This thesis explores the feasibility of high power impulse magnetron sputtering (HiPIMS) to synthesize hydrogenated amorphous carbon (a-C:H) thin films in Ar-hydrocarbon ambient and the relationship between process parameters, gas phase composition and film properties. To this purpose a stable process based on HiPIMS and direct current magnetron sputtering (DCMS) has been developed. Four series of amorphous carbon thin films were deposited by hybrid HiPIMS-DCMS and pure DCMS processes at 15 mTorr pressure using different Ar-acetylene compositions and a substrate bias from 0 to -350 V. The effect of Ar-acetylene compositions and depositions processes on the film properties was investigated by characterizing the films using scanning electron microscopy (SEM), x-ray reflectometry (XRR), nanoindentation and elastic recoil detection analysis (ERDA). Moreover the process characterization was done by recording the optical emission spectrum and current and voltage waveforms of the hybrid HiPIMS-DCMS discharge. The characterization of the films revealed that the hybrid HiPIMS-DCMS process is a powerful tool for controlling the amorphous carbon film properties such as density, deposition rate, hardness and hydrogen content.

Abstract In this study, copper oxide thin films prepared by DC reactive magnetron sputtering using a Cu target were studied. By changing the oxygen partial pressure ratios and sputtering power and deposition temperatures during sputtering, we obtained copper oxide thin films with different properties. The structures of copper oxide thin films were characterized by glancing incident angle X-ray diffraction. Clear crystal orientation at (002) plane were observed at 50% and 60% oxygen partial pressure ratio. The preferred orientation at (111) plane were observed with heating substrate to 200¢J. The optical and electrical properties of cupric oxide thin films were measured by UV-VIS spectrophotometer and four-point probe system. The cupric oxide thin films deposited with heating substrate to 200¢J exhibited the resistivity of 0.77£[-cm and optical band gap of 1.57 eV. Keywords¡G cupric oxide, thin film, magnetron sputtering, band gap

In the process of sputtering, what a system operator concerns are the sputtering rate, target utilization, and substrates uniformity. All of them are influenced by variables such as electromagnetic environment, chamber temperature, and pressure. In thin film manufacturing, targets bombarded by ions will sputter atoms to the substrates in order to make thin films; therefore, when a certain target zone is extensively bombarded by ions, target surface will become thinner. In general, when certain part of the target is penetrated, it is no longer usable while utilization rate only from 30 to 50 percent. It causes considerable waste and relatively higher costs. As a result, the objective of this study is to enhance target utilization and the sputtering rate through appropriate adjustment in the structure of the existing DC Magnetron Sputtering System (MSS). Since, the magnetic field distribution in the chamber will be appropriately adjusted inside the DC MSS with extra iron annulus and active compensation magnetizations being added. However, in order to get the better structural refinement of DC MSS it needs a thorough design and management based on Taguchi Method. Then, based on such structural adjustment, electron trajectories on top surface of targets can be conveniently controlled, and target erosion patterns and the number of ions bombarding the target will be indirectly controlled. It will, as a result, achieve the objective of this study by enhancing not only the target utilization efficiency but the sputtering rate.

The purpose of this study is to investigate the effects on DC sputtered thin films after different surface treatments on aluminum targets. Abrasive papers and nonwovens were used to polish the aluminum targets before sputtering. Surface morphology of the aluminum targets before and during sputtering were characterized using surface profiler. In addition, the erosion rate of the aluminum targets was obtained by measuring the changes of the erosion depth with sputtering time at a fixed processing condition. On the other hand, the surface morphology and electrical characteristics of the deposited thin films with respect to different aluminum targets were investigated. We found that surface roughness of the treated aluminum targets is of great importance to the stability of the film quality.

To smooth the substrate depositions of DC magnetron sputter (MS), such that the supplementary electrical and mechanical adjustment efforts can be alleviated, a refinement scheme that can be applied directly to the existing DC MS will be introduced. By properly controlling the magnetic and electric fields inside the vacuum chamber, trajectories of those atoms that are sputtered from the target surface can be more spread out. In addition, with the resultant higher plasma density, chance of collisions among the sputtered atoms and those Ar ions in the plasma will also be increased, hence the resulting distributions of target atoms deposited on the substrate surface will certainly be evened out. To further confirm such concepts, a rational emulating process that can explore both the atom sputtering process from the target and those collisions at the chamber with different three-dimensional magnetic and electric field environments is also developed. Thus the associated performance investigations on the DC MS with different magnetron arrangements can then be conveniently carried out.

Silicon heterojunction solar cells, a-Si:H/c-Si, are promising technology for future photovoltaic systems. An a-Si:H/c-Si heterojunction solar cell combines the advantages of single crystalline silicon photovoltaic with thin-film technologies. This thesis reports a detailed survey of heterojunction silicon solar cells with p-type wafer fabricated by magnetron sputtering and Plasma Enhanced Chemical Vapor Deposition (PECVD) techniques at low processing temperature. In the first part of this study, magnetron sputtering method was employed to fabricate a-Si:H thin films and then a-Si:H/c-Si solar cells. Amorphous silicon (a-Si:H) films were grown on glass in order to perform electrical and optical characterizations. The J-V characteristics of the silicon heterojunction solar cells were analyzed as a function of a-Si:H properties. It was shown that a-Si thin films with well-behaved chemical and electronic properties could be fabricated by the magnetron sputtering. Hydrogenation of the grown film could be achieved by H2 introduction into the chamber during the sputtering. In spite of the good film properties, fabricated solar cells had poor photovoltaic parameters with a low rectification characteristic. This low device performance was caused by high resistivity and low doping concentration in the sputtered film. The second part of the thesis is dedicated to heterojunction solar cells fabricated by PECVD. In this part a systematic study of various PECVD processing parameters were carried out to optimize the a-Si:H(n) emitter properties for the a-Si:H(n)/c-Si(p) solar cell applications. In the next stage, a thin optimized a-Si:H(i) buffer layer was included on the emitter side and on the rear side of the c-Si(p) to improve the surface passivation. Insertion of an a-Si:H(i) buffer layer yielded higher high open circuit voltage (Voc) with lower fill factor. It was shown that high Voc is due to the efficient surface passivation by the front/rear intrinsic layer which was also confirmed by the measurement of high effective lifetime for photo-generated carriers. Low fill factor on the other hand is caused by increasing resistivity of the solar cells by inserting low conductivity a-Si:H(i) layers.

The DC magnetron sputtering system (MSS) is used in microelectronic industries, and is a key device in the thin film depositions manufacturing process. The major influence factors of the DC magnetron sputtering system operational performance such as operational time and target utilization, which are due to unsatisfactory interactions between electrons and electromagnetic field inside the sputter. This study hopes to improve an established DC MSS, by employing commercial finite element analysis software that will be calculated the flux density, and using three-dimensional equation of motion to estimate the behavior of electrons inside the sputter; furthermore, in the light of the influence electrons position and speed, proposed refinements that the magnetic field above the target is controlled to make the performance improvement. Results from a study showed that the operational trajectory of the electrons at different magnetic flux density levels on top of the target after an operational period, the proposed refinements can increase the sputtering efficiency by as much as 30%. Other than that, through the similarities and dissimilarities between the additional magnetic fields and the main magnetic flux direction, the target erosion profiles with the refinements are more evenly spread out; reduction in the target material consumptions can also be expected.

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The thin film technology is of great importance in modern society and is a key technology in wide spread applications from electronics and solar cells to hard protective coatings on cutting tools and diffusion barriers in food packaging. This thesis deals with various aspects of thin film processing and the aim of the work is twofold; firstly, to obtain a fundamental understanding of the sputter deposition and the reactive sputter deposition processes, and secondly, to evaluate sputter deposition of specific material systems with low friction properties and to improve their performance.From studies of the reactive sputtering process, two new methods of eliminating the problematic and undesirable hysteresis effect were found. In the first method it was demonstrated that an increased process pressure caused a reduction and, in some cases, even elimination of the hysteresis. In the second method it was shown that sufficiently high oxide content in the target will eliminate the hysteresis. Further studies of non-reactive magnetron sputtering of multi-element targets at different pressures resulted in huge pressure dependent compositional gradients over the chamber due to different gas phase scattering of the elements. This has been qualitatively known for a long time but the results presented here now enable a quantitative estimation of such effects. For example, by taking gas phase scattering into consideration during sputtering from a WS2 target it was possible to deposit WSx films with a sulphur content going from sub-stoichiometric to over-stoichiometric composition depending on the substrate position relative the target. By alloying tungsten disulphide (WS2) with carbon and titanium (W-S-C-Ti) its hardness was significantly increased due to the formation of a new titanium carbide phase (TiCxSy). The best sample increased its hardness to 18 GPa (compared to 4 GPa for the corresponding W-S-C coating) while still maintaining a low friction (µ=0.02) due to the formation of easily sheared WS2 planes in the wear track.

Doctor of Philosophy / First part of the thesis is focused on experimental preparation of new hard quaternary amorphous materials Si-B-C-N with high thermal stability. Materials were prepared in the form of thin films using reactive magnetron sputtering. The technique used proved to be suitable for reproducible synthesis of these materials. The Si-B-C-N films were generally found to be amorphous with low compressive stress and good adhesion to silicon or glass substrates. The process and film characteristics were controlled by varying the sputter target composition, the Ar fraction in the N2–Ar gas mixture, the negative rf-induced substrate bias, and the substrate temperature. Main conclusions describe the relationships between process parameters, discharge and deposition characteristics and film properties (elemental composition, chemical bonding structure, material hardness, compressive stress or electrical conductivity of materials prepared). Second part of the thesis is focused on ab-initio simulations of structures of experimentally prepared Si-B-C-N materials. In the performed liquid-quench simulations, the Kohn-Sham equations for the valence electrons are expanded in a basis of plane wave functions, while core electrons were represented using Goedecker-type pseudopotentials. We simplified the ion bombardment process by assuming that the primary impact creates a localized molten region of high temperature and sufficiently short cooling time, commonly referred to as a thermal spike. Main conclusions deal with N2 formation in studied materials, effect of implanted Ar on structure and properties of prepared materials, ability of Si to relieve that part of compressive stress which is caused by implanted Ar, and ability of B to improve thermal stability of Si-B-C-N materials. The calculated results are compared with experiment.