Engineered Low Resistivity Titanium-Tantalum Nitride Films by Atomic Layer Deposition
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ENGINEERED LOW RESISTIVITY TITANIUM-TANTALUM NITRIDE FILMS BY ATOMIC LAYER DEPOSITION Ana R. Londergan, Jereld L. Winkler, Kim Vu, Lawrence Matthysse, Thomas E. Seidel and Ofer Sneh Genus Inc., Sunnyvale, CA 94089 ABSTRACT Atomic Layer Deposition (ALD) is an emerging ultra-thin film deposition technique for advanced microelectronics applications. Enabling features of ALD are precise control over film thickness, excellent conformality and relative insensitivity to wafer size. Additionally, ALD allows interface and film engineering that can be utilized to maximize device performance within the minimum feature size requirements. This paper reports on the compositional, structural and electrical properties of engineered Ti-Ta-N composite films grown by ALD at 360oC. For a wide range of composition these Ti-Ta-N films exhibit resistivity from 500 to 2000 µΩ-cm, high density, and 100 % step coverage. Additionally, the ability to control texture by changing film composition is established. Based on experimental results, an approach to grow Composite Engineered Barriers by ALD (CEBA) is described that could provide a solution to the challenging barrier requirements. INTRODUCTION Introduction of new materials and manufacturing technologies is gradually becoming the choice that the semiconductor industry makes as it strives to continue improvement in device performance. In particular, innovative barrier is needed for the emerging copper interconnects, that is a 100% conformal and ultra-thin layer with good diffusion barrier properties and low resistivity [1]. Additionally, it has to provide strong adhesion to both upper and lower interfaces and promote preferred Cu texture. These functions put conflicting requirements on the material properties of the barrier, and thus may be difficult to accomplish by just one film composition. One approach to meet these requirements is to employ barrier films composed of multiple sublayers with tuned properties. An enabling technique for such film engineering is atomic layer deposition (ALD). ALD is realized by alternating self-limited reactions between the molecular precursors and the reactive surface of the growing film [2]. When the reactions are allowed to reach saturation, kinetics factors no longer play a role and the film growth is controlled by thermodynamics. As a result, the material properties, such as structure, composition, and electrical conductivity are dictated by thermodynamics factors, such as temperature and minimization of surface free energy as the film grows. Consequently, the films exhibit the universal benefits of ALD: 100% conformality, high density, exceptional repeatability and thickness control, and moderate sensitivity to wafer size. Additionally, when the substrate surface is appropriately prepared to be reactive with one of the precursors, ALD growth proceeds without nucleation, resulting in sharp interfaces with strong chemical bonding, which is highly desirable for good adhesion and barrier performance. An example where thermodynamics factors promote the for
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