TaCN-based metal films were grown by metal-organic chemical-vapor deposition (MOCVD) and atomic vapor-deposition (AVD). Thermal decomposition at 500ºC leads to com-positions of approximately Ta0.50C0.4N0.1 (“TaCN”), whereas a reactive process using NH3 leads to the formation of Ta0.65C0.1N0.25 (“Ta2N”) films. All films are nearly amorphous as grown and recrystallize only weakly after spike annealing at 1050°C. The thermal stability of TaCN/HfSiO4 and Ta2N/HfSiO4 stacks during spike annealing at 1050°C was studied and Si and Hf outdiffusion into TaCN or Ta2N was observed. The effective work functions of TaCN and Ta2N on HfSiO4 were found to be as high as 4.9 eV after high thermal budget. It is demonstrated that the effective work function can be further increased to 5.1 eV after high thermal budget by the insertion of a thin Al2O3 capping layer between HfSiO4 and the metal films.

The scaling of contemporary metal-insulator-metal (MIM) capacitors requires oxides of higher dielectric constant (>10), such as hafnium oxide (∼18) and titanium oxide (∼40). Intensive research of these oxides and oxide stacks is needed to develop them into high quality electronic materials for their application as capacitors in high temperature environments. High-k dielectrics such as HfO2 and HfO2/TiO2/HfO2 have been grown by thermal oxidation to fabricate MIM capacitors on SiO2/Si substrates and on sapphire substrates also. The thermally grown Al/HfO2/TiO2/HfO2/Pt/Ti/SiO2/Si MIM capacitor is reported here for the first time. The MIM capacitor using HfO2/TiO2/HfO2 dielectric film shows a similar frequency dependence using HfO2 dielectric on a SiO2/Si substrate, whilst its voltage linearity coefficients, leakage current and temperature coefficient are higher than the capacitor employing HfO2 dielectric. The MIM capacitor with HfO2 dielectric fabricated on sapphire substrate shows the strongest frequency dependence, voltage linearity coefficient and temperature dependence which is related to the surface roughness of substrate. The high capacitance density of these capacitors, ranging from 5.21 fF/µm2, meets the ITRS requirements for analog capacitor up to 2012. The MIM capacitor using 30nm HfO2 dielectric film illustrates highest capacitance density, 5.21 fF/µm2, a VCC of 236 ppm/V2, a temperature coefficient of 290 ppm/ºC, measured up to 300 ºC, and leakage current density which is 1.3 × 10−7 A/cm2 at 1V.

Due to continued transistor scaling, the work function tuning of metal gates has become important for advanced CMOS applications. The primary objective of this research is to understand the tuning of the MoxSiyNz (also referred to as MoSiN) gate work function through the incorporation of nitrogen. A molybdenum silicide (MoSi2) target was reactively sputtered in nitrogen (N2) and argon (Ar) plasma. The amount of nitrogen in the MoSiN films was varied by controlling the gas flow ratio, RN = N2/(N2+Ar). Capacitance-voltage (CV) and internal photoemission (IPE) measurements are used to extract the work function (ϕm) of the MoSiN gate. A decrease in the MoSiN work function was observed from ∼4.7eV to ∼4.4eV for an increase in the gas flow ratios from 10% to 40%. The SIMS depth profiles suggested a uniform distribution of nitrogen throughout the films. The XPS surface analysis confirmed a steady increase in the total nitrogen concentration in the MoSiN films as gas flow ratio was increased. The increase in N2 concentration corresponded directly with the lowering of the MoSiN work function. These results clearly demonstrated that the MoSiN work function maybe altered over ∼0.3 eV tuning window by adjusting the N2 concentration in these films.

Post annealing of Hf-silicate thin film grown by ALD was done with different kind of nitrogen gas and order of annealing. Annealing conditions are as follows: (1) NO gas only, (2) NH3 gas only, (3) NO gas + NH3 gas, and (4) NH3 + NO gas. With these conditions, the physical and electrical properties of nitrided Hf-silicate films were analyzed. Content of nitrogen is decreased with post NO gas annealing. In case of NH3, content of nitrogen is much higher than NO case. Most nitrogen atoms were distributed between Si substrate and Hf-silicate film for NO gas annealing. However, with NH3 gas annealing, nitrogen atoms were distributed in the whole Hf-silicate film evenly. Leakage current was decreased with post NO gas annealing and flat band voltage was also decreased.

Important material properties of dielectric oxide films fabricated by aqueous chemical solution deposition, such as crystallization, topography, contamination and interfacial layer were evaluated and related to the films' dielectric properties.

Functional ultrathin films (<20 nm thickness) of zirconia, barium zirconate and strontium niobate were deposited. The films were all subjected to the same thermal treatment, based on the high similarity of their precursors' thermal decomposition behavior. The evolution of the films' chemical purity as a function of temperature and the effect of annealing on the interfacial SiO2 layer was studied by grazing angle ATR-FTIR. The films' crystallization behavior was dependent on film thickness and composition as shown by high temperature XRD. C-V characterization of the films demonstrated a k-value in the same order of magnitude as for the ZrO2 reference material. This is lower than the bulk material's value, thus leaving room for further optimization of the current materials or alternatively selection of other material compositions.

Amorphous LaAlO3 high-k oxide was grown in a molecular beam epitaxy reactor on p-Si(001) using a thin γ-Al2O3 epitaxied buffer layer. Interfaces were free of SiO2 or silicates and remained abrupt despite the high temperature used for annealing, as X-ray photoelectron spectroscopy showed. Electrical measurements performed on as-deposited samples revealed a dielectric constant value close to that of the bulk, small equivalent oxide thickness and low density of interface states. But some negative charges were present, leading to a flat band voltage shift. Post deposition annealing with forming gas can correct this effect.

The atomic layer deposition of HfO2 thin films is studied on Si(100) and GaAs(100) surfaces. The films are grown using tetrakis(dimethylamido)hafnium (TDMAH) and H2O precursors at a deposition temperature of 275°C. The Si surfaces used include a H-terminated surface and an OH-rich chemical oxide. GaAs substrates are subjected to two different pre-deposition treatments involving an HF and a NH4OH wet chemical etch that has been shown to remove most of the Ga and As native oxides. Spectroscopic ellipsometry (SE) confirms linear growth rates of 1.05±0.05 Å/cycle for all surfaces. Rutherford backscattering spectrometry (RBS) shows that steady-state growth of 2.6×1014 Hf/cm2/cycle is reached after 10 ALD cycles for the HF-etched GaAs surface. X-ray photoelectron spectroscopy (XPS) indicates the presence of native oxides on both GaAs starting surfaces after 10 cycles due to postdeposition surface oxidation. However, the presence of the native oxide is not detected for thicker 15 and 20 cycle samples indicating passivation of the surface and suppression of the interfacial layer formation.

Oxides have always been an integral part of semiconductor manufacturing both in front and back-end processing. With the necessary increase in performance, the demand on these oxides has been increasing leading to their (future) replacement by more complex materials, such as high-k's in gate oxide and metal gates. With the increasing material complexity, a thorough characterization of all aspects of these materials is necessary, covering, for instance, surfaces and interfaces, nucleation, growth, atomic structure, …

This article focuses on the characterization of front-end oxides and their interfaces. It shows that detailed information can be achieved by sophisticated experimental techniques such as synchrotron radiation, high energy ERD or AtomProbe but that adequate sample preparation and/or analysis by a combination of more routinely available techniques may achieve similar results. This is shown through the study of three different systems/problems in the gate stack analysis. We will first focus on the determination of substrate surface preparation conditions before deposition and their influence on growth mode and the growth characteristics by different growth techniques (ALD, MOCVD, …). Second, we present the possibilities of compositional depth profiling of thin layers both with nuclear techniques and Angle-Resolved XPS. Finally, we will show that using conventional XPS and a combination of front and back-side analysis, the interface between high-k oxide and metal gates can be investigated. More examples of gate stack characterization can be found elsewhere

Formation energies and electronic properties of oxygen vacancies in amorphous HfO2 gate dielectrics are investigated by employing the first-principles method based on the density functional theory. We have found that the formation energy of neutral oxygen vacancy in amorphous HfO2 distributes from 4.7 to 6.1 eV, most of which is lower than the value for cubic HfO2, 6.0 eV. We also investigated the stabilities of the Vo pairs in various charged state and compared with those in amorphous SiO2. We found that Vo++ is stabilized in the vicinity of Vo in SiO2. In HfO2, however, this does not happen. This suggests the difference of defect propagation mechanism in HfO2 and SiO2.

The (001) preferentially oriented CCTO thin film was grown on Pt/Ti/TiO2/Si (100) substrate by pulsed laser. I-V and C-V relationships of the CCTO thin film showed characteristics typical of a tunnel metal-insulator-semiconductor (MIS) structure and its capacitance response is the origin of the high apparent dielectric constant observed in CCTO thin films. The very thin insulating layer on top of the film can be reduced in thickness by treatment in HCl acid, as shown by smaller threshold voltages in the I-V curves. The overall behavior is compatible with a conduction activation energy of ∼80 to 100 meV in the bulk of the film, and a diffusion potential at the interface of 500 to 800 meV. The acceptor concentration is of the order of 1019cm−3.

The properties of lanthanum silicate (LaSiOx) gate stacks on GaAs substrates have been examined, comparing different GaAs pretreatments; namely a) as-received, b) HCl-treated, and c) sulphur-treated. X-ray photoelectron spectroscopy of the As 3d, Ga 3d, and Ga 2p binding energy peaks were used to reveal the chemical nature of the stacks. After a 400 °C in situ anneal in 10−6 torr pO2, the LaSiOx chemically reduces the As oxides from the as-received GaAs, while Ga oxide species remain. HCl and S-treated GaAs similarly show no As oxides, and a much smaller degree of Ga oxides than the as-received case. The Ga-S bonding may be responsible for lowering the tendency towards Ga oxidation for the S-treated case. On p-type, Zn-doped GaAs, 3.0 nm lanthanum silicate films produce MOS device EOT values of 2.38 nm, 1.51 nm, and 1.37 nm, on as-received, HCl-treated, and S-treated substrates, respectively. The high EOT for the as-received GaAs corresponds to the thicker Ga oxide and elemental As at the interface. The decreases in both Ga oxide and elemental As at the interface of the S-treated stack appears to be related to it having the lowest EOT devices.