Copper Chemical Vapor Deposition using a Novel Cu(II) Precursor for Contact Via Filling Process
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0990-B08-27
Copper Chemical Vapor Deposition using a Novel Cu(II) Precursor for Contact Via Filling Process Hideaki Zama, Yuuji Nishimura, Michiyo Yago, and Mikio Watanabe Institute for Semiconductor Technologies, ULVAC,Inc., 1220-1 Suyama, Susono, Shizuoka, 410-1231, Japan
ABSTRACT Chemical vapor deposition (CVD) of copper using both a novel Cu(II) β-diketonate source and hydrogen reduction process was studied to fill contact vias with the smallest diameter in the 32nm and more advanced generation chip. Pure Cu films were grown under the condition with the product of hydrogen partial pressure and H2/Cu source molar ratio being over 1,000,000. We succeeded in filling the 40-nm-diameter contact vias by optimizing the growth condition of the Cu-CVD in both substrate temperatures and reaction pressures.
INTRODUCTION Chemical vapor deposition (CVD) of copper is a promising method for ULSI interconnect technology. In general, the CVD precursors are metallorganic Cu compounds, the most favored being ligand-stabilized Cu(I) and Cu(II) β-diketonates. In particular, Cu(I) β- diketonates, mainly Cu(hfac)TMVS[1-3], have been frequently used, being liquid at room temperature and showing high vapor pressure and low decomposition temperature. On the otherhand, there had been basic works that Cu(II) β-diketonates, e.g., Cu(hfac)2[4], were applied before the development of Cu(hfac)TMVS. The properties of the Cu(II) β-diketonates are not enough to grow Cu films on practical wafers. Because most Cu(II) β-diketonate is solid at room temperature and has lower vapor pressure and higher decomposition temperature than Cu(hfac)TMVS. The disproportionation reaction from Cu(hfac)TMVS to Cu has a few problems as follows; (i) It is difficult to occur the reaction on metal surfaces except Cu. (ii) The reaction synthesizes Cu(hfac)2 as a by-product, which is the bigger size molecule and has the lower vapor pressure than Cu(hfac)TMVS. The problem (ii) is serious to be application to fine contact vias, because it is difficult to desorb the by-product from the bottom of those. In this paper, we report on the development of the Cu-CVD using a new Cu(II) β-diketonate as a Cu source and hydrogen as a reducing agent. We expect to improve the stepcoverage by optimizing substrate temperature and reaction pressure and realize the filling process for fine contact vias in 32nm and more advanced generation chips.
EXPERIMENTAL DETAILS Our experimental setup is a typical system of thermal CVD for 8-inch wafer equipped with a liquid delivery system, a gas shower plate, a ceramic substrate heater, and a dry-sealed vacuum
pump. The Cu source is a novel Cu(II) β-diketonate, Cu(sopd)2 (=C24H46CuO6Si2), with lower melting point and lower decomposition temperature than the conventional one. It is solid at room temperature and is dissolved in n-octane. The gaseous source is supplied by a vaporizer in the liquid delivery system. The Cu film was deposited on a vanadium nitride (VN) glue layer grown from a vanadium-amido source by the thermal CVD. The substrate tem
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