G. Golan

Hot-Probe method for evaluation of impurities concentration in semiconductors

Abstract Electrical, optical, and mechanical properties of thin films significantly differ from those of bulk materials. Therefore, characterization methods for evaluation of thin film properties became highly important. A novel approach to the well known “Hot-Probe” method is proposed and applied in our work. The conventional Hot Probe characterization method enables only the definition of a semiconductor type, P or N, by identifying the majority charged carriers. According to the new Hot Probe technique, one can measure and calculate the majority charged carriers concentration and its dynamic parameters. Feasibility proof of the upgraded Hot Probe method was done in Si and Ge bulk, and in thin film semiconductor samples.

Electroless-deposited Ag-W films for microelectronics applications

Abstract Thin Ag–W films, with a tungsten concentration of up to 3.2 at.% and a thickness in the range 20–300 nm, were directly deposited on Si(100) substrate by the electroless (auto-catalytic) method. The deposition characteristics and the thin film electrical and physical properties were studied as a function of the bath composition. The role of tungsten in the silver matrix was studied via measurements of the film microhardness and thermal stability as a function of the thin film composition. Ag–W films thicker than 200 nm had a shiny appearance with good reflectivity and their specific electrical resistivity was 2 μΩ cm. The specific resistivity of films increased with decreasing thickness. Exposure of electroless silver films to air at 200°C for a few h causes them to tarnish severely and their sheet resistance to significantly increase, while similar Ag–W films were not affected under the same conditions. Therefore, we assume that silver–tungsten films can be used for applications that require reliable conducting thin films, such as packaging and interconnects for microelectronics.

Simulation and experimental investigation of optical transparency in gold island films

Localized surface plasmons-polaritons represent collective behavior of free electrons confined to metal particles. This effect may be used for enhancing efficiency of solar cells and for other opto-electronic applications. Plasmon resonance strongly affects optical properties of ultra-thin, island-like, metal films. In the present work, the Finite Difference Time Domain (FDTD) method is used to model transmittance spectra of thin gold island films grown on a glass substrate. The FDTD calculations were performed for island structure, corresponding to the Volmer-Weber model of thin film growth. The proposed simulation model is based on fitting of experimental data on nanostructure of ultra-thin gold films, reported in several independent studies, to the FDTD simulation setup. The results of FDTD modeling are then compared to the experimentally measured transmittance spectra of prepared thin gold films and found to be in a good agreement with experimental data.

Pedagogical Communication Patterns in Collaborative Telelearning

Collaborative learning is an indispensable part of Telelearning Distance Education courses. It is naturally implemented via such activities as data collection, projects, and field studies. The worldwide revolution in the telecommunication environment that has been gathering momentum in recent years is bringing radical changes in the collaboration channels. To prepare for these changes, it is vital to identify and solve a wide range of educational and organizational problems involving the embedding of learning and teaching procedures in a telecommunication rich environment. This article is concerned with the pedagogical communication patterns between students and tutors. The result of evaluating students behavior in a set of telelearning Computer Science courses show that they differentiate between the personal dimension of communicating with others and the group dimension which enable true collaborative work. The former depends mainly on the extent to which they need help, whereas the later depends on the design of the group collaboration and the creative leadership of the class teacher or the tutor.

Design and analysis of a novel tunable optical filter

In this paper, an improved design of a tunable optical filter device which is driven by a piezoelectric actuator is proposed. The device can be used either as a tunable optical filter for discrete wavelength alignment or as a dynamic optical filter. The tunable filter is electrostatically driven and consists of three main parts: The electromechanical stage, the suspension and the thin film optical filter. The electromechanical stage and the suspension were designed using graph presentation methods, studied numerically using the finite element method (FEM). The thin film optical filter was designed by a thin film design software. The electromechanical stage was integrated with the suspension and tested as an angular driver of thin-film tilt interference filter for dense-wavelength division demultiplexing system applications.

Novel approach to sputtered tantalum film resistors with controlled pre-defined resistance

Abstract A controlled magnetron sputtering method to obtain precision thin-film tantalum resistors with preset resistance values, is presented. These tantalum film resistors consist of layers of pure tantalum atoms and tantalum oxides. The proposed sputtering method is based on a previous mathematical modeling developed by the authors. With this modeling, one can predict the final product performance as a function of its technological deposition parameters. Feasibility tests to obtain tantalum and tantalum oxide film resistors with a controlled range of resistances, were done on a dedicated sputtering set-up. As a reactive agent in the experimental tests, only residual gases were used. Using the proposed model, precision film resistors with repeatable properties, were achieved in direct relations to the sputtering process parameters. It was found that only two major independent parameters are influencing the resistivity of the tantalum films: (a) the argon pressure in the vacuum chamber; and (b) the sputtering high voltage given to the target. A threshold level of tantalum phase transition from metal to dielectric, was found. Around this threshold level all types of pre-defined resistance may be achieved. The resistance stability of the obtained films, following an annealing Vacuum Photothermal Processing (VPP) was studied as well. It was shown that the electrical properties of the obtained resistors following a VPP treatment were improved with a better resistance stability.

A linear model application for the design of transparent conductive In203 coatings

Abstract Highly transparent conductive indium oxide (In 2 O 3 ) thin films were prepared by DC magnetron sputtering using a pure indium oxide target in an argon atmosphere. A linear programming method for the production design of these thin films using a sputtering process was proposed. Sputtering model calculations were founded on the ‘random partial sections in a multi-factors space’ theory. The obtained model was further optimized by the ‘precipitous rise’ method in order to obtain optimal processing parameters. The chosen active factors of the sputtering process (independent of each other) were: argon pressure; substrate temperature; target voltage; and deposition duration. As a result of the optimization process, the obtained transparent conductive indium oxide thin films had the following parameters: transparency in 550 nm—90.7% (including the glass substrate having an absolute transparency of 91.08%); resistivity of up to 0.043 ω cm for a 2500 A film thickness.

Integrated thin film heater-thermocouple systems

Abstract A novel system of integrated thin-film heater with an embedded thermocouple was developed. Thin-film metallic heaters are widely used today in various fields of electronics and microelectronics applications. The main goal of the heater is usually to maintain the temperature in the heated zone. A deterministic method to manufacture an in situ heater––thermocouple system, with a pre-determined heater resistance, to give a required heat power, was developed. In order to examine this novel method, thin-film heaters were made using layers of Al and NiCr alloys. The temperature of the thin-film heater was measured while heating by an embedded thin-film thermocouple, positioned in the vicinity of the heater. This thin-film thermocouple system consisted of Ni–Ag alloy. A precise control of the growing heater film, while deposition, became possible using a simultaneous measurement of the heater sample resistance.

GENERAL TECHNOLOGICAL MODELING METHOD FOR THE DESIGN OF TRANSPARENT CONDUCTIVE IN2O3 ELECTRODES

Highly conductive transparent indium oxide (In2O3) thin films were prepared by DC magnetron sputtering using pure indium oxide targets in a pure argon (Ar) atmosphere. A linear programming method for the design and optimization of the process was used. The physical model of the sputtering process was based on randomly selected sections of the parameter space. The processing model was optimized by the “steep rise” method, using the mathematical model gradient to obtain optimal parameters. The active independent factors of the sputtering process were Ar pressure during the process, substrate temperature, target voltage and deposition time. As a result of the optimization process, the transparent conductive indium oxide thin films had the following characteristics: Transmittance (T) was 90.7% at λ=550 nm on glass substrates with an uncoated external T=91.1% and resistivity of up to 0.043 Ω cm for a 250 nm film thickness. Thus, the linear model method for the design and optimization of this multiparameter phy...

Ring etching zones on magnetron sputtering targets

Abstract A practical and theoretical investigation into a method for estimating the forms and dimensions of etching zones on magnetron sputtering targets is presented. This estimation is based on detailed geometry considerations of the internal arrangement of the vacuum chamber and the sputtering parameters. It is proved theoretically and experimentally that etching zones on sputtering targets are in a ring shape and that their location and dimensions are independent on the target material or dimensions.