Physical Properties and Diffusion Characteristics of CVD-Grown TiSiN Films
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PHYSICAL PROPERTIES AND DIFFUSION CHARACTERISTICS OF CVD-GROWN TiSiN FILMS Dalaver Anjum, Katharine Dovidenko, Serge Oktyabrsky, Eric Eisenbraun, Alain E. Kaloyeros UAlbany Institute for Materials and School of Nanosciences and Engineering, University at Albany-SUNY, Albany, 12222 ABSTRACT TiSiN films grown by chemical vapor deposition were characterized to evaluate the properties relevant to the application as a diffusion barrier in Cu-based interconnects. The films were grown using TiI4 + SiI4 + NH3 + H2 chemistry at substrate temperature, 370 °C, and SiI4 to-TiI4 precursor flow rate ratio of 30. The combined results from x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) revealed that the bulk of Ti32Si21N42 films were predominantly consisted of a mixture of cubic TiN and amorphous SiNx phases. The specific electrical resistivity of the films was about 2000 µΩ-cm which is a few times higher than that of sputtered TiSiN films having similar composition and thicknesses. The 40 nm-thick barrier appeared to be thermally stable against Cu diffusion at the annealing temperatures up to 550 °C. Breakdown of this diffusion barrier occurred at 600 °C and was accompanied by the formation of Cu3Si protrusions at the TiSiN/Si interface. INTRODUCTION The continuing demand to improve the performance of integrated circuits (IC) has lead to the need to replace aluminum with an interconnect material which has better electrical properties. The new interconnect material being used in IC manufacturing is copper (Cu) due to its better electrical properties as well as better electromigration resistance [1]. Unfortunately, the interaction between silicon (Si) or interlevel dielectrics (ILD) and Cu is strong and detrimental to the performance of Si-based ICs even at temperatures below 200 °C [2]. Thus, it is necessary to implement a diffusion barrier layer between Si or ILD and Cu. Titanium nitride (TiN) is one of the most widely used barrier materials in both Cu and Al-based metallization [3]. However, it is suggested that the Cu diffusion proceed primarily through the grain boundaries in TiN [4], which will create a stability problem in the next generations of ICs with reduced feature size. To eliminate the grain boundary diffusion, several groups have investigated amorphous or nanocrystalline materials for diffusion barriers [5-6]. One of the most promising materials for microelectronics is titanium-silicon-nitride. Excellent barrier properties have been demonstrated for sputtered TiSiN [5]. However, the poor step coverage of the sputtering process remains an obstacle to application of these films in ultralarge scale integrated (ULSI) devices. Chemical vapor deposition (CVD) technique is widely used to deposit more conformal barrier films on aggressive structures. In this work, we report on the material properties and diffusion characteristics of CVD-grown TiSiN films. EXPERIMENTAL METHODS Depositions of the TiSiN films were performed in a custom-designed 8” warm wall CVD reactor. Both solid precursors (
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