AVS 46th International Symposium
    Electronic Materials and Processing Division Tuesday Sessions
       Session EM-TuA

Paper EM-TuA7
Evidence of Aluminum Silicate Formation at the Al@sub2@O@sub3@/Si Interface for Thermal and Plasma Enhanced Chemical Vapor Deposited Al@sub2@O@sub3@ Thin Films

Tuesday, October 26, 1999, 4:00 pm, Room 608

Session: High Dielectric Constant Materials and Thin Oxides
Presenter: D. Niu, North Carolina State University
Authors: D. Niu, North Carolina State University
T.M. Klein, North Carolina State University
G.N. Parsons, North Carolina State University
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An important issue in the determination of a suitable high k gate dielectric for advanced CMOS device is the stability of the material with the Si substrate. An insulator with a covalent nature, a limited number of oxidation states and a resistance to ionic transport would be an attractive candidate for this application. This paper investigates the properties of thin Al@sub2@O@sub3@ films as a possible higher-k (12~15) alternative to SiO@sub2@. The films were formed in a 6" compatible triode plasma reactor which was also used for thermal CVD. A variety of aluminum precursors were studied, including Al acetylacetonate, Al sec-butoxide, and Al isopropoxide. A new liquid precursor, triethyl-dialuminum tri-sec-butoxide was also tested. The new precursor is safe, easy to handle and does not decompose with prolonged heating at 150°C. O@sub2@, N@sub2@O and H@sub2@O were used as oxygen sources in both plasma and low temperature (300-400°C) thermal deposition. In the thermal process, H@sub2@O resulted in deposition rates >10 Å/sec, with Ea=0.16 eV, compared to 0.1 Å/sec and Ea=1.1 eV for O@sub2@ precursor. IV, CV, TEM, ellipsometry and nuclear reaction profiling were used to characterize thin (20-300 Å) Al@sub2@O@sub3@ films on silicon. The films show acceptably low leakage current, 3X10@super-5@ A/cm@super2@ at 1 V for a 5 nm thick film. In some process conditions, clear evidence for mixing of aluminum oxide and silicon is observed in the capacitance measurement, consistent with the optical and structural evaluations. A fit of the capacitance data to a simple model is used to predict the dielectric constant of aluminum silicate layer.