Showing papers in "Journal of Vacuum Science & Technology B in 1991"
TL;DR: In this paper, a method for performing attractive mode force potentiometry with submillivolt accuracy and a typical spatial resolution of order 50 nm is presented, which permits measurements to be made in air on specimens which may be passivated or oxidized, conducting or semiconducting, with virtually no sensitivity to oxide thickness or character.
Abstract: A method is presented for performing attractive‐mode force potentiometry with submillivolt accuracy and a typical spatial resolution of order 50 nm. The technique permits measurements to be made in air on specimens which may be passivated or oxidized, conducting or semiconducting, with virtually no sensitivity to oxide thickness or character. An initial demonstration is presented showing voltage measurements on a commercial operational amplifier.
376 citations
TL;DR: A partial review of the development of schemes for making sharp points for use in various microscopies is presented in this paper, with an emphasis on electropolishing methods and some minor techniques.
Abstract: A partial review of the development of schemes for making sharp points for use in various microscopies is presented. The major and some minor techniques are discussed with emphasis on electropolishing methods.
299 citations
TL;DR: In this paper, a batch process for the microfabrication of silicon force sensors was developed, which mainly involves a combination of wet and dry etching techniques, results in cantilevers and tips suitable as general purpose force sensors.
Abstract: We have developed a batch process for the microfabrication of silicon force sensors. A force sensor typically consists of a tip mounted onto a cantilever which is connected to a handling piece. The sensors are being used as microprobes and force transducers in scanning force microscopes. Our sensors are etched from single crystal silicon. The process, which mainly involves a combination of wet and dry etching techniques, results in cantilevers and tips suitable as general purpose force sensors. The newly developed batch microfabrication process is superior to the process which uses wet etching of individual metal wires and it differs substantially from the known process to produce thin film cantilevers with and without integrated tips. The sensors have been applied in various microscopes, and with different types of operation including the repulsive, attractive, and magnetic force mode.
286 citations
TL;DR: In this article, the bulk properties of cubic GaN/GaAs were investigated by cathodoluminescence, which revealed a broad midgap peak as well as several sharp emission peaks just below the expected band gap.
Abstract: We present the first comprehensive investigation of the bulk properties, both optical and structural, of cubic GaN as grown by plasma‐assisted molecular‐beam epitaxy on vicinal (100) GaAs substrates. X‐ray measurements determined the crystal structure of GaN/GaAs to be cubic with a lattice constant of 4.5 A. High resolution transmission electron microscopy revealed a high density of planar defects propagating along the GaN {111} planes. The majority of the defects originated from disordered regions at the GaN/GaAs interface. The optical properties of the films were investigated by cathodoluminescence which revealed a broad midgap peak as well as several sharp emission peaks just below the expected band gap. The data imply that the room temperature band gap of cubic GaN is approximately 3.45 eV.
276 citations
TL;DR: In this paper, the results of a study of the mode transitions in the helicon source when used in the geometry required for plasma processing are presented and the basic characteristics of high density (>5×1011 cm−3 in the processing chamber at 500 W) and low plasma potential (∼15 V) are observed in this configuration.
Abstract: The results of a study of the mode transitions in the helicon source when used in the geometry required for plasma processing are presented. We find that the basic characteristics of high density (>5×1011 cm−3 in the processing chamber at 500 W) and low plasma potential (∼15 V) are observed in this configuration. The mode transitions can be interpreted in terms of the dispersion relation for the helicon wave. A study of the initial plasma breakdown has also been made and the results have aided in the understanding of the operation of the helicon source during pulsed plasma etching.
225 citations
TL;DR: In this paper, a series of experiments at the Universite de Montreal designed to investigate the influence of ω on the power balance between the high frequency (hf) field and the plasma, and plasma processing of materials.
Abstract: It is now generally accepted that the frequency ω/2π at which a high frequency (hf) discharge is sustained has considerable influence on the properties of the plasma. For example, the electron density obtained for a given hf power density deposited into the plasma is usually higher at microwave than at radio frequencies (rfs). This paper reviews a series of experiments at the Universite de Montreal designed to investigate the influence of ω on the power balance between the hf field and the plasma, and the plasma processing of materials. For the two particular etching and deposition processes which are described here, the ‘‘optimum’’ frequency (at which the process is most efficient) appears to be in the range between 50 and 100 MHz. This suggests that converting a plasma process from 13.56 to 2450 MHz does not necessarily lead to the greatest possible process enhancement, and that optimization may require the plasma reactor to be constructed in such a way as to allow the excitation frequency to be changed. To provide insight into these results, the most recent models dealing with the influence of ω on the electron energy distribution are reviewed and extended to calculate parameters that can be compared with our experimental data.
168 citations
TL;DR: In this article, a gold scanning tunneling microscope (STM) tip was used as a miniature solid-state emission source for directly depositing nanometer-size gold structures, which was demonstrated in ultrahigh vacuum on gold substrates, and in air on gold and platinum substrates.
Abstract: We have demonstrated that a gold scanning tunneling microscope (STM) tip can be used as a miniature solid‐state emission source for directly depositing nanometer‐size gold structures. The process has been demonstrated in ultrahigh vacuum on gold substrates, and in air on gold and platinum substrates. Studies made in air suggest that the process is fast, repeatable, and field‐induced. The emission mechanism is believed to be field evaporation of tip atoms, which is enhanced by the close proximity of the substrate. The technique has been used to write several thousand features with no apparent degradation of the tip’s ability to write. Elevated and room temperature studies show the written structures to be stable over periods of weeks, in contrast to some previous STM measurements of gold self‐diffusion.
158 citations
TL;DR: In this article, the exact solutions of Laplace's equations for the tip/sample geometry were presented, and it was shown that the field enhancement associated with such tip plasmons is instrumental for inelastic tunneling and light emission during scanning tunneling microscopy.
Abstract: The electromagnetic fields that can build up around metallic or dielectric pointed tips are of increasing interest in context with the new scanning probe microscopies (tunneling, near‐field optics, Coulomb and van der Waals forces etc.). The paper presents exact solutions of Laplace’s equations for the tip/sample geometry. For suitable media, plasmons are found whose electric fields are highly localized in the gap region. We believe that the field enhancement associated with such tip plasmons is instrumental for inelastic tunneling and light emission during scanning tunneling microscopy.
154 citations
TL;DR: In this paper, the authors measured the electrostatic and contact forces between a tip and a graphite surface in a force microscope, which uses a polarizing optical interferometer.
Abstract: We have been measuring the electrostatic and contact forces between a tip and a graphite surface in a force microscope, which uses a polarizing optical interferometer. For large distances where the electrostatic force predominates, the data are analyzed in terms of a model which introduces the elongated shape of an actual tip. We find that the macroscopic tip has to be taken into account when analyzing the experimental data. The model allows us to deduce the effective radius of the tip which is operative in the electrostatic interaction. We also analyze the contact problem. The attractive part is consistent with van der Waals (vdW) forces. The repulsive regime shows an anomalously small level deflection which is attributed to the deformation of the sample surface. The adhesion of the tip sample is also measured.
154 citations
TL;DR: In this paper, an overview of scanning force microscopy with applications to electrostatic, magnetostatic and atomic forces operating in the contact and noncontact mode is presented, highlighting the main achievements in this field.
Abstract: We present an overview of scanning force microscopy with applications to electrostatic, magnetostatic, and atomic forces operating in the contact and noncontact mode, and highlight the main achievements in this field.
141 citations
TL;DR: The cathodoluminescence wavelength imaging (CLWI) method as discussed by the authors uses a focused focused electron beam across the area under investigation to obtain a 3D image of the atomic-scale morphology of QW interfaces.
Abstract: Luminescence experiments provide a powerful and nondestructive approach to the e x s i t u investigation of semiconductorheterointerfaces which might be buried up to several μm below the surface in a given complex sample structure. Combined with the ability of taking images simply by scanning the exciting focused electron beam across the area under investigation, lateral fluctuations of electronic properties like the variation of the fundamental band gapE g (x,y) can be directly visualized by scanning cathodoluminescence(CL). The novel experimental approach, cathodoluminescence wavelength imaging (CLWI), which involves recording of a complete CLspectrum at every scanning position (x,y), yields direct 3D images of the atomic‐scale morphology of quantum wells(QWs) as sensed by the QWexciton: similar to the tip of a scanning tunneling microscope, the exciton samples the local fluctuations of QW thickness L z and transforms this structural information L z (x,y) into a spectral one, the lateral variation of band gapE g (x,y) and thus the CL emission wavelength λ(x,y). Topological maps of QW interfaces can thus be recorded at various positions and at various magnifications. The interface roughness can be investigated statistically at lateral resolution starting with the diameter of the QWexciton up to the mm regime. The same experimental principle for recording λ(x,y) and E g (x,y) maps is successfully applied for the analysis of patterned structures. In the nonlattice‐matched system GaAs on Si, the lateral strain variation causes E g (x,y) fluctuations and can thus be directly imaged by CLWI. Metalorganic chemical vapor deposition grown GaAs layers on micropatterned Si(001) substrates show strongly inhomogeneous doping with Si impurities. By means of CLWI the strong increase of this Si incorporation in the vicinity of free {111} surfaces is measured and Si concentration maps are recorded across the complete sample pattern.
TL;DR: In this paper, an attractive force microscope using photothermal vibration is presented, where a cantilever is vibrated by the optical absorption of a laser beam whose intensity modulation frequency is at resonance frequency, and the vibration is detected by an optical deflection method.
Abstract: An attractive force microscope using photothermal vibration is presented. A cantilever is vibrated by the optical absorption of a laser beam whose intensity modulation frequency is at resonance frequency, and the vibration is detected by an optical deflection method. The characteristics of the photothermal vibration and the attractive force gradient versus tip‐sample distance have been measured with a Ni foil cantilever. Topographic images of digital memory disks made from a polycarbonate and Mg–Al alloy were recorded.
TL;DR: In this article, a single unified etching/oxidation treatment is described for sharp microtips of silicon, which have potential applications as field emitters and as electrical or mechanical microsensors.
Abstract: Sharp microtips of silicon have potential applications as field emitters and as electrical or mechanical microsensors. This study describes a single unified etching/oxidation treatment that results in uniform tips with controlled radii of atomic dimensions or larger. Variations in the etching/oxidation treatment form multiple tips with two or four tips per etched pyramid, which offer the possibility of higher emission current density for field emitter applications, and higher sensitivity for microsensor applications.
TL;DR: In this paper, the scanning tunneling microscope reveals that Ni deposited on Au(111) at room temperature forms regular arrays of two-dimensional islands with a narrow size distribution, and the apparent Ni island height (1.9 A) is bias independent and agrees with a hard-sphere model of pseudomorphic Ni/Au(111).
Abstract: The scanning tunneling microscope reveals that Ni deposited on Au(111) at room temperature forms regular arrays of two‐dimensional islands. The islands grow with spacing 73 A in rows 140 A apart at sites determined by the Au(111) ‘‘herringbone’’ reconstruction. This nucleation at evenly spaced sites yields islands with a narrow size distribution. The apparent Ni island height (1.9 A) is bias‐independent and agrees with a hard‐sphere model of pseudomorphic Ni/Au(111). The behavior of Ni is contrasted with Au deposited on Au(111), for which far fewer islands are formed.
TL;DR: Many technologies for resolution improvement and new optical image formation technologies such as phase shifting and focus latitude enhancement exposure (FLEX) are reviewed, and a future perspective on optical lithography is discussed.
Abstract: The development of optical lithography has promoted the development of ultralarge scale integration (ULSI) devices. However, optical lithography is now facing serious obstacles due to the limitations in wavelength. Higher resolution with sufficient depth of focus is the most important requirement for ULSI engineers. To satisfy this requirement, many technologies for resolution improvement and new optical image formation technologies such as phase shifting and focus latitude enhancement exposure (FLEX) are reviewed, and a future perspective on optical lithography is also discussed in this paper.
TL;DR: For the first time, images of red blood cells made under these conditions with resolution down to about 10 nm are shown, indicating the wide range of possibilities of this method for studying dynamical processes of living organisms in situ with high spatial resolution.
Abstract: We have developed an underwater atomic force microscope (AFM) based on detection by tunneling for investigations of single living cells. The AFM setup allows compensation of the electrochemical potentials involved and is integrated into a high magnification optical microscope. Small living cells are sucked onto a microcapillary and are brought into contact with a cantilever for imaging. The cells are kept alive under appropriate physiological conditions while maintaining high resolution to image their molecular structures. For the first time, images of red blood cells made under these conditions with resolution down to about 10 nm are shown. In addition, changes induced by higher salt concentration and by the sticking of antibodies to the cell surface were observed. This indicates the wide range of possibilities of this method for studying dynamical processes of living organisms in situ with high spatial resolution.
TL;DR: In this paper, the authors describe the ordered structures observed, as well as the extent of ordering, in specific III/V alloys and the effects of ordering on the fundamental properties.
Abstract: The phenomenon of spontaneous atomic scale ordering was first reported for semiconductor alloys only ∼5 years ago. Since that time, ordering has been observed in nearly all III/V alloy systems. This paper will describe the ordered structures observed, as well as the extent of ordering, in specific III/V alloys. The effects of ordering on the fundamental properties will be described briefly. The paper will emphasize a summary of our current understanding of the phenomenon. Both thermodynamic and kinetic factors play a role in determining the degree of order for specific epitaxial growth parameters and on which planes the compositional modulations occur.
TL;DR: In this article, the atomic structure of the clean electrode surfaces and of different ordered Cu adsorbate layers were resolved for submonolayer electrodeposits of copper on the three low-index planes of gold in situ by STM.
Abstract: We have investigated submonolayer electrodeposits of copper on the three low‐index planes of gold in situ by STM The atomic structure of the clean electrode surfaces and of different ordered Cu adsorbate layers were resolved For submonolayer Cu coverages on Au(111) and Au(100), deposited under potential control from sulfuric acid solutions, various ordered structures were observed, where the Cu adatoms are arranged in hexagonal or quasihexagonal lattices The larger Cu‐Cu distances in these structures, as compared to the pseudomorphic (1×1) Cu islands formed in vacuum deposits even at low coverages, demonstrate the structure determining role of the coadsorbed anions For Cu deposition on Au(110) only a (1×1) Cu adlayer was observed These results are in good agreement with recent ex situ LEED data
TL;DR: In this article, the authors used scanning tunneling microscopy to study the morphology of the first monolayer of Ag on room-temperature Au(111) and found that Ag atoms diffuse freely on Au terraces but are not mobile along or across step edges.
Abstract: Novel properties of metal monolayers and superlattices are likely to depend on the detailed morphology of monolayer growth. We find, using scanning tunneling microscopy, that the ‘‘simple’’ system of Ag on room‐temperature Au(111) exhibits a morphological instability in the formation of the first monolayer. Monolayer‐high Ag protrusions grow outward from atomic steps onto atomic terraces. The structure of the deposits on a nanometer scale shows that Ag atoms diffuse freely on Au terraces but are not mobile along or across step edges that separate the terraces. The result is a complex growth front characteristic of diffusion‐limited aggregation with local relaxation. This causes strong inhomogeneity in local coverage, so that even at 1.1 ml average coverage there are large areas [(1000 A)2] of exposed Au. Experiments with step structures intentionally created by tip impact suggest that atoms on step edges are not highly mobile at room temperature, so that the dominant mechanism for local smoothing of these deposits is relaxation intrinsic to the aggregation process.
TL;DR: In this paper, the early stages of Si(111)•7×7 oxidation using scanning tunneling microscopy and scan tunneling and photoemission spectroscopies have been studied.
Abstract: The early stages of Si(111)‐7×7 oxidation using scanning tunneling microscopy and scanning tunneling and photoemission spectroscopies have been studied. It has been found that there are at least two different oxygen‐containing sites being formed. Their different surface site distributions and behavior as a function of O2‐ exposure show them to be two distinct early products. By correlating the spectroscopic results and the results of theoretical calculations one is able to identify one of these products as involving an O atom tying up an adatom dangling bond with a second O atom inserted in one of the adatom back bonds, while the other involves a single O atom inserted in an adatom back bond. The preference of these products for the faulted half of the 7×7 unit cell and for corner‐adatom sites is explained in terms of a site‐dependent sticking coefficient involving a process analogous to the gas‐phase ‘‘harpooning’’ processes. It is shown that the majority of the resulting molecular precursors involve O2 ...
TL;DR: In situ electrochemical scanning tunneling microscopy (STM) was applied to singlecrystal platinum(111), rhodium(111, and palladium(111) surfaces in an aqueous sulfuric acid solution as discussed by the authors.
Abstract: In situ electrochemical scanning tunneling microscopy (STM) was applied to single‐crystal platinum(111), rhodium(111), and palladium(111) surfaces in an aqueous sulfuric acid solution. Atomically flat surfaces of Pt(111) are roughened in solutions by the electrochemical oxidation–reduction cycle. It is shown that a single potential cycle causes the formation of many adatoms and very small clusters on the Pt(111) terrace. A steady‐state surface structure can be clearly observed after applying a few potential cycles. The STM image is composed of regularly arrayed islands whose diameter and height are in the ranges of 2–3 and 0.5–0.75 nm, respectively. Atomically flat terrace‐step structures can be also observed on Rh(111) and Pd(111) surfaces. The effect of oxidation–reduction cycle on these surfaces is also discussed.
TL;DR: In this article, the consequences of tip-substrate interactions were investigated using large-scale molecular dynamics simulations for a large (001) gold tip and a Ni(001) surface.
Abstract: The consequences of tip–substrate interactions are investigated using large‐scale molecular dynamics simulations for a large (001) gold tip and a Ni(001) surface. The simulations reveal processes of adhesive contact formation upon approach of the tip to the substrate, tip elongation, and formation of an extended ordered neck upon retraction of the tip from contact, (111) reconstruction of the interfacial gold layers and the atomistic mechanisms of tip flattening and increase in contact area upon compression past the adhesive contact point. The hysteresis in the force versus tip to sample distance relationship, found upon approach and subsequent separation of the tip from the sample, is related to processes induced by adhesion and intermetallic bonding. The atomic‐scale mechanisms underlying the jump‐to‐contact phenomenon at small tip to surface separation (∼4.2 A) and of the inelastic processes and structural transformations involved in tip elongation, neck formation, and tip compression are discussed, and the results are compared to our earlier studies of a nickel tip interacting with a goldsurface.
TL;DR: Whitlock et al. as discussed by the authors discussed the performance of CO2 snow cleaning on a variety of materials typically encountered in a surface analysis laboratory, including metals, semiconductors, and insulators.
Abstract: Controlled expansion of high purity carbon dioxide through a nozzle forms a high velocity ‘‘snow’’ stream that effectively removes both particulate and thin film contaminants from silicon wafer surfaces [W. Whitlock, Presented at the 20th Annual Meeting of the Fine Particle Society, Boston, MA, August 22, 1989 (unpublished); R. Sherman and W. Whitlock, J. Vac. Sci. Technol. B 8, 563 (1990)]. This process will clean surfaces leaving no detectable film residue as well as reduce adventitious (native) hydrocarbon surface content. This article discusses the performance of CO2 snow cleaning on a variety of materials typically encountered in a surface analysis laboratory. Cleaning tests were performed on metals (aluminum and copper sheets), semiconductors (Si and InP wafers), and insulators (ceramics, laser optics, glass plates, and polymers). Performance is judged primarily through x‐ray photoelectron spectroscopy measurements with primary consideration given to reduction of surface hydrocarbons. These measurements are compared with samples which were cleaned with a conventional solvent process. The results indicate that CO2 snow cleaning is comparable to solvent cleaning in its effectiveness for removal of hydrocarbon films. Recommendations are made for the use of CO2 snow cleaning in both industrial and laboratory applications.
TL;DR: In this paper, the tensile stress of a sputter-deposited tungsten (W) film was calculated using the interatomic forces acting on the grain boundary.
Abstract: The mechanism for the cause of stress in a sputter‐deposited tungsten (W) film has been clarified. The tensile stress of the film was calculated using the interatomic forces acting on the grain boundary. The average distance of the grain boundary gaps was determined from the measured film density assuming the film had homogeneous size rectangular grains. The calculated and measured stress values were in good agreement in the high working gas pressure region. The difference between these values in the low working gas pressure region has been able to be explained by the compressive stress due to the peening effect of Ar. The low stress in the high pressure region was obtained by large opened grain boundaries which produced low film density. A low film density causes a low x‐ray stopping power. The film deposited in the low pressure region is suitable as an x‐ray absorber because of its high film density.
TL;DR: In this paper, the authors have used micromachined silicon sensors consisting of a monolithic silicon cantilever with integrated silicon tip and performed a detailed characterization of the tip geometry and resonance properties.
Abstract: Scanning force microscopy (SFM), operated in the attractive imaging mode, enables the precise measurement of the force between tip and sample over a tip–sample distance ranging from contact to tens of nanometers. The basic long range interactions (>1 nm: i.e., hydrodynamic, electrostatic, van der Waals, and capillary forces) between tip and sample have been measured and will be discussed. Each force leads to a different mode of operation in profiling samples. The most critical part of the SFM is the force sensor. Exact knowledge of the sensor properties is required for the interpretation of SFM measurements. We have used micromachined silicon sensors consisting of a monolithic silicon cantilever with integrated silicon tip and have performed a detailed characterization of the tip geometry and resonance properties. Examples of surface images on different samples (conductors, insulators and biological materials) and structures, ranging from atomic steps up to several microns high features, have been investi...
TL;DR: In this article, the formation of a high-density plasmoid in an inductively coupled radio frequency (11.4 MHz) discharge in argon is described, and a quantitative description of plasma properties over an useful range of vapor pressure, 0.02-0.2 Torr, and rf power, 50-400 W.
Abstract: Experimental observations concerning the formation of a high‐density plasma in an inductively coupled radio frequency (11.4 MHz) discharge in argon are described. These observations are complemented by probe measurements that provide a quantitative description of plasma properties over an useful range of vapor pressure, 0.02–0.2 Torr, and rf power, 50–400 W. It is shown that a dense plasma of the order of 1012 cm−3 can be easily formed, having the configuration of a luminous plasmoid embedded in a low‐density, 1010 cm−3, diffuse plasma.
TL;DR: In this paper, the authors used a scanning tunneling microscope (STM) to directly imaged nalkane and nalkanol layers at the liquid-graphite interface.
Abstract: We have directly imaged n‐alkane and n‐alkanol layers at the liquid–graphite interface using a scanning tunneling microscope (STM). The layers possessed a high degree of two‐dimensional ordering, and the adsorbate was observed to enhance the tunneling current. The results of this study agree with calorimetric and surface mass measurements, and show that these macroscopic measurements can aid in the selection of systems suitable for imaging with the STM.
TL;DR: In this paper, the authors demonstrate that a similar measurement can be made with the atomic force microscope using the previously demonstrated capacitive force sensing mode, by applying appropriate bias to the force tip, depletion-induced capacitive variation is mapped over regions of varying dopant density.
Abstract: Recently, high‐resolution mapping of dopant concentration has been demonstrated with the scanning capacitance microscope (SCM). Here, we demonstrate that a similar measurement can be made with the atomic force microscope using the previously demonstrated capacitive force sensing mode. By applying appropriate bias to the force tip, depletion‐induced capacitive variation is mapped over regions of varying dopant density. This method has a predicted sensitivity comparable to the SCM, and in addition allows imaging of trapped charge, as well as an independent measurement of the surface topography. Results of first‐order model calculations are presented which give estimates as to the limits in sensitivity and resolution of this method
TL;DR: Using electroluminescence associated with scanning tunneling microscope in AlxGa1−xAs heterostructures, this paper showed that luminescence due to recombination can be induced within single quantum wells of dimensions down to a few nm and can also be used to image them.
Abstract: Using electroluminescence associated with scanning tunneling microscope in AlxGa1−xAs heterostructures, we show that: (a) luminescence due to recombination can be induced within single quantum wells of dimensions down to a few nm and can also be used to image them, (b) the energy of bulk bands can be determined, and (c) transport parameters can be measured, e.g., the thermalization length and the diffusion length of minority electrons. This technique opens up new possibilities for the study and characterization of semiconductors and devices—including the possibility of studying surface states and single trapping centers associated with lattice defects, impurities, chemisorbed species, etc.
TL;DR: In this paper, the major species present in a fluorocarbon plasma environment were simulated and independently controlled using radical and ion beams in an ultrahigh-vacuum apparatus, and the beams used in this study were chosen to determine the importance of CFx radicals in a CF4 plasma; the beams included F and CF2, with a beam of Ar+ to simulate energetic ion bombardment.
Abstract: The major species present in a fluorocarbon plasma environment were simulated and independently controlled using radical and ion beams in an ultrahigh‐vacuum apparatus. The beams used in this study were chosen to determine the importance of CFx radicals in a CF4 plasma; the beams included F and CF2, with a beam of Ar+ to simulate energetic ion bombardment. Both CF2 and F enhance the etching yield of SiO2 under energetic Ar+ bombardment; however, the enhancement with F is twice that seen with CF2 at similar fluxes. When CF2 and F fluxes are used simultaneously, F dominates and the CF2 flux has little effect on the overall etching yield. Combined with previous work on Si substrates, these results are consistent with qualitative theories for SiO2/Si selectivity in fluorocarbon plasmas. Possible elementary steps in the ion‐enhanced etching process are proposed and reduced to a two‐parameter model which represents the process as ion‐enhanced neutral adsorption followed by ion‐induced reaction to form volatile ...