Integration of ALD-TaN Liners on Nanoporous Dielectrics
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Integration of ALD-TaN Liners on Nanoporous Dielectrics Bum Ki Moon,(a),* Tadashi Iijima,(b) Sandra Malhotra,(c) Andrew Simon,(c) Thomas Shaw,(c) E. Todd Ryan,(d) Cathy Labelle,(d) Nick Fuller,(c) Tibor Bolom,(d) Derren Dunn,(c) Philip Flaitz,(c) Sanjay Mehta,(c) Keishi Inoue,(e) and Vincent McGahay (c) 2070 Route 52, Zip 32A, Hopewell Junction, NY 12533, USA, (a)Infineon Technologies NA, Corp., (b)Toshiba America Electronic Components, Inc., (c)IBM Microelectronics, (d)AMD Corp., (e) Sony Electronics Inc. *e-mail: [email protected] ABSTRACT Ultra-thin ALD-TaN/PVD-Ta liners have been developed to prevent Cu diffusion into porous interlayer dielectric (ILD) materials envisioned for future copper interconnections. The porous ultra-low k (p-ULK) film is prepared using the spin-on method, and typical k-value and the average pore size of p-ULK used in this paper are 2.3 and 2-3 nm, respectively. Interaction and phenomena at the ILD/ALD-TaN interface have been investigated, and the electrical measurements of samples with a bi-layered ALD-TaN/PVD-Ta barrier were performed after completing the metallization and CMP process. A deep penetration of ALD-TaN was observed on the as-deposited p-ULK, which is due to the interconnected pore structures. However, the surface of the p-ULK is drastically changed after the etch process, where changes are attributed to plasma damage and re-deposition of etched species. Pores can therefore be sealed during the etch process. Furthermore, the plasma damage makes the sidewall more hydrophilic, which may promote the growth of ALD-TaN layer. Based on EELS and EDS profiles, there is no signature of TaN penetration into the etched p-ULK at M1 level with a sharp Ta peak, which indicates excellent stability of ultra-thin ALD-TaN liner. An oxidation test in air ambient and at elevated temperature confirmed the barrier properties of the stacked ALD-TaN/PVD-Ta layers. Any weak point in the barrier allows the Cu to oxidize and to make a color change under an optical microscope. However, all of our samples showed no color change, which implies that the barrier is very uniform and stable. Electrical properties measured at M1 showed excellent results. Our results demonstrate the ability to successfully integrate ALD-TaN barriers with a nanoporous ULK film. INTRODUCTION To enable future Cu interconnection technologies, RC (resistance-capacitance) reduction is essential [1]. There are several ways to reduce RC values, i. e., (1) thinning Cu barrier thickness, (2) reducing the k (dielectric coefficient) value of interlayer dielectric (ILD) material, (3) Cu grain size control, (4) damage repair, and (5) device design optimization, etc. In recent years, the development of thinner Cu barriers has been reported [2 – 4], which were prepared using PVD (physical vapor deposition), CVD (chemical vapor deposition) or ALD (atomic layer deposition). Compared to other techniques, ALD provides excellent step-coverage, uniformity and composition control on the atomic level. Also, it shows a wider process wi
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