In-situ monitoring of nucleation stage during aluminum-CVD for nano-structure control
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In-situ monitoring of nucleation stage during aluminum-CVD for nano-structure control T. Iino , M. Sugiyama1 and Y. Shimogaki Department of Materials Engineering, University of Tokyo 1 Department of Chemical System Engineering, University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan TEL&FAX:+81-3-5841-7131 E-mail: [email protected] ABSTRACT Initial nucleation of Al in chemical vapor deposition (CVD) using dimethyl-aluminumhydride was observed in order to obtain a principle for enhancing the nucleation density. The analysis employed in situ surface reflectivity measurement combined with X-ray photoelectron spectroscopy and scanning electron microscopy at the typical stage of reflectivity behavior. During the incubation period between the injection of DMAH and the nucleation of Al, a constant amount of Al existed on the surface while no nuclei was observed. The precursor of the nuclei seemed not DMAH itself but the reaction product of the adsorbed DMAH. The activation energy for reciprocal of the incubation period, which may be an index of the reaction rate of the adsorbed layer, is slightly larger than for the continuous growth of Al. INTRODUCTION As the feature scale of the interconnets in integrated circuits continues to shrink, filling narrow holes and trenches becomes more significant. Complete filling of narrow structures require the formation of thinnest possible continuous film with smooth surface. Filling holes with 100 nm of diameter will require a smooth continuous film of 30 nm in thickness. High nucleation density will certainly be a solution: smooth film with 30-nm thickness will require the nucleation density of 1011 cm-2. For Al films formed by chemical vapor deposition (CVD), which is a promising candidate for fabricating the all-aluminum dual damascene structures, such a thin continuous film have been a challenge. The nucleation density of Al is reported to depend on the nature of underlying TiN [1,2]. Deposition conditions such as precursor concentration and temperature should also affect the nucleation density. In this work, initial nucleation stage of CVD-Al was investigated in order to elucidate the mechanism of nucleation and improve the nucleation density of Al. In situ surface reflectivity measurement [3,4] for probing the roughness of the surface was combined with the X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The condition with slow deposition rate was intentionally selected in order to closely observe the surface during the initial nucleation stage. Based on the observation, referring to the reaction model for continuous growth of Al [5], a phenomenological model for the nucleation of CVD-Al will be discussed. P5.2.1
EXPERIMENTAL Figure 1 shows the cold-wall CVD reactor with load-lock chamber employed in this work. The surface roughening of aluminum was monitored in situ using the laser light reflectivity measurement. The wavelength of the laser light was 670 nm. The angle of incident and reflection were 45 °. The reflectivity was me
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