Structures of ultra-thin atomic-layer-deposited TaNx films

Abstract

Atomic layer deposition ͑ALD͒ is an attractive technique in fabrication of microelectronics presently and in the future, for its accurate thickness control in atomic scale, excellent conformality, and uniformity over large areas at low temperature. It has been adapted and used in deposition of ultrathin TaN x films as diffusion barriers for Cu metallization. In this study, composition, structure, and stability of ultra-thin ͑1.5-10 nm͒ atomic layer deposited films are characterized by a set of complementary analytical techniques. The results indicate that the N to Ta atomic concentration ratio in the ALD TaN x films is approximately 2, independent of the film thickness and annealing up to 750°C. Hydrogen, oxygen, and carbon are detected as impurities within the as-deposited films. The as-deposited ALD TaN x films have an fcc NaCl-type nanocrystalline structure even when the film thickness is 1.5 nm. Following thermal anneal at 600°C and higher, the films do not undergo a structural change except for an increase in grain size and a decrease in the lattice constant. X-ray photoelectron spectra results indicate that all the Ta atoms in the films are bonded ionically with the surrounding N atoms. An ex situ thermal treatment at 600°C for 1 h removes the O, which penetrated the layers, by a reduction reaction with the residual H and results in densification of the ALD films. Our analysis of the experimental results indicates that the excess of N atoms of the ALD TaN x films is mainly due to Ta vacancies in the fcc NaCl-type structure. The structural and compositional characteristics of the films explain why the films serve as good diffusion barriers to Cu metallization.

Synthesis and in situ characterization of low-resistivity TaNx films by remote plasma atomic layer deposition

“…42 For several thermal ALD processes of Ta 3 N 5 films reported in the literature, the amorphous crystal structure was also observed. 4,9,20,43 It is obvious from aforementioned results that ͑a small fraction of͒ N-containing plasmas FIG. 6.…”

Direct measurement of the nitrogen content by XPS in self‐passivated TaNx thin films

“…[1] However, below a thickness of 10 nm, they are nearly amorphous and correspond to several superimposed cristallographic states in the [30][31][32][33][34][35][36][37][38][39][40] • range. [1] The X-ray diffraction (XRD) data cannot be used to evaluate the nitrogen content in TaN x thin films with a thickness below 10 nm.…”

Study on microstructural, chemical and electrical properties of tantalum nitride thin films deposited by reactive direct current magnetron sputtering

“…This peak shift indicates the transition from a metallic to a nitridic binding state (Wang et al 2003). According to Wu et al (2004) who analysed tantalum nitride thin films with XPS, the energies for metallic binding are 21.9 eV (5f 7/2) and 24 eV (5f 5/2), whereas for hexagonal closest packed TaN in powder form values of 22.9 eV (5f 7/2) and 25 eV (5f 5/2) are determined.…”

“…Typically, they are used for resistors because of their excellent long term stability (Abdin and Val 1979;Lovejoy et al 1996) and as diffusion barriers in copper based conductor lines for microelectronic applications (Chang et al 2004;Wieser et al 2002;Chen et al 1999). For the synthetization of TaN x films reactive sputter deposition is a standard, but the successful application of other techniques like chemical vapour deposition (CVD) (Hieber 1974), atomic layer deposition (ALD) (Wu et al 2004) and ion beam assisted deposition (IBAD) (Wei and Shieh 2006;Baba and Hatada 1996) is also reported in literature. To obtain TaN x films with tailored film properties, however, one of the most challenges is to control the implementation of nitrogen into the growing film, thus strongly influencing the phase composition, the microstructure as well as electrical and chemical material parameters.…”