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To harness the wealth of success and computational power from the microelectronics industry, lab-on-a-chip (LOAC) applications should be fully integrated with silicon platforms. This works demonstrates a dielectrophoresis-based LOAC device built entirely on silicon using standard CMOS (complementary metal oxide semiconductor) processing techniques. The signal phases on multiple electrodes were controlled with only four electrical contacts, which connected to the device using three metal layers separated with interlayer dielectric. Indium tin oxide was deposited on a milled plastic lid to provide the conductivity and optical clarity necessary to electrically actuate the particles and observe them. The particles and medium were in the microfluidic chamber formed by using conductive glue to bond the plastic milled lid to the patterned silicon substrate. A correlation between the particle velocities and the electric field gradients was made using video microscopy and COMSOL Multiphysics ® simulations.

This work describes results obtained from detailed TEM, TED, HREM and SIMS analysis of the as-implanted and annealed microstructures of high dose (O.lxl0 17/cm2 to 1.7xl0¹⁸/cm²) oxygen implanted silicon (Si). Molecular oxygen (O₂⁺) has been implanted into Si wafers at equivalent energies of 200keV/O + , 90keV/O +, 70keV/O+ and 50keV/O+ to form, after annealing in flowing N₂ or Ar + ½ %O₂, buried SiO₂ layers below single crystal surface Si layers. This process is called Separation by the IMplantation of OXygen (SIMOX). The energies and doses investigated are potentially suitable for the fabrication of two types of "thin-film" SIMOX substrates, which have major potential benefits for high-performance CMOS devices. This work is concerned with investigating the as-implanted and annealed microstructures, understanding the basic processes and mechanisms taking place during implantation and annealing, and establishing optimum fabrication parameters. Similar microstructures and changes in microstructure as a function of the dose are observed for the different implant energies investigated. For all the different energies and doses investigated, SiO₂ precipitates are present after implantation. Five different precipitate morphologies are observed. The precipitate morphology depends on the oxygen concentration and the depth below the surface. The local and long range strain also play a role in determining the precipitate morphology. For doses of 0.5xl0¹⁸O/cm² to 0.7xl0¹⁸O/cm² at 200keV defects at the wafer surface are non-uniformly distributed across the implanted area. The regions of defects are in plan-view rectangular in shape with edges parallel to <100> directions. The percentage of the implanted surface that is covered by these rectangular regions depends on both the dose and the time-averaged beam current density. This is the first known report of such non-uniform distribution across the implanted area of defects at the wafer surface and their occurrence in regions with precise rectangular shapes. Previously unreported "line" defects below the peak of the as-implanted oxygen distribution for these energies are investigated. They are considered to be platelets on {100} planes and edge dislocation loops on {110} planes. After annealing, two major types of defects are present, threading dislocations in the surface Si layer and Si islands within the buried SiO₂ layer. Correlation of as-implanted and annealed microstructure suggests that the threading dislocations originate in the defects present at the wafer surface after implantation and grow down during annealing. The Si islands originate from Si isolated from the surface Si layer and the substrate during implantation or annealing. The optimum dose for forming a SIMOX structure at a particular energy with both a low threading dislocation density and a low Si island density is just greater than the minimum dose for forming a continuous buried SiO₂ layer after annealing. In order to try and reduce the density of Si islands within the buried SiO₂ layer, graded low energy implants and interim rapid thermal anneals are investigated. Their influence on the microstructure is reported. The experimental results enable, for the implantation and anneal conditions used, the likely threading dislocation and Si island density after annealing to be estimated for a particular dose and energy. Simple models have been proposed for calculating typical oxygen diffusion lengths during implantation, the thicknesses of the buried SiO₂ and surface Si layers after annealing and conversely the implant dose and energy required to fabricate a SIMOX substrate with a certain thickness of buried SiO₂ and a certain thickness of surface Si layer after annealing. Thin-film SIMOX substrates consisting of a thin surface Si layer above a thin buried oxide layer suitable for high-performance "fully depleted" CMOS devices have been successfully fabricated by implanting doses of ≥0.35 and ≥0.33xl0¹⁸O/cm² at energies of 90keV and 70keV, repectively. Thin-film SIMOX substrates with a thin buried oxide layer below a standard thickness surface Si layer suitable for radiation hard circuits with reduced circuit self-heating have been successfully fabricated by implanting doses of ≥0.56xl0¹⁸ O/cm² at an energy of 200keV.

This thesis is primarily concerned with the evaluation and comparison of the dielectric behaviour of materials which may find application as substrates in microelectronic high-performance packaging. In the introductory chapter the factors governing the choice of the most suitable dielectric substrate for compatibility with silicon technology are reviewed; it is shown that in addition to good dielectric properties the thermal conductivity is important if high power packages are required together with the ability to obtain good matching of thermal expansion coefficients. This is followed by a survey of the present theories of dielectric behaviour with special emphasis on the Universal law of dielectric response and its applicability to oxide and glass ceramics which exhibit hopping conductivity. The experimental methods for the measurement of dielectric parameters are outlined in Chapter 3 which includes an account of techniques developed for studying materials only available as powders. The three substrate systems studied were aluminium oxide, aluminium nitride and glass-on-molybdenum and in the case of the two former materials a range of both pure and impure specimens were examined both in single crystal and sintered polycrystalline form. The detailed experimental results are presented and discussed in the three succeeding chapters for each of the materials in turn; these results include the values of permittivity and dielectric loss, measured over a frequency range of 5 x 10(^2) Hz to 1 x 10(^7) Hz, the temperature variation of permittivity both in the low temperature (85K to 293k) and high temperature (20ºC to about 600ºC) regions and the d.c. and a.c. conductivity in the high temperature range. In their pure form each of these materials would be suitable as a substrate, having permittivities at room temperature of ϵ ' (_s) = 10.2 for polycrystalline Al(_2)(^0)(_3), ϵ' (_s) = 9.2 for polycrystalline AlN (which has a thermal conductivity of about one-hundred times that of alumina) and ϵ' (_s) - 6.5 for glass-on-molybdenum and dielectric losses in the region of tan δ - 10(^-3). The effect of impurities is shown to be very significant leading in all cases to some increase in permittivity and a much larger increase in dielectric loss. The measurements made on powders are given and discussed in Chapter 7. In the studies on the powders used as starting materials for the manufacture of substrates it was shown that by making measurements at low temperature (77K) the effects of intergranular space charge polarization could be overcome yielding information valuable for quality control of impurity content; measurements made on powders of some high temperature oxide superconducting materials are also given. The final chapter, Chapter 8, summarises the overall conclusions of the research and makes some suggestions for future work.