In this paper, boron diffusivities in HfSiON high-k gate dielectric films are systematically investigated for a wide range of the film composition. Boron diffusivities in HfSiON (1000°C) change from 3X10−17cm2/sec to 3X10−15cm2/sec according to the change in the chemical composition of the films. These diffusivity values are higher than that in SiON but lower than that in HfO2. We found that higher Hf/(Hf+Si) results in great increase of diffusivities. On the other hand, higher nitrogen concentration in the film leads to the reduction in diffusivity, in the case of the same Hf/(Hf+Si). In addition, crystallization of HfSiON with the same chemical composition gives rise to an anomalous increase in diffusivities, indicating that the micro-crystallized film structure of HfSiON critically affects the microscopic mechanism of boron diffusion in this material.

MOS capacitors were fabricated from MOCVD HfO2 and HfxSiyO gate dielectrics with ALD TaN / PVD Ta metal electrodes. Dielectrics with 1.8 to 2.6 nm capacitance equivalent thickness (CET) were investigated with gate leakage (Jg) of 1×10−7 to 1×10−3 A/cm2 at Vg = Vfb−1V in accumulation. In addition to the C-V and I-V characterization of the MOSCAPs, XPS physical characterization was performed on monitor wafers to determine composition and physical thickness. From the combined results of the electrical and physical characterization, the relative dielectric constants of the Hf-Si-O films and the metal electrode work functions are determined, and simple models for the compositional dependence of the dielectric constant are formulated. Capacitors with the same dielectric composition and thickness exhibited 100 mV Vfb change when the thickness of the ALD TaN electrode layer was changed from 40-80Å. This change is attributed to a change in the work function of the aggregate TaN / Ta metal electrode. Workfunctions were found to be located near middle of the Si band gap, with workfunctions of 4.6 eV to 4.7 eV.

Carrier transport properties and electronic structure of an n-type transparent oxide semiconductor, InGaO3(ZnO)5, were investigated using single-crystalline thin films. Room-temperature Hall mobility strongly depends on carrier concentration, and rapidly increased from ∼ 2 cm2(Vs)-1 to > 10 cm2(Vs)-1 around the carrier concentration (Nth ∼3 × 1018 cm−3. This change is associatedwith insulator-metal transition. These results are explained by a model similar to Anderson localization, in which shallow semi-localized states are formed originating from random distribution of Ga3+ and Zn2+ ions in the intrinsic crystal structure of InGaO3(ZnO)5. The present conclusion suggests that electron densities larger than Nth are necessary to attain high performances in drift carrier devices fabricated using InGaO3(ZnO)5. It was demonstrated that transparent filed-effect transistors exhibited good performances such as a “normally-offcharacteristics”, an on/off current ratios as large as 105 and a field-effect mobility ∼80 cm2(Vs)-1when high-k material, amorphous HfOx, was used as a gate insulator.

Hf-family compounds have been widely studied as high k gate dielectric materials, they can be elaborated in a wide range of deposition techniques but ALD and MOCVD are the most advanced. In this contribution, the deposition of pure HfO2 is performed by Atomic Vapour Deposition, which is a sort of pulsed-mode MOCVD. The precursor, diluted into a solvent, is pulsed through specific injectors (TriJet®), micro-droplets are vaporised and distributed to the substrate through a showerhead. ATR-FTIR and Hg-probe measurements have been extensively used to evaluate the materials. The advantage of this specific MOCVD system is that it allows working within a wide range of liquid injection frequencies. Thus, we have been able to show that the frequency of injection has a huge impact on the structural and electrical properties of the material. It has been evidence that working at low frequencies is crucial in order to get good electrical behaviour. Higher temperature deposition shows also a clear benefit. An EOT of 1.15 nm with 6.10−2 A/cm2 at |Vfb| + 1 V, that is to say about 3 orders of magnitude below what is obtained with SiO2 has been obtained on capacitors with TiN gate. This is a very good achievement fore pure HfO2 deposited by MOCVD.

This work has been made in the frame of MEDEA + T207 European project with the help of Air Liquide and Epichem.

The formation of interfacial oxide between high-k and Si creates a two-layer dielectric in the MOS structure. In this paper, we present a model to describe electrical breakdown in the two-layer dielectric. Depending on the thickness ratio of the two dielectric layers, electrical breakdown can occur either in one dielectric after the other or simultaneously. In the case of one-by-one breakdown, the current through the two-layer dielectric shows three regimes with applied voltage: tunneling through two layers, tunneling through one layer, and breakdown for both layers. Our model has been compared with experimental data obtained from the HfOx/SiO2 MOS structure, and a good agreement is achieved. This model can be used to estimate either the thickness, breakdown field, or dielectric constant of each of the two dielectric layers. It can also predict the overall breakdown voltage for different combinations of dielectric layers. When combined with C-V measurements, more information about the two-layer dielectric is obtained.

Processing of BST thin films is becoming more and more important for microwave electronics and for its probable incorporation in future high density DRAM's. A co-relation between processing and final device characteristics is of utmost importance. Differences in microstructure and electrical properties were observed when chemical solution deposited thin films were annealed using a conventional diffusion furnace, rapid thermal annealing furnace with different heating ramps, and a hot plate for pyrolysis prior crystallization. The solution was made with the propionate route and then deposited on Pt coated silicon wafers. Cross-sectional SEM's were performed on the different films. It was found that the microstructure depended on the annealing method of the film. The electrical properties of the films were also found to vary considerably. Frequency dependence of the dielectric constant was studied. The leakage study on different films was performed at different temperatures.

Thin films deposited via atomic layer deposition at low temperature tend to be less dense than bulk material and typically require high temperature post deposition annealing for densification and removal of unreacted precursor ligands. We have found that improved film densification can be achieved by interval annealing, in which in-situ moderate temperature (∼420°C) rapid thermal anneals are performed after every n deposition cycles. HfO2 film density and refractive index were found to increase with decreasing anneal interval (more frequent annealing). The highest density films could be achieved only by every-cycle annealing and could not be achieved by post deposition annealing. The densified every cycle annealed films have been shown to have improved equivalent thickness and leakage and decreased interfacial layer thickness.