The plasma abatement system co-developed by Rf Environmental, Inc. and Texas A & M University has been effective at destroying the global warming gases CF4 and C4F8. The destruction of greenhouse gases, specifically perfluorocompounds, hydrofluorocompounds, chlorofluorocompounds (PFCs, HFCs, CFCs) and SF6, is paramount to significantly affecting atmospheric pollution. The premise of this study was to examine the design of the plasma abatement system for Global Warming Gases (GWGs) and its abatement potential for these gases. The first goal was to reduce the cost of ownership by examining the cooling system. The cost of an air cooling design was $1400/yr. The intent was to reduce the amount of air used or use a different medium that would produce the same amount of heat transfer. A liquid cooling system design had a cost of only $150/yr. A C4F8 abatement experiment was run on the liquid cooling design. The abatement process resulted in a destruction removal efficiency (DRE) of C4F8 of 97.5 percent. A lower operational cost unit was developed, but the operational performance was less than previous investigations. The second goal was to simulate the semiconductor radio frequency etching process and abate the output gases of the C4F8 and SiO2 reaction. The outcomes of this experiment included a microwave simulation of the radio frequency etching reaction and an abatement that resulted in a 99.98 plus/minus .05 percent DRE for C4F8 with no formation of any other CFC gases. The third goal was to simulate the etching process and abate the output gas, CF4 using H2O vapor as the additive gas. The outcomes of this experiment included a microwave simulation of the radio frequency etching reaction and an abatement that resulted in a 99.96 plus/minus .05 percent DRE for CF4 with no formation of any other CFC gases. A low cost of ownership and effective abatement levels will make this system viable for commercial use. The latest data shows the amount of PFC emissions from the semiconductor industry was 3.6 Tg CO2 Eq. The use of this or a similar abatement technology will have a significant impact on reducing environmental pollution.

High aspect ratio polymeric micro-patterns are ubiquitous in many fields ranging from sensors, actuators, optics, fluidics and medical. Second generation PDMS molds are replicated against first generation silicon molds created by deep reactive ion etching. In order to ensure successful demolding, the silicon molds are coated with a thin layer of C[subscript 4]F[subscript 8] plasma polymer to reduce the adhesion force. Peel force and demolding status are used to determine if delamination is successful. Response surface method is employed to provide insights on how changes in coil power, passivating time and gas flow conditions affect plasma polymerization of C[subscript 4]F[subscript 8]. / Singapore-MIT Alliance (SMA)

L’objectif de ce mémoire de maîtrise est de développer des outils de diagnostics non-invasifs et de caractériser in-situ les dérives de procédé dans un réacteur industriel utilisé en production pour la gravure profonde du silicium par le procédé Bosch. Ce dernier repose sur l’alternance d’un plasma de SF6 pour la gravure isotrope du Si et d’un plasma de C4F8 pour la passivation des parois dans l’optique d’obtenir des tranchées profondes et étroites. Dans un premier temps, nous avons installé une sonde courant-tension sur la ligne de transmission du signal rf au porte-substrat pour l’étude de son impédance caractéristique et un spectromètre optique pour l’étude de l’émission optique du plasma. Nos travaux ont montré que l’évolution temporelle de l’impédance constitue un excellent moyen pour identifier des changements dans la dynamique du procédé, notamment une gravure complète de la photorésine. De plus, à partir des spectres d’émission, nous avons pu montrer que des produits carbonés sont libérés du substrat et des parois lors de l’alternance passivation/gravure et que ceux-ci modifient considérablement la concentration de fluor atomique dans le plasma. Dans un second temps, nous avons développé un réacteur à « substrat-tournant » pour l’analyse in-situ des interactions plasma-parois dans le procédé Bosch. Nos travaux sur ce réacteur visaient à caractériser par spectrométrie de masse l’évolution temporelle des populations de neutres réactifs et d’ions positifs. Dans les conditions opératoires étudiées, le SF6 se dissocie à près de 45% alors que le degré de dissociation du C4F8 atteint 70%. Le SF6 est avant tout dissocié en F et SF3 et l’ion dominant est le SF3+ alors que le C4F8 est fragmenté en CF, CF3 et CF4 et nous mesurons plusieurs ions significatifs. Dans les deux cas, la chaîne de dissociation demeure loin d’être complète. Nous avons noté une désorption importante des parois de CF4 lors du passage du cycle de passivation au cycle de gravure. Un modèle d’interactions plasmas-parois est proposé pour expliquer cette observation. / The purpose of this master thesis is to develop non-invasive diagnostic tools for in-situ characterization of process drifts in an industrial reactor used in production for deep silicon etching by the Bosch process. This process alternates between a SF6 plasma for isotropic Si etching and a C4F8 plasma for sidewall passivation to achieve deep and narrow trenches. In this context, a current-voltage probe was installed on the rf transmission line to the substrate holder for impedance studies and an optical spectrometer for plasma optical emission spectroscopy. We have shown that the time evolution of the impedance represents an excellent tool for monitoring changes in the process dynamics, including the complete removal of the photoresist due to process drifts. In addition, based on emission spectroscopy, we have demonstrated that carbon products are released from the substrate and reactor walls during etching. A « spinning-wall » reactor was also developed for in-situ analysis of plasma-wall interactions. The main objective of our work on this reactor was to characterize the time evolution of the population of reactive neutrals and positive ions by plasma sampling mass spectrometry. Over the range of experimental conditions investigated, the percent dissociation of SF6 was 45%, while the one of C4F8 was 70%. SF6 was mostly dissociated in F and SF3, with SF3+ as the dominant ion. C4F8 is essentially fragmented in CF, CF3 and CF4 with many significant ions. In both cases, the dissociation chain remained incomplete. An important desorption of CF4 from the reactor walls was observed when going from passivation to etching cycles. A plasma-wall interaction model was proposed to explain such observation.