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With the scaling of devices, integration of porous ultra low-κ dielectric materials into Cu interconnect becomes necessary. Low-k dielectric materials usually consist of a certain number of methyl groups and pores incorporated into a SiO₂ backbone structure to reduce the dielectric constant. They are frequently exposed to various plasmas, since plasma is widely used in VLSI semiconductor fabrication such as etching, ashing and deposition. This dissertation is aimed at exploring the interaction between plasma and low-κ dielectric surfaces. First, plasma assisted the atomic layer deposition (ALD) of Ta-based Cu barriers. Atomic layer deposition of Ta barriers is a self-limited surface reaction, determined by the function groups on the low-κ dielectric surface. But it was found TaCl₅ precursor could not nucleate on the organosilicate low-κ surface that was terminated with methyl groups. Radical NH[subscript x] beam, generated by a microwave plasma source, could activate the surface through exchanging with the methyl groups on the low-κ surface and providing active Si-NH[subscript x] nucleation sites for TaCl₅ precursors. Results from Monte Carlo simulation of the atomic layer deposition demonstrated that substrate chemistry was critical in controlling the film morphology. Second, the properties of low-κ dielectric materials tended to degrade under plasma exposure. In this dissertation, plasma damage of low-κ dielectric surface was investigated from a mechanistic point of view. Both carbon depletion and surface densification were observed on the top surface of damaged low-κ materials while the bulk remained largely uninfluenced. Plasma damage was found to be a complicated phenomenon involving both chemical and physical effects, depending on chemical reactivity and the energy and mass of the plasma species. With a downstream plasma source capable of separating ions from the plasma beam and an in-situ x-ray photoelectron spectroscopy (XPS) monitoring of the damage process, it was clear that ions played a more important role in the plasma damage process. Increase of dielectric constant after plasma damage was mainly attributed to moisture uptake and was confirmed with quantum chemistry calculation. Annealing was found to be effective in mitigating moisture uptake and thus restoring κ value. Finally, oxygen plasma damage to blanket and patterned low-κ dielectrics was studied in detail. Energetic ions in oxygen plasma contributed much to the loss of film hydrophobicity and dielectric constant through the formation of C=O and Si-OH. Based on results from residual gas analyses (RGA), three possible reaction paths leading to carbon depletion were proposed. This was followed by analytical solution of the evolution of carbon concentration during O₂ plasma damage. O₂ plasma damage to patterned CDO film was studied by TEM/EELS. And the damage behavior was simulated with Monte Carlo method. It was found that the charging potential distribution induced by plasma was important in determining the carbon loss in patterned low-k films. The charging potential distribution was mainly related to the geometry of low-k trench structures. To recover the dielectric constant, several recovery techniques were tried and briefly discussed. / text

The optimisation of I-alkene polymerisation processes by highly active metallocene systems such as racSBIZrMe2 activated by [Ph3C][CN{B(C6Fs)3h] (I) or by [Ph3C][B(C~s)4] (II) was perfonned. Subsequently. a systematic quantitative study of ligand effects on polymerisation activity, molecular weight and polymer microstructure was carried out. Non-bridged and bridged C2y-symmetry zirconocene dimethyls and dichlorides alkylated (or alkyl exchanged) by AlBu'3 (TIBA) and activated by 1 are much less active than Crsymmetric zirconocenes. Propene polymerisations catalysed by those systems afford low molecular weight atactic polypropene. TIBA rapidly alkylates dichloride zirconocenes affording pre-catalysts which, once activated, give a catalytic profile comparable with that obtained with dimethyl zirconocenes. Activities of Crsymmetry raczirconocenes / AlBui3 / I or [Ph3C][H2N{B(C6Fs)3h] (III) in propene polymerisation decrease according to the order SBMbiZrCh (17) > SBIZrCh (16) > EBIZrCh (13) > MBBIZrCh (18) > EBIDMZrCh (19) > EBTHIZrCb (20) > SBSCZrCh (14) > SBBCZrCh (15). These values are not distorted by side effects such as mass transport limitation, so represent real activities, which are the highest reported to date for most of these catalysts under the experimental conditions fixed. The molecular weight of polypropene obtained in propene polymerisation reactions at 1 bar monomer pressure and 20°C ranges from high to low molecular weight (336000 to 4600 g/mol), decreasing according to the precatalyst, in the following order: SBMbiZrCh (17) > SBIZrCh (16) > MBBIZrCh (18) > EBIZrCh (13) > EBTHIZrCh (20) > SBsczrCh (14) > EBIDMZrCh (19) > SBBCZrCh (15). Experiments carried out at 1 bar of monomer pressure and 60°C afford polymers of medium to low molecular weight and the same trend. The order of isotacticity and regiospecificity of the polypropene obtained is: SBMbiZrCh (17) > SBSCZrCh (14) > SBBCZrCh (15) > MBBIZrCh (18) >EBIZrCh (13) > EBDMIZrCh (19) The trityl salt 1 generates more active catalysts than III for the polymerisations perfonned at 20°C, but the situation is reversed at 60 0c. The molecular weight of the polymers obtained by systems activated by III is slightly higher than those obtained using I under both experimental regimes (20 and 60°C / 1 bar). Reactions of L2ZrMe2 (where 4, L= CsMes; 6, L= CSMe4H) with III in presence of AIMe3, fonn [(~)Zr(JlMe) 2AIMe2][H2N{B(C6Fs)3h] (23, L= CsMes; 24, L= CSMe4H) whereas with I, ~ZrMe(Il-Me)B-(C6F5h and L2ZrMe(Il-NC)B-(C6FS)3 were obtained. The protolysis reaction ofY[N(SiMe3)2h with (2-C~sN=CH)(6-Bu)C6H30H (HL3 ) led to a variety of products. Y[N(SiMe3)2h(L3) (29), alongside Y[N(SiMe3)2](L3)2 (30) and Y(L3h (31) were synthesised. M(CH2SiMe3)2(THF)(Ll) (25, M = Sc; 26, M = Y; and L 1 = 2,3,6-Me3C6H3N=CH(6-Bu')C~30H) are highly effective catalysts for the ring-opening polymerisation of E-caprolactone. 26 and 30 also initiate polymerisation of cyc10hexene oxide (CHO).

In this study, the synergistic elfects of ethylene-propane and ethylene-dimethyl ester (DME) mirtures on soot formation were investigated experimentully using u coflow dilfusion flame burnen The soot volume fraction, soot particle diameter and number density were measured and compured to the homogenous mixture. Addition of DME and propane to the ethylene fuel increased soot volume fraction in the ethylene flames. The ethylene- propnne has more pronounced synergistic ffict in compsrison to the ethylene-DME flame* This is due to the fact that during the decomposition of propane some methyl radicals are generated, The reuctions related to these methyl radicals promote the formation of propargyl rodiculs and conseqaently the formation of benzene through propargyl self-reaction and finally to the soot formation. Althoagh DME decomposition produces methyl, the C-O bond in the DME removes some carbon from the reaction puth that produces soot, Hence the soot formation in ethylene-DME mixture is much slower than that in ethylene-propane mixtuFe,

Six experiments investigating the relationship of familiarity and context to the processing of metaphor are presented. Experiment 1 compares time to understand sets containing idiom or metaphor targets following 1-2 sentence contexts in four conditions: NONLITERAL, where the context was completed by an idiom or metaphor, PARAPHRASE, where the same context was completed by a literal target with the same meaning, SURPRISE, where the context was completed by a less-anticipated literal target, and LITERAL, where the target from the NONLITERAL condition was used in its literal sense in a different context. In Experiment 2, sets of dead metaphors replaced the idiom sets, and the metaphor sets had novel metaphors. Experiment 3 matched the targets in each condition for overall printed word frequency, to investigate whether word familiarity was interacting with type of usage. It also included an UNFAMILIAR condition, where the same context was completed by a much less familiar word used literally. Experiment 4 took 20 contexts from Experiment 3 and asked subjects to generate their own endings. Experiment 5 replicated Experiment 3 but with a two-target semantic choice instead of a single response. Experiment 6 shortened contexts and reduced their information content. Its purpose was to see how much context was contributing to understanding, and whether some conditions would be more affected than others. The results may be interpreted as indicating that familiarity with the use of a word is important in determining speed of understanding. Dead metaphors could be understood just as quickly as words used literally, but novel metaphors took longer. Contextual expectations are also a powerful adjunct to the understanding process. When expectations are thwarted, errors and understanding time increases. Metaphor understanding is interpreted as a class-inclusion process in the manner described by Glucksberg and Keysar (1990), where a word used metaphorically is viewed as a prototypical exemplar of a hierarchically superordinate class that becomes extended to incorporate the context topic. This process takes time, but metaphors have a response latency advantage over surprising or unfamiliar literal words encountered in context. When context is reduced, metaphors are still advantageous in terms of time, but are less useful to depth of understanding.

Maternal effects can be key determinants of female fitness through their influence on early life survival. In salmonids, three main sources of mortality in early life can be attributed to redd superimposition, predation, and starvation (meditated by territory limitation). The influence of different agents of mortality will depend on maternal phenotype (e.g. body size) and within-season reproductive timing. An individual-based model, incorporating both stochastic and deterministic processes, was developed to assess how the relationships between maternal fitness, maternal phenotype (body size) and spawning timing were affected by these different sources of mortality. I found that maternal size influenced fitness under some, but not all circumstances. Larger size was beneficial when predation mortality was low, territories were limited, and/or spawner density was high. Spawning time also influenced maternal fitness; early spawned juveniles were favoured when territories were limited, whereas later spawned juveniles were favoured when predation mortality was high. Component Allee effects at low spawned densities were also detected in some simulations. These results suggest that the fitness consequences of maternal phenotype depend on the sources of mortality present. The fact that these context-dependent sources of offspring mortality in early life may vary between habitats or between years increases the difficulty in identifying the correlates of maternal fitness in salmonid fishes.

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