E. Rabinovitch

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.

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...

Effects of electron beam generated in vacuum photo-thermal processing on metal–silicon contacts

Abstract The influence of electron beam during vacuum photo-thermal processing (VPP) treatment of metal–silicon contacts, was studied. This is the first experimentally evidence for a novel effect of potential barrier variations in metal-semiconductor contacts following a VPP. The possibility to control the potential barrier in metal–silicon contacts was shown. The same nature of influence of electron beam on the potential barrier between silicon and other metals such as: Ti and Ni were presented as well. The potential barriers in: Ti–Si and Ni–Si were varied from 0.605 to 0.785 eV and from 0.571 to 0.672 eV, respectively. Furthermore, it was found experimentally that the metallic surface order in the metal-silicon pair, following VPP, was dramatically improved. Surface roughness was decreased and the electrical conductivity was increased. Finally, the influence of a non-coherent irradiation on the properties of metal-silicon contacts was studied.

Bilayer structure of PdAl2O3 for UV vidicon applications

Abstract A bilayer structure of PdAl 2 O 3 was developed as a signal plate for vidicon TV tubes. The 20 A thick Pd layer served as the conducting plate while the 30–50 A thick Al 2 O 3 coating functioned as the transparent protecting film. The obtained signla plates had a sheet resistance of 2.5 KΩ and a transmission coefficient of 71% at a wavelength of 250 nm. The main advantage of vidicons equipped with such signal plates is to have a dark current of less than 0.05 nA, which is suitable for UV applications. The PdAl 2 O 3 bilayers were produced by a novel sputtering method.

Linear model application for the design of transparent conductive In/sub 2/O/sub 3/ electrodes

Transparent conductive coatings with high electrical conductivity and maximum optical transparency attracts much attention in recent years. Most of the works published till present in this field were concentrated in the physical analysis and design of thin film coatings. In this paper we present a different approach to the fabrication design of transparent conductive thin films. Instead of analyzing complex physical models of the final product, a mathematical linear model to control the processing stages of these films production is presented. This linear model is based on a mathematical approach which optimize the processing procedure parameters to yield the best coating performance. The main idea in this linear model optimization procedure lies in finding functions extremums using their derivatives and gradients. The Transparent Conductive Oxide (TCO) Indium Oxide thin films (In/sub 2/O/sub 3/) were obtained by DC magnetron sputtering from pure Indium Oxide target in an argon atmosphere. The obtained transparent conducting thin films had the following parameters: -Transparency in 550 nm wavelength-90.7% (including the glass substrate with an absolute transparency of 91.08%); -resistivity of 0.043 /spl Omega//spl middot/cm for a 2525 /spl Aring/ film. As a result of this work the linear model was found to be a useful instrument for the general fabrication design of thin film systems.

Characteristics of indium oxide films prepared by DC magnetron sputtering

Highly conductive transparent indium oxide (In/sub 2/O/sub 3/) thin films were prepared by DC magnetron sputtering using pure indium oxide targets. Sputtering was done in a pure Argon (Ar) atmosphere with a residual pressure of less than 4/spl times/ 10/sup -5/ Torr. The substrate temperature was varied during the sputtering process from room temperature to 250/spl deg/C. Some of the In/sub 2/O/sub 3/ samples were given a post-deposition heat treatment while still in vacuum. The indium oxide films were deposited on borosilicate glass plates 0.13/spl plusmn/0.17 mm thick and on optical slide glasses 1 mm thick. The resultants films were characterized for their optical, electrical and mechanical properties. Results show that films with resistivity as low as 2.7/spl times/10/sup -3/ /spl Omega/cm, and transmittance as high as 92% in the visible range (400/spl plusmn/650 nm) can be obtained by gaining a complete control on the process parameters. A variance in the electrical, mechanical and optical properties of the In/sub 2/O/sub 3/ films was found in layers made on borosilicate glass substrates.

Plasma enhanced ion plating system

An anode plasma enhanced ion plating deposition system for high quality rapid deposition was constructed and investigated. This system is based on the modified multipurpose vacuum station VUP-5, however may be adopted for any other construction. Vacuum chamber base pressure was kept below 2/spl times/10/sup -5/ Torr. System configuration of the novel ion plating is similar to the conventional vacuum thermal evaporation system but the deposition process is different. In the proposed process gaseous forced discharge in the steams of the evaporated materials is used. The heating filament of the crucible, containing the material to be evaporated, is used as the hot electron source. When the filament temperature is sufficient for the material to evaporate, the electrons irradiated from the filament generate ion flux from the material steam. In order to increase electron concentration in the flux a quasi-homogeneous magnetic field, made of two permanent magnets, with a magnetic field of /spl sim/1000 Oe, positioned in the vacuum chamber is applied. The DC voltage varies between 0 V to 3000 V. This system is also equipped with a gas inlet line to let a glow discharge to be generated with inert or reactive gas. The main advantage of this novel development lie in its ability to obtain stoichiometric films as alloys, compounds, and new materials which are products of the reaction between ions of reactive gas and ions of evaporated materials. The ion plating system is axis-symmetrical.