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We report on an experimental and theoretical study of the growth of SiC films and of the profile development of the silicon underlayer. SiC features were grown via the direct reaction of the silicon substrate with C60 precursors. Two masking configurations were used to investigate the effects of bulk and surface diffusion on SiC film growth. Without a diffusion barrier (i.e., a patterned SiO2 mask with regions of silicon initially exposed directly to C60), voids formed in the substrate beneath the growing SiC layer, which ultimately controlled the final thickness of the SiC film. Pronounced faceting was observed at the early stages of growth on crystalline silicon. When a tungsten diffusion barrier was used to prevent bulk diffusion (i.e., tungsten covering silicon in non-SiO2 masked regions), significant undercutting resulted beneath the oxide and SiC layers without void formation. A profile simulation was developed to model the time evolution of the silicon underlayer when this diffusion barrier is used...

B–SiO2 films formed by chemical vapor deposition on silicon substrates were analyzed by time-of-flight secondary ion mass spectrometry using slow Xe44+ and Th70+ as primary ions. Boron concentrations of 2×1021 cm−3 determined directly from positive secondary ion spectra agree with results from elastic recoil detection measurements, indicating strong decoupling of positive secondary ion production probabilities from elemental ionization potentials in the intense electronic sputtering induced by highly charged ions. Results demonstrate advantages of highly charged ions for quantitative analysis of surface near layers of materials.

An ion beam etching study designed to characterize the kinetic and transport processes important in the ion-assisted etching of silicon in molecular chlorine was performed. Monoenergetic argon ion beams were directed normal to a silicon wafer that was simultaneously exposed to a background of molecular chlorine, thereby simulating a low temperature rf plasma etching process. The ion-induced etching yield scaled with the square root of the ion energy for a surface saturated with adsorbed chlorine. Moreover, the yield was found to depend strongly on the ion to neutral flux ratio which was varied over two orders of magnitude. A kinetic model in which the dissociative sticking probability and the yield scale linearly with surface coverage was developed and was found to be consistent with the yield data in the ion energy range of 90–300 eV. Its applicability to etching topography was tested with additional experiments where patterned silicon wafers (with oxide masks and with a range of features and linewidths)...

A nearly monoenergetic beam of argon and chlorine ions with kinetic energy from 40 to 900 eV and intensity up to 30 μA/cm2 is used to study the etching of Si. The etch rate and ion current density at the surface are simultaneously measured to obtain the etch yield. The ratio of atomic chlorine (Cl+) to molecular chlorine (Cl+2) ions striking the surface is measured by a quadrupole mass spectrometer. In the absence of any chlorine, the Ar ion sputtering of silicon at 120 eV is about 0.05 silicon atoms removed per ion and monotonically increases to 1 silicon atom per ion at 800 eV. The Ar+‐induced etch yield increases by about an order of magnitude when the surface is simultaneously exposed to a neutral molecular chlorine flux sufficient to produce saturation coverages from the effusive doser. An etch yield of 0.13 silicon atoms removed per incident Ar ion is measured at an Ar+ energy of 50 eV, which also monotonically increases to 4 silicon atoms removed per incident argon ion at 700 eV. The etch yield fur...

Coincidence counting in highly charged ion based secondary ion mass spectroscopy has been applied to the characterization of selective tungsten deposition via disilane reduction of tungsten hexafluoride on a patterned SiO2/Si wafer. The high secondary ion yield and the secondary ion emission from a small area produced by highly charged ions make the coincidence technique very powerful.

The binding energy and E(k∥) dispersion of the n=1 image potential state have been measured on Ni(111) using angle‐resolved two‐photon photoemission. The binding energy, en=1, is found to be 0.8±0.1 eV. The E(k∥) dispersion relation is well described by an effective mass m*/me, of 1.0±0.1, in disagreement with earlier momentum‐resolved inverse photoemission results, but in agreement with theoretical predictions based on a phase analysis of the n=1 image state wave function. Two‐photon photoemission spectra were also recorded for Ni(111)‐p(2×2)‐O, showing the disappearance of the image state and the emergence of a weak, broad, nondispersive feature attributable to two‐photon photoemission from states originating near the Fermi level.

An ion beam etching study, designed to characterize the important kinetic and transport processes involved in the ion-assisted etching of silicon in both molecular and atomic chlorine, was performed. Monoenergetic argon ions were directed normal to a silicon wafer that was simultaneously exposed to a neutral molecular and/or atomic chlorine beam. Dissociation of the beam was induced by thermally heating the graphite tip of an effusive source via electron impact. Beam composition was characterized using a quadrupole mass spectrometer and was found to be in excellent agreement with a thermodynamic equilibrium model at the source pressure and tip temperature. Unpatterned polysilicon wafers were etched to determine the ion-induced etching yields as a function of ion energy, ion to neutral flux ratio, and neutral flux composition. A physically based kinetic model was developed to represent the yield data, incorporating chlorine adsorption, atomic to molecular chlorine surface recombination, and the ion-induced...

We have analyzed wafers with submicron copper lines on Ta/SiO2/Si by time-of-flight secondary ion mass spectrometry with highly charged projectiles. The goal of the study was to diagnose the effectiveness of different cleaning solutions during brush scrubbing after chemical mechanical polishing. The advantage of projectiles like Xe44+ lies in the fact that they produce up to three orders of magnitude more secondary ions than singly charge projectiles. Detection of molecular ions (e.g., Cu oxide, Cu hydrocarbon, and alumina ions) enables a detailed assessment of surface conditions on wafers. Analysis of correlations in secondary ion emission from individual impacts gives insight into the chemical structure and homogeneity on a length scale of about 10 nm.

Lines of C60 films with widths between 3 and 5 μm and heights of 0.4–0.8 μm have been patterned on a Si(100) substrate using photoresist and liftoff techniques. Smooth 50 A root mean square roughness films were detected by atomic force microscopy. Auger depth profiling showed no impurities in the film. Fourier transform infrared spectroscopy confirmed the film was composed of C60. An estimate of the C60 sticking probability onto a growing C60 film is ∼0.2.

The lifetime of a laser‐induced surface excitation on Al2O3(1120) that leads to detectable emission of neutral or positively charged particles and further to optical surface damage is measured to be a ∼200 ps by varying the delay between pairs of 80 ps pulses at 1064 nm. The dependence of the emission threshold fluence on the time delay between laser pulses suggests a low order absorption process.

The adsorption of NO on the diamond C(111)-(2x1) surface was studied in the presence of 226nm laser radiation and in the absence of such excitation. Without laser radiation, sticking was not observed on either the diamond C(111)-(1x1) or the reconstructed (2x1) surfaces for ambient (background) NO exposure in an ultra-high vacuum apparatus. The adsorption probability was estimated to be less than 10-8 based on the detection limit of oxygen in Auger electron spectroscopy of 0.3% of a monolayer. Diamond surfaces exposed to ambient NO (purified at 150 K) and 600 μJ/cm2 laser pulses significantly increased the adsorption of NO (see figure 1). Exposures were performed on and off the A2Σ1/2 (v'=0, J'=13/2) ← X2∏3/2(v"=0,J"=13/2) resonance; no significant differences were found. 226 nm photons were of sufficient energy to excite electrons across the ~5.5 eV band gap in diamond. However, the reaction saturated at an oxygen adatom coverage of less than 2% of a monolayer which suggested the adsorption proceeded on "defect sites" on the surface. The natural type IIa diamond was cleaved in air to expose the (111) surface and mechanically polished with 0.25 μm diamond abrasive in olive oil to produce a hydrogen-saturated surface with a mirror finish. Heating the sample to 800 K gave sharp (1x1) LEED patterns. Heating the sample to above 1275 K to remove the hydrogen produced three rotated domains of the (2x1) reconstructed surface.