The outstanding properties of SiO2, which include high resistivity, excellent dielectric strength, a large band gap, a high melting point, and a native, low defect density interface with Si, are in large part responsible for enabling the microelectronics revolution. The Si/SiO2 interface, which forms the heart of the modern metal–oxide–semiconductor field effect transistor, the building block of the integrated circuit, is arguably the worlds most economically and technologically important materials interface. This article summarizes recent progress and current scientific understanding of ultrathin (<4 nm) SiO2 and Si–O–N (silicon oxynitride) gate dielectrics on Si based devices. We will emphasize an understanding of the limits of these gate dielectrics, i.e., how their continuously shrinking thickness, dictated by integrated circuit device scaling, results in physical and electrical property changes that impose limits on their usefulness. We observe, in conclusion, that although Si microelectronic devices...

Ultrathin (<4 nm) SiO2 and Si-O-N gate dielectric layers for silicon microelectronics: Understanding the processing, structure, and physical and electrical limits

A review is presented of the recent advances in the study of oxygen precipitation and of the main properties of oxide precipitates in silicon. After a general overview of the system ‘‘oxygen in silicon,’’ the thermodynamics and the kinetics of the precipitate formation are treated in detail, with major emphasis on the phenomenology; subsequently, the most important techniques for the characterization of the precipitates are illustrated together with the most interesting and recent results. Finally, the possible influence of oxygen precipitation on technological applications is stressed, with particular attention to recent results regarding device yield. Actually, the essential novelty of this review rests on the attempt to give an extended picture of what has been recently clarified by means of highly sophisticated diagnostic methods and of the influence of precipitation on the properties of semiconductor devices.

Oxygen precipitation in silicon

The growth of ultrathin oxide films by the thermal oxidation of Si(100) at 1020--1170 K and in ${10}^{\mathrm{\ensuremath{-}}1}$--${10}^{\mathrm{\ensuremath{-}}3}$ Torr ${\mathrm{O}}_{2}$ pressure has been studied by high-resolution medium-energy ion-scattering spectroscopy (MEIS). To develop a fundamental understanding of very thin oxide film growth, we utilize sequential isotopic exposures ${(}^{18}$${\mathrm{O}}_{2}$ followed by $^{16}\mathrm{O}_{2}$). MEIS readily distinguishes $^{18}\mathrm{O}$ from $^{16}\mathrm{O}$ and the depth distribution for both species can be determined quantitatively with high accuracy. Our results show that the traditional phenomenological models for silicon oxidation cannot be applied to the initial oxidation. For very thin oxide films (15--25 \AA{}), we find overlapping isotope depth profiles in the film. For thicker films (g40 \AA{}), we find that several key aspects of the Deal-Grove model (oxygen diffusion to the Si-${\mathrm{SiO}}_{2}$ interface and oxide formation at and/or near that interface) are consistent with our results. We also observe $^{18}\mathrm{O}$ loss from the surface after reoxidation in $^{16}\mathrm{O}_{2}$. The complex oxidation behavior during the initial oxidation is likely to be a combination of interfacial, near-interfacial, and surface reactions.

Growth mechanism of thin silicon oxide films on Si(100) studied by medium-energy ion scattering.

Dislocation Dynamics and Mechanical Properties of Crystals

The reduction and reoxidation of submonolayer coverages of TiO2 deposited onto MCM-48 were investigated. The deposited TiO2 was characterized by Raman and UV−visible spectroscopy. Raman spectra sho...

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A Study of Oxygen Vacancy Formation and Annihilation in Submonolayer Coverages of TiO2 Dispersed on MCM-48†

The origin of x-ray diffraction peaks observed on the crystal truncation rods (CTR's) in reciprocal space for thermally grown ${\mathrm{SiO}}_{2}$ films has been investigated by large-scale atomistic simulation of silicon oxidation. Three models of ${\mathrm{SiO}}_{2}$ on Si(001), Si(111), and Si(113) were formed by introducing oxygen atoms in crystalline Si from the surfaces in an atom-by-atom manner. The ${\mathrm{SiO}}_{2}$ structures are classified as being amorphous in conventional characterizations, but retain the residual order originating from the {111} atomic planes in their parent crystals. The calculated diffraction patterns exhibit intensity peaks with Laue-function-like fringe profiles along the CTR's, at positions depending on the substrate orientations, agreeing quite well with experimental results.

Residual order within thermally grown amorphous SiO 2 on crystalline silicon

The growth velocities of deformation twins in the tangential direction are measured in silicon single crystals by the four‐point bending method for temperatures between 350 and 500 °C and for shear stresses τ between 80 and 550 MPa. Stress and temperature dependences of the twin growth are found to satisfy the same empirical power‐law equation as that for the motion of slip dislocations. Comparing the velocity of twin growth with that of slip dislocations, it is found that the activation energy is not much different between them, but the stress dependence of the twin growth is larger than that of the slip dislocation. The latter fact relates to the twinning dominantly observed under the high‐stress condition (τ>260 MPa). Referring to the subsequent paper [J. Appl. Phys. 61, ▪▪▪ (1987)], the velocity data in this report are representative of the velocity of individual twinning partial dislocations which move on the coherent twin boundary.

Velocity of twinning partial dislocations in silicon

Thermal oxidation of silicon was conducted under the application of external compressive or tensile stress at relatively low oxidation temperature. The effect of external stress appeared in different ways depending on the oxidation temperature. While the stress effect of oxidation at 800°C was well interpreted with the linear-parabolic oxidation model (L-P model), that at a temperature lower than 700°C contradicted the L-P model and strongly suggested the existence of an oxidation reaction of interstitial silicon atoms in the oxide.

Effects of External Stresses on the Low Temperature Thermal Oxidation of Silicon

Compression tests were performed on heat‐treated silicon crystals. Yield stresses of crystals depended strongly on the size and density of precipitates induced by heat treatments. Transmission electron microscope observation revealed that SiO2 precipitates larger than a few thousand angstroms became the nucleation sites of glide dislocations, causing a decrease in the yield stress, and that microprecipitates of less than several hundred angstroms acted as obstacles to dislocation movement.

Mechanical properties of heat-treated Czochralski-grown silicon crystals

Oxidation Properties of Hydrogen-Terminated SI (001) Surfaces Following Use of a Hyperthermal Broad Atomic Oxygen Beam at Low Temperatures : Instrumentation, Measurement, and Fabrication Technology

Masataka Umeno

Papers

Residual order within thermally grown amorphous SiO 2 on crystalline silicon

Velocity of twinning partial dislocations in silicon

Effects of External Stresses on the Low Temperature Thermal Oxidation of Silicon

Mechanical properties of heat-treated Czochralski-grown silicon crystals

Oxidation Properties of Hydrogen-Terminated SI (001) Surfaces Following Use of a Hyperthermal Broad Atomic Oxygen Beam at Low Temperatures : Instrumentation, Measurement, and Fabrication Technology