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It is currently recognized that the airway epithelium plays a pivotal role in orchestrating inflammatory, immune, and regenerative responses to allergens, viruses and environmental pollutants that contribute to asthma pathogenesis. The impact of pollen on respiratory epithelium is multifaceted and goes beyond the direct barrier damage driven by the best-known Type-2 response. After pollen-driven activation, airway epithelial cells play an active role in triggering several pathways. In particular, the release of epithelial cytokines (or alarmins) activates both innate and adaptive immunity, with downstream effects implicated to the pathogenesis of asthma. Pollutants also have a pleiotropic effect on respiratory epithelium. Diesel exhaust particles can directly damage the respiratory epithelium with consequent barrier dysfunction, increased permeability, and local inflammation, but they can also activate Th2 responses. Innate immune responses also are triggered by pollutants through release of epithelial cytokines and redox-sensitive pathways that generate mechanical and immunologic changes in the respiratory epithelium. In addition to the typical Type-1 immune response, respiratory virus infections stimulate type-2 innate lymphoid cells in the airway epithelium to release epithelial cytokines. Finally, the action of epithelial triggers on airway smooth muscle is the central element in the induction of remodeling and hyperreactivity of the airways in asthma. This article reviews the pathophysiology and functions of the airway epithelium and the role of epithelial damage by different triggers in the development, persistence, and exacerbations of asthma.

The data presented here come from surveys carried out thanks to a PIM (Initiative PIM - Initiative pour les Petites Îles de Méditerranée) mission on the satellite islands, islets and rocks of Elba and Pianosa islands, aimed at improving knowledge of the terrestrial natural heritage of the Tuscan Archipelago. A list of islands, islets and rocks with resident reptiles is provided. &nbsp

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Identification and assay of sugars in olive drupes during their ripening phase is evaluated by tandem mass spectrometry. Recent achievements have shown that the quality of an extra virgin olive oil can be directly correlated to the ripening degree of the drupes that is likely linked to their saccharides content. An innovation in this peculiar food chain is now proposed that considers a high throughput assessment of the carbohydrate content by a recently introduced protocol based on the gas-phase chemistry of sugar-cesium adducts by ESI-MS/MS.

A coated conical antenna capable of wideband or dual band operation is here proposed and experimented. The antenna is intended for vehicular applications, where robustness and height reduction are a premium. Dielectric and magnetic coating of the radiating cone allows a two octave band operation, but only moderate size reduction. A more compact conical antenna, capable of dual-band operation, can be implemented at the expense of little reduction of radiation efficiency and gain by introducing distributed capacitive loading, a grounding strip and a proper matching network. The design procedure of the isolated antenna was essentially based on an analytical method, while the radiation behavior of the device mounted over a car roof was analyzed using a full-wave numerical approach based on the method of moments.

We have developed and used an infrared diode laser absorption spectroscopy diagnostic to measure concentrations of fluorocarbon radicals, including CF, CF2, and CF3, during selective oxide etching with a low-pressure, high-density plasma reactor. The fluorocarbon radicals are the precursors for the etch process, as well as for the protective polymer that provides selectivity to the nonoxidized materials. The ability to measure the radical concentrations is important for developing a reproducible oxide etch process. We utilize wavelength modulation to increase the detection sensitivity for operation at the low pressures used in high-density plasma reactors. We use a N2O reference cell to provide wavelength calibration, facilitating identification of the fluorocarbon absorption lines. The N2O cell also provides actinometric calibration, which allows us to compare measurements under different experimental conditions and at different times. We present measurements in an inductively coupled plasma (ICP) etch t...

l-Alanine polypeptide thin films were synthesized via atomic layer deposition (ALD). Instead of using an amino acid monomer as the precursor, an l-alanine amino acid derivatized with a protecting group was used to prevent self-polymerization, increase the vapor pressure, and allow linear cycle-by-cycle growth emblematic of ALD. The successful deposition of a conformal polypeptide film has been confirmed by FTIR, TEM, and Mass Spectrometry, and the ALD process has been extended to polyvaline.

We have developed an empirical model of AlAsySb1−y composition during molecular beam epitaxy as a function of growth temperature, growth rate, As2-flux, and Sb2-flux, using response surface methodology. In order to facilitate data collection from a large number of experiments, we have applied desorption mass spectroscopy as an in situ measure of alloy composition. A quadratic model is found to fit the data well, identifying trends and several interactions between growth parameters.

The electrochemical behavior of tungsten during chemical mechanical polishing (CMP) was observed in order to investigate a proposed blanket passivation and abrasion mechanism for tungsten removal. The experiments were performed in a cell that allowed electrochemical measurements to be made during polish. Polish rates were determined from the same samples used in the cell. Alumina-based polish slurries containing potassium iodate, ferric nitrate, or ammonium persulfate were used. DC polarization experiments show no evidence of passive film formation on the tungsten during polish. Tungsten oxidation rates measured during polish account for removal rates that are 1 to 2 orders of magnitude below the measured polish rate. Values of the charge-transfer resistance (measured by ac impedance spectroscopy) during polish are 1 to 2 orders of magnitude higher than expected from the polish rate, thus corroborating the dc-based data. Polish rates under potentiostatic conditions were also measured. The current required to maintain the metal anodic of the open-circuit potential is well below the current expected from measured polish rates, assuming complete oxidation of the tungsten. The polish rate during cathodic potentiostatic conditions ({minus}0.5 V with regard to the open-circuit potential) was similar to the polish rate at open circuit. The authors conclude thatmore » the formation of a blanket passive layer does not significantly contribute to tungsten removal during CMP.« less

A synopsis of Boraginaceae subfam. Hydrophylloideae and Heliotropioideae in Italy is given, as the first contribution to the treatment of the family for the project Flora Critica d'Italia. The work is mainly based on the critical study of herbarium material conserved in most of the Italian collections. All the relevant floristic reports were examined and all the specific names of taxa reported from the National territory were typified, as well as a number of infraspecific ones. Seven species are recognized, only three of which in genus Heliotropium are autochtonous, with one represented by an endemic subspecies. A complete floristic treatment is provided, including analytical keys, distribution maps and lists of selected “specimina visa”, as well as original iconographies to help with species identification.

A synopsis of Boraginaceae subfam. Hydrophylloideae and Heliotropioideae in Italy is given, as a first contribution to the treatment of this family for the project Flora Critica d'Italia. The work is mainly based on the critical study of herbarium material conserved in the most of the Italian collections. All the relevant floristic reports were examined and all the specific names of taxa reported from the National territory were typified, as well as a number of infraspecific ones. Seven species are recognized, only three of which in genus Heliotropium are autochtonous, with one represented by an endemic subspecies. Analytical keys, distribution maps and lists of selected “specimina visa” are ncluded, as well as original iconographies to help with species identification.

High‐density magnetic‐field‐free plasma sources produce plasmas that are opaque to radio frequency (rf) fields in the 0–200 MHz frequency range. Thus plasma currents from a biased substrate flow to ground along reactor surfaces. We investigate some consequences of this rf skin effect in an inductively coupled plasma source with densities of 1011–1012 cm−3 in argon. Magnetic probe measurements confirm that capacitively coupled rf fields are localized near the reactor surfaces. Electric probes were used to measure the voltage on the surface of a biased platen without a substrate. We find that the rf wavelength and phase velocity along reactor surfaces are reduced by a factor of ∼5 compared to free space. This reduced wavelength is attributed to a surface wave which can be analyzed using a formalism similar to that for Trivelpiece–Gould modes.

We have characterized a new helicon plasma source with an end‐launch antenna configuration. Power at 13.56 MHz is coupled via a four‐turn flat spiral coil into an m=0 helicon mode with the application of a weak (B≳5 G) axial magnetic field. Plasma parameters were measured with Langmuir probes, and the structure and absorption of the helicon wave fields were determined with magnetic induction probes. Plasma densities of 1011–1012 cm−3 were produced in argon for pressures in the 1–100 mTorr range with a 5–60 G magnetic field. Radio frequency power absorption occurs primarily via collisionless Landau damping for pressures below 5–10 mTorr and collisional damping dominates at higher pressures. Single pass absorption occurs for magnetic fields less than 20 G. This source does not require a separate source chamber, and thus combines the compactness of flat coil inductively coupled sources with the advantages of remote plasma generation found in wave supported sources. The source can be easily optimized for a va...

Identification and assay of sugars in olive drupes during their ripening phase is evaluated by tandem mass spectrometry. Recent achievements have shown that the quality of an extra virgin olive oil can be directly correlated to the ripening degree of the drupes that is likely linked to their saccharides content. An innovation in this peculiar food chain is now proposed that considers a high throughput assessment of the carbohydrate content by a recently introduced protocol based on the gas-phase chemistry of sugar-cesium adducts by ESI-MS/MS.

Auxiliary power supply systems for rolling stock are less standardized today due to railway specific products with low lot sizes, thus requiring specific system engineering effort and making maintenance and refurbishment difficult. An overview on a standardization initiative is given defining target supply systems for future trains with its essential system interfaces.

We present measurements of the propagation and absorption of the 2.45 GHz waves which produce the plasma in an electron cyclotron resonance (ECR) etch tool. Measurements verify that the absorption occurs within the Doppler‐broadened resonance location where ‖ω− ωce‖ ≲ k∥vte and B≲950±25 G. A ray tracing calculation is used to model power deposition in the ECR source region. Plasma radial uniformity improves when the microwaves are allowed to propagate several wavelengths (≳5) before absorption occurs. An explanation for this improved source uniformity is the fact that whistler waves refract toward regions of lower density which, when combined with ECR absorption at the low‐density location, forces the profile toward radial uniformity. This effect explains previous observations of flat density profiles in configurations where the magnetic field at the microwave window is raised well above the resonant field. Etch rate uniformity is found to be closely correlated to the ion current density uniformity across...

We have improved the operational characteristics of an electron cyclotron resonance (ECR) plasma etch tool by optimizing the coupling of the 2.45‐GHz microwaves to the plasma. Improved coupling is achieved by using a right‐hand circularly polarized (r.h.c.p.) mode which is matched to the plasma impedance through a quarter‐wave transformer. This design reduces microwave reflected power typically to

This paper reviews three different methods that may be used for measurement of the electron densities and temperatures in low-temperature process plasmas: electrostatic probes, microwave interferometry, and Thomson scattering. Each has certain advantages: probes offer high spatial resolution, but are invasive and can be difficult to interpret; microwaves offer high time resolution and ease of interpretation, but offer only limited spatial information; Thomson scattering gives high spatial resolution and is non-invasive, but is practically restricted to densities above 10 11 cm −3 .

A molecular-scale interpretation of interfacial processes is often downplayed in the analysis of traditional water treatment methods. However, such an approach is critical for the development of enhanced performance in traditional desalination and water treatments. Water confined between surfaces, within channels, or in pores is ubiquitous in technology and nature. Its physical and chemical properties in such environments are unpredictably different from bulk water. As a result, advances in water desalination and purification methods may be accomplished through an improved analysis of water behavior in these challenging environments using state-of-the-art microscopy, spectroscopy, experimental, and computational methods.

We report atomic layer deposition of an ultrathin hybrid organic/inorganic film on a porous support and its conversion to a high flux, high selectivity membrane. Through chemical passivation of the internal support porosity and remote oxygen plasma activation of the support surface, ALD of a bis(triethoxysilyl)ethane precursor is confined to the immediate surface of the support, allowing formation of a 5 nm thick film spanning the underlying porosity. UV/ozone removal of the C2 porogen creates a microporous membrane with a He/SF6 selectivity >104 and a substantial He flux of 5.3 sccm/bar·cm2. Prior to conversion, these ultrathin films are of interest as low k dielectric sealing layers. Use of bridging ligands with other shapes and sizes should enable generalization of this approach to other demanding separation problems.

Diversi studi indicano che negli ultimi anni si è verificato un aumento degli eventi estremi di temperatura in periodo estivo con possibili gravi ripercussioni sulla salute umana: l'estate 2003 ne è l'esempio più eclatante. Sono stati analizzati gli episodi di ondate di calore sull'Italia e le estati più calde e la loro correlazione con la posizione ed intensità dei due rami della corrente a getto. Sono stati quindi analizzati i trend e alcuni indici climatici estremi in estate nel periodo 1955-2004 in Toscana. I risultati mostrano un generale aumento degli eventi estremi e delle temperature, soprattutto nei valori massimi, sia a livello di bacino che di regione, ed un aumento della variabilità interannuale. A livello locale la presenza nella regione di moltissimi "sottoclimi" pone problemi di gestione importanti da qui l'esigenza di un monitoraggio climatico e degli eventi estremi.

On a porous substrate, regular atomic layer deposition (ALD) not only takes place on top of the substrate but also penetrates into the internal porosity. Here we report a plasma-assisted process in which the ALD precursors are chosen to be nonreactive unless triggered by plasma, so that ALD can be spatially defined by the supply of plasma irradiation. Since plasma cannot penetrate within the internal porosity, ALD has been successfully confined to the immediate surface. This not only gives a possible solution for sealing of porous low dielectric constant films with a conformal layer of nm-scale thickness but also enables us to progressively reduce the pore size of mesoporous materials in a sub-A/cycle fashion for membrane formation.

Lyme's disease is a commonly found disorder whose etiological agent is a spirochete named Borrelia burgdorferi. Its clinical presentation is usually well known, and three stages are described. However it may present symptoms which may resemble many infectious or autoimmune diseases as well. The aim of the present study is to describe a case of first stage Lyme's disease whose main clinical picture is muscoloskeletal involvement, which may mimic dermatomyositis. Many subtle characteristics (age of onset, atypical cutaneous rash) together with the involvement of muscular masses other than scapular or pelvic ones, and the bio-humoral positivity for anti-Borrelia antibodies allowed correct diagnosis to be made. We emphasize that instrumental and invasive examinations, such as electromyography and muscular biopsy, were not diagnostic in such cases.

The synthesis and glycine/NMDA and AMPA receptor affinities of a set of ethyl (+/-) 1-N-carbamoyl-1,2,3,4-tetrahydro-3-oxoquinoxaline-2-carboxylates 1-11 and those of their constrained analogue (+/-) 1,2,3,3a,4,5-hexahydroimidazo[1,5-a]quinoxaline-1,3,4-triones 12-24 are reported. Compounds 1-11 bear a side-chain at position 1 which has been spatially constrained in compounds 12-24. Most of the reported tricyclic derivatives 12-24 showed glycine/NMDA binding activity comparable to that of their corresponding bicyclic analogues 1-11 providing further evidence that the spatial orientation of the side-chain is an important structural requirement for glycine/NMDA receptor antagonists.

Polyurethane polishing pads are commonly used for chemical-mechanical polishing (CMP) of semiconductor wafers. Structural, chemical, and mechanical property changes of the polishing pads due to CMP are examined. Tungsten and oxide film layers are polished from the wafer surface using the polishing pad and abrasive slurry system. The polishing pad surface is flattened with polishing, and hence, reducing the effective area for slurry transport. The abrasive is used for abrading off the film from the surface. W, Al, I, and K accumulate in the polishing pad after tungsten CMP and Si accumulates after oxide CMP. Material accumulates in the pad pores and grooves. Electron Microprobe X-ray Analysis and Wavelength Dispersive Spectrometry (WDS) were used to examine the changes across the thickness of the pad. Fourier Transform Infrared Spectroscopy (FTIR) was used to determine the changes to the polyurethane isocyanate group. The reduction in the isocyanate group and increase in the hydroxyl group after tungsten CMP indicates that a hydrolysis reaction of the isocyanate to form carboxylic acid occurs.

A simple and fast method for the separation of d - and l -lactic acid enantiomers by thin-layer chromatographic silica gel precoated plates impregnated with Cu(II) is proposed. The two lactic acid enantiomers, dissolved in acetone, are deposed on these plates, d - and l -lactic acids form complexes with Cu(II), with different R f values, suitable for radiochemical measurements. The real separation was confirmed by enzymatic tests carried out on spots of d and l forms scraped from the chromatographic plates. Total radioactivity of 14 C-labeled d - and l -lactic acids was recovered. A Cu/lactic acid complex is evidenced.

Aim of the present study is to describe a case of extranodal lymphoma localized in paravertebral site, near to thoracic spine. The clinical onset of the affection was as a radicular sciatalgic pain, resistant to long-term current therapy by NSAIDs, and determined by neuroradicular involvement by the neoplastic bulk. The interest of the present case is determined by: 1) the presence of a pain which, for a long while, mimicked one of the most trivial painful syndromes; 2) the fact that extranodal lymphomas are not so rare ones. An extensive research of such entities is therefore mandatory; 3) the diagnosis was made by means of non-invasive examination, and needle biopsy was performed only to confirm a picture which was already patent.

Two novel antagonists of the glycine-NMDA receptor have been synthesized and tested for their ability to displace [3H]glycine from its specific binding site in rat brain cortical membranes. The 3-substituted pyrazino[1,2,3-de]quinoxalin-2,5,6-triones 1a-b contain all the essential pharmacophoric descriptors of a glycine receptor antagonist. A model is proposed for the binding of these compounds that includes some of the interactions postulated for the potent glycine-NMDA receptor antagonist L-689,560.

During the first 50 years of the American Vacuum Society (1953–2003), technology has advanced greatly. But the most impressive and conspicuous advance has been in computational power, due to the exponential increase in computing power at an exponentially decreasing cost per function. Many of our readers will remember the “Macro-Mechanical System” called a slide rule that was symbolic of engineers and scientists in the 1950s and 1960s. From the slide rule of the past to today’s desktop and notebook computers, possessing speed, storage, and power capability that dwarf the mainframes of the recent past, what a transformation!

This work had the following objectives: (i) to integrate temporal analysis (N30 peak) with power-spectrum topographic mapping of short-latency somatosensory evoked potentials (SEPs) recorded in parkinsonian and normal control subjects; and (ii) to analyze with a new statistical approach the between-group topographical differences in both the time and frequency domains. The principal aim was to better determine the topography of the scalp frontal areas where the amplitude of the N30 wave was previously found to be significantly reduced in parkinsonians. The statistical procedure was based on the combined use of descriptive data analysis (DDA) and multivariate analysis. In the context of DDA, an improved version of significance probability mapping (SPM) was used by which it is possible to evaluate home- and nonhomoscedastic data with parametric tests. The statistical evaluation of between-group differences was performed with the multivariate Hotelling's T/sup 2/ test and the associated post hoc test. With this statistical procedure, it was possible to determine that the between-group statistical differences in both the temporal and power spectrum distributions were localized only in midline and contiguous contralateral frontal areas of the scalp. >

The synthesis, unambiguous proof of structure and benzodiazepine receptor affinity and efficacy of 2-phenyl-1,2,4-triazolo[1,5-c][1,3]benzoxazin-5-one 1 are reported. The in vitro biological data indicate that 1 may be the lead compound of a new class of benzodiazepine antagonist-inverse agonist ligands.

The synthesis and the benzodiazepine receptor activity of some pyrazolo[1,5-a]quinoxalines bearing various substituents on the tricyclic heteroaromatic system are reported. Only one of the tested compounds showed some receptor affinity.

The synthesis, the benzodiazepine binding activity and the "in vitro" biological effect of some 1,2,4-triazolo[1,5-a]quinoxalines, 3-aza-analogues of some previously reported pyrazolo[1,5-a]quinoxalines, are described. Molecular modelling is used to define the structural requirements of the benzodiazepine recognition site which influence the affinity and different efficacy of these rigid ligands.

The one-pot synthesis and the benzodiazepine receptor binding activity of some imidazo[2,1-a]phthalazines bearing different substituents at position-2 and/or 3 and/or 6 is reported. The dissimilar binding results of the reported compounds are discussed in relation to the nature and/or position of the substituents on the tricyclic ring system.

The synthesis and the GABAA binding activity of a series of 1-amino-2-alkylphthalazinium bromides (series A) and 1-amino-3-alkylphthalazinium bromides (series B) bearing different substituents at position-4 are reported. Some compounds of series A, bearing a lipophilic substituent at position-4, showed a good binding activity as well as in vivo convulsant activity.

A series of 1,3-disubstituted[1]benzopyrano[2,3-c]pyrazol-4-ones were synthesized and tested in vitro as A1 and A2 adenosine receptor ligands. The binding results and a molecular modelling study indicated that the presence of a proton donor group in the N6-H region of adenosine and the 7-NH region of xanthine, respectively and occupancy of the A2 lipophilic area by a moiety endowed with an electrostatic effect are essential for receptor affinity and A2-selectivity.

We describe a rare case of superior sagittal sinus thrombosis in a young man (26 years) with undiagnosed ulcerative colitis. The patient was hospitalized with headache and paresis of the right arm and leg. he had had rectal bleeding and diarrhea for the previous 4 weeks. Despite the fact that heparin therapy is still considered controversial, we successfully treated our patient with low doses of sub-cutaneous heparin. He did not suffer any side-effect.

Electron cyclotron resonance (ECR) plasmas are used for processing applications such as etching and deposition. Coupling to whistler waves in the plasma is one factor determining the operational characteristics of ECR sources. Improved coupling can be achieved by launching a right hand circularly polarized (RHCP) mode which is matched to the plasma impedance through a quarter wave transformer which also serves as the vacuum window. This design can eliminate the need for additional external tuning for a wide range of plasma conditions. The experimental results are in good agreement with a plasma impedance model. Measurements of coupling versus density, magnetic field, window dielectric constant, and pressure are presented.

The synthesis of some 1,3- and 1,2- disubstituted [1]benzopyrano-pyrrol-4-ones is reported as well as their benzodiazepine receptor affinity, as measured by the ability to displace [3H]flunitrazepam from its specific central binding. The structure-activity relationships on the whole series of disubstituted [1]benzopyrano-pyrrol-4-ones show the importance of the presence of the 1-aryl substituent and the size limitation of the 3-substituent. The size of the latter seems also to be important for the "in vitro" efficacy.

The electron density of a plasma is an important parameter because it governs the rate of production of reactive species and ions. Overall reaction rates in deposition and etching processes depend on the electron density. Microwave interferometry is a rapid and relatively nonperturbing diagnostic method for the measurement of a line-averaged electron density. The practical aspects of microwave interferometry are examined here. Bench top studies of the simulated plasma environment are described addressing the questions of electrode multipassing wall reflection and plasma gradients. Finally actual electron density data taken in a 13. 56 MHz planar -diode reactor for Ar SF6 and Ar + 02 plasma are presented. It was determined that the plasma densities fall in the range of 10 8to 10 cm3 with the Ar plasma being at least an order of magnitude denser than SF6 for the same pressures and powers.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have developed a plasma activated atomic layer deposition (PA-ALD) process to produce a few-nm-thick conformal SiO2 cap layer that seals the pores of patterned and unpatterned self-assembled mesoporous low-k dielectric films for integrated circuit fabrication. Tetraethoxysilicate plus O2 and hexamethyldisilazane plus O2 were used as the ALD precursors. In both cases, the plasma was formed in Ar and O2 during the O2 exposure step. By choosing the plasma conditions appropriately, we were able to ensure that unlike conventional ALD, the SiO2 deposition did not occur in the pores. We found that the PA-ALD process did not change the dielectric constant of the mesoporous film. Additionally, we found that for a 1.6 nm thick film, the N2 permeance of the capped film was reduced by a factor of 1600 compared to the uncapped film.

Maintaining dimensional control and adequate throughput during the etching of submicron features requires plasma etch tools that operate at low pressures and high densities, such as inductively coupled plasmas (ICPs). Unfortunately, in this regime, it has proven difficult to achieve a stable, reproducible chemistry for selective oxide etching of contacts and vias. In particular, it is difficult to control the passivating polymer film which provides etching selectivity to silicon, nitride, and photoresist. As a first step toward sorting out the complicated oxide etching chemistry, we have measured and modeled the kinetics of the polymer film deposition in an ICP reactor for C2F6/H2 and CHF3 chemistries. Using a unique application of statistical design of experiments, we have explored the pressure range of 3–15 mTorr, power range of 300–2000 W, residence times from 0.5 to 1.0 s, and magnetic field from 0 to 24 G. Polymer deposition rates on a bare Si wafer are measured using a laser interferometer. The conc...

Wave propagation and absorption have been studied experimentally in an electron cyclotron resonance (ECR) plasma etch reactor operating at 2.45 GHz, with various microwave couplers. A coaxial rf probe was used to measure the wave amplitude along the reactor axis, and radial profiles of the plasma ion saturation current were determined by a Langmuir probe. A single mode whistler wave was detected, and wave absorption was found to occur at magnetic fields corresponding to an ECR frequency which is Doppler-shifted above the cold resonance. The radial uniformity of the plasma is strongly determined by the radial power distribution of the microwave coupler at lower magnetic fields where absorption occurs near the microwave window. Plasma radial transport also influences the resulting profile, especially for modes which are hollow in the center, such as the TM01. Under conditions where the waves propagate from the window without absorption for several wavelengths, the waves refract towards regions of lower density where subsequent ionization tends to correct non-uniform plasma profiles. A model is presented and yields predictions which are in good agreement with the data. The model allows calculation of wave trajectories by ray-tracing techniques and includes simple plasma transport and power deposition.

The initial operation of an electron cyclotron resonance (ECR) plasma etch tool, utilized in a downstream configuration for SF6 etching of polysilicon is described. Practical operational characteristics that are generic to high‐density, wave‐supported plasma sources operated in downstream configurations were explored. A method for improved coupling of the microwave power to the ECR source is described. This method eliminates the need for external tuning. The effect of wall impurities on the plasma and etching characteristics is also considered. A scheme for conditioning the walls to alleviate the effects of impurities is presented. Finally, the complicated relationship between the ECR source plasma and the downstream wafer is considered, by examining the scaling of the plasma electron density in the two regions with microwave power and gas pressure. The phenomena discussed here apply to other etching chemistries and can have a significant impact on process integrity and ease of operation.