to form an equivalent material depth of about 4.5 nm, and the NEXAF structure reveals that the nitrogen has probably formed AlN, and the Ti has also diffused to form a titanium–aluminum compound.

Chemical Shift of Electron Energy-Loss Near-Edge Structure on the Nitrogen K-Edge and Titanium L3-Edge at TiN/Ti Interface

“…Especially, TiN is widely used as contact electrodes in semiconductor devices (Ouellet et al, 1996; Mao & Hopwood, 2004). To date, many studies to elucidate the interface structure between thin films composed TiN x layers have been performed using not only X-ray diffractometry (Kim et al, 2002; Montes de Oca Valero et al, 2005), X-ray photoelectron spectroscopy (XPS) (Conard et al, 1999; Schuler et al, 2001), and Rutherford backscattering spectroscopy (Schuler et al, 2001) but also high-resolution transmission electron microscopy and energy dispersive spectroscopy (Nam et al, 2001; Kim et al, 2002; Montes de Oca Valero et al, 2005). Because a number of failures in devices are caused by unexpected chemical reactions at interfaces when device dimensions are reduced (Mitsui et al, 2001), it becomes important for failure analysis to obtain information on the chemical bond as well as elemental composition with high spatial resolution.…”

“…To date, many studies to elucidate the interface structure between thin films composed TiN x layers have been performed using not only X-ray diffractometry~Kim et al, 2002;Montes de Oca Valero et al, 2005!, X-ray photoelectron spectroscopy~XPS! Conard et al, 1999;Schuler et al, 2001!, andRutherford backscattering spectroscopy~Schuler et al, 2001! but also high-resolution transmission electron microscopy and energy dispersive spectroscopy~Nam et Kim et al, 2002;Montes de Oca Valero et al, 2005!.…”