Classical Annealing Research Articles

Analysis and Optimisation of New Implantation and Activation Mechanisms in Ultra Shallow Junction Implants using Scanning Spreading Resistance Microscopy (SSRM)

AbstractWithin this paper we have demonstrated the unique capability of scanning spreading resistance microscopy (SSRM) in order to evaluate and optimize the recent approaches towards the formation of advanced p-MOS devices. As shown in this paper, such an optimization requires a detailed 2D-analysis on completely processed devices as two-dimensional interactions may cause (unexpected) lateral diffusion and (de) activation of underlying profiles. Emphasis will be on junction formation using Ge- pre-amorphization and carbon based cocktail implantation coupled with activation based on solid phase epitaxial regrowth and/or millisecond laser anneal. In the case of a Ge-pre-amorphization implant followed by solid phase epitaxial regrowth, SSRM shows an obvious relationship between the presence of defects in the end of range region and halo implant de-activation. Based on the quantified 2D-profiles we can extract the lateral and vertical junction depths as well as the lateral and vertical abruptness of the extension region. A drastic reduction of the lateral diffusion for the cocktail implant versus the standard reference devices with classical spike annealing is eminent. At the same an important reduction of the lateral diffusion of the source/drain implants (HDD) under the spacer can be seen. The SSRM results also highlight the impact of different activation mechanisms on the channel implants (in particular on the shape of the halo pockets).

Quantum annealing in a kinetically constrained system

Classical and quantum annealing is discussed in the case of a generalized kinetically constrained model, where the relaxation dynamics of a system with trivial ground state is retarded by the appearance of energy barriers in the relaxation path, following a local kinetic rule. Effectiveness of thermal and quantum fluctuations in overcoming these kinetic barriers to reach the ground state are studied. It has been shown that for certain barrier characteristics, quantum annealing might by far surpass its thermal counter part in reaching the ground state faster.

Optimization by quantum annealing: Lessons from simple cases

This paper investigates the basic behavior and performance of simulated quantum annealing (QA) in comparison with classical annealing (CA). Three simple one dimensional case study systems are considered, namely a parabolic well, a double well, and a curved washboard. The time dependent Schr\"odinger evolution in either real or imaginary time describing QA is contrasted with the Fokker Planck evolution of CA. The asymptotic decrease of excess energy with annealing time is studied in each case, and the reasons for differences are examined and discussed. The Huse-Fisher classical power law of double well CA is replaced with a different power law in QA. The multi-well washboard problem studied in CA by Shinomoto and Kabashima and leading classically to a logarithmic annealing even in the absence of disorder, turns to a power law behavior when annealed with QA. The crucial role of disorder and localization is briefly discussed.

Optimization by quantum annealing: Lessons from hard satisfiability problems

The path integral Monte Carlo simulated quantum annealing algorithm is applied to the optimization of a large hard instance of the random satisfiability problem (N = 10,000). The dynamical behavior of the quantum and the classical annealing are compared, showing important qualitative differences in the way of exploring the complex energy landscape of the combinatorial optimization problem. At variance with the results obtained for the Ising spin glass and for the traveling salesman problem, in the present case the linear-schedule quantum annealing performance is definitely worse than classical annealing. Nevertheless, a quantum cooling protocol based on field-cycling and able to outperform standard classical simulated annealing over short time scales is introduced.

Comparisons of multi-source localization and spatial filtering techniques

Localization of moving sources in a multiple source environment has been investigated with simulated annealing algorithms. Results obtained, both by classical annealing and by fast simulated annealing using a rotated coordinate basis, are presented. The fast annealing method varies from the classical method in that each parameter is varied only once per temperature reduction, resulting in many fewer iteration calls per inversion. Accuracy and efficiency for these methods as a function of signal-to-noise ratio are examined using simulated data containing a weak source in the presence of a loud interferer. A method for filtering element level data prior to inversion is compared to subarray processing for effectiveness in localizing the source of interest. The effect of varying the level of the weak source relative to the level of the interferer, as well as the sources azimuthal separation, is also presented. Comparisons between an equally spaced horizontal line array (HLA) and an HLA with nonuniform sensor spacing are made. Finally, comparisons of the inversion techniques for a real data set from a nonuniformly spaced HLA at a Gulf of Mexico site, where ground truth bottom properties have been established, are discussed. [Work sponsored by ONR.]

ITO spin-coated porous silicon structures

Porous silicon (PS)-based structures were formed by deposition of an indium tin oxide (ITO) onto PS surface using the sol–gel spin coating route. Two types of thermal annealing processes, classical and rapid thermal annealing, were used in order to crystallise the ITO films. The initial photoluminescence of the PS layers is partly preserved. The morphology of ITO/PS structure was investigated by cross-sectional transmission electron microscopy (XTEM) and by Rutherford backscattering spectrometry (RBS) measurements.

Excimer Laser Crystallization of SnO2:Sb Sol-Gel Films

Instead of classical or rapid thermal annealing, KrF excimer laser irradiation has been successfully applied to crystallize dried SnO2:Sb films elaborated by a sol-gel process. The penetration of the crystallization front below the film surface, as imaged by transmission electron microscopy, is controlled by the laser fluence and the number of pulses and can thus be confined in the film itself without affecting sensitive substrates. All films laser irradiated at fluences higher than 40 mJ/cm2 become conductive. At constant laser fluence, the electrical sheet resistance goes through a minimum with increasing number of pulses. The consequence of film's densification and morphology on electrical properties is discussed.

Quantum annealing by the path-integral Monte Carlo method: The two-dimensional random Ising model

Quantum annealing was recently found experimentally in a disordered spin-$\frac{1}{2}$ magnet to be more effective than its classical, thermal counterpart. We use the random two-dimensional Ising model as a test example and perform on it both classical and quantum (path-integral) Monte Carlo annealing. A systematic study of the dependence of the final residual energy on the annealing Monte Carlo time quantitatively demonstrates the superiority of quantum relative to classical annealing in this system. In order to determine the parameter regime for optimal efficiency of the quantum annealing procedure we explore a range of values of Trotter slice number P and temperature T. This identifies two different regimes of freezing with respect to efficiency of the algorithm, and leads to useful guidelines for the optimal choice of quantum annealing parameters.

Rapid thermal annealing procedure for densification of sol-gel indium tin oxide thin films

In this work, we report on the interest of the rapid thermal annealing (RTA) for densification of sol-gel (SG) indium tin oxide (ITO) thin films. The crystalline structure of these ITO films was visualized by transmission electron microscopy (TEM) and corresponding electron diffraction pattern were compared with data from pure In 2O 3. The average grain size, measured from TEM micrographs, ranges from 5 to 50 nm. The film densification was followed by Rutherford backscattering spectrometry coupled with cross-section TEM observations. A comparison with classical annealing is discussed.

Tin-doped indium oxide thin films deposited by sol–gel dip-coating technique

Indium tin oxide (ITO) thin films were prepared by the sol–gel dip-coating (SGDC) technique. The microstructure and electrical properties of ITO thin films crystallized using rapid thermal annealing (RTA) were compared with those of films prepared by classic thermal annealing (CTA). ITO thin films were successfully prepared by CTA at 500 °C for 30–60 min. At the same temperature of 500 °C and with a 6 min RTA treatment, the film exhibits electrical resistivity values close to the CTA ones. The crystalline structure of the ITO films was visualized by high-resolution transmission electron microscopy (HRTEM) and electron diffraction patterns compared with that of pure In 2O 3. The average grain size, measured from TEM micrographs, ranges from 5 to 20 nm. The process of film densification was also followed by Rutherford backscattering spectrometry (RBS).

Theory of Quantum Annealing of an Ising Spin Glass

Probing the lowest energy configuration of a complex system by quantum annealing was recently found to be more effective than its classical, thermal counterpart. By comparing classical and quantum Monte Carlo annealing protocols on the two-dimensional random Ising model (a prototype spin glass), we confirm the superiority of quantum annealing relative to classical annealing. We also propose a theory of quantum annealing based on a cascade of Landau-Zener tunneling events. For both classical and quantum annealing, the residual energy after annealing is inversely proportional to a power of the logarithm of the annealing time, but the quantum case has a larger power that makes it faster.

The effects of deposition and annealing conditions on crystallographic properties of sputtered barium ferrite thick films

Abstract The development of devices combining a ferrite with a semiconductor chip is a major focus of current research and could make use of vacuum deposition techniques of magnetic films. Barium hexaferrite (BaFe12O19; BaM) thick films are deposited here using an rf non-reactive sputtering system. Because the as-deposited films are amorphous and non-magnetic, two kinds of post-deposition annealing are employed, which are referred to here as classic thermal annealing (CTA) and rapid thermal annealing (RTA). The effects of annealing conditions on the properties of BaM films are studied using vibrating sample magnetometry (VSM), scanning electron microscopy (SEM) with an EDX probe and X-ray diffractometry (XRD). The first results show a good stoichiometry of the layer and a crystallization above 800 °C. The magnetic properties are closed to that of the bulk BaM. Progress is still necessary to obtain a temperature more compatible with microelectronic technologies (below 500 °C).

A simple approach to time-inhomogeneous dynamics and applications to (fast) simulated annealing

We study time-inhomogeneous stochastic dynamical systems with vanishing noise. Conditions implying strong ergodicity are proposed; the asymptotic probability distribution is characterized and we estimate the speed of relaxation. Applying these results to simulated annealing enables us to introduce systems that converge faster than a classical annealing dynamics determined by a Gibbs factor.

UV Photoannealing and RTP of Thin Sol-Gel Films

AbstractVarious annealing methods for sol-gel films have been investigated. Thermal, photothermal, RTP and excimer laser annealing have been used to convert sol-gel precursor films into oxidic films. RTP annealing of sol-gel films yields better results than classical thermal annealing or excimer laser irradiation. Photochemical effects during RTP annealing contribute to obtain high-quality oxide films. The various annealing methods are illustrated by the annealing of alkoxide precursor films of tantalum, iron, nickel and yttrium.

On the Origin of Internal Gettering Suppression in Low Carbon CZ Silicon by Rapid Thermal Annealing

The influence of classic and rapid thermal annealing pretreatments under nitrogen or hydrogenated ambients on thermal donor formation and on the further oxygen nucleation step were studied. A rapid thermal annealing at 1200°C under a nitrogen ambient delayed the formation of thermal donors. If nitrogen was replaced by a hydrogenated ambient, thermal donor formation was largely enhanced. In each case further nucleation was affected. A modification of the precipitation path due to rapid thermal annealing is proposed to be at the origin of the tremendous effect of a prior lamp anneal on the internal gettering process. The classic heterogeneous nucleation of the platelets would be prevented and the precipitation would proceed through a homogeneous path leading to precipitates unable to getter metal impurities.

Constrained nonlinear optimization approaches to color-signal separation

Separating a color signal into illumination and surface reflectance components is a fundamental issue in color reproduction and constancy. This can be carried out by minimizing the error in the least squares (LS) fit of the product of the illumination and the surface spectral reflectance to the actual color signal. When taking in account the physical realizability constraints on the surface reflectance and illumination, the feasible solutions to the nonlinear LS problem should satisfy a number of linear inequalities. Four distinct novel optimization algorithms are presented to employ these constraints to minimize the nonlinear LS fitting error. The first approach, which is based on Ritter's superlinear convergent method (Luengerger, 1980), provides a computationally superior algorithm to find the minimum solution to the nonlinear LS error problem subject to linear inequality constraints. Unfortunately, this gradient-like algorithm may sometimes be trapped at a local minimum or become unstable when the parameters involved in the algorithm are not tuned properly. The remaining three methods are based on the stable and promising global minimizer called simulated annealing. The annealing algorithm can always find the global minimum solution with probability one, but its convergence is slow. To tackle this, a cost-effective variable-separable formulation based on the concept of Golub and Pereyra (1973) is adopted to reduce the nonlinear LS problem to be a small-scale nonlinear LS problem. The computational efficiency can be further improved when the original Boltzman generating distribution of the classical annealing is replaced by the Cauchy distribution.

Charged particle activation analysis study of the oxygen outdiffusion from Czochralski-grown silicon during classical and rapid thermal annealing in various gas ambient

Oxygen outdiffusion from Czochralski silicon has been studied under various atmospheres, such as oxygen, nitrogen, and argon/hydrogen (10%). The enhancement of the oxygen diffusion coefficient by hydrogen has been confirmed. Besides, thermal treatments in a halogen lamp furnace has led to a 100-fold higher oxygen diffusion coefficient under a neutral atmosphere, and to a 1000-fold enhancement under a hydrogenated atmosphere. Moreover, in this latter case, a level at 6.5×1017 atoms cm−3 in the oxygen profile has been observed at the surface of the sample. Electron-hole pair generation under intense ultraviolet radiation eventually combined with the presence of hydrogen is likely responsible for the anomalously high oxygen diffusion during rapid thermal processing.

Effects of furnace annealing and simultaneous laser excitation on copper and gold diffusion in amorphous germanium

Abstract Diffusion of Au and Cu in amorphous germanium was produced by CW Ar laser excitation during furnace heating. Comparison with classical furnace annealing shows a lowering of the crystallization temperature and an increase of the diffusion rate. A transmission electron microscopy study (imaging and electronic diffraction) shows the formation of metastable compounds. The results are analyzed in relationship to the transient sequence of the produced metastable phases.

Thermal evolution of W/Si and W/C multilayers under pulsed laser heating and classical annealing

The thermal behaviour of nanometer-thick W/Si and W/C multilayers was studied because they can be used as X-ray optics under intense synchrotron X-ray beams. Two types of annealing were performed: pulsed laser annealing and classical thermal annealing in a furnace. Depending on the composition and the structure of the layered materials, thermal stability or diffusion mechanisms were observed and analysed by X-ray scattering, transmission electron microscopy and Auger electron spectroscopy. Simulations of the small angle X-ray scattering curves take well account of the thermal evolution under homogenous furnace annealings and allowed us to compare the resulting evolution under short laser irradiation. Under both treatments, the final state was the crystallization in the tetragonal WSi 2 phase for samples containing silicon, and the partial graphitization of the carbon and the W 2C compound formation for samples containing carbon.

Thermal evolution of X/C multilayers (with X=W, Ni, or SiWSi): A systematic study

The thermal behavior of X/C multilayers (nanometer-thick layers made of tungsten, nickel, or SiWSi alternating with carbide or pure carbon) was studied. Two types of annealing were performed: the pulsed laser annealing in air and the classical thermal annealing in a vacuum furnace. Depending on the composition and the structure of the layered materials, thermal stability or diffusion mechanisms were observed and further analyzed by small-angle x-ray scattering, transmission electron microscopy, and Auger electron spectroscopy. The results show that the period expansion and the reflectivity evolution, that were observed in some cases after treatment, are caused both by structural changes into the layers and by exchange of matter between layers. These changes always induce a partial graphitization of the amorphous carbon and, in the case of W/C multilayers, the formation of a W2C compound.