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27 Oct 2003

Volume 83, Issue 17, pp. 3447-3628

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 3453 (2003); http://dx.doi.org/10.1063/1.1622431 (3 pages)

Giacomo Scalari, Stéphane Blaser, Lassaad Ajili, Jérôme Faist, Harvey Beere, Edmund Linfield, David Ritchie, and Giles Davies
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Characteristics of LaAlO3 gate dielectrics on Si grown by metalorganic chemical vapor deposition

Ai-Dong Li, Qi-Yue Shao, Hui-Qin Ling, Jin-Bo Cheng, Di Wu, Zhi-Guo Liu, Nai-Ben Ming, Cathy Wang, Hong-Wei Zhou, and Bich-Yen Nguyen

Appl. Phys. Lett. 83, 3540 (2003); http://dx.doi.org/10.1063/1.1622794 (3 pages) | Cited 27 times

Online Publication Date: 20 October 2003

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Amorphous LaAlO3 (LAO) gate dielectric thin films have been deposited on Si substrates using La(dpm)3 and Al(acac)3 sources by low-pressure metalorganic chemical vapor deposition. The growth mechanism, interfacial structure, and electrical properties have been investigated by various techniques. The ultrathin films show smaller roughness of ∼0.3 nm, larger band gap of 6.47 eV, and good thermal stability. The growth follows a chemical dynamic control mechanism. High-resolution transmission electron microscopy confirms there exists no interfacial layer, or only thinner ones, between LAO and Si. X-ray photoelectron spectroscopy analyses reveal that the thinner interfacial layer is compositionally graded La–Al–Si–O silicate and Al element is deficient in the interfacial layer. The reliable value of equivalent oxide thickness around 1.2 nm of LAO/Si has been achieved. © 2003 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
68.35.Ct Interface structure and roughness
68.60.Dv Thermal stability; thermal effects
73.61.Ng Insulators
68.37.Lp Transmission electron microscopy (TEM)
79.60.Jv Interfaces; heterostructures; nanostructures
71.20.Ps Other inorganic compounds

Carbonate formation during post-deposition ambient exposure of high-k dielectrics

Theodosia Gougousi, Dong Niu, Robert W. Ashcraft, and Gregory N. Parsons

Appl. Phys. Lett. 83, 3543 (2003); http://dx.doi.org/10.1063/1.1623316 (3 pages) | Cited 20 times

Online Publication Date: 20 October 2003

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When thick films of group-III (La, Y)- and group-IV (Hf, Zr)-based high-k dielectrics are exposed to ambient for several months, Fourier transform infrared spectroscopy shows formation of carbonate species in the film bulk, likely due to reaction with atmospheric CO2. Group-III-based films show signs of carbonate feature growth within 10 min of air exposure, especially in films processed at relatively low temperatures (<600 °C). Carbonate formation is verified also for group-IV-based films, but at a significantly reduced concentration. Post-exposure annealing can reduce the carbonate observed in the IR spectra. However, post-exposure annealing likely does not remove carbon contamination, and it results in interface silicon oxide growth. The observed reactions of high-k films with the ambient may impose significant constraints on the post-deposition handling of high-k films. © 2003 American Institute of Physics.
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77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
78.66.Nk Insulators
78.30.Hv Other nonmetallic inorganics
68.35.Dv Composition, segregation; defects and impurities
61.72.Cc Kinetics of defect formation and annealing

La–silicate gate dielectrics fabricated by solid phase reaction between La metal and SiO2 underlayers

Heiji Watanabe, Nobuyuki Ikarashi, and Fuminori Ito

Appl. Phys. Lett. 83, 3546 (2003); http://dx.doi.org/10.1063/1.1622107 (3 pages) | Cited 23 times

Online Publication Date: 20 October 2003

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La-based high-k gate dielectrics were fabricated by reoxidation of thin La layers deposited on SiO2 underlayers. Interface reaction that causes metal diffusion through the oxide underlayer increases permittivity of the oxide and forms high-quality La–silicate films. We successfully fabricated ultrathin La–silicates of equivalent oxide thickness ranging from 0.75 to 1.6 nm with low-leakage current by controlling the interface solid phase reaction. We characterized degradation in the silicate film caused by electrical stressing and demonstrated the effectiveness of high-temperature annealing to improve the reliability of silicate dielectrics. Moreover, it was found that water absorption during exposure to air causes positive fixed charge in the silicate (flatband voltage shift), but degradation can be annealed out at relatively low temperatures. © 2003 American Institute of Physics.
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77.55.-g Dielectric thin films
77.22.Ch Permittivity (dielectric function)
61.72.Cc Kinetics of defect formation and annealing
68.35.Fx Diffusion; interface formation
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