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  • 1985-1989  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6200-6209 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma sheaths are often assumed to be collision free; however, high-voltage cathode sheaths are typically thicker than the mean free path for charge transfer collisions at pressures encountered in glow discharge processing equipment (greater than 10 mTorr). In this paper, the potential distribution in a plasma sheath is determined by solving Poisson's equation self-consistently using a kinetic theory nonlocal ion transport model for charge transfer collisions. The relationship between the potential distribution, ion flux, and thickness of a plasma sheath is presented for arbitrary values of the sheath thickness relative to the mean free path for charge transfer. The results may be used to estimate the ion flux from measurements of the sheath thickness and potential drop across the sheath. Ion energy distribution functions and a one-parameter approximation to the numerically determined potential distribution are also presented. These results apply to rf discharges in a time-averaged sense when the ion sheath transit time is much longer than the rf cycle time, and they apply to high-voltage cathode sheaths in "abnormal'' dc and low-frequency rf discharges. The present model is compared to earlier self-consistent sheath models, including the collision-free approximation, the local mobility model, and a nonlocal fluid approximation known as the viscous drag model.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4664-4675 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper describes a model that simulates etching profiles and process latitudes in glow-discharge bombardment-induced reactive-etching processes. Numerical results are presented for the pattern-transfer step in trilayer lithography, but this analysis is applicable to many other pattern-transfer processes. The inputs to the interface-evolution model described here are a kinetic model for the yield per incident energetic particle and a statistical mechanical model that relates the incident-yield-weighted angular distribution to the pressure, sheath thickness, and sheath voltage drop. The kinetic model is based on experimental evidence and assumes that the yield per bombarding particle is proportional to its energy. The resulting interface-evolution equation is mathematically analogous to a free-surface evolution equation in hydrodynamics. This convective partial differential equation is reduced to a coupled set of ordinary differential equations via the method of characteristics and solved numerically. More general energy-dependent yields are easily incorporated in the present formulation, but angle-dependent yields are more difficult and are not treated here. This model describes how shadowing of the surface being etched results in proximity effects in line etching and aspect-ratio-dependent etching rates in trench etching. Simulated profiles are compared to experimental trilayer etching profiles and qualitatively describe their shape and the trends that are observed as pressure or other processing parameters are varied. Simulations showing the effect of angular distributions, line proximity, and trench aspect ratio on process latitudes in trilayer lithography are presented and discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 3-20 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theory is presented to describe the time-dependent and steady transport properties of composite media containing randomly placed, aligned slender fibers. The formalism is based on a diagrammatic representation of the multiple scattering expansion for the configurational-averaged Green's function. Several topological reductions are performed on the series to remove long-wavelength singularities and to render the theory self-consistent. Approximations based on partial summation of the renormalized series have structures that are similar to, but distinct from, effective medium theories. The present approach is systematic and retains a unique subset of the multiple scattering series at each level of approximation. The formalism is appliedto the specific cases of steady diffusion-controlled reaction and heat conduction in composites that contain slender, aligned rods. Both the dilute and semidilute regimes are investigated. Theseresults for the diffusion-controlled reaction problem are new, and known results are recovered for heat conduction in the case of highly conductive rods. However, the method has uncovered a new semidilute expansion for the latter problem. The screening of disturbances in fibrous composites is also discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 2405-2425 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theory is developed to describe the heat transfer in composites containing highly conducting fibrous inclusions under conditions in which the average temperature field scales on lengths comparable to the length of the included fibers. Thus, in contrast to previous developments, the fiber samples the details of a rapidly varying temperature field rather than simply a local linear field. Using the method of averaged equations and slender body theory, the average "extra flux'' created by the presence of the fibers is demonstrated to be an integral of the temperature gradient about any point weighted by a function which is the appropriate nonlocal conductivity. This representation of the thermal transport in the material is derived explicitly for (a) dilute composites in which nf l3(very-much-less-than)1, where nf is the number density of the fiber and l is their length; and (b) semidilute composites in which nfl3(very-much-greater-than)1 but nflb2(very-much-less-than)1, where b is the fiber thickness. In both instances the expressions derived are rigorously valid for fibers that are very long and thin. Associated with the derivation of the semidilute nonlocal theory is the first complete derivation of the semidilute local result, which justifies the arguments made by Batchelor [J. Fluid Mech. 46, 813 (1971)] and demonstrates the mechanisms of "screening'' in these multiparticle systems.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 31 (1988), S. 2769-2780 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a previous publication [Phys. Fluids 31, 728 (1988)], the evolution of the orientation distribution in a dilute suspension of axisymmetric "tracer'' particles flowing through a bed of fixed fibers or spheres was determined under conditions in which hydrodynamic interactions played a dominant role in determining particle orientation. In this paper, the previous results are extended to account for the effects of Brownian motion on the tracer particles and for different configuration statistics of the force in the fixed bed. In the former case, orientational evolution equations are developed and solutions obtained that are valid for large values of the rotary Peclet number (the parameter regime of greatest interest). In the latter case, it is demonstrated that, when the disturbance flow ceases to have fore–aft symmetry, a small orientational drift and dispersion are introduced into the resulting evolution equations. The latter effects are particularly important since they will occur in all fixed beds because of interactions between bed particles.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 878-881 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Physical bombardment plays a dominant role in the O2 reactive ion etching (RIE) pattern transfer step in multilevel lithography. Etching rates are determined by the flux and energy distribution of the bombarding ions and energetic neutrals (charge transfer products), while anisotropy is determined by their directionality. Measurements of the sheath thickness and voltage drop may be used to estimate flux, energy distribution, average energy, and angular distribution of ions and the energetic neutral products of charge transfer collisions. The estimated flux of bombarding particles allows measured etching rates to be converted into yields. The trends for the etching rate as a function of pressure, bias voltage, and other system variables reflect a single fundamental trend for the yield as a function of bombardment energy. Etching rates of an organic novolac polymer are proportional to the energy flux from bombarding particles while the yield per bombarding particle is proportional to its energy. These kinetics are combined with angular distribution and interface evolution models to predict etching profiles in multilevel lithography.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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