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10 Jun 2002

Volume 80, Issue 23, pp. 4291-4461

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Electrical and physical characteristics of ultrathin hafnium silicate films with polycrystalline silicon and TaN gates

S. Gopalan, K. Onishi, R. Nieh, C. S. Kang, R. Choi, H.-J. Cho, S. Krishnan, and J. C. Lee

Appl. Phys. Lett. 80, 4416 (2002); http://dx.doi.org/10.1063/1.1485123 (3 pages) | Cited 31 times

Online Publication Date: 31 May 2002

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Metal-oxide-semiconductor transistors of ultrathin hafnium silicate films (equivalent oxide thickness (EOT) of 12.5–14 Å) with polycrystalline silicon and metal (TaN) gates have been demonstrated. Well-behaved transistor characteristics and EOT stability of Hf silicate with n+ polysilicon indicates good compatibility with polysilicon gate process without use of barrier layer. Transmission electron microscopy analysis indicates that the films have no top interfacial layer with both TaN and polysilicon gates. The films also remain amorphous and show no indication of phase separation even after a 950 °C dopant activation anneal. Hf silicate films also show excellent transistor characteristics with TaN gate. NH3 pretreatment results in degraded transistor characteristics for TaN and poly gate samples. Good capacitance–voltage characteristics and negligible hysteresis (<10 mV) was observed in the capacitors after a 1000 °C activation indicating good electrical stability at high temperatures and minimal charge trapping. © 2002 American Institute of Physics.
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77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
85.30.Tv Field effect devices
73.61.Ng Insulators
85.30.De Semiconductor-device characterization, design, and modeling
68.37.Lp Transmission electron microscopy (TEM)
68.35.Ct Interface structure and roughness
81.40.Gh Other heat and thermomechanical treatments

The role of the OH species in high-k/polycrystalline silicon gate electrode interface reactions

Theodosia Gougousi, M. Jason Kelly, and Gregory N. Parsons

Appl. Phys. Lett. 80, 4419 (2002); http://dx.doi.org/10.1063/1.1485122 (3 pages) | Cited 18 times

Online Publication Date: 31 May 2002

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In this letter, reactions occurring at the interface between polycrystalline silicon (poly-Si) and LaSiOx high-dielectric-constant (high-k) insulating layers are characterized using x-ray photoelectron spectroscopy. Dielectrics were formed by sputter deposition of metal on silicon, followed by oxidation at 900 °C. Amorphous silicon was deposited on top by plasma-enhanced chemical vapor deposition from silane, followed by anneal at 650–1050 °C. We show that if the dielectric layer is exposed to sufficient water vapor before polysilicon deposition, annealing at 1050 °C for 10 s is sufficient to completely oxidize ∼ 25 Å of deposited silicon. Minimal reaction is observed without deliberate water exposure. This demonstrates the importance of the dielectric surface condition in determining reactivity of high-k/polysilicon interfaces. © 2002 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
81.65.Mq Oxidation
68.35.Fx Diffusion; interface formation
79.60.Jv Interfaces; heterostructures; nanostructures
61.72.Cc Kinetics of defect formation and annealing

Phase coexistence in Pb(Fe2/3W1/3)O3–PbTiO3 solid solutions

Liliana Mitoseriu, Paula M. Vilarinho, and João L. Baptista

Appl. Phys. Lett. 80, 4422 (2002); http://dx.doi.org/10.1063/1.1485131 (3 pages) | Cited 25 times

Online Publication Date: 31 May 2002

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The crystalline symmetry of the solid solution formed by a relaxor and a ferroelectric material with formula: (1−x)Pb(Fe2/3W1/3)O3–xPbTiO3, with various x was investigated, at T = 300 K. A continuous change from pseudocubic to tetragonal symmetry, with cell parameters dependent on the PbTiO3 amount, was found. In a large range of compositions, from x = 0.20 to x = 0.37, both phases coexist, with different relative amounts. © 2002 American Institute of Physics.
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81.30.Dz Phase diagrams of other materials
64.75.-g Phase equilibria
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
61.66.Fn Inorganic compounds
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