Este trabalho teve como objetivo principal a fabricação de fotodetetores do tipo Metal-Semicondutor-Metal (MSM) com corrente de escuro da ordem de 1 nA, responsividade da ordem de 0,1 A/W e razão fotocorrente/corrente de escuro de pelo menos 10. Estes valores asseguram que os fotodetetores obtidos tenham sensibilidade suficiente para serem utilizados em sensores ópticos integrados. Todos os materiais utilizados na construção dos fotodetetores MSM são compatíveis com processos convencionais de fabricação em microeletrônica, facilitando a integração com outros dispositivos em estado sólido. O semicondutor utilizado nos fotodetetores foi o silício, na forma monocristalina ou policristalina. Como material de eletrodo, foi utilizado o alumínio, o titânio ou o níquel. No processo de fabricação básico, foram utilizados apenas três etapas: deposição do filme metálico, fotolitografia e corrosão, confirmando a simplicidade de fabricação desse fotodetetor. Através da construção de dispositivos com diferentes geometrias e diferentes combinações dos materiais citados acima, foi possível verificar a influência que a estrutura cristalina do semicondutor, tipo de dopagem do semicondutor, geometria e material de eletrodo tem sobre o desempenho e o comportamento dos MSMs. O comprimento de onda de 632,8 nm foi utilizado na caracterização dos dispositivos, devido a sua disponibilidade e o desenvolvimento de guias ópticos utilizando esse comprimento de onda em trabalhos anteriores do nosso grupo de pesquisa. Os melhores resultados obtidos foram com as amostras de Si monocristalino tipo-p com eletrodos de titânio. Na amostra sinterizada à 250°C foi obtido um valor da corrente de escuro de 4,8 nA e, na amostra de referência, foi obtido um valor de responsividade de 0,28 A/W. / The goal of this work was the fabrication of Metal-Semiconductor-Metal (MSM) photodetectors with the following characteristics: dark current of about 1 nA, responsivity of about 0.1 A/W and dark/photocurrent ratio of at least 10. These values ensure that the photodetectors have enough sensitivity to be used in integrated optic sensors. All materials used in the fabrication of the MSM are compatible with conventional microelectronic manufacture process, so that the photodetectors can be more easily integrated with other solid-state devices. The semiconductor used in the photodetectors was silicon, in single crystal and polycrystalline form. As material of electrodes, aluminum, titanium or nickel had been used. The basic fabrication process consists of only three steps: metal film deposition, photolithography and etching, which confirm the simplicity of the fabrication of this device. Building MSMs with different geometries and making combinations with the materials cited above, gave the possibility to verify the influence that crystalline structure of the semiconductor, doping type of the semiconductor, geometry and electrode material have on the behavior of the photodetectors. The wavelength of 632.8 nm was used in the characterization of the devices, due to its availability and the development of optic waveguides using this wavelength in previous works of our research group. The best results were obtained with the samples fabricated using single crystal Si p-type with titanium electrodes. The sample annealed at 250°C had dark current value of 4.8 nA and, the reference sample had responsivity of 0.28 A/W.

O presente trabalho foi realizado com o objetivo de contribuir para o desenvolvimento tecnológico de sensores eletroquímicos utilizados na detecção de íons, especificamente, de íons de hidrogênio (H+). Na primeira parte do trabalho é descrito e discutido o estado da arte de sensores eletroquímicos de H+, principalmente de dispositivos sensíveis a íons do tipo ISFET (Transistor de Efeito de Campo Sensível a Íons). O foco principal do presente trabalho foi na proposta de fabricação e caracterização funcional de um eletrodo modificado com moléculas de azul de metileno baseado na tecnologia de silício poroso. Os resultados obtidos neste trabalho mostraram que filmes de silício macroporoso modificados com azul de metileno atuam como eletrodos de trabalho com elevada taxa de transferência de elétrons, permitindo sua aplicação em dispositivos sensores eletroquímicos associado à técnica de voltametria cíclica. Os resultados observados nos voltamogramas deste eletrodo mostraram elevada sensibilidade a mudanças de pH da solução, parâmetro associado à concentração de íons de H+. A resposta do sensor foi monitorada pela intensidade de corrente de pico e posição do potencial de pico da reação redox das moléculas de azul de metileno do eletrodo macroporoso modificado. Os eletrodos modificados com azul de metileno em filmes de silício microporoso mostraram uma elevada resistência elétrica, impossibilitando sua aplicação como sensores utilizando-se a técnica de voltametria cíclica. No entanto, devido a sua elevada superfície especifica (600 m2/cm3), estes eletrodos foram aplicados na detecção de íons através da técnica de impedância eletroquímica. Os resultados obtidos com os eletrodos de silício poroso modificado com azul de metileno abrem grandes perspectivas de aplicação em biossensores e Chips de DNA. / This work was done focused on contributing to the technologic development of electrochemical sensors employed in ions detection, specifically, hydrogen ions (H+). At the first part of the work, the H+ electrochemical sensors review is showed and discussed; mainly of the ion sensitive devices know as ISFET device (Ion Sensitive Field Effect Transistor). The work was focused in the purpose of fabrication and functional characterization of a modified electrode with methylene blue molecules based on porous silicon technology. The results obtained with this work showed that macroporous silicon films modified with methylene blue act as work electrodes with high electron transference rate, allowing their application in electrochemical sensor devices using cyclic voltammetry technique. The cyclic voltammetry experimental results of this electrode showed high sensibility to pH changes of the solution, parameter related to the H+ ion concentration. The sensor response was monitored by the intensity of peak current and peak potential position of the redox reaction of methylene blue molecules on modified porous silicon electrode. The modified electrodes with methylene blue on microporous silicon films showed a high electric resistance, making impossible their application as sensors employing the cyclic voltammetry technique. However, due to their high specific surface (600 m2/cm3), these electrodes were applied to ion detection through the electrochemical impedance technique. The results achieved with the porous silicon electrodes modified with methylene blue open great perspectives of application in biosensors and DNA Chips.

Dramatic advances are taking place in the microelectronic industry. The feature size continues to scale down and it is expected that the minimum feature size on the integrated circuit is expected to reach 9 nm by 2016, and there will be more than 8 billion transistors on a 310 cm² chip, according to various available roadmaps. Subsequently, this reduction in feature size would require the first-level input-output interconnects to decrease in pitch size to meet the increased number of transistors on the chip. Also, to minimize the on-chip interconnect delay, development of low-K dielectric/copper will become increasingly common in future devices. However, due to the low fracture strength of low-K dielectric, it is essential that the first-level interconnects exert minimal force on the die pads and therefore, do not crack or delaminate the low-K dielectric material. It is also preferable to have a wafer-level packaging approach to facilitate test-and-burn in and to produce known-good dies. Based on these growing demands from the microelectronics industry, there is a compelling need to develop innovative interconnect technologies. This thesis aims to develop one such innovative interconnect — G-Helix interconnect. G-Helix is a scalable lithography-based wafer-level electroplated compliant interconnect that has the potential to meet the fine-pitch first-level chip-to-substrate interconnect requirements. The three-mask fabrication of G-Helix is based on lithography, electroplating and molding (LIGA-like) technologies, and this fabrication can be easily integrated into large-area wafer-level fine-pitch batch processing. In this work, the fabrication, assembly, experimental reliability testing, and numerical physics-based modeling of the G-Helix interconnects will be presented. The fabrication of the interconnects will be demonstrated at 100μm pitch on a 20 x 20 mm die in a class 10/1000 cleanroom facility. The wafers with compliant interconnects will be singulated into individual dies and assembled on substrates using Pb/Sn eutectic solder. The assembly will then be subjected to air-to-air thermal cycling between 0℃and 100℃ and the reliability of the compliant interconnect will be assessed. In addition to the thermo-mechanical reliability testing, some of the dies with free-standing interconnects will also be used for measuring the compliance of the interconnects by compressing with a nanoindenter. In parallel to the experimental research, a numerical analysis study will also be carried out. The numerical model will use direction-, temperature, time-dependent, and time independent material constitutive properties as appropriate. The thermo-mechanical fatigue life of the compliant interconnect assembly will be determined and compared with the experimental data. Recommendations will be developed for further enhancement of reliability and reduction in pitch size.

Air-gap structures are of particular interest for packaging of microelectromechanical systems (MEMS). In this work, an overcoat material is used to cover a sacrificial polymer, which protects the MEMS device during packaging. Once the overcoat is in place, the sacrificial polymer is thermally decomposed freeing the MEMS structure while the overcoat dielectric provides mechanical protection from the environment. An epoxy POSS dielectric was used as a high-selectivity etch mask for the PPC and a rigid overcoat for the structure leading to the process improvements. The packaging structures can be designed for a range of MEMS device sizes and operating environments. However, the air-cavity structures need additional rigidity to withstand chip-level packaging conditions. Metalized air cavity packages were molded under traditional lead frame molding pressures and tested for mechanical integrity. The experimental molding tests and mechanical models were used to establish processing conditions and physical designs for the cavities as a function of cavity size. A semi-hermetic package was created using an in-situ sacrificial decomposition/epoxy cure molding step for creating large cavity chip packages. Through the optimization of the air cavity, new materials and processes were tested for general microfabrication. The epoxy POSS dielectric provides a resilient, strong inorganic/organic hybrid dielectric for use in microfabrication and packaging applications. Polycarbonates can be used for low cost temporary adhesives in wafer-wafer bonding. An improved electroless deposition process for silver and copper was developed. The Sn/Pd activation was replaced by a cost efficient Sn/Ag catalyst. The process was shown to be able to deposit adherent copper on smooth POSS and silicon dioxide surfaces. Electroless copper was demonstrated on untreated silicon oxide wafers for TSV sidewall deposition.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

Thesis (M.S.M.E.)--University of South Florida, 2003. / Title from PDF of title page. Document formatted into pages; contains 87 pages. Includes bibliographical references.

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