Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2007. / Banerjee, Sujit, Committee Member ; Orloff, David, Committee Member ; Patterson, Tim, Committee Co-Chair ; Ahrens, Fred, Committee Co-Chair.

Semiconductor devices are built using hyperpure silicon and very controlled levels of doping to create desired electrical properties. Contamination can alter these precisely controlled electrical properties that can render the device non-functional or unreliable. It is desirable to determine what impurities impact the device and control them. This study consists of four parts: a) determination of acceptable SCI (Standard Clean 1) bath contamination levels using VPD-DSE-GFAAS (Vapor Phase Decomposition Droplet Surface Etching Graphite Furnace Atomic Absorption Spectroscopy), b) copper deposition from various aqueous HF solutions, c) anion contamination from fluoropolymers used in chemical handling and d) metallic contamination from fluoropolymers and polyethylene used in chemical handling. A technique was developed for the determination of metals on a silicon wafer source at low levels. These levels were then correlated to contamination levels in a SCI bath. This correlation permits the determination of maximum permissible solution contaminant levels. Copper contamination is a concern for depositing on the wafer surface from hydrofluoric acid solutions. The relationship between copper concentration on the wafer surface and hydrofluoric acid concentration was determined. An inverse relationship exists and was explained by differences in diffusion rates between the differing copper species existing in aqueous hydrofluoric acid solutions. Finally, sources of contamination from materials used in chemical handling was studied. The predominant anion contamination from fluoropolymers was found to be fluorides. Metallic contamination from fluoropolymers and polyethylene was also studied. The primary metal contamination comes from the actual fabrication of the polymer and not from the polymer resin.

Particle contamination control is a critical issue for the semiconductor industry. In the near future, this industry will be concerned with the chemical identities of contaminant particles as small as 0.01 pm in size. Therefore, analytical techniques with both high chemical sensitivity and spatial resolution are required. Transmission electron microscopy (TEM) provides excellent spatial resolution and yields structural and compositional information. It is rarely used, however, due to the difficulty of sample preparation. The goals of this research are to promote the use of TEM as an ultrafine particle analysis tool by developing new sample preparation methods, and to exploit the new TEM techniques for analysis of particles in semiconductor processing fluids. A TEM methodology for the analysis of particulate contaminants in fluids with an elemental detectability limit as low as 0.1 part per trillion (ppt), and a particle concentration detectability limit as low as 1 particle/ml for particles greater than 0.2 pm was developed and successfully applied to the analysis of particles in HF, H202, de-ionized (DI) water, and on the surface of an electronic device. HF samples from three manufacturers were examined. For HF (B), the maximum particle concentration was 8.3 x 103 particles/ml. Both a viscous material and lath-shaped particles were observed. The Sb concentration was less than 0.6 part per billion (ppb). HF (C) was the cleanest. CaF2 and TiO2 particles were identified in HF (D). For H2 02, iron and tin oxides and hydroxides were identified. The maximum particle concentration was 990 particles/ml. The Sn and Fe concentrations were less than 0.3 ppb. Spherical and dendritic particles were observed. For DI water, spherical and dendritic particles (<2 particles/ml), and particles containing Fe or Si with concentrations less than 0.1 ppt were observed. Contaminants on an electronic device surface were also analyzed. Clusters of small particles were determined to be a mixture of aluminum oxides and aluminum silicates.

CNPQ / Enterococcus sp. podem ser isolados de seres humanos, animais e ambiente; possuem alta tolerância a fatores extremos como pH, temperatura e concentração salina. Desempenham papel importante como cultura starter em vários produtos como iogurtes e queijos, além de serem produtores de enterocinas. Contudo, é crescente seu potencial como agentes causadores de sérias infecções, podendo adquirir alta resistência a antimicrobianos e biocidas. Os equipamentos na indústria alimentícia estão propensos à alta contaminação microbiológica devido à presença de substratos para os microrganismos, e quando não higienizados permitem que os microrganismos se desenvolvam até formarem biofilmes, contaminando o produto final. Este estudo teve por finalidade realizar o isolamento de cepas do gênero Enterococcus de equipamentos das linhas de processos de embutidos cárneos cozidos e de iogurtes, identificar através de técnicas moleculares as espécies dos isolados, verificar a suscetibilidade biocida a sete formulações de diferentes desinfetantes de uso industrial e ação destes sobre o biofilme. Nas amostras coletadas na linha de iogurtes não houve o crescimento de colônias indicativas. Das 36 amostras coletadas nas linhas de produção de embutidos cárneos cozidos, selecionou-se 40 colônias que ao submeter à avaliação genotípica, obtivemos que 70,0% (28 isolados) possuíam o gene tuf que identifica o gênero Enterococcus sp. Identificamos que 7,1% pertenciam aos gêneros E. faecium, 7,1% E. gallinarum, 7,1% E. casseliflavus/E. flavencens e 78,7% dos isolados não foram identificados ao nível de espécie com os oligonucleotídeos iniciadores utilizados neste estudo. Ao avaliar a ação de sanitizantes sobre células de Enterococcus sp. na presença de água verificou-se que nenhum produto utilizado conseguiu ser totalmente eficiente no controle do desenvolvimento dos enterococos em presença de água. Nos testes utilizando BHI e sanitizante os isolados apresentaram menor desenvolvimento na presença do sanitizante amônia quaternária D em todos os tempos, sendo que nos tempos 15 minutos, 1, 2, 3 e 24 horas não houve desenvolvimento. O maior desenvolvimento ocorreu na presença dos produtos dióxido de cloro, hipoclorito de sódio e ácido peracético em todos os tempos, sendo que para os dois primeiros produtos todos os isolados foram resistentes em todos os tempos. Independente do tipo de sanitizantes e biofilme formado, nenhum agente químico foi eficaz na eliminação total das células de Enterococcus. Nota-se que os biofilmes formaram-se mesmo sobre as superfícies sanitizadas, mesmo que tenham sido utilizados as concentrações e tempo médios recomendados pelos fabricantes. É indispensável ressaltar que os resultados confirmam a importância de ações preventivas nas indústrias para evitar a resistência dos microrganismos a determinados compostos e maximizar a eficiência dos procedimentos de higienização aplicados. / The Enterococcus sp. may be isolated from humans, animals and environment. It presents high tolerance to extreme factors such as pH, temperature and salt concentration. It has an important role as a starter culture in different products such yogurts and cheeses, and as producers of enterocinas. However, its potential as agents of serious infections has increasing, especially because can acquire high resistance to antimicrobials and biocides. The food industry equipment’s are willing to high microbiological contamination due to the presence of substrates for microorganisms. When dirty, allow the microorganisms grow and biofilm formation, contaminating the final product. The aim of this work was isolated the genus Enterococci strains of equipment’s on pork cooked sausages and yogurts lines, identified through molecular techniques and check the biocide susceptibility of seven formulations of different industrial disinfectants and the action of these on the biofilm. On the yogurts line samples analyzed there was no grow of indicative colonies. Of the 36 samples analyzed in the sausage line, 40 colonies were selected to undergo genotypic evaluation, showing that 70.0% (28 isolates) had the tuf gene that identifies the genus Enterococcus sp. It was verified that 7.1% belonged to the genus E. faecium, 7.1% E. gallinarum, 7.1% E. casseliflavus/E. flavencens and 78.7% of the isolates were not identified to species level using the oligonucleotides used in this study. In assessing the sanitizing action on cells of Enterococcus sp. in the presence of water there was no product that could be used effectively on grow control of enterococci. In tests using BHI and sanitizing the isolates were less developed in the presence of quaternary ammonia sanitizer D at all times, and in the time 15 minutes, 1, 2, 3 and 24 hours there was no development. Further development occurred in the presence of chlorine dioxide, sodium hypochlorite and peracetic acid at all times, and for the first two products all isolates were resistant at all times. Regardless of the sanitizers and biofilm formed, no chemical agent was effective in complete elimination of Enterococcus cells. Note that biofilms were formed even on the sanitized surfaces even though the average concentration-time recommended by the manufacturer was used. Indispensable to emphasize that the results confirm the importance of preventive actions in the industries to avoid the resistance of microorganisms to certain compounds and maximize the efficiency of applied hygiene procedures.