Characterization of Atomic Layer DepositedWN x C y Thin Film as a Diffusion Barrier for CopperMetallization
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E10.9.1
Characterization of Atomic Layer Deposited WNxCy Thin Film as a Diffusion Barrier for Copper Metallization Soo-Hyun Kim, Su Suk Oh, Hyun-Mi Kim, Dae-Hwan Kang1, Ki-Bum Kim, Wei-Min Li2, Suvi Haukka2, and Marko Tuominen2 School of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea 1 Research Institute of Advanced Materials, Seoul National University, Seoul 151-742, Korea 2 ASM Microchemisty Ltd., FIN-02631 Espoo, Finland ABSTRACT The film properties of WNxCy films deposited by atomic layer deposition (ALD) using WF6, NH3, and triethylboron source gases were characterized as diffusion barrier for Cu metallization. It is noted that the as-deposited film shows an extremely low resistivity of about 350 µΩ-cm with a film density of 15.37 g/cm3. The film composition measured from Rutherford backscattering spectrometry shows W, C, and N of approximately 48, 32, and 20 at.%, respectively. Transmission electron microscopy analyses show that the as-deposited film is composed of face-centered-cubic phase with a lattice parameter similar to both β-WC1-x and βW2N with an equiaxed microstructure. The barrier property of this ALD-WNxCy film at a nominal thickness of 12 nm deposited between Cu and Si fails only after annealing at 700 oC for 30 minutes while the sputter-deposited Ta (12 nm) and ALD-TiN (20 nm) fail at 650 and 600 oC, respectively. It is thought that the superior diffusion barrier performance of ALD-WNxCy/ film is the consequence of both nanocrystalline equiaxed grain structure and the formation of high density film. INTRODUCTION Atomic layer deposition (ALD) is being increasingly used to deposit extremely thin films used in semiconductor devices. Since this process is mainly relying on a chemisorption and surface reaction by the sequential delivery of source gases, this technique has the advantages of depositing uniform thin film layer with controlled stoichiometry and an extremely conformal film [1, 2]. Because of these advantages, ALD process is being considered as a promising process technique to deposit future generations of barrier layers, gate dielectrics, and high-k dielectrics. Still, however, it is not clear whether the films deposited by ALD process will meet the film qualities of each application as compared to those deposited by other film deposition techniques. One major application of ALD process is the diffusion barrier layer since this layer requires a conformal deposition down to less than 5 nm in thickness. In this reason, many transition metal nitrides have been deposited by ALD process in order to develop a suitable diffusion barrier for Cu metallization [3-13]. For instance, ALD-TiN film with low resistivity (~200 µΩ-cm), extremely good step coverage, and low Cl content (< 2 at.%) could be obtained by ALD process [5]. However, the use of TiCl4 and NH3 is known to bring about the Cu pitting when TiN film is deposited directly on Cu surface as a result of Cl-containing by-product [5]. In addition, the barrier properties of this TiN film are not good enough d
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