Articles you may be interested inDegradation mechanism of Schottky diodes on inductively coupled plasma-etched n-type 4H-SiCThe mechanisms underlying selective etching of a SiO 2 layer over a Si or Si 3 N 4 underlayer, a process of vital importance to modern integrated circuit fabrication technology, has been studied. Selective etching of SiO 2 -to-Si 3 N 4 in various inductively coupled fluorocarbon plasmas (CHF 3 , C 2 F 6 /C 3 F 6 , and C 3 F 6 /H 2 ) was performed, and the results compared to selective SiO 2 -to-Si etching. A fluorocarbon film is present on the surfaces of all investigated substrate materials during steady state etching conditions. A general trend is that the substrate etch rate is inversely proportional to the thickness of this fluorocarbon film. Oxide substrates are covered with a thin fluorocarbon film ͑Ͻ1.5 nm͒ during steady-state etching and at sufficiently high self-bias voltages, the oxide etch rates are found to be roughly independent of the feedgas chemistry. The fluorocarbon film thicknesses on silicon, on the other hand, are strongly dependent on the feedgas chemistry and range from ϳ2 to ϳ7 nm in the investigated process regime. The fluorocarbon film thickness on nitride is found to be intermediate between the oxide and silicon cases. The fluorocarbon film thicknesses on nitride range from ϳ1 to ϳ4 nm and the etch rates appear to be dependent on the feedgas chemistry only for specific conditions. The differences in etching behavior of SiO 2 , Si 3 N 4 , and Si are suggested to be related to a substrate-specific ability to consume carbon during etching reactions. Carbon consumption affects the balance between fluorocarbon deposition and fluorocarbon etching, which controls the fluorocarbon steady-state thickness and ultimately the substrate etching.

Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. For various fluorocarbon processing chemistries in an inductively coupled plasma reactor, we have observed relatively thick ͑2-7 nm͒ fluorocarbon layers that exist on the surface during steady state etching of silicon. In steady state, the etch rate and the surface modifications of silicon do not change as a function of time. The surface modifications were characterized by in situ ellipsometry and x-ray photoelectron spectroscopy. The contribution of direct ion impact on the silicon substrate to the etching mechanism is reduced with increasing fluorocarbon layer thickness. Therefore, we consider that the silicon etch rate is controlled by a neutral etchant flux through the layer. Our experimental data show, however, that ions play an import role in the transport of silicon etching precursors through the layer. A model is developed that describes the etch kinetics through a fluorocarbon layer based on a fluorine diffusion transport mechanism. The model is consistent with the data when one or two of the following roles of the ions on the etching process are assumed. The first role is an enhancement in the diffusivity of fluorine atoms through the fluorocarbon layer and an enhancement in the reaction probability of fluorine in the fluorocarbon layer. In this case the fluorine is assumed to originate from the gas phase. The second role includes ion fragmentation and dissociation of the fluorocarbon surface molecules.

DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:

We report the effect of nickel and tungsten contamination on the etch behavior of silicon. This is studied in a molecular beam setup, where silicon is etched by XeF 2 and Ar ϩ ions. The etch process is directly monitored by the SiF 4 reaction products which leave the surface. The effect of contamination appears very pronounced after the ion beam is switched off: it leads to a temporary enhancement of the spontaneous etch rate on a time scale of 500 s. With traces of contamination on the order of 0.01 ML, the etch rate may be enhanced by a factor of 2 for W and somewhat less for Ni. It is concluded that the contamination moves into the silicon by diffusion to vacancies created by the Ar ϩ ions. For 1 keV Ar ϩ ions the contamination moves to a depth of 25 Å, comparable to the penetration depth of the ions. After etching a 170 Å thick layer, the catalytic effect of contamination is reduced to less than 5%. A simple model, which describes the measured effect of contamination very well, indicates that only 3% of the contamination is removed when a monolayer of silicon is etched away. Besides this catalytic effect there are indications that contamination can also lower the etch rate under certain conditions, because of the formation of silicides. From the measurements no conclusions could be drawn about the underlying mechanism of etch rate enhancement.

An intense, slow and cold beam of metastable Ne(3s) 3 P 2 atoms. (February 8, 2018) We employ laser cooling to intensify and cool an atomic beam of metastable Ne(3s) atoms. Using several collimators, a slower and a compressor we achieve a 20 Ne * flux of 6 × 10 10 atoms/s in an 0.7 mm diameter beam traveling at 100 m/s, and having longitudinal and transverse temperatures of 25mK and 300µK, respectively. This constitutes the highest flux in a concentrated beam achieved to date with metastable rare gas atoms. We characterize the action of the various cooling stages in terms of their influence on the flux, diameter and divergence of the atomic beam. I. BRIGHTENING RARE-GAS ATOMIC BEAMSThe efficiency with which metastable rare gas atoms can be produced in gas discharge sources is notoriously low, usually only on the order of 10 −5 with the highest reported value being 10 −3 for helium [1]. Traditionally, therefore, metastable rare gas atomic beams have shown much smaller flux and density than alkali-metal beams. In recent years, several groups [2-17] have tried to bridge this gap by employing laser cooling techniques [18] to intensify rare gas beams. At the same time, atomic beams could be made slow and monochromatic.The principle of beam intensification using laser manipulation of atomic trajectories was illustrated by Sheehy et al in a 1990 paper [19]. The essential element in any such scheme is a laser collimator, whose purpose is to increase the solid angle under which atoms can leave the source and still contribute to the beam flux further downstream. This is achieved by cooling the velocity component transverse to the atomic beam axis. The collimator completely determines the maximum gain in beam flux that can be obtained with laser cooling. Without collimation, the flux of atoms through a constant area decreases geometrically with its distance from the source; with collimation, this flux is essentially constant. Collimators for rare gas atomic beams have been employed by several groups [2][3][4][5][11][12][13][14][15]17].Since transverse cooling takes a certain time and thus a certain transverse distance, laser collimation inevitably leads to large-diameter atomic beams whose density may be rather low despite the increased beam flux. The solution to this, according to Ref. [19], is to focus the beam and re-collimate it at the focal point. This idea was implemented in its purest form by Hoogerland et al [2] who used a separate magneto-optical lens (MOL) followed by a second collimator. Scholz et al [6], Nellissen et al [7] and Schiffer et al [8] developed a magneto-optical compressor (MOC) in which both focusing and collimation occur within the same device. The mayor difference between a MOL and a MOC is the time spent within the device interacting with the laser fields: a compressor is basically a lens with a focal length shorter than the length of the interaction region. In order for the length of the MOC to stay within reasonable limits, laser slowing of the atomic beam [18,20] between collimator and...