Properties of Tin Thin Films Deposited by ALCVD as Barrier for Cu Metallization
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PROPERTIES OF TiN THIN FILMS DEPOSITED BY ALCVD AS BARRIER FOR CU METALLIZATION Alessandra Satta, Gerald Beyer, Karen Maex1 IMEC, Kapeldreef 75, B-3001 Leuven, Belgium Kai Elers, Suvi Haukka ASM Microchemistry, Kutojantie 2B, P.O. Box 132, FIN-02631 Espoo, Finland A.Vantomme IKS, K. U. Leuven, Celestijnenlaan 200 D, B-3001 Leuven, Belgium 1
Also at E. E. Dept., K. U. Leuven, Belgium
ABSTRACT In advanced multi-level metallization schemes, the application of copper as interconnect metal requires the prevention of Cu diffusion into the active area and into interlevel dielectrics by total encapsulation of Cu with barrier films. Critical requirements for diffusion barriers are very small thicknesses, low resistivity, low deposition temperature and conformality on high aspect ratio trenches and vias. For this application, we have studied TiN films deposited by atomic layer chemical vapour deposition (ALCVD) at 400oC and 350oC. This paper discusses the ALCVD TiN films properties and compares them to the properties of TiN deposited by ionized physical vapour deposition (I-PVD). The ALCVD TiN deposited at 400oC exhibits a resistivity comparable to I-PVD TiN resistivity. However, the ALCVD films deposited at 350oC show higher resistivity. The Cl residue in ALCVD films is 1.5% at 400oC and 3% at 350oC. The microstructure is fine-grained. A very high level of conformality on trenches characterizes the ALCVD TiN films. We believe this property gives a clear advantage over the sputtered I-PVD TiN since its coverage in high aspect ratio trenches and vias is expected to be limited for the future devices interconnection scheme. INTRODUCTION Nowadays copper is accepted as interconnect metal in advanced metallization schemes, because it offers a lower resistivity and a superior electromigration resistance compared to Al and its alloys. The major drawbacks of the Cu metallization are the fast Cu diffusion and drift into interlevel dielectrics. Consequently, in order to benefit from the advantages offered by Cu as an interconnect metal, a high quality and high performance diffusion barrier is necessary. Therefore, the choice of the diffusion material as well as the choice of the deposition technique of the barrier are important key Cu interconnect issues.1 Hence, the need for an alternative deposition technique for metal barriers is progressively increasing. The new deposition technique should ensure several critical properties of the deposited barrier film, like ultra thin and uniform thickness, low resistivity, low deposition temperature, as well as conformality on high aspect ratio trenches and vias, and barrier effectiveness. We propose the atomic layer chemical vapour deposition (ALCVD)2 as a technique to deposit TiN as diffusion barrier for Cu interconnect. Though ALCVD may be considered a special mode
D6.5.1
of a conventional CVD process, the characteristics of the two techniques are substantially different. ALCVD is based on the alternate supply of the precursors and the saturation of each individual surface reaction between
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