Browsing by Author "Wu, X"

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Characterization of interfacial layer of ultrathin Zr silicate on Si(100) using spectroscopic ellipsometry and HRTEM
(2004-05-01)
Ahn, H
;
Chen, HW
;
Landheer, D
;
Wu, X
;
Chou, LJ
Optical properties and the film thickness of interfacial layer formed between the ultrathin as-deposited Zr silicate films and the Si substrate were investigated by the variable-angle spectroscopic ellipsometry (SE), the high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). Five Zr silicate films were deposited by using oxygen-based Zr(O-i-Pr)(2)(thd)(2) and Si(O-t-Bu)(2)(thd)(2) as precursors in a pulse-mode metalorganic chemical-vapor deposition (MOCVD) apparatus to investigate the influence of the choice of ambient gas (oxygen or NO) on the formation of the interfacial layers during the oxidation and the deposition of the Zr silicate films. HRTEM images clearly show the existence of the amorphous interfacial layer below the Zr silicate layer. The interfacial layers are found to be Zr-free from the XPS study. In SE analysis, the interfacial layers were described best as the mixture of SiO2 and SiO in the Bruggeman effective medium approximation (BEMA). The evident reduction of the interfacial layer due to the intentionally grown ultrathin oxynitride buffer layer was observed for the Zr silicate film deposited under a carefully designed growing condition. Any source of oxygen during the growth of the film results in the thicker, but self-limited interfacial layer. (C) 2004 Elsevier B.V. All rights reserved.
Characterization of thin ZrO2 films deposited using Zr(O '-Pr)(2)(thd)(2) and O-2 on Si(100)
(2002-05-01)
Chen, HW
;
Landheer, D
;
Wu, X
;
Moisa, S
;
Sproule, GI
The properties of ZrO2 films deposited using molecular oxygen and a recently developed precursor, zirconium Zr(O-i-Pr)(2)(thd)(2) have been investigated. The organometallic was dissolved as a 0.15 molar solution in octane and introduced into the deposition chamber using a liquid injection system. The deposition rate was insensitive to molecular oxygen flow but changed with liquid injection rate and was thermally activated in the range 390 degreesC-550 degreesC. Carbon concentrations, <0.1 at.%, the detection limit of the x-ray photoelectron spectroscopy depth profiling measurements, were obtained at the lowest deposition temperatures and deposition rates. High-resolution transmission electron microscopy showed the films to be polycrystalline as deposited, with a zirconium silicate interfacial layer. After proper annealing treatments, an equivalent oxide thickness (EOT) of around 2.3 urn has been achieved for a 5.2 nm thick film, with a leakage current two orders of magnitude lower than that Of SiO2 with the same EOT. Promising capacitance-voltage characteristics were also achieved, but some improvements are required if these films are to be used as a gate insulator. (C) 2002 American Vacuum Society.
Physical and electrical characterization of ZrO(2) gate insulators deposited on Si(100) using Zr(O(i)-Pr)(2)(thd)(2) and O(2)
(2002-06-01)
Chen, HW
;
Huang, TY
;
Landheer, D
;
Wu, X
;
Moisa, S
The characteristics of ultrathin ZrO(2) films deposited using molecular oxygen and the zirconium precursor Zr(O(i)-Pr)(2)(thd)(2) [where O(i)-Pr is isopropoxide and thd is 2,2,6,6-tetramethyl-3,5-heptanedionate] were investigated. The organometallic was dissolved as a 0.15 M solution in octane and introduced into the deposition chamber using a liquid injection system. The deposition rate was insensitive to molecular oxygen flow but changed with liquid injection rate and was thermally activated in the range 390-550degreesC. No evidence of Zr-C and Zr-Si bonds were found in the X-ray photoelectron spectroscopy (XPS), spectra, and carbon concentrations, 0.1 atom %, the detection limit of the XPS depth profiling measurements, were obtained at the lowest deposition temperatures and deposition rates. High-resolution transmission electron microscopy showed the ZrO(2) films to be polycrystalline as deposited, with an amorphous zirconium silicate interfacial layer. The effects of postdeposition annealing were also demonstrated. After proper annealing treatments, promising capacitance-voltage and current-voltage characteristics were achieved. A film with an equivalent oxide thickness of 2.3 nm showed current reductions of approximately two orders of magnitude when compared to SiO(2), but some improvements are required if these films are to be used as a gate-insulator beyond the 100 nm CMOS (complementary metal oxide semiconductor) technology node. (C) 2002 The Electrochemical Society.
Physical and electrical characterization of ZrO2 gate insulators deposited on Si(100) using Zr(O-i-Pr)(2)(thd)(2) and O-2
(2002-06-01)
Chen, HW
;
Huang, TY
;
Landheer, D
;
Wu, X
;
Moisa, S
The characteristics of ultrathin ZrO2 films deposited using molecular oxygen and the zirconium precursor Zr(O-i-Pr)(2)(thd)(2) [where O-i-Pr is isopropoxide and thd is 2,2,6,6-tetramethyl-3,5-heptanedionate] were investigated. The organometallic was dissolved as a 0.15 M solution in octane and introduced into the deposition chamber using a liquid injection system. The deposition rate was insensitive to molecular oxygen flow but changed with liquid injection rate and was thermally activated in the range 390-550degreesC. No evidence of Zr-C and Zr-Si bonds were found in the X-ray photoelectron spectroscopy (XPS), spectra, and carbon concentrations, 0.1 atom %, the detection limit of the XPS depth profiling measurements, were obtained at the lowest deposition temperatures and deposition rates. High-resolution transmission electron microscopy showed the ZrO2 films to be polycrystalline as deposited, with an amorphous zirconium silicate interfacial layer. The effects of postdeposition annealing were also demonstrated. After proper annealing treatments, promising capacitance-voltage and current-voltage characteristics were achieved. A film with an equivalent oxide thickness of 2.3 nm showed current reductions of approximately two orders of magnitude when compared to SiO2, but some improvements are required if these films are to be used as a gate-insulator beyond the 100 nm CMOS (complementary metal oxide semiconductor) technology node. (C) 2002 The Electrochemical Society.
Structure and thermal stability of MOCVD ZrO2 films on Si (100)
(2003-04-01)
Wu, X
;
Landheer, D
;
Graham, MJ
;
Chen, HW
;
Huang, TY
The structure and thermal stability of ZrO2 films grown on Si (1 0 0) substrates by metalorganic chemical vapor deposition have been studied by high-resolution transmission electron microscopy, selected area electron diffraction and X-ray energy dispersive spectroscopy. As-deposited films consist of tetragonal ZrO2 nanocrystallites and an amorphous Zr silicate interfacial layer. After annealing at 850degreesC, some monoclinic phase is formed, and the grain size is increased. Annealing a similar to6 nm thick film at 850degreesC in O-2 revealed that the growth of the interfacial layer is at the expense of the ZrO2 layer. In a 3.0 nm thick Zr silicate interfacial layer, there is a 0.9 nm Zr-free SiO2 region right above the Si substrate. These observations suggest that oxygen reacted with the Si substrate to grow SiO2, and SiO2 reacted with ZrO2 to form a Zr silicate interfacial layer during the deposition and annealing. Oxygen diffusion through the tetragonal ZrO2 phase was found to be relatively easier than through the monoclinic phase. (C) 2003 Elsevier Science B.V. All rights reserved.
Ultrathin zirconium silicate films deposited on Si(100) using Zr(O(i)-Pr)(2)(thd)(2), Si(O(t)-Bu)(2)(thd)(2), and nitric oxide
(2003-07-01)
Chen, HW
;
Huang, TY
;
Landheer, D
;
Wu, X
;
Moisa, S
Ultrathin Zr silicate films were deposited using Zr(Oi-Pr)(2)(tetramethylheptanedione,thd)(2), Si(O(t)-Bu)(2)(thd)(2) and nitric oxide in a pulse-mode metallorganic chemical-vapor deposition apparatus with a liquid injection source. High resolution transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and medium energy ion scattering were employed to investigate the structure, surface roughness, chemical state, and composition of the films. The nitric oxide used as oxidizing gas, instead of O(2), not only reduced the thickness of the interfacial layer but also removed the carbon contamination effectively from the bulk of the films. The as-deposited Zr silicate films with a Si: Zr ratio of 1.3:1 were amorphous, with an amorphous interfacial layer 0.3-0.6 nm thick. After a spike anneal in oxygen and a 60 s nitrogen anneal at 850degreesC, these films remained amorphous throughout without phase separation, but the interfacial layer increased in thickness. No evidence of Zr-C and Zr-Si bonds were found in the films by XPS and carbon concentrations <0.1 atom %, the detection limit, were obtained. The hysteresis, fixed charge density, and leakage current determined from capacitance-voltage analysis improved significantly after postdeposition anneals at 850 degrees C and the films exhibited promising characteristics for deep submicrometer metal-oxide-semiconductor devices. (C) 2003 The Electrochemical Society.