Feature Sidewalls Research Articles

A Model Analysis of Feature Profile Evolution and Microscopic Uniformity during Polysilicon Gate Etching in Cl2/O2 Plasmas

A phenomenological model has been developed to simulate the feature profile evolution of polycrystalline silicon (poly-Si) gate etching in Cl2/O2 plasmas. The model takes into account the deposition of etch products, surface oxidation, and the forward reflection of energetic ions on feature sidewalls. To describe the formation of multilayer SiClx or SiClxOy on feature surfaces during etching, the substrates consist of a number of small cells or lattices of atomic size in the computational domain; this model provides a nanometer-scale representation of the feature geometry and the chemical constituents therein. The inelastic or nonspecular reflection of incoming ions from feature surfaces and the penetration of ions into substrates are incorporated into the model by calculating the trajectory of ions through successive binary collisions with substrate atoms. Etching experiments were performed to evaluate and improve the accuracy of the model. To analyze the effects of the control variables of a plasma reactor on profile evolution, the simulated profiles for different gas flow ratios and incident ion energies were compared with the etched profiles obtained in the experiments. The numerical results reproduced the behaviors of profile anomalies such as sidewall tapering and microtrenches at the corner of the feature bottom, upon varying the incident fluxes of O neutrals and etch by-products, and the incident energy of ions. Moreover, the simulated profiles exhibited passivation layers deposited on feature sidewalls, which is a similar geometry to those obtained in the experiments.

Is actinometry reliable for monitoring Si and silicone halides produced in silicon etching plasmas?: A comparison with their absolute densities measured by UV broad band absorption

SiCl x radicals, the silicon etching by-products, are playing a major role in silicon gate etching processes because their redeposition on the wafer leads to the formation of a SiOCl x passivation layer on the feature sidewalls, which controls the final shape of the etching profile. These radicals are also the precursors to the formation of a similar layer on the reactor walls, leading to process drifts. As a result, the understanding and modelling of these processes rely on the knowledge of their densities in the plasma. Actinometry technique, based on optical emission, is often used to measure relative variations of the density of the above mentioned radicals, even if it is well known that the results obtained with this technique might not always be reliable. To determine the validity domain of actinometry in industrial silicon-etching high density plasmas, we measure the RF source power and pressure dependences of the absolute densities of SiCl x (x = 0−2), SiF and SiBr radicals, deduced from UV broad band absorption spectroscopy. These results are compared to the evolution of the corresponding actinometry signals from these radicals. It is shown that actinometry predicts the global trends of the species density variations when the RF power is changed at constant pressure (that is to say when only the electron density changes) but it completely fails if the gas pressure, hence the electron temperature, changes.

Is actinometry reliable for monitoring Si and silicone halides produced in silicon etching plasmas? A comparison with their absolute densities measured by UV broad band absorption

SiClx radicals, the silicon etching by-products, are playing a major role in silicon gate etching processes because their redeposition on the wafer leads to the formation of a SiOClx passivation layer on the feature sidewalls, which controls the final shape of the etching profile. These radicals are also the precursors to the formation of a similar layer on the reactor walls, leading to process drifts. As a result, the understanding and modelling of these processes rely on the knowledge of their densities in the plasma. Actinometry technique, based on optical emission, is often used to measure relative variations of the density of the above mentioned radicals, even if it is well known that the results obtained with this technique might not always be reliable. To determine the validity domain of actinometry in industrial silicon-etching high density plasmas, we measure the RF source power and pressure dependences of the absolute densities of SiClx (x = 0−2), SiF and SiBr radicals, deduced from UV broad band absorption spectroscopy. These results are compared to the evolution of the corresponding actinometry signals from these radicals. It is shown that actinometry predicts the global trends of the species density variations when the RF power is changed at constant pressure (that is to say when only the electron density changes) but it completely fails if the gas pressure, hence the electron temperature, changes.

BCl3/N2 Plasma for Advanced non-Si Gate Patterning

AbstractAs conventional materials in CMOS manufacturing, Si as a gate material and SiO2 as a gate dielectric, approach their performance limit, the search for new materials becomes key point. Patterning of the new stacks containing these materials require both new plasma etch chemistries and new approaches.We propose a BCl3/N2 based plasma mixture for the advanced gate patterning (in this case pure Ge gates and TaN metal gates). There are three reasons to select this combination:a) The gas mixture generates Cl* species able to etch a diversity of materials, b) it is selective towards Si due to formation of passivating Si-B bonds and c) it improves profile control possibly by formation of a passivating BN-like film on feature side walls. It was found that BCl3 in presence of N2 results in a film deposition if no bias is applied to the substrate (i.e. there is no ion bombardment). The film is hexagonal BN-like since the characteristic peaks corresponding to the in-plane B-N and out-of-plane B-N-B bonds were found in FTIR spectra. The composition of the film surface as found by XPS is B, N and O (as no O2 is present in the plasma it may be a result of oxidation in the atmosphere), the amount of Cl is approx. 1%. The film is soluble in water that makes its removal easy. The deposition rate can be as high as 300 nm/min depending on plasma power, pressure, flow rates and BCl3 to N2 ratio.We propose to use the BCl3/N2 mixture to etch materials too sensitive to Cl-based plasma. Pure BCl3 plasma might distort gate profiles, as materials are etched in a lateral direction as well, this is the case, e.g. for pure Ge gates. Addition of small amount of nitrogen (5% to 10%) to the BCl3 plasma preserves the vertical profile, apparently by the formation of a passivating BN-like layer on the vertical surfaces where there is no ion bombardment. Too high nitrogen concentration results in positively sloped gate profile or even in the etch stop that could be attributed to the too high deposition rate that exceeds the etch rate. All experiments have been performed in Lam Versys 2300 etch chamber.

Plasma etching of high- k and metal gate materials

Etching characteristics of high- k dielectric materials (HfO 2) and metal electrode materials (Pt, TaN) have been studied in high-density chlorine-containing plasmas at pressures around 10 mTorr. The etching of HfO 2 was performed in BCl 3 without rf biasing, giving an etch rate of about 5 nm/min with a high selectivity of >10 over Si and SiO 2. The etching of Pt and TaN was performed in Ar/O 2 with high rf biasing and in Ar/Cl 2 with low rf biasing, respectively, giving a Pt etch rate of about several tens nm/min and a TaN etch rate of about 200 nm/min with a high selectivity of >8 over HfO 2 and SiO 2. The etched profiles were outwardly tapered for Pt, owing to the redeposition of etch or sputter products on feature sidewalls, while the TaN profiles were almost anisotropic, probably owing to the ion-enhanced etching that occurred.

Feature-scale model of Si etching in SF6∕O2 plasma and comparison with experiments

We have developed a semiempirical feature scale model of Si etching in SF6∕O2 plasma. The kinetic parameters in the model are determined by matching simulated profiles with experimentally observed feature profiles obtained at various pressures, rf-bias voltages, and O2 mole fraction in the feed gas. The model parameters are further constrained by using information about the relative radical concentrations, ion flux, and ion energy obtained from plasma diagnostics. Excellent agreement between experiments and simulations is obtained. The combined experimental and simulation study reveals that chemical etching in the lateral direction is significantly reduced through competitive adsorption of O on the feature sidewalls and subsequent formation of a fluorinated oxide layer that passivates the sidewalls. The flux of F and SFx radicals is focused toward the feature bottom due to increased neutral reflection off the passivated sidewalls. The net result is enhanced etching in the vertical direction and improved feature anisotropy with decreasing F-to-O ratio (increasing O2 fraction). However, too much O2 addition eventually leads to the slowing down of the vertical etch rate as O adsorption on active surface sites dominates even at the feature bottom.

Identification of halogen containing radicals in silicon etching plasmas and density measurement by UV broad band absorption spectroscopy

Silicon etching by-products play a major role in silicon gate etching processes because they are the precursors to SiOClX passivation layer formation on feature sidewalls and on reactor walls. As a result, the understanding and modelling of these processes relies on the knowledge of the absolute value of SiClX (SiBrX) fluxes to the surfaces exposed to the plasma. However, only a few experimental data on the absolute concentration of SiClX etch byproducts are available in the literature. In this work, we show that broad band UV absorption spectroscopy can be used to measure the absolute densities of SiClX (X = 0–2), SiFX (X = 1–2) and SiO species, as well as to detect SiBr molecules. In addition, a new absorption spectrum has been observed and attributed to the SiClF radical. We have used a state of the art silicon gate etching process operating in a low pressure high density HBr/Cl2/O2/CF4 plasma etching a 200 mm diameter silicon wafer to produce the different radicals.The absorption bands of these species are all located in the 200–400 nm spectral region. Absorbances of 10−4 could be detected with a good signal to noise ratio in a few seconds exposure time using a Xe arc light source and a photodiode array detector. Details of the experimental procedure used to measure absorption spectra and to extract absolute concentrations from these spectra are presented, including a discussion concerning the influence of the monochromator spectral resolution on the absolute density determination for atomic species.

Model for photoresist trim etch in inductively coupled CF4/O2 plasma

A two-dimensional model for photoresist (PR) trim etching in an inductively coupled CF4/O2 plasma is described. The model couples a Hybrid Plasma Equipment Model based simulation of the plasma reactor with a string-based model for PR feature surface evolution. The etch mechanism in the feature profile simulation considers chemical etching and physical sputtering of PR, fluorocarbon polymer deposition on PR, polymer etching, and etching and redeposition of bottom antireflecting coating (ARC). O atoms are the primary PR trim etch precursor in the mechanism and F atoms play a major supporting role. Modeling results show that polymer deposition impacts feature profile and trim etch rate under conditions where large amount of CFx radicals are generated in the plasma. Since trim etching is primarily driven by neutral atoms who have a broad angular distribution, closely spaced feature sidewalls can become tapered during trimming and dense features trim at a slower rate than isolated structures. PR trim etch rate exhibits nonmonotonic dependence on CF4 fraction in the CF4/O2 gas mixture. F extraction of H from PR enhances O atom reactivity with PR at low CF4 fractions, enhancing PR trim etch rate with increasing CF4 fraction. When CF4 fraction increases beyond 10%, trim etch rate decreases due to O depletion and polymer deposition. Trim etch rate increases monotonically with coil power and saturates at large coil powers. This dependence has been linked to O2 dissociation characteristics and polymer deposition. Increase in rf bias voltage enhances ion energy, which results in ARC layer etching and PR sputtering. Consequent ARC redeposition on PR sidewalls slows down trim etching of PR.

Feature profile evolution in high-density plasma etching of silicon with Cl2

A Monte Carlo based profile simulator was constructed that incorporated the dominant reaction mechanisms of surface chlorination under simultaneous neutral and ion bombardment, surface etching, and ion reflection. The profile simulation is based on the kinetics model developed from beam studies that measured the ion energy, ion and neutral fluxes and ion angular dependencies of Cl+ ion-enhanced etching with Cl. The profile evolution of patterned samples with oxide hard mask etched in an inductively coupled plasma etcher were simulated. The mechanisms of undercutting and microtrenching forming were discussed. Ions scattered from the neighboring hardmask were primarily responsible for the undercutting, while ions reflected from bowed feature sidewalls were primarily responsible for the microtrenching. The profile evolutions under different processing conditions were compared with experimental results and some etching artifacts were characterized and discussed. The neutral-to-ion ratio was found to influence the surface chlorination significantly, thus causing variation of profile evolution. Higher ion energy would give more ideal profiles due to increased ion directionality. However, higher ion energy also increased the etching rate and reduced the chlorination at the bottom of the feature. The reduced chlorination of the feature bottom relative to the sidewall increases the ratio of lateral etching to vertical etching, and decreases the etching anisotropy. The influence of SiCl2 deposition and mask angle on feature profile evolution were also investigated.

Semiempirical profile simulation of aluminum etching in a Cl2/BCl3 plasma

A semiempirical profile simulator to predict topographic evolution during Cl2/BCl3 plasma etching of photoresist patterned Al lines has been developed. Given incident flux distributions, the profile simulator uses a combination of a particle based Monte Carlo algorithm and analytic ray-tracing algorithm for solving feature-scale ion and neutral flux transport, respectively. We use angular and energy distributions for reflected ions that are consistent with experimental observation and molecular dynamic simulations. Etch yields with energy and angular dependence are experimentally determined for physical sputtering and ion-enhanced etching. The spontaneous etch rate of A1 by chlorine and the spontaneous desorption rate of Cl from photoresist are estimated from experimental results. Sticking coefficients for etchant, chlorine, and depositor, CClx, and depositing flux are determined by fitting simulated profiles to experimental data. A semiempirical site-balance model is developed to compute the surface coverage of etchant. The reaction probability of neutrals at surfaces is self-consistently determined from the surface coverage at incident location. Competition between etching and deposition on feature sidewalls is modeled. A shock-tracking method is used to advance the profile using computed etch/deposition rates. Simulation results are presented which demonstrate that facet formation, aspect ratio dependent etching, and critical dimension gain, are captured accurately by the calibrated profile simulator. In addition, the calibrated profile simulator along with results of a 23 design of experiments in which photoresist and Al etch rates were measured on open frame wafers have been used to create a plasma reactor model. The reactor model relates the operational parameters including inductively coupled power, rf bias and gas flow ratio to the flux variables, i.e., Cl flux, ion flux, ion energy, and depositor flux, that are used as inputs to the profile simulator. In this manner, calibration of the profile simulator requires a minimum of high resolution, expensive, patterned wafers. The reactor model so created is shown to be in quantitative agreement with results from the hybrid plasma equipment model (Ref. 1).

Silicon etching yields in F2, Cl2, Br2, and HBr high density plasmas

Etching yields of silicon in F2, Cl2, Br2, and HBr high density plasmas have been measured as a function of ion bombardment energy, ion bombardment angle, and plasma composition. This information contributes to a database of experimental values needed for feature profile evolution modeling. For all plasma chemistries, the etching yield increases approximately with the square root of ion energy. Pure Cl2 and pure HBr plasmas have very similar etching yields. Silicon etching rates are lower in HBr plasmas than in Cl2 plasmas due to lower ion fluxes, not lower etching yields. The dependence of the etching yield on ion bombardment angle is significantly different for Cl2 and HBr plasmas. The etching yield in Cl2 plasmas decreases rapidly for ion angles above 60° (measured from the surface normal), which results in significant ion scattering from the sidewalls, and may cause the sidewall bowing and microtrenching seen when patterning polysilicon with Cl2 plasmas. The etching yield in HBr plasmas decreases more gradually with the ion angle, resulting in less ion reflection from the feature sidewalls and may explain the much less pronounced sidewall bowing and microtrenching typically seen when patterning polysilicon with HBr plasmas. HBr plasmas have higher etching yields than Br2 plasmas due to the ability of H atoms to increase the surface coverage and penetrate farther into the silicon lattice. As the temperature of the silicon increases, the etching yield in HBr plasmas decreases, due to the reduced surface coverage by adsorbed Br and H atoms.

Modeling and simulation of feature-size-dependent etching of metal stacks

Aspect ratio dependent etching (ARDE) has often been observed in various etching processes. During etching of metal films in a high density plasma reactor, this phenomenon is more prominent. With a high amount of ARDE present, the narrow spaces will not be cleared unless there is enough overetch, which removes an excessive amount of the underlying layers. The main focus of this article is on the understanding of the mechanisms behind metal ARDE. The results from an extensive design of experiments on the subject were utilized for this study. SPEEDIE, the Stanford etching and deposition profile simulator, was used to develop and test appropriate models. The Langmuir adsorption model with added surface recombination of the adsorbed species, both etchants and inhibitors, was used to model the phenomenon. The added surface recombination acts as the major species loss mechanism on the feature sidewalls. The simulation results indicate that a process with inhibitors, which are highly adhesive to the metal surface and which do not like to recombine with the etchants to form volatile products, will lead to a low degree of ARDE. This is in agreement with experimental results which showed that the addition of CHF3 to the Al etch process helps to reduce the ARDE in narrow space regions.

Transfer etching of bilayer resists in oxygen-based plasmas

Thin film imaging offers the possibility of extending 248 nm lithography to sub 150 nm resolution. We have been working on a 248 nm bilayer imaging scheme which utilizes a thin Si-containing resist on top of a thick, planarizing underlayer. The image is developed in the top layer and transferred to the underlayer via O2-based plasma etching. This article focuses on three aspects of the critical transfer etch process: etch resistance of the imaging resist, profile control and resist roughening. The imaging resist thickness loss is very fast during the first few seconds of the etch after which the rate diminishes. The relative importance of three phenomena that can explain this nonlinear behavior: oxidation of silicon, deprotection of resist moieties, and plasma etching of resist, are discussed. Fourier transform infrared studies on imaging resist films indicate minimal deprotection-related film thickness losses. X-ray photoelectron spectroscopy analyses of etched films indicate that the extent of surface oxidation increases initially and then becomes constant. Thus, the etching of this category of resists can be described as a combination of the oxidation of the silicon species and sputtering of the oxide-like layer formed. Post-transfer etch profiles using an O2 plasma are shown, and methods to reduce imaging resist faceting and thickness loss either by modifying the imaging layer silicon content or by using passivating plasma chemistries are discussed. The effect of different etching chemistries and processing conditions on imaging layer roughening and striation formation on underlayer sidewalls are explained with the aid of scanning electron microscopy micrographs and atomic force microscopy images of etched feature sidewalls. It is shown that the SO2–O2 etch significantly reduces the sidewall roughness from the postlithograpy values. The ∼3.5 nm rms sidewall roughness observed postetch is comparable to postdeveloped roughness values measured for mature single layer resists. The printing of 125 nm line/space patterns and 150 nm trench features with 10:1 aspect ratios in the underlayer is also demonstrated.

Transition Metals for Selective Chemical Vapor Deposition of Parylene-Based Polymers

A novel method for realizing selective growth of parylene-N and parylene-C synthesized by chemical vapor deposition is presented. Exposure of surfaces to transition metals, metal salts, and organometallic complexes, such as those of iron, ruthenium, platinum, palladium, copper, and silver, is found to inhibit polymer deposition on the substrate. The maximum thickness of the selectively grown polymer films is dependent on the monomer delivery rate to the surface and metal inhibitor used, and for lower growth rates on surfaces patterned with iron, structures 1.4 μm and 4.1 μm in thickness are realized for parylene-N and parylene-C, respectively. The selectively deposited polymer films show no overgrowth onto the metallized areas of the substrate and the slope of the feature sidewalls is steeper than 1.1.μm/μm. Once polymer nucleation finally occurs on the metal films, the morphology of the deposited polymer layer reflects the effectiveness of the metal in preventing polymer deposition. For substrates with little effect on polymer deposition the film morphology consists of uniformly distributed small nodules reflecting multiple polymer nucleation sites on the surface. When the metal initially inhibits polymer growth, the morphology has significantly larger grains, indicating fewer nucleation sites. Possible mechanisms underlying the selective growth are discussed.

Fluorine Incorporation Effects in Cl2 Plasma Etching of Silicon: Quadrupole Mass Spectrometer Analysis

We investigated the etch characteristics of Si in plasmas with addition of fluorine in an electron cyclotron resonance etching system. The addition of fluorine‐containing gas, , increased the etch rate and selectivity, whereas anistropy was decreased. The ion‐assisted etch mechanism was dominant in a pure plasma, whereas chemical etching was dominant at the ratio of 0.65 of gas flow rate . In the transition region, 0.65-0.9, the small addition of the fluorine containing gas brought about the generation of fluorine radicals, and this can chemically detach the chlorinated layer on feature sidewalls. Anistropy was abruptly reduced by this chemical etching. © 1999 The Electrochemical Society. All rights reserved.

Analytical modeling of silicon etch process in high density plasma

Plasma etching of silicon is one of the important etching processes used in modern integrated circuit manufacturing and micro-electro-mechanical systems fabrication. A good understanding of this process leads to better models which are the key to easier and less costly plasma etching process design. The main focus of this paper is on the simulation of the ion reflection from feature sidewalls and the resulting microtrenches. Pure Cl2 plasma was used for experiments because of the simple chemistry. SPEEDIE (Stanford etching and deposition profile simulator) was used in this work. Langmuir adsorption model was used for etching kinetics. Self-consistent calculations were done for fluxes using surface coverage dependent sticking probabilities. For ion reflection, it was assumed that the reflected ions come off with a distribution about the specular reflection angle. This distribution is modeled as cosnθ (θ is the deviation from the specular angle) and is important in getting the correct shape for microtrenches in simulations. A three-dimensional (3D) calculation of the reflection flux was done taking into account the 3D angular distribution of the incoming ions. The ion reflection efficiency was deducted from the silicon ion enhanced etching yield versus ion angle of incidence data. The simulation results match the experimental profiles fairly well.

Parametric Study of NiFe and NiFeCo High Density Plasma Etching Using CO / NH 3

Maximum etch rates of were obtained for and thin films in inductively coupled plasmas (ICP). There is a small chemical contribution to the etch mechanism (i.e., formation of metal carbonyls) as determined by a comparison with Ar and physical sputtering. The etch rates are a strong function of ion flux, ion energy, pressure, substrate temperature, and discharge composition. The discharge should be ‐rich to achieve the highest etch rates. Several different mask materials were investigated, including photoresist, thermal oxide, and deposited oxide. Photoresist etches very rapidly in and use of a hard mask is necessary to achieve pattern transfer. Due to its physically dominated nature, the chemistry appears suited to shallow etch depth (≤0.5 μm) applications, but mask erosion leads to sloped feature sidewalls for deeper features. © 1999 The Electrochemical Society. All rights reserved.

Relative merits of Cl2 and CO/NH3 plasma chemistries for dry etching of magnetic random access memory device elements

A typical magnetic random access memory stack consists of NiFe/Cu/NiFeCo multilayers, sandwiched by contact and antioxidation layers. For patterning of submicron features without redeposition on the sidewalls, it is desirable to develop plasma etch processes with a significant chlorinated etch component in addition to simple physical sputtering. Under conventional reactive ion etch conditions with Cl2-based plasmas, the magnetic layers do not etch because of the relatively involatile nature of the chlorinated reaction products. However, in high ion density plasmas, such as inductively coupled plasma, etch rates for NiFe and NiFeCo up to ∼700 Å min−1 are achievable. The main disadvantage of the process is residual chlorine on the feature sidewalls, which can lead to corrosion. We have explored several options for avoiding this problem, including use of in situ and ex situ cleaning processes after the Cl2-etching, or by use of a noncorrosive plasma chemistry, namely CO/NH3. In the former case, removal of the chlorine residues with in situ H2 plasma cleaning (to form volatile HCl that is pumped away), followed by ex situ solvent rinsing, appears effective in preventing corrosion. In the latter case, the CO/NH3 plasma chemistry produces metal carbonyl etch products, that are desorbed in the simultaneous presence of an ion flux. The etch rates with CO/NH3 are much lower than with Cl2 over a broad range of source powers (0–1500 W), radio frequency chuck powers (50–450 W), pressures (1–30 mTorr) and plasma compositions. We have tried substitution of CO2 for CO, and addition of Ar to produce faster etch rates, without success. Maximum rates of ∼300 Å min−1 for NiFe and NiFeCo were obtained with CO/NH3 under optimum conditions. The etched sidewalls tend to be sloped because of mask erosion during plasma exposure, in contrast to the case of Cl2-based chemistries where the sidewalls are vertical.

Ion-Enhanced Dry Etching of Magnetic Multilayers: Post-Etch Cleaning and Effects of UV Illumination

AbstractPatterning of magnetic multilayer structures of the type used for MRAMs (e.g. NiFeCo/CoFe/Cu/CoFe/NiFeCo) is generally performed with ion milling, but this can degrade the coercivity of small (micron-size) MRAM elements and lead to sidewall redeposition. In high ion density reactive plasmas (Cl2/Ar) it is possible to produce ion-enhanced desorption of otherwise involatile halogenated reaction products, and achieve practical etch rates (∼600 Å/min) for the multilayers. However, removal of the chlorinated etch products from the feature sidewalls is critically important to avoid corrosion. We have used de-ionized water rinsing or in-situ exposure to H2, O2 or SF6 plasmas for removal of these etch residues. Some slight degradation in magnetization was observed in O2 plasma treated structures, but the other cleaning procedures produced no change in magnetic properties and excellent long-term stability. UV illumination of the sample surface during etching is also found to enhance etch rates, as has been reported previously for room temperature etching of Cu.[1]

Energetic ion bombardment of SiO2 surfaces: Molecular dynamics simulations

Numerous profile evolution simulation studies strongly suggest that ions reflecting with glancing angles from etched feature sidewalls are responsible for microtrench formation at the feature bottom. Within these studies such reflections are traditionally assumed specular, where the ion retains all of its incident energy. In this study, we gauge the validity of that assumption by describing the distributions of reflected ion energies, Er, reflected ion angles (polar, θr; azimuthal, φr; and total scatter, αr), obtained via MD simulations of Ar+ bombardment of model SiO2 surfaces. We modeled the physics of the surface atom interactions using an empirical interatomic potential energy function developed by Feuston and Garofalini [J. Chem Phys. 89, 5818 (1988)]. We considered Ar+ ion energies, Ei, of 100 and 200 eV, and incident polar angles, θi, of 0°, 30°, 45°, 60°, 75°, and 85°, measured from the macroscopic surface normal. Each (Ei,θi) combination was used to generate a unique roughened model oxide surface by repeated ion bombardment of an initially crystalline configuration. We observed that the degree to which a surface is roughened (as measured by the fractal dimension of the surface height distribution function, Δbc[h]) is a weak function of bombarding ion incident angle for angles less than 85°. We discuss the sensitivity of the (Er,θr,φr) distributions to incident ion energy and angle, and to roughness characteristics of the target surface. We compare the reflection data to the predictions of the binary collision model. We report sputter yields as functions of incident angle and energy, and discuss the distributions in energy of the sputtered products. We discuss the implications of the reflection distributions and surface character for feature scale simulation.