Tantalum Nitride Interface Layer Influence on Dielectric Properties of Hafnium Doped Tantalum Oxide High Dielectric Constant Thin Films

Lü

et al. 2005

J. Electrochem. Soc.

Self Cite

A 5 Å thick tantalum nitride ͑TaN x ͒ interface layer was inserted between an 8 nm Zr-doped tantalum oxide ͑TaO x ͒ high-k film and a silicon substrate to improve dielectric properties for metal-oxide-semiconductor ͑MOS͒ gate dielectric applications. Compared to the Zr-doped TaO x film without the TaN x interface, the stacked structure showed improvement in the dielectric constant, leakage current density, and dielectric breakdown strength. However, the flatband voltage shift and interface state densities were slightly degraded. Hysteresis of C-V curves did not change substantially with this TaN x insertion. Structural and chemical analyses, i.e., secondary ion mass spectroscopy ͑SIMS͒ and X-ray photoelectron spectroscopy ͑XPS͒, were done to investigate this TaN x interface layer. The results suggested that TaN x reacted with oxygen atoms from the high-k film and formed tantalum oxynitride ͑TaO x N y ͒ after being annealed at 700°C in O 2 , which may be responsible for the observed improvement on dielectric properties.

Section: Journal Of the Electrochemical Societymentioning

confidence: 99%

Influence of a 5 Å Tantalum Nitride Interface Layer on Dielectric Properties of Zirconium-Doped Tantalum Oxide High-k Films

Tewg

Lü

et al. 2005

J. Electrochem. Soc.

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“…The doping method can decrease leakage current and enhance the k value of TaO film, and an inserted 5 TaN interface layer can reduce the formation of a low-quality SiO interface layer between the TaO and the silicon wafer [1]- [3]. In spite of these promising characteristics, reliability studies are needed in order to fully understand the time-dependent performance of high-k dielectrics.…”

Section: Introductionmentioning

confidence: 99%

“…A detailed description of the preparation process can be found in [1]. The current-voltage (IV) and capacitance-voltage (CV) curves were measured using an HP 4140B picoampere meter and an HP 4284A LCR meter, respectively.…”

Section: Introductionmentioning

confidence: 99%

Dielectric Relaxation and Breakdown Detection of Doped Tantalum Oxide High-k Thin Films

Luo

IEEE Trans. Device Mater. Relib.

2004

While TaO x , HfO x , ZrO x , Hf-doped TaO x , and Zr-doped TaO x thin films are promising high-k gate dielectric candidates, their intrinsic reliability has not yet been investigated. In this paper, the authors examine some fundamental reliability aspects of these high-k films through ramp voltage stress testing. By studying dielectric relaxation and analyzing the transient conductivity, the breakdown mode of the tested high-k film is identified; a sensitive method of breakdown detection in ramped voltage tests is proposed and investigated. Index Terms-Dielectric relaxation, high-dielectric, thin film breakdown.Wen Luo (S'03-M'04) received the B.E. degree in precision instruments

“…[20][21][22][23][24][25] In addition to the physical properties, the influences of these electrodes to dielectric characteristics were studied.…”

mentioning

confidence: 99%

Zirconium-Doped Tantalum Oxide Gate Dielectric Films Integrated with Molybdenum, Molybdenum Nitride, and Tungsten Nitride Gate Electrodes

Tewg

Lü

2005

J. Electrochem. Soc.

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Electrical properties of zirconium-doped tantalum oxide ͑Zr-doped TaO x ͒ high-k gate dielectric films integrated with Mo, MoN, and WN gate electrodes were studied. The Zr-doped TaO x film with the Zr/͑Ta + Zr͒ ratio of 0.33, which showed good dielectric properties in previous studies, was used as the high-k film in this study. A single metallic Zr/Ta alloy target was used for the sputter deposition. The resistivities of the MoN and WN films were minimized by adjusting the N 2 concentration in the sputtering gas, i.e., 10% N 2 ͑90% Ar͒ for MoN and 2.5% N 2 for WN, respectively. Microstructures of the gate electrodes were investigated with X-ray diffraction. Current density, equivalent oxide thickness, breakdown strength, flatband voltage, hysteresis, interface state density, and frequency dispersion of capacitors with different gate electrode materials were analyzed and compared. Device characteristics changed drastically with the gate electrode material, mainly due to the difference in work functions.Continuous shrinkage of channel length and gate oxide thickness of metal oxide semiconductor ͑MOS͒ transistors contributes to improved device performance and high circuit density. However, a number of obstacles have emerged from this strategy, for example, a high gate tunneling leakage current, polycrystalline silicon ͑poly-Si͒ gate depletion, high gate resistance, boron penetration into the gate dielectric, and reliability. 1-5 When the silicon oxide gate dielectric layer is replaced by a high dielectric constant ͑high-k͒ film, the leakage current problem can be solved because a thick gate dielectric layer can be used. 1,2 In principle, some of these problems may be solved by replacing the poly-Si gate with a metal gate. 2 For example, with a poly-Si gate electrode, the capacitance equivalent thickness ͑CET͒ of an MOS capacitor is influenced by three factors: ͑a͒ the contribution from the silicon substrate, i.e., the quantum mechanical effect, ͑b͒ the dielectric layer itself, and ͑c͒ the carrier depletion layer in the poly-Si gate. 6 The replacement of the poly-Si gate with a metal gate could eliminate the polydepletion, thus reducing the CET by 3-5Å without a substantial increase in leakage current. 2 In addition, the gate resistivity can be reduced. Without the boron-doped poly-Si gate, the boron penetration problem does not exist.It was reported that the electrical characteristics of the high-k gate dielectric film actually depend on the properties of the gate electrode material, such as work function and interface thermal stability. 7,8 Therefore, there are many requirements for the gate electrode material. For an n-MOSFET, the metal gate needs a work function of 4.1-4.3 eV; for a p-MOSFET, it needs to be 5.0-5.2 eV. 9 Other requirements include thermal stability in contact with the gate dielectric film, ease of hydrogen diffusion for the dielectric interface passivation, and a simple deposition method. 10,11 Theoretical studies showed that the gate work function could vary significantly with the metal's micros...