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MOSFET devices have, recently, been considered the basic building element in any electronic IC circuit or system. The great advances achieved by modem technologies has made it possible to scale-down considerably the MOSFET device (channel length L smaller than 0.5μm and oxide thickness smaller than 400Å) which appreciably influences the device performance and its operating parameters.

This Thesis is concerned with the establishment of a Database for electronic component reliability data. Previous research on the reliability of electronic components has mostly originated from accelerated life test studies. However, this Database contains information on field failure data. In addition, the Database was designed specifically for the purpose of exploration of the data in order to establish the potential factors which may contribute to the reliability of electronic components.

Multi-Chip Modules (MCMs) are considered as the next major step in the evolution of high performance microelectronic packaging. Advances in the performance of very high speed MCMs are limited by problems associated with interconnecting devices using metallic interconnects within the module. The need for faster interconnects for gigabit logic MCMs has been discussed in this thesis. Techniques to avoid the problem of taking high speed interconnections through multilayer substrates include radiative and optical techniques. The present research work concentrates on a radiative interconnection technique.

Induction billet heating is a well-established industrial process for preheating prior to forging, rolling and extrusion. In many cases the application of induction heating techniques has been hindered by the inability of existing methods of work coil design to easily produce a design which will give a non-uniform power density along the surface of a workpiece.

Research in MOS-gated power semiconductor devices with combined bipolarlVIOS action has been motivated by the continuous industrial need for highly efficient devices with reduced power losses and high impedance gate control. The Insulated Gate Bipolar Transistor (IGBT) and the IVIOS Controlled Thyristor (MCT) have been among the first :tvIOS-gated bipolar devices with high blocking capability and reduced on-state power losses. Presently these devices are fabricated using the conventional DIVIOS technology. Recently, a new technology, trench technology, has emerged in the field of low voltage power :tvIOSFETs. This thesis discusses the fundamental physical and geometrical advantages of the trench technology over the conventional technologies for high voltage devices. New physical phenomena such as channel length modulation, enhanced channel charge and the PIN diode effect are reported for the first time. A physically-based on-state analytical model for Trench Insulated Gate Bipolar Transistors (Trench IGBTs) is developed. Furthermore, the present study proposes a novel bipolar-MOS concept, termed Inversion Layer Injection. Unlike in conventional bipolar-MOS devices where the bipolar emitter is formed by a "static" semiconductor layer (e.g. n+ type), in this case the bipolar emitter is constituted by mobile carriers ( e.g. electrons), which can be directly controlled by an external gate electric field. Based on this physical principle, a trench-gated device termed the Inversion Layer Emitter Thyristor is proposed. The ILET has the potential to achieve an optimum on-state/turn-off performance and is suitable for a very wide range of applications which require voltage ratings from 400 V up to 5 KV and operating current densities from 100 A/cm2 to 500 A/cm2 . The Inversion Layer Injection concept is further employed in a novel class of power semiconductor devices called Lateral In version Layer Emitter Transistors (LILETs ). The LILETs exhibit low on-state losses, very fast switching time, improved gate control and flexible mode operation. It is concluded that the Trench IGBT and ILET will play the major role in the next generation of high voltage vertical power devices. At the same time, the LILETs are regarded as potential CMOS compatible structures for power int egrated circui ts which can replace the conventional Lateral In sulated Gate Bipolar Transistors (LIGBTs).

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The investigation covers two possible areas of application of magnetic fluids, one involving the production of torque by means of rotating magnetic fields and the other the use Of magnetic fluids in the separation of non-magnetic ores on a density basis. The' emphasis-was upon the use of cheap, primitive ferrofluids Le'. non-collOidal suspension of relatively large particles. a Moskowitz and Rosensweig were the first to report electromechanical energy conversion with a rotating magnetic field. Their theory is not confirmed by their experimental results, howevert nor the fact that the fluid can rotate in the opposite direction to the field. This phenomenon has been investigated experimentally for a range of field intensities, wave velocities, particle sizes, volume loading and fluid viscosities. The torque per unit volume has been found to be related linearly to the volume loading but-nonlinearly to the frequency of the supply, field intensity and viscosity. For the primitive ferrofluids the results clearly indicate a combination of saliency and hysteresis torques. No satisfactory explanation for the reverse motion of the fluid has been produced and attempts to quantify the energy transfer have not been successful. Due to the inherently low permeability of the fluid, the torque per unit volume is much smaller than for conventional a. c. machines. Primitive magnetic fluids have also been shown to have potential in the separation of ores according to their densities. The novelty of this work is that the particles, which flocculate in the presence of stationary fields, are kept in suspension by agitation caused by a rotating wave. This agitation also serves to reduce the effective viscosity which at high volume loading can be high at zero field conditions. An effective specific gravity of about 12 has been obtained. The experimental results confirm the theory that the magnetic force in the linear condition is proportional to the magnetic energy - density gradient (in space) but with saturation the force is proportional to the field gradient and independent of body shape. A practical system seems to be feasible.

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