Рефераты To dynamical theory of electrothermal degradation and NDT of defects in metal

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To dynamical theory of electrothermal degradation and NDT of defects in metal
To dynamical theory of electrothermal degradation and NDT of defects in metal-dielectric-metal (MDM) structuresValentin M. Bogomol'nyiMoscow Institute of Technology, 141220, Moscow Region, Pushkinsky raion, Cherkizovo-1, RussiaABSTRACT On base of the solid state physics and theory of nonlinear oscillations interpretations a development of the thermofluctuation fatique of mechanics theory is formulated. It is shown that electrical damage haves resonance nature. An influence of the electron processes on the first time pre-breakdown stage with mainly of microdefects formation is considered. The proposed theory contents consideration of polarization of the local domains the "cross-pieces" between neighbouring micropores, which formed elementary electrical dipoles. Strong external constant electrical field lead to negative differential resistance of the local dielectric domains with N-or S-type current-voltage-characteristic (CVC) parts and as result to current oscillations and electromagnetic wave radiation from MDM structure (as in Gunn's diode). On base of A. Puankare's limit cycles nonlinear oscillations theory it is shown that defects formation leads to selfexciting current oscillations and microwave radiation. This information can be used in thermosense NDT and, that is principal, for elimination of the defects, which arised under fabrication of electronic devices. Keywords: Electrothermal, resonance, degradation, dielectric, polarization, thermosense1. INTRODUCTION Dielectric thin films aging and breakdown is a phenomenon of major technological significance in optoelectronics, micro- and nanoelectronics. Study of the microdefects formation haves a practical interest at first for improvement of industrial electronic devices quality. On other hand the specially used structure defects lead to sensors, diodes and transistors functional parameters enhance1. Pre-breakdown reversible effects are used in radars as sources of high-frequency radiation (0,1 - 103 GHz), for signals amplification in GHz diapason, where usual transistor not can be used, thermistors, electronic switching2, low-voltaic "cold" cathodes. Reversible breakdown used in "electrical forming" - an known technology process fabrication of the vacuum luminescent screens and origins of high energy electron radiation. By this in space regular local defects (high conducting microchannels, which content low - temperature plasm) are formed in voltage controlled - negative -resistance MDM structures, considered in this work. Interest to study of electrical degradation connected also with an elaboration of high reliability optoelectronic metal - oxide - semiconductor (MOS) devices on base Si - SiO2, Si - SiN4, which used in computer technique, memory and recording elements. The surface of dielectric, contacting with metal electrode, is the most likely domain, where destruction takes place3,5. Local defects on surface are seats of electrical and temperature field concentrations, where origins of the mechanical destruction and electromagnetic radiation are located. The main structure defects - dislocations (linear, plane, screw) arise as rule in all electronic devices under their fabrication. For example, distinction between temperature - expansion - coefficients at dielectric surface metalization lead to creation in GaAs density of dislocations - 108cm-2.When an electrical breakdown event occurs local evaporation of the electrode material can be so that this regions become electrically and mechanically disconnected from the rest structure and a complete series of measurements can be made to renew of devices reliability, physical background of these methods is aim of this work.B.K. Ridley suggested a breakdown essence in SiO2 based devices, which contents the assumption of the presence of ~100 protuberance at electrode surface. Greatly current injection enhanced at protuberances produces high temperature filaments in which dissociation of ion coupling takes place. The resulting positive ions drift to the cathode, producing a positive feedback connection on the current, which lead to its instability and oscillations4-9
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