In this thesis, we present a new Poly - Si TFT process method to overcome Self - heating effect and Floating body effect. The main drawback of a conventional Poly - Si TFT is the existence of self - heating effect and floating body effect. The self - heating effect leads to drain current reduced and the floating body effect leads to premature device breakdown and kink effects. Here, we utilize all kinds of different isolation technologies to form non - continuing buried layer. Between the non - continuing buried layer there are pass ways, which contact the active region and the substrate directly. Because of conventional LOCOS isolation technology has longer bird¡¦s beak, the familiar method of SILO and PBL isolation technologies are used to reduce bird¡¦s beak. Also, we use STI isolation technology to build up non - continuing buried layer, which can control the width of pass way more easily. It is proved from the measurement that the pass way can slow down the self - heating effect and the floating body effect successfully.

One of the poly-Si thin-film cells developed at the University of New South Wales (UNSW) is the EVA cell. In this work, SiN films for EVA cells as an antireflection/barrier coating were investigated. In addition, the effect of hydrogenation pre-treatment of solid phase crystallisation (SPC) on grain size and open-circuit voltage (Voc) was investigated. The SiN films deposited by PECVD were examined for uniformity of the thickness and the refractive index of the films across the position of the samples in the PECVD deposition system. A spectrophotometric analysis was used to determine these film properties. It was found that these properties were very uniform over the deposition area. Good repeatability of the depositions was also observed. A series of SiN film depositions by reactive sputtering were also performed to optimize the deposition process. Parameters adjusted during the deposition were nitrogen flow rate, substrate bias, and substrate temperature. By investigating the deposition rate, refractive index, and surface roughness of the films, the three deposition parameters were optimised. The effects of post SiN deposition treatments (a-Si deposition, SPC, RTA, and hydrogenation) on thickness and refractive index of both SiN films deposited by PECVD and reactive sputtering were investigated by using samples which have the same structure as the EVA cells. The thickness of the PECVD SiN films decreased about 6 % after all the treatments. On the other hand, the thickness reductions of the reactively sputtered SiN films were very small. The refractive index of the PECVD SiN films increased about 0.6 % after the treatments, whereas that of the reactively sputtered SiN films decreased 1.3 % after the treatments. As a possible method to improve the performance of EVA cells, hydrogenation of a-Si was investigated as a pre-treatment of SPC process. There were no obvious differences in the grainsize and the Voc of the EVA cells with and without the hydrogenation. Therefore it is likely that the hydrogenation pre-treatment of SPC does not have a beneficial effect on the performance of EVA cells.

Thin-film solar cells are widely recognised to have the potential to compete with fossil fuels in the electricity market due to their low cost per peak Watt. The Thin-Film Group at the University of New South Wales (UNSW) is engaged in developing polycrystalline silicon (poly-Si) thin-film solar cells on glass using e-beam evaporation technology. We believe our solar cells have the potential of significantly lowering the manufacturing cost compared to conventional, PECVD-fabricated thin-film solar cells. After years of materials research, the focus of the Group??s work is now moving to the metallisation of evaporated solar cells. Minimising various kinds of losses is the main challenge of the cell metallisation procedure, within which the contact resistance is always a big issue. In this thesis, the contact resistance of aluminium contacts on poly-Si thin-film solar cells on glass is investigated. To the best of the author??s knowledge, this is the first ever contact resistance investigation of Al contacts on evaporated poly-Si material for photovoltaic applications. Various transmission line models (TLM) are employed to measure the contact resistance. An improved TLM model is developed to increase the measurement precision and, simultaneously, to simplify the TLM pattern fabrication process. In order to accommodate the particular requirements of poly-Si coated glass substrates, a TLM pattern fabrication process using photolithography is established. Furthermore, a Kelvin sense tester is set up to ensure an accurate measurement of the contact resistance. After establishment of the TLM technique at UNSW, it is successfully tested on singlecrystalline silicon wafer samples. The thermal annealing process of the contacts is also optimised. Then, the general behaviour of Al contacts on uniformly doped poly-Si films (i.e., no p-n junction) is investigated using the verified TLM technique. The long-term stability of the contacts is also studied. This is followed by an investigation of the contact resistance of the back surface field and emitter layers of different types of poly-Si thin-film solar cells. Finally, a novel contact resistance measurement model is proposed that is believed to be able to overcome the measurement bottleneck of the transmission line models.

There were three poly-Si TFT made by ELA, SLS, and HREC. The HREC TFT had better reliability than ELA TFT and SLS TFT under AC and hot carrier stress. And the effect of bending in SLS TFT was more obvious then ELA TFT, it provide us a better choose to develop a flexible TFT LCD. In poly-Si TFT, the photon current would decrease if there was a grain boundary in the channel. In all parameters include both manufacture and measurement the HREC TFT had better behaviors than ELA TFT and SLS TFT. But there also some shortcomings we must overcome include we muse growth a heat-retaining layer extra and must etch it and the poly-Si/heat-retaining etch rate and so on.

Thin-film solar cells are widely recognised to have the potential to compete with fossil fuels in the electricity market due to their low cost per peak Watt. The Thin-Film Group at the University of New South Wales (UNSW) is engaged in developing polycrystalline silicon (poly-Si) thin-film solar cells on glass using e-beam evaporation technology. We believe our solar cells have the potential of significantly lowering the manufacturing cost compared to conventional, PECVD-fabricated thin-film solar cells. After years of materials research, the focus of the Group??s work is now moving to the metallisation of evaporated solar cells. Minimising various kinds of losses is the main challenge of the cell metallisation procedure, within which the contact resistance is always a big issue. In this thesis, the contact resistance of aluminium contacts on poly-Si thin-film solar cells on glass is investigated. To the best of the author??s knowledge, this is the first ever contact resistance investigation of Al contacts on evaporated poly-Si material for photovoltaic applications. Various transmission line models (TLM) are employed to measure the contact resistance. An improved TLM model is developed to increase the measurement precision and, simultaneously, to simplify the TLM pattern fabrication process. In order to accommodate the particular requirements of poly-Si coated glass substrates, a TLM pattern fabrication process using photolithography is established. Furthermore, a Kelvin sense tester is set up to ensure an accurate measurement of the contact resistance. After establishment of the TLM technique at UNSW, it is successfully tested on singlecrystalline silicon wafer samples. The thermal annealing process of the contacts is also optimised. Then, the general behaviour of Al contacts on uniformly doped poly-Si films (i.e., no p-n junction) is investigated using the verified TLM technique. The long-term stability of the contacts is also studied. This is followed by an investigation of the contact resistance of the back surface field and emitter layers of different types of poly-Si thin-film solar cells. Finally, a novel contact resistance measurement model is proposed that is believed to be able to overcome the measurement bottleneck of the transmission line models.

One of the poly-Si thin-film cells developed at the University of New South Wales (UNSW) is the EVA cell. In this work, SiN films for EVA cells as an antireflection/barrier coating were investigated. In addition, the effect of hydrogenation pre-treatment of solid phase crystallisation (SPC) on grain size and open-circuit voltage (Voc) was investigated. The SiN films deposited by PECVD were examined for uniformity of the thickness and the refractive index of the films across the position of the samples in the PECVD deposition system. A spectrophotometric analysis was used to determine these film properties. It was found that these properties were very uniform over the deposition area. Good repeatability of the depositions was also observed. A series of SiN film depositions by reactive sputtering were also performed to optimize the deposition process. Parameters adjusted during the deposition were nitrogen flow rate, substrate bias, and substrate temperature. By investigating the deposition rate, refractive index, and surface roughness of the films, the three deposition parameters were optimised. The effects of post SiN deposition treatments (a-Si deposition, SPC, RTA, and hydrogenation) on thickness and refractive index of both SiN films deposited by PECVD and reactive sputtering were investigated by using samples which have the same structure as the EVA cells. The thickness of the PECVD SiN films decreased about 6 % after all the treatments. On the other hand, the thickness reductions of the reactively sputtered SiN films were very small. The refractive index of the PECVD SiN films increased about 0.6 % after the treatments, whereas that of the reactively sputtered SiN films decreased 1.3 % after the treatments. As a possible method to improve the performance of EVA cells, hydrogenation of a-Si was investigated as a pre-treatment of SPC process. There were no obvious differences in the grainsize and the Voc of the EVA cells with and without the hydrogenation. Therefore it is likely that the hydrogenation pre-treatment of SPC does not have a beneficial effect on the performance of EVA cells.

ポリSi薄膜トランジスタ（TFT）の高性能化について、理論的、技術的な観点から種々の問題点を導き、特にトラップ密度や粒径の大小がTFTの電気的特性に与える影響を詳細に解析し、イオン注入やその後のアニール技術などによって充分に実証を行ったものである。特にエキシマレーザアニール（ELA）を用いた、全工程が下地に影響を与えない低温プロセスは、LSIの微細化とガラス上素子特性の向上に資するものとして有益な知見と考えられる。 / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

Renewable and clean energy is urgently needed to cope with the climate crisis. Photovoltaics (PV) has been the fastest growing technology in the clean energy market due to its low cost, and the abundance of solar energy. The capacity of silicon-based PV is rapidly expanding with evolving technologies. Passivating the solar cell’s electrical contacts is a widely accepted strategy for the PV industry to improve device power conversion efficiency (PCE). Polycrystalline silicon (Poly-Si) passivating contacts are one of the promising concepts in the emerging class of passivating contacts. In this dissertation, the passivation mechanism of Poly-Si passivating contacts is investigated. Moreover, the influence of dopant diffusion on the passivation quality is revealed. To address the side-effects of dopant diffusion, a thin buffer layer is inserted between the Poly-Si(p) layer and the $SiO_x$ layer. With such a buffer layer, the passivation of the Poly-Si passivating contact is improved, which in turn, enhances the device PCE. In addition to passivating contacts, this dissertation also explores carrier-selective contact of crystalline silicon (c-Si) and low work function metal – Li. Li is a very reactive metal which makes the fabrication process a challenge. To overcome such a challenge, the c-Si/ Li contact is fabricated by thermally decomposing stable $Li_3N$ powder instead of metal evaporation. The c-Si/Li contact shows an excellent electron-selective transport performance with a 0.39 eV energy barrier. Full-area Si/Li rear contact devices are fabricated, and >19% PCE and >80% fill factor are achieved. To accelerate the device optimization, a physical model embedded machine-learning approach is applied to transparent conductive oxide (TCO) materials optimization. In this work, empirical correlations between sputtering parameters and the deposited TCOs’ electrical properties are established. Then a Bayesian Parameter Estimation (BPE) algorithm is applied to learn the empirical model. With this BPE network, the TCOs’ electrical properties are successfully predicted with limited material characterizations. Thanks to the combination of BPE and a physical model network, the material optimization process is significantly accelerated. In summary, this dissertation explores different aspects to develop novel passivating and carrier-selective contacts for c-Si solar cells, and introduces an approach to accelerate the development processes.

This thesis deals with the main aspects in chemical vapordeposition (CVD) of silicon (Si) and silicon-germanium (Si1-xGex) films for high-speed bipolar transistors.In situdoping of polycrystalline silicon (poly-Si)using phosphine (PH3) and disilane (Si2H6) in a low-pressure CVD reactor was investigated toestablish a poly-Si emitter fabrication process. The growthkinetics and P incorporation was studied for amorphous Si filmgrowth. Hydrogen (H) incorporated in the as-deposited films wasrelated to growth kinetics and the energy for H2desorption was extracted. Film properties such asresistivity, mobility, carrier concentration and grain growthwere studied after crystallization using either furnaceannealing or rapid thermal annealing (RTA). In order tointegrate an epitaxial base, non-selective epitaxial growth(NSEG) of Si and SiGe in a lamp-heated single-waferreduced-pressure CVD reactor was examined. The growth kineticsfor Si epitaxy and poly-Si deposition showed a differentdependence on the deposition conditions i.e. temperature andpressure. The growth rate difference was mainly due to growthkinetics rather than wafer surface emissivity effects. However,it was observed that the growth rate for Si epitaxy and poly-Sideposition was varying during growth and the time-dependencewas attributed to wafer surface emissivity variations. A modelto describe the emissivity effects was established, taking intoconsideration kinetics and the reactor heating mechanisms suchas heat absorption, emission andconduction. Growth ratevariations in opening of different sizes (local loading) andfor different oxide surface coverage (global loading) wereinvestigated. No local loading effects were observed, whileglobal loading effects were attributed to chemical as well astemperature effects. Finally, misfit dislocations formed in theSiGe epitaxy during NSEG were found to originate from theinterface between the epitaxial and polycrystalline regions.The dislocations tended to propagate across the activearea. <b>Keywords:</b>chemical vapor deposition (CVD), bipolarjunction transistor (BJT), heterojunction bipolar transistor(HBT), silicon-germanium (SiGe), epitaxy, poly-Si emitter,in situdoping, non-selective epitaxy (NSEG), loadingeffect, emissivity effect

<p>This thesis deals with the main aspects in chemical vapordeposition (CVD) of silicon (Si) and silicon-germanium (Si_1-xGe_x) films for high-speed bipolar transistors.<i>In situ</i>doping of polycrystalline silicon (poly-Si)using phosphine (PH₃) and disilane (Si₂H₆) in a low-pressure CVD reactor was investigated toestablish a poly-Si emitter fabrication process. The growthkinetics and P incorporation was studied for amorphous Si filmgrowth. Hydrogen (H) incorporated in the as-deposited films wasrelated to growth kinetics and the energy for H₂desorption was extracted. Film properties such asresistivity, mobility, carrier concentration and grain growthwere studied after crystallization using either furnaceannealing or rapid thermal annealing (RTA). In order tointegrate an epitaxial base, non-selective epitaxial growth(NSEG) of Si and SiGe in a lamp-heated single-waferreduced-pressure CVD reactor was examined. The growth kineticsfor Si epitaxy and poly-Si deposition showed a differentdependence on the deposition conditions i.e. temperature andpressure. The growth rate difference was mainly due to growthkinetics rather than wafer surface emissivity effects. However,it was observed that the growth rate for Si epitaxy and poly-Sideposition was varying during growth and the time-dependencewas attributed to wafer surface emissivity variations. A modelto describe the emissivity effects was established, taking intoconsideration kinetics and the reactor heating mechanisms suchas heat absorption, emission andconduction. Growth ratevariations in opening of different sizes (local loading) andfor different oxide surface coverage (global loading) wereinvestigated. No local loading effects were observed, whileglobal loading effects were attributed to chemical as well astemperature effects. Finally, misfit dislocations formed in theSiGe epitaxy during NSEG were found to originate from theinterface between the epitaxial and polycrystalline regions.The dislocations tended to propagate across the activearea.</p><p><b>Keywords:</b>chemical vapor deposition (CVD), bipolarjunction transistor (BJT), heterojunction bipolar transistor(HBT), silicon-germanium (SiGe), epitaxy, poly-Si emitter,<i>in situ</i>doping, non-selective epitaxy (NSEG), loadingeffect, emissivity effect</p>