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Recent experimental studies of fluorocarbon (FC) plasmas etching various substrates suggest that ions will transport initially bound fluorine (F) through overlying FC films, thereby defluorinating these films and inducing fluorination reaction with the underlying substrate material. Simulations of thermal CF2 on Si with simultaneous bombardment by energetic Ar+ demonstrate this defluorination phenomenon, showing that F is separated from adsorbed CF2 and mixed into the underlying Si, initiating etching. Additionally, this creates dangling bonds on the surface where CF2 may adsorb. Thus, our simulations show that F and C uptake is enhanced by energetic rare gas ion impact, the number of Si–F bonds is greatly increased, and the resultant Si etch rate is higher than expected from physical sputtering alone. The results are compared to experimental measurements made under similar conditions, and the mechanisms of ion-induced F transport are identified.

Photoluminescence (PL) studies of SF6/O2 plasma‐induced defect formation in n‐type silicon samples are reported. Ion bombardment of the silicon surface during the SF6 reactive‐ion etching (RIE) is shown to introduce defects giving rise to a broad PL band in the 0.70–1.00 eV spectral range and to the carbon‐related C and G lines. The role of oxygen during SF6/O2 RIE on the photoluminescence observed is analyzed. It is argued that oxygen contamination enhances the formation of PL centers via the creation of extended defects, such as oxygen precipitates. A lattice contraction nearby these extended defects is suggested to be responsible for the observed splitting of the C and G lines as well as the shift of the phosphorous bound exciton line detected after SF6/O2 RIE.

With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO2 and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (C4F8 and CHF3) and synchronized, plasma-based Ar+ ion bombardment [D. Metzler et al., J. Vac. Sci. Technol., A 32, 020603 (2014) and D. Metzler et al., J. Vac. Sci. Technol., A 34, 01B101 (2016)]. For low energy Ar+ ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have a strong impact on etch depth per cycle of SiO2 and Si but is limited with regard to control over material etching selectivity. Ion energy over the 20–30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF3 has a lower FC deposition yield for both SiO2 and Si and also exhibits a strong substrate dependence of FC deposition yield, in contrast to C4F8. The thickness of deposited FC layers using CHF3 is found to be greater for Si than for SiO2. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 A are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 A for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.

The impact of reactive‐ion‐etching (RIE) on the near‐surface crystal quality of Czochralski silicon has been studied by photoluminescence spectroscopy. The presence of carbon‐related defects is investigated as a function of the pressure during CF4 RIE. The effects of adding hydrogen to the plasma as well as the time of treatment are studied and discussed in terms of defect formation and etch rate. Photoluminescence spectra of samples recorded after a magnetically enhanced reactive‐ion‐etching process are also presented. The introduction of defects depending on the self‐bias voltage and the etch rate are investigated for different magnetic fields.

The dry etching characteristics of strained Si1−xGex, x≤0.22, thin films (≤1 μm thick) and elemental Si and Ge in CF2Cl2 reactive ion etching plasmas have been studied by measuring etch rates using in situ ellipsometry, etch profiles using scanning electron microscopy (SEM), and surface‐chemical aspects by employing x‐ray photoelectron spectroscopy (XPS). The etch rates of the Si1−xGex alloys increase as a function of Ge content and fall between the etch rates of pure Si and Ge. The etch rate ratios of Si1−xGex over Si and Ge over Si1−xGex are ∼1.5 and ∼2.4 at a Ge content of 22%, respectively. SEM photographs of the trench profiles in Si1−xGex alloys with either SiO2 or photoresist masks show directional etching characteristics of the CF2Cl2 reactive ion etching process. The chemically shifted intensities of the Si 2p(1/2, 3/2) and Ge 2p(3/2) core levels indicate a 1‐ or 2‐monolayer‐thick reaction layer on the Si1−xGex alloy surface as a result of CF2Cl2 reactive ion etching. Residual Cl is identified as...

The variation of photoluminescence (PL) spectra obtained with silicon exposed to various plasmas as a function of plasma etch treatment conditions is reported. Phosphorus‐ or boron‐doped covering a large range of doping concentrations, Czochralski or float‐zone‐grown silicon crystals were investigated. The effect of various etching gases on the luminescence spectra as well as the effects of subsequent annealings are reported. Two types of recombination process are observed: (i) The first gives rise of sharp luminescence lines, such as the W (1018 meV), X (1040 meV), T (935 meV), I (965 meV), G (967 meV), C (790 meV), and P (767 meV) lines, which are known to originate from defects produced by high‐energy irradiation and then manifest damage of the crystalline material. Other sharp PL lines at 1015, 1008, and 997 meV were introduced upon annealing at 400 °C. (ii) The second recombination process induces broad lines or bands in the photoluminescence spectra. The formation and nature of the defects giving rise to both recombination processes are discussed in terms of the plasma conditions and starting material.The variation of photoluminescence (PL) spectra obtained with silicon exposed to various plasmas as a function of plasma etch treatment conditions is reported. Phosphorus‐ or boron‐doped covering a large range of doping concentrations, Czochralski or float‐zone‐grown silicon crystals were investigated. The effect of various etching gases on the luminescence spectra as well as the effects of subsequent annealings are reported. Two types of recombination process are observed: (i) The first gives rise of sharp luminescence lines, such as the W (1018 meV), X (1040 meV), T (935 meV), I (965 meV), G (967 meV), C (790 meV), and P (767 meV) lines, which are known to originate from defects produced by high‐energy irradiation and then manifest damage of the crystalline material. Other sharp PL lines at 1015, 1008, and 997 meV were introduced upon annealing at 400 °C. (ii) The second recombination process induces broad lines or bands in the photoluminescence spectra. The formation and nature of the defects giving ri...

Defects introduced by reactive‐ion etching and plasma etching using deuterium have been studied in boron‐doped Si with the photoluminescence (PL) technique. We have observed a set of broad luminescence bands in the below‐band‐gap range between 1.05 and 0.8 eV. These bands change in intensity as well as in photon energy with annealing. This has been studied by isochronal annealing treatments from 75 to 800 °C in steps of 50 °C, each for 30 min. Directly after the plasma treatment we observe overlapping broad bands at liquid‐He temperature, with a peak around 0.9 eV and a half‐width of about 100 meV. There is a large shift of these bands to higher photon energy after the annealing step at 325 °C, peaking at about 0.925 eV with a half‐width of about 60 meV. The intensities of the broad PL bands increase with increasing annealing temperature up to about 375 °C, while they decrease in intensity at higher temperatures. The changes in PL intensity of the broad bands after annealing are shown to be related to the...

When fabricating microscopic features in SiO2 layers using low pressure, high-density fluorocarbon plasmas, microtrenching has commonly been observed. Microtrenching has been explained either as due to ion scattering from sloped sidewalls or negative charging of the sidewalls by electrons, and the influence of the associated electric field on ion trajectories. In this work, we show that a weak magnetic field produces a significant asymmetry in microtrenching. Our results demonstrate unambiguously that electron-based sidewall charging is to a significant extent responsible for microtrenching, and, more generally, that differential charging is an important effect in microstructure fabrication using high-density plasmas.

The slowdown of the oxide etch rate with width of submicrometer structures is known as reactive ion etching (RIE) lag and has been explained by ion shadowing and differential charging of the sidewalls, among other effects [R. A. Gottscho and co‐workers, J. Vac. Sci. Technol. B 10, 2133 (1992)]. Here we show for an inductively coupled high density plasma reactor working in the pressure regime from 6 to 20 mTorr that inverse RIE lag is primarily observed, i.e., the etch rates increase as the width of the microstructures decrease. Inverse RIE lag, which was first discussed by Vitkavage et al. [Tegal Plasma Proceedings Symposium, San Francisco, 1991 (unpublished)], may be explained by considering the neutral flux distribution at the structure bottom. The neutral flux has a stronger dependence on the aspect ratio than the ion flux due to its isotropic velocity distribution. The neutral flux distribution has been modeled and is consistent with etching profiles observed at high pressure.

By comparing the etching characteristics of silicon and silicon nitride in CF4/O2/N2 microwave downstream plasmas we demonstrate clearly how low concentrations of energetic species can play a dominant role in remote plasma processing: Injection of 5% N2 to a CF4/O2 plasma increases the silicon nitride etch rate by a factor of 7, while not significantly affecting the bulk composition of the discharge. Downstream injection of N2 is ineffective. Using surface spectroscopies we directly show a dramatic enhancement of the reactivity of fluorine and oxygen atoms with silicon and silicon–nitride surfaces upon N2 injection to the discharge. Our results can be explained by the production of energetic metastable species in the discharge region which transport energy to the gas‐surface interface.

We characterize and distinguish two regimes of atmospheric pressure plasma (APP) polymer interactions depending on whether the electrical interaction of the plasma plume with the surface is significant (coupled) or not (remote). When the plasma is coupled to the surface, localized energy deposition by charged species in filaments dominates the interactions with the surface and produces contained damaged areas with high etch rates that decrease rapidly with plasma source-to-sample distance. For remote APP surface treatments, when only reactive neutral species interact with the surface, we established specific surface-chemical changes and very slow etching of polymer films. Remote treatments appear uniform with etch rates that are highly sensitive to feed gas chemistry and APP source temperature.

X‐ray photoelectron spectroscopy has been used to investigate the effect of varying substrate bias when silicon is etched in a CF4 electron cyclotron resonance plasma. After etching, the silicon surface is found to be covered by a two layer structure consisting of damaged, fluorinated silicon and a fluorocarbon overlayer. The thickness of the fluorinated silicon layer depends on the self‐bias voltage. Reduction of the ion energy leads to a thinner fluorinated layer as well as a lower etch rate, suggesting that damage and fluorination of the crystal lattice are important in the ion enhanced etching of silicon in fluorine containing plasmas.

In situ ellipsometry has been used to measure in real time the surface damage introduced during electron cyclotron resonance (ECR) plasma etching of silicon as a function of rf bias to the substrate. CF4 and SF6 plasmas were employed. For all ECR plasma operating conditions, the amount of Si surface damage increases with the rf bias voltage, without an apparent damage threshold. It is shown that the surface damage depends on the ion current to the substrate and the gas, with SF6 plasmas resulting in the least surface damage.

A picosecond ultrasonics technique has been used to detect interfacial fluorocarbon (CFx) layers as thin as 0.5 nm between aluminum and silicon. The presence of the CFx material reduces acoustic damping and heat loss from the Al film into the Si substrate. This provides a means for noninvasive identification of organic/polymeric contaminants at the buried interface and potentially for characterizing interfacial mechanical properties.

The complex refractive index at a wavelength of 632.8 nm of strained epitaxial SiGe layers on silicon substrates has been determined as a function of the germanium content using in situ ellipsometry during reactive ion etching. The germanium concentration was obtained from Rutherford backscattering. These index values are used to invert the ellipsometry equations. Using this principle, the Ge concentration depth profile of an unknown SiGe structure can be determined from an in situ ellipsometry measurement sequence that is taken while the unknown sample is being etched

Gallium‐implanted p+ layers in Si were exposed to atomic hydrogen from a plasma. It was found that very large hydrogen concentrations, up to 7.5 times larger than the peak Ga concentration of 7×1019/cm3, segregated into the p+ layer during treatment at 200 °C. The shape of the hydrogen concentration profile was similar to that of the Ga profile. Ion channeling showed that the H atoms did not occupy simple high‐symmetry sites in the lattice, and electron microscopy revealed the presence of extended {111} stacking fault defects associated with the layer of high hydrogen concentration. A mechanism to account for these findings is suggested.

Light emitted from a plasma during reactive ion etching and reflected by the wafer surface at a grazing angle is utilized to determine the remaining film thickness with an accuracy of ±30 A. This promises a more flexible etching approach, e.g., tailoring the final stage of etching to minimize lattice damage.

Surface modifications of silicon induced by electron cyclotron resonance (ECR) etching with CF4 is studied using x‐ray photoemission spectroscopy and Raman scattering techniques. It is shown that a silicon sample etched by ECR exhibits a thinner surface residual layer compared to those exposed to reactive ion etching (RIE) or hybrid ECR/RIE. Evidence of plasma‐induced structural disorder in the silicon surface was only observed in the RIE‐etched sample.

Reactive ion etching of Si and SiO2 in SF6 plasmas in which the samples are mounted on a liquid‐nitrogen‐cooled electrode has been studied. At this temperature SF6 condenses on the electrode surface, but it is possible to maintain a plasma. Si etch anisotropy has been demonstrated at low temperature, in agreement with previous studies. Mass spectrometry and optical emission spectroscopy indicate that fluorine is the dominant species in the plasma because SF6 and SFx species are removed from the gas phase by condensation.

We describe a plasma‐based dry etching procedure which permits selective etching of Si over Ge with a Si/Ge etch rate ratio of over 70 and negligible etching of the Ge underlayer. This is achieved in a SF6/H2/CF4 gas mixture by the formation of a thin (≂3 nm) involatile etch stop layer on the Ge surface which consists of Ge‐sulfide and carbonaceous material.

We describe controlled, self-limited etching of a polystyrene polymer using a composite etching cycle consisting of sequential deposition of a thin reactive layer from precursors produced from a polymer-coated electrode within the etching chamber, modification using O2 exposure, and subsequent low-pressure Ar plasma etching, which removes the oxygen-modified deposited reactive layer along with ≈0.1 nm unmodified polymer. Deposition prevents net etching of the unmodified polymer during the etching step and enables self-limited etch rates of 0.1 nm/cycle.

We investigate elastic buckling as a driving force for roughening of polystyrene, a model resist, during plasma etching. Force curve measurements of the effective modulus of etched polystyrene films, along with modeling which accounts for adhesive forces and surface corrugation, show that an extremely stiff modified layer results from Ar-ion etching, with the modulus increasing with incident energy. The results are in good quantitative agreement with analysis based on the observed dominant corrugation wavelength, and buckling theory providing the corrugation is taken into account.

Roughening of nanoscale polymer masks during plasma etching (PE) limits feature critical dimensions in current and future lithographic technologies. Roughness formation of 193 nm photoresist (PR) is mechanistically explained by plasma-induced changes in mechanical properties introduced at the PR surface (∼2 nm) by ions and in parallel in the material bulk (∼200 nm) by ultraviolet (UV) plasma radiation. Synergistic roughening of polymer masks can be prevented by pretreating PR patterns with a high dose of He plasma UV exposure to saturate bulk material modifications. During subsequent PE, PR patterns are stabilized and exhibit improved etch resistance and reduced surface/line-edge roughness.

We report interactions of low pressure Ar, H2, and Ar/H2 mixture plasmas with a-C:H films. Surface evolution and erosion of a-C:H films were examined for ion energies up to 200 eV by rf biasing the substrates. Film surfaces were characterized using in situ ellipsometry, x-ray photoelectron spectroscopy, and atomic force microscopy. Multilayer models for steady-state modified surface layers are constructed using ellipsometric data and compared with results of molecular dynamics (MD) simulations and transport of ions in matter (TRIM) calculations. We find that Ar plasma causes a modified layer at the surface that is depleted of H atoms. The depth and degree of this modification is strongly depending on Ar ion energies. This depletion saturates quickly during plasma exposure (

The uncontrolled development of nanoscale roughness during plasma exposure of polymer surfaces is a major issue in the field of semiconductor processing. In this paper, we investigated the question of a possible relationship between the formation of nanoscale roughening and the simultaneous introduction of a nanometer-thick, densified surface layer that is formed on polymers due to plasma damage. Polystyrene films were exposed to an Ar discharge in an inductively coupled plasma reactor with controllable substrate bias and the properties of the modified surface layer were changed by varying the maximum Ar+ ion energy. The modified layer thickness, chemical, and mechanical properties were obtained using real-time in situ ellipsometry, x-ray photoelectron spectroscopy, and modeled using molecular dynamics simulation. The surface roughness after plasma exposure was measured using atomic force microscopy, yielding the equilibrium dominant wavelength λ and amplitude A of surface roughness. The comparison of mea...

Surface roughness development of photoresist (PR) films during low pressure plasma etching has been studied using real-time laser light scattering from photoresist materials along with ellipsometric and atomic force microscopy (AFM) characterization. We show that evolution of the intensity of light scattered from a film surface can be used to study the development of surface roughness for a wide range of roughness starting from subnanometer to few hundred nanometers. Laser light scattering in combination with ellipsometry and AFM is also used to study the reticulation mechanism of 193 and 248 nm PRs during argon plasma processing. We employ a three-layer model (modified layer, rough layer, and bulk film) of the modified PR surface (193 and 248 nm PRs) to simulate and understand the behavior of ellipsometric Ψ-Δ trajectories. Bruggeman’s effective medium approximation is employed to study the roughness that develops on the surface after reticulation. When the glass transition temperature of the organic mat...

Molecular dynamics (MD) simulations have been carried out to examine the effects of Ar+, Ar+/H, and Ar+/F bombardment of a model polystyrene (PS) surface. For bombardment with 100 eV Ar+ only, the simulations show the formation of a heavily cross-linked dehydrogenated damaged layer in the near-surface region after some initial fluence, consistent with plasma and beam system experimental results. The 1–2 nm thick amorphous carbon-rich modified layer has a much lower sputter yield compared to that of the virgin PS, which has a H:C ratio of 1. Simultaneous bombardment of the damaged dehydrogenated PS layer with 300 K H or F radicals and 100 eV Ar+ can facilitate the removal of the layer as well as inhibit its initial formation. The development of the steady-state dehydrogenated layer under Ar+-only bombardment results from a competition between the breaking of carbon-hydrogen bonds (which leads to dehydrogenation and subsequent cross-linking) and the breaking of carbon-carbon bonds (which leads to sputtering...

The roles of ultraviolet/vacuum ultraviolet (UV/VUV) photons, Ar+ ion bombardment and heating in the roughening of 193nm photoresist have been investigated. Atomic force microscopy measurements show minimal surface roughness after UV/VUV-only or ion-only exposures at any temperature. Simultaneous UV/VUV, ion bombardment, and heating to surface temperatures of 60–100°C result in increased surface roughness, and is comparable to argon plasma-exposed samples. Ion bombardment creates a modified near-surface layer while UV/VUV radiation results in loss of carbon-oxygen bonds up to a depth of ∼100nm. Enhanced roughness is only observed in the presence of all three effects.

Results are presented from molecular dynamics (MD) simulations of 100eV Ar+ bombardment of a model polystyrene (PS) surface. The simulations show that the system transitions from an initially high sputter yield (SY) for the virgin polymer to a drastically lower SY as steady state is approached. This is consistent with corresponding ion beam experiments. The MD indicates that this drop in SY is due to the formation of a heavily cross-linked, dehydrogenated damaged layer. The thickness and structure of this layer are also consistent with ellipsometry and x-ray photoelectron spectroscopy measurements of Ar plasma-exposed PS samples.

Czochralski silicon samples containing different amounts of interstitial oxygen were irradiated with 2‐MeV electrons at room temperature to a fixed dose of 1.0×1018 electrons/cm2. Prior to irradiation the interstitial oxygen content of similar specimens had been varied in a controlled way by precipitating different amounts of the dispersed oxygen by suitable heat treatments. The introduced divacancy density correlates linearly to the concentration of the interstitial oxygen. A certain concentration of divacancies is always introduced, independent of the amount of interstitial oxygen present. Our data show that the divacancy concentration correlates much better to the density of introduced vacancy‐oxygen complexes than to the initially present dissolved oxygen concentration. Different models for the oxygen enhancement of divacancy production are discussed.

Magnetron plasmas are of great current interest for semiconductor manufacturing applications because of their high ion density and low operating pressure. We have studied the properties of a magnetron ion etching system using CF4 and CF4/O2 with respect to the plasma chemistry and the interaction of the plasma with both the etched substrate and the chamber walls. The higher dissociation and ionization rates lead to significant changes in the species present in the plasma as compared to a conventional reactive ion etching (RIE) plasma. The F atom concentration in a CF4 magnetron plasma is much higher than in a RIE plasma. The addition of O2 leads to only a small further enhancement and produces a decrease in the Si etch rate. The highly dissociated species in the magnetron plasma produce less C‐F polymer, both on the wafer and on the chamber walls, relative to RIE. Sputtering of Al from the electrode produces a substantial deposit of AlFx on the chamber walls, but not on the wafer.

The effects of reactive‐ion etching and plasma etching (using deuterium) on the electrical properties of silicon have been studied employing capacitance‐voltage measurements of Schottky diodes and secondary ion mass spectrometry. Both significant hydrogen penetration, which causes electrical deactivation of the boron dopant, and radiation damage result from the plasma exposure. A model is suggested to explain our results.

Tantalum pentoxide thin films on p‐type Si substrates were prepared by thermal oxidation at 525–550 °C of electron‐beam deposited Ta. Polycrystalline Ta2O5 films were formed by heat treating the amorphous Ta2O5/Si structures at temperatures of 900–1000 °C for times of up to 2.5 h in Ar or dry O2. The amorphous films crystallized into the low temperature β‐Ta2O5 modification. The electrical properties of the polycrystalline Ta2O5 films on Si were studied employing Al/Ta2O5/Si metal‐insulator‐semiconductor capacitors. Films which were crystallized in Ar show higher leakage for all fields than comparable amorphous films. Heat treatments (900–1000 °C) in dry O2 for times greater than 30 min produce films with similar leakage at fields lower than 0.6 MV/cm, but increased leakage at higher fields. Increasing the temperature or the length of time of the high temperature oxidation step reduces the leakage. After 30 min at 1000 °C in dry O2, a leakage current density of 9.6×10−9 A/cm2 at an applied field of 0.7 MV/cm can be achieved (insulator about 70 nm thick). The conductivity of the dielectric films increases irreversibly (dielectric breakdown) if a current density of 1.93 ×10−4 A/cm2 or higher is forced through the insulator; for a specimen oxidized for 30 min at 1000 °C, this corresponds to a breakdown field of about 1.0 MV/cm. The effective dielectric constant eeff of crystallized Ta2O5 films on Si is higher than that of amorphous Ta2O5 on Si and can be as high as 30. For isochronal oxidations at different temperatures greater than about 900 °C a decrease of eeff is observed, which increases with increasing oxidation temperature. For isothermal oxidations at high temperatures eeff decreases as a function of oxidation time. Auger electron sputter profiles of high‐temperature oxidized Ta2O5/Si structures indicate a thin SiO2 layer at the Ta2O5/Si interface. The formation kinetics of this SiO2 layer as a function of oxidation time and temperature enables a consistent explanation of all electrical measurement results.

In situ x‐ray photoelectron spectroscopy (XPS), etch rate measurements, and optical emission spectroscopy have been used to examine the etching characteristics of tungsten in CF4/O2 reactive ion etching plasmas. It is found that the etch rate maximum of tungsten occurs at a proportion of oxygen in excess of that required to produce the maximum gas phase fluorine atom concentration, and this cannot be explained by using an etch mechanism model similar to that developed for silicon. XPS results have been used to identify tungsten oxyfluoride (WOF4) on the etched surface, and a model for tungsten etching is proposed that involves tungsten oxyfluoride as an important etch product.

The properties of a patterned semiconductor structure have been utilized to enable spatially resolved analysis of the surface chemistry of a contact hole reactive ion etching process by x‐ray photoemission spectroscopy. The topography of the semiconductor structure in combination with angle resolved analysis has been used to cause geometrical shadowing and to enable selective area analysis. Differences in the conduction characteristics of silicon and photoresist and concomitant electrostatic charging of the insulating photoresist layer made fluorocarbon films on photoresist and silicon nonequivalent and allowed to unambiguously assign their spatial origin.

Fluorocarbon film deposition onto Si and its influence on the measured Si etch rate in CF4/H2 reactive ion etching in a symmetric two electrode reactor has been studied as a function of CF4/H2 feed gas composition, total gas flow, and applied rf power. For reactive ion etching, the fluorocarbon film thickness on Si increases as the percentage x of H2 in CF4/x% H2 is increased. The fluorocarbon film thickness depends on the total gas flow and is greater for greater gas flows. The observed Si etch rate is controlled by the fluorocarbon film. The Si etch rate is directly proportional to the inverse of the F,C‐film thickness for fluorocarbon films thicker than ∼10 A, which may indicate a diffusion‐limited mechanism. Both in‐diffusion of fluorine and out‐diffusion of SiF4 etch product through the fluorocarbon film are consistent with the decrease of the Si etch rate. The relative importance of the lowering of the atomic F concentration in the gas phase on the Si etch rate, e.g., by the H scavenging mechanism, has also been studied. This reaction can be important for conditions where either the inner walls of the etching apparatus can be maintained free of C,F film throughout the etching experiment, and/or a low hydrogen concentration (≤20%) in the CF4/H2 feed gas is used. For a fixed gas composition of CF4/40% H2, the rf‐power dependence of the C,F‐film thickness and of the Si etch rate was studied. In reactive ion etching, i.e., if rf power is supplied to the bottom (substrate) electrode, at first a monotonic rise in deposited fluorocarbon film thickness with increasing rf power is observed; at high rf‐power levels a dramatic decrease in the C,F‐layer thickness occurs, which is concomitant with a greater intensity of near surface lattice disorder (from ion channeling studies) and Si etching. Silicon etching is not observed for lower rf powers. In cases where rf power was supplied to the top electrode only, C,F‐film deposition has been observed and no Si etching. These data are consistent with a recombinant model of etch anisotropy.

Tantalum pentoxide thin films (60–80 nm thick) on silicon were prepared by thermal oxidation at 430–675 °C of electron‐beam evaporated Ta. The tantalum layers had been deposited by electron‐beam evaporation onto the Si substrates held at room temperature (RT) or heated to 150 °C during Ta evaporation. The dc conduction properties and the dielectic strength of the Ta2O5 films were studied employing Al/Ta2O5/Si capacitors. The smallest conductivity was found for Ta2O5 films formed from Ta deposited onto Si held at RT during evaporation and oxidized at 490 °C for 1 h in dry O2. This minimum conductivity corresponds to a leakage current of 1×10−7 A/cm2 at an applied field of 1 MV/cm (Al negative on p‐type Si substrates). The dc conduction characteristics can be interpreted by assuming Poole–Frenkel conduction. For Ta2O5 formed from Ta which had been deposited onto Si substrates held at 150 °C during evaporation, the conductivity is smallest for a film which had been oxidized at 430 °C for 1 h (lowest oxidatio...

Numerical tests of possible models for the oxygen dependence of the divacancy introduction rate in silicon electron irradiated at room temperature were performed on a computer. Only the model in which oxygen traps Si self‐interstitials can reproduce all the experimental data. Our modeling results (in conjunction with the experimental data) imply that during room‐temperature electron irradiation of Si the indirect production of divacancies can be more important than the direct production of V2 via the single‐collision process.

The effect of reactive‐ion etching (RIE) and plasma etching (PE) using deuterium on the electrical properties of boron‐doped p‐type silicon has been studied employing junction capacitance measurements on Schottky diodes. Deep‐level transient spectroscopy (DLTS) measurements on the treated samples revealed the presence of a number of previously unreported near‐surface traps. These comprise hole traps H(0.44) and H(0.54) at 0.44 and 0.54 eV above the valence band, respectively, and an electron trap E(0.46) at 0.46 eV below the conduction band. The H(0.44) observed directly after the RIE treatment increases in concentration as the sample is annealed to 200 °C, whereas the E(0.46) and H(0.54) are detected in the PE samples directly after etching and annealing at 100 °C, respectively. The depth profiles of the observed traps have been determined, and their annealing behavior is studied up to 200 °C. E(0.46) and H(0.54) are tentatively associated with strain‐induced defects resulting from hydrogen platelet form...

The electrical characteristics of Al/Ta2O5/Si metal‐insulator‐semiconductor (MIS) capacitors were studied. Ta2O5 thin films on n‐ and p‐type silicon had been prepared by thermal oxidation of sputter or electron‐beam deposited Ta films. The direct current leakage was found to be about 3×l0−6 (Al positive) or 6×l0−5 A/cm2 (Al negative) at an applied field of 1 MV/cm. The breakdown strength is between 3 and 4 MV/cm (Al negative on p‐type Si). The dielectric constant is 22–30 when measured at 1 MHz. The flat‐band voltage is positive (+0.81±0.09 V) and exhibits an instability with respect to voltage‐time stresses at room temperature. It can shift to more positive (maximum shift ∼−2 V) or more negative values (maximum shift ∼‐2 V), depending on the conditions of the voltage‐time stress. A post‐metal (after the deposition of the Al electrodes) anneal of the MIS structure at 400 °C for 30 min in 90% Ar–l0% H2 yields a negative flat‐band voltage (−0.08±0.11 V) and partly removes the instability.

Our ability to develop and build ever smaller microelectronic devices depends strongly on the capability to generate a desired device pattern in an image layer (photoresist) by lithography and then to transfer this pattern into the layers of materials of which the device consists. In the past the pattern transfer was almost exclusively accomplished by wet etching. Chemical dissolution of a film region that had to be removed took place in a suitable solvent. Although the wet etching processes stop precisely at a chemically different underlying layer, they typically have isotropic etch characteristics, which cost the researcher control over critical lateral dimensions. Such a tradeoff is not acceptable in the manufacture of micron‐ and submicron‐scale devices, and wet, solution‐based etching techniques were replaced in the late 1970s by dry, directional etching processes using plasmas or ion beams. Figure 1 shows a plasma‐based dry etching system at IBM. In dry etching processes, surface atoms are removed v...