Chemical Routes to Ultra Thin Films for Copper Barriers and Liners
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Chemical Routes to Ultra Thin Films for Copper Barriers and Liners John Ekerdt1, Jinhong Shin1, Wyatt Winkenwerder1, Hyun-Woo Kim1, Kelly Thom1, Gyeong S Hwang1, Kyriacos Agapiou2, and Richard A Jones2 1 Chemical Engineering, University of Texas at Austin, 1 University Station, C0400, University of Texas at Austin, Austin, TX, 78750 2 Chemistry and Biochemistry, University of Texas at Austin, 1 University Station, A5300, University of Texas at Austin, Austin, TX, 78750 EXTENDED ABSTRACT Ruthenium shows considerable potential as a seed layer and adhesion layer in advanced metallization schemes and may also function, alone or in concert with an under layer, as a copper diffusion barrier. Microstructure and thickness uniformity are key film parameters. This talk describes the use of alloying constituents to force the growth of amorphous ruthenium films and to stabilize the amorphous films that are grown, and describes the surface chemistry that controls film growth on amorphous and polycrystalline substrates. In general, Ru films are polycrystalline because of Ruís high surface energy, which results in a 3D, Volmer-Weber growth mode. Extending insight into amorphous structure gained from the bulk metallic glass literature one can anticipate that Ru will form various coordination polyhedra with metalloids, such as boron and phosphorus. Provided these polyhedra form during atomic layer deposition or chemical vapor deposition, an amorphous thin film should grow. This talk presents the growth and stability of amorphous Ru-P alloy films through the use of single source precursors, such as cis-ruthenium(II)dihydridotetrakis-(trimethylphosphine), cis-RuH2(PMe3)4 [1] and dual sources such as Ru3(CO)12 and P(C6H5)3 or PMe3 [2]. The films contain zero-valent Ru and P. Ab initio molecular dynamics calculations show that Ru-P alloys with moderate P content (~20%) can result in a glassy structure exhibiting topological and strong chemical short-range order. In the Ru80P20 structure, the P-centered polyhedra prefer the tri-capped trigonal prism packing phase with Veronoi index [1]. In addition, the Ru-P system shows the medium-range order arising from packing the ìquasi-equivalentî P-centered Ru clusters in three-dimensional space. The structural model based on melt-quenching simulations support the experimental results that find ~ 13-15 % P is required to produce an amorphous film. Surface studies suggest the trimethylphosphine ligands from cis-RuH2(PMe3)4 undergo demethylation and desorb at the growth conditions and readsorb, and subsequently incorporate the P into the Ru film [1]. These studies led to an exploration of dual sources, Ru3(CO)12 for Ru and P(CH3)3 for P that reinforced the results that about 15% P is required to form the amorphous microstructure. Carbon levels are difficult to establish with Ru and high resolution X-ray photoelectron spectroscopy studies with a monochromatic source and fitting routines that lead to zero percent carbon in a Ru standard, result in the C levels in listed Table 1. Film prop
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