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This work focuses on the microstructural characteristics of Y2O3 thin films and interfaces, which is related to their suitability as high-k replacement for SiO2 gate dielectrics in future transistor devices. The films were grown directly on silicon (001) substrates by electron-beam evaporation in a molecular beam epitaxy chamber under ultrahigh vacuum conditions. At an optimum growth temperature, ∼450 °C, high crystalline quality films were obtained, albeit with a heteroepitaxial relationship Y2O3 (110)//Si (001) and Y2O3 [001]//Si 〈110〉, which favors the formation of a potentially harmful complex microstructure. The latter consists of large (submicron-sized) domains containing smaller (10–30 nm) inclusions with perpendicular crystal orientations. Despite predictions for thermodynamic stability and low O2 partial pressure in the chamber, the chemical reaction of Y2O3 with Si could not be avoided. Indeed, a nonuniform interfacial amorphous layer with thickness 5–15 A was observed, while YSi2 was formed at ...

Yttria sY2O3d is one of the candidate materials actively studied as a high dielectric constant replacement of amorphous silicon dioxide in downscaled microelectronic devices. An understanding of the physical properties of yttria epilayers on silicon is both a required prerequisite for applications and of fundamental interest. Using x-ray absorption spectroscopy at both the yttrium and oxygen K edges we study the local atomic and electronic structure in Y2O3 epilayers deposited on Sis001d. We find that above a thin near - interface layer the epilayers have a local atomic and electronic structure bearing a close similarity to that of bulk yttria; however, there is an increase in static disorder with decreasing thickness which can be correlated to an increase of the defectivity. The unoccupied electronic structure, as probed by near edge spectra at the cation and oxygen edges, is very similar to that of bulk yttria; we present and discuss simulations within the real - space full multiple scattering formalism which are quite successful in reproducing the experimental line shape. In the near - interface layer we detect the presence of silicon oxide, as reported for this and other systems previously; a new finding is that yttrium -silicon bonds are present in the interface layer, forming the precursors to the formation of yttrium silicide which develops into a long range ordered phase at higher deposition temperatures. We compare our observations with available theoretical predictions on the thermodynamic stability of yttria in comparison to silicon dioxide, yttrium silicide, and yttrium silicate; the predictions are not confirmed by experiment as far as the 2 nm thick interface layer is concerned.

Yttria (Y{sub 2}O{sub 3}) is one of the candidate materials actively studied as a high dielectric constant replacement of amorphous silicon dioxide in downscaled microelectronic devices. An understanding of the physical properties of yttria epilayers on silicon is both a required prerequisite for applications and of fundamental interest. Using x-ray absorption spectroscopy at both the yttrium and oxygen K edges we study the local atomic and electronic structure in Y{sub 2}O{sub 3} epilayers deposited on Si(001). We find that above a thin near - interface layer the epilayers have a local atomic and electronic structure bearing a close similarity to that of bulk yttria; however, there is an increase in static disorder with decreasing thickness which can be correlated to an increase of the defectivity. The unoccupied electronic structure, as probed by near edge spectra at the cation and oxygen edges, is very similar to that of bulk yttria; we present and discuss simulations within the real - space full multiple scattering formalism which are quite successful in reproducing the experimental line shape. In the near - interface layer we detect the presence of silicon oxide, as reported for this and other systems previously; a new finding is that yttriummore » -silicon bonds are present in the interface layer, forming the precursors to the formation of yttrium silicide which develops into a long range ordered phase at higher deposition temperatures. We compare our observations with available theoretical predictions on the thermodynamic stability of yttria in comparison to silicon dioxide, yttrium silicide, and yttrium silicate; the predictions are not confirmed by experiment as far as the 2 nm thick interface layer is concerned.« less

The carrier transport mechanisms in as-grown LaAlO3 and La2Hf2O7 high-k insulator layers deposited on n- and p-Si were deduced from temperature dependent C-V and I-V characteristics correlated with photoelectric measurements. Large, parallel shifts in the high frequency C-V curves are explained by the presence of a large density of interface states and an approximate analytical formula relating the density of states to the C-V shift is deduced. The space charge limited current is explained by the existence of impurity channels situated energetically near the conduction or valence band of silicon.

Photoelectrical measurements have shown that the current flow through La2Hf2O7 and LaAlO3 high-k insulator layers deposited on silicon takes place via impurity channels. A space charge limited current is evidenced, for different insulator thicknesses and temperatures, by the square law dependence of current versus voltage. The analysis demonstrates that this space charge limited (SCL) current in thin insulator films can be explained only by the presence of impurity channels situated near the Fermi level of the injecting contact. Many other aspects related to the SCL current behavior were found.

Thin insulator films of the high-κ dielectric HfO2 are deposited on Ge(100) substrates by evaporating Hf in atomic oxygen beams after in situ thermal desorption of the native oxide in ultrahigh vacuum and subsequent treatment of the clean Ge surface in oxygen and nitrogen. It is shown that HfO2 forms atomically sharp interfaces with Ge and behaves as an excellent insulator with dielectric permittivity κ∼25, which is close to the expected bulk value. Very low equivalent oxide thickness of 0.75 (±0.1) nm with a low gate leakage current of ∼4.5×10−4A∕cm2 at 1 V in accumulation is achieved. Strong frequency dispersion of the inversion capacitance and low frequency behavior of the high frequency capacitance–voltage curves is observed. This is attributed to a combined effect of a high generation rate of minority carriers due to impurity traps and the high intrinsic carrier concentration in Ge, which result in a short minority carrier response time.

We have prepared RuO2 and SrRuO3 thin films for application as gate electrodes in CMOS technology. RuO2 and SrRuO3 films exhibit satisfactory stability in oxygen atmosphere at elevated temperatures. RuO2 films decompose in reducing atmosphere. Extracted work function values for RuO2 electrode are around 5.1 eV, confirming that RuO2 is a suitable candidate for pMOS gate electrode application.

The search for high dielectric constant (high- k ) oxides to replace silicon dioxide for future CMOS devices is a formidable task. Key issues are definitely good structural and electrical properties as well as high quality interfaces between the high- k and the semiconductor substrate. In this work we study the local structure of ultra thin Y 2 O 3 films and Y 2 O 3 /Si interface, by using Y k -edge X-ray absorption spectroscopy (XAS) in grazing incidence geometry. Y 2 O 3 epilayers (2–20 nm thick) are grown on Si (0 0 1) by MBE at 450 °C and some of them are in-situ annealed at 500 °C for 30 min. In the as grown epilayer, XAS reveals the presence of Y–Si and Y–O correlations at the Y 2 O 3 /Si interface. The in-situ annealing produces a rearrangement of the local atomic environment at the interface and only Y–O correlations are detected. The local structural quality of the epilayers improves with thickness and annealing.