Effect Of Argon Ion Bombardment Research Articles

Electron and ion beam degradation effects in AES analysis of silicon nitride thin films

AbstractSilicon nitride films are currently investigated by AES combined with ion profiling techniques for their stoichiometry and oxygen content. During this analysis, ion beam and primary electron effects were observed. The effect of argon ion bombardment is the preferential sputtering of nitrogen, forming “covalent” silicon at the surface layer (AES peak at 91 eV). The electron beam irradiation results in a decrease of the covalent silicon peak, either by an electron beam annealing effect in the bulk of the silicon nitride film, or by an ionization enhanced surface diffusion process of the silicon (electromigration). By the electron beam annealing, nitrogen species are liberated in the bulk of the silicon nitride film and migrate towards the surface where they react with the covalent silicon. The ionization enhanced diffusion originates from local charging of the surface, induced by the electron beam.

An auger and eels study of iron sulfide (FeS 2, F 7S 8 and FeS) surfaces

Auger and electron energy loss spectroscopy (EELS) were used to study the iron sulfide (FeS 2, Fe 7S 8 and FeS) surfaces. A characteristic M 2.3VV Auger doublet with a separation of 5.0 eV was observed on the Sulfides. An assignment of the electron energy loss peaks was made based on the energy dependence of the loss peaks and previous photoemission results. In addition to interband transitions and core level excitations, two volume plasmons and two surface plasmons were tentatively identified. The effect of argon ion bombardment was studied by monitoring the changes observed in the EELS spectra with sputtering time. Peaks with strong iron and sulfur character were observed. Heating the damaged sulfides results in reconstruction of the sulfide surfaces through migration of sulfur. For the undamaged sulfides, changes in the EELS spectra are due to variations in surface composition and crystallographic structure. For all the sulfides under study, some evidence of sulfur segregation to the surface was observed. Finally, the reactions of the sulfides with simple gases, such as H 2, CO and O 2 were studied. Heating with H 2 results in removal of elemental sulfur from the surface. CO reacts with Fe on the damage FeS 2 and Fe 7S 8 surfaces. The reaction products can be removed with H 2. All the sulfides are easily oxidized by oxygen to form α-Fe 2O 3. The reactions of H 2S and CO with clean Fe surfaces were also studied using EELS.

XPS studies of the effect of argon ion bombardment on standard reference material 470: Glass K-411

The effect of Ar ion bombardment on Standard Reference Material 470: Glass K-411 with a composition of (Fe, Ca, Mg) 1.9Si 2O 6, was studied by means of XPS. Results show Fe to be most sensitive to ion induced damage, while no effect on the main photoelectron peaks of Ca, Si and O was observed. The oxygen, however, developed a small peak at lower BE (∼ 5.5 eV) of the main O 1 s peak on sputtering. This peak was correlated to an iron peak, Fe β, which developed also on sputtering, and the resultant oxide is believed to exist as a separate surface phase. O was found to be sputtered selectively with respect to Ca and Si which keep a constant atomic ratio. Mg could not be studied in the present composition.

XPS studies of the effect of argon ion bombardment on standard reference material 470: Glass K-411

XPS studies of the effect of argon ion bombardment on standard reference material 470: Glass K-411

Initial stage of sputtering in silicon oxide

The effect of argon ion bombardment on a silicon oxide film prepared on a Si(111) surface by dry oxidation was investigated by measuring partial yield spectra in addition to the oxygen induced Si 2p core level shift. The experimental observations can be understood such that the SiO2 network is decomposed at the initial stage of argon ion bombardment. In the following stage of bombardment, the silicon oxide films are sputter etched resulting in a decrease in the oxide film thickness.

Hydrocarbon formation in the reaction of atomic hydrogen with pyrolytic graphite and the synergistic effect of argon ion bombardment

The reactions of atomic hydrogen with pyrolytic graphite have been investigated by an atomic beam technique. Up to temperatures of 800 K atomic hydrogen reacts with graphite forming CH 4 and C 2-compounds with a reaction probability of about 2 × 10 −4. Above 1000 K no hydrocarbons have been found. A hydrogen atom exposure of the graphite with simultaneous bombardment by Ar + ions drastically enhanced the hydrocarbon formation up to a factor of 100 exhibiting a characteristic temperature behaviour with a maximum at about 800 K. As main reaction product CH 3 is formed together with some CH 4 and C 2-compounds. When the Ar + beam is turned off the enhancement of the reaction probability is only slowly decreasing with further hydrogen bombardment. In contrast to ion bombardment no significant influence of simultaneous electron irradiation on hydrocarbon formation has been observed.

Surface studies of InP by electron energy loss spectroscopy and Auger electron spectroscopy

We have used Auger Electron Spectroscopy (AES) and Electron Energy Loss Spectroscopy (ELS) to study the effect of argon ion bombardment on the structural and electronic properties on InP(110) surfaces, and the effect of different surface treatments on InP(100) wafers. Even at a low dose (1.5×10 15 cm -2) and low energy (250 eV) argon ion bombardment on oxidized InP(110), P is preferentially sputtered away, leaving the surface with In islands, as indicated by the appearence of In surface and bulk plasmon peaks in the ELS spectra. ELS also reveals the presence of excess elemental In on InP(100) wafers etched in HCl.

Effects of sputtering on the surface composition of niobium oxides

X‐ray photoelectron spectroscopy and Auger electron spectroscopy have been used to study the effect of argon ion bombardment on the composition of NbO, NbO2, and Nb2O5. Preferential sputtering of oxygen from the surfaces of these oxides was observed. The use of lower ion energy (500 eV) resulted in more reduction of the oxides than that observed while using higher energy (2000 eV) ions. This energy dependence of preferred sputtering is attributed to changes in the sputtering mechanism. Difficulties associated with interpreting the results of sputter depth profiling of oxidized niobium surfaces are discussed.

The effects of argon ion bombardment on the electrical properties of tantalum thin film strain gauges

Electron-beam-evaporated tantalum films were bombarded at normal incidence with a collimated beam of 40 keV argon ions to doses of up to 3 × 10 17 ions cm -2. The conduction mechanism in the as-deposited films (for thickness greater than 200 Å) appears to be a combination of metallic and activated tunnelling with some evidence for an increase in the latter component with increasing oxygen concentration. There is also evidence for the existence of at least two activation energies. After bombardment with low doses of argon the resistivity and temperature coefficient of resistivity (TCR) shift markedly towards values expected for very pure tantalum films, probably as a result of radiation-enhanced diffusion and preferential sputtering of oxygen combined with rearrangement of the film to form large precipitates of b.c.c. tantalum. There is also a significant increase in the strain gauge factor γ from an average of 3 up to a value of 5.2 at similar doses, possibly as a result of microstructural changes enhancing strain-induced changes in the metallic conduction paths of the film. The metallic phase appears to be metastable as resistivity increases with time (up to 2 years) at room temperature, probably because of reaction with oxygen near the film-substrate interface. For higher doses the resistivity rises (but not in a way expected for sputter etching), the TCR changes from a large positive value to a small negative one and γ drops towards a value of 2 which is the predicted value for tantalum on glass. These results indicate that for high doses of argon a single-phase stable compound with a low sputtering rate is formed, probably by reaction with the glass substrate. This compound has a mixture of activated tunnelling and metallic conduction with the strain gauge factor apparently determined by the metallic component of conduction.

An Auger electron spectroscopy-secondary ion mass spectrometry study of layers of Cu-Ni and Ag-Au alloys modified by ion bombardment

The effects of argon ion bombardment on the surface layers of Cu-Ni and Ag-Au alloys were studied. Mechanisms considered were preferential sputtering, enhanced diffusion and thermodynamic segregation. An Auger electron spectroscopy-secondary ion mass spectrometry combined system was used to determine the composition-depth profiles from several tens of ångströms below the surface. The variation of the depth profile in the layer modified as a result of ion bombardment revealed that above room temperature the outermost layer was always enriched with copper or silver for the respective alloys compared with the second and the third layers. The results indicated that thermodynamic segregation played an important role in determining the depth profile of the altered layer as well as preferential sputtering and enhanced diffusion.

Effect of argon ion bombardment on metal complexes and oxides studied by x-ray photoelectron spectroscopy

Effect of argon ion bombardment on metal complexes and oxides studied by x-ray photoelectron spectroscopy

Ellipsometric study of the effect of argon ion Bombardment on the structure and reactivity of Ag (111)

The effect of low-energy ion bombardment on the surface structure of Ag(111) and on the reactivity towards oxygen has been investigated by ellipsometry and LEED. Bombardments were carried out with argon ions with energies between 200 and 550 eV and at current densities of 0.33 to 2.0 micro A/cm 2 . The ellipsometric parameters, Δ and ψ, increase during the removal of an adsorbed layer and decrease upon prolonged bombardment. The first fast decrease at the start of the bombardment of a clean surface is ascribed to argon implantation and the subsequent slower and finally constant rates of change of Δ and ψ to the formation of clusters of vacancies and interstitials in a thin (∼100 Å) layer at the surface. The highest change in Δ amounted to 10°, as yet without an indication to reach a limiting value. The LEED pattern of a heavily bombarded surface is not much different from that of an annealed surface. The optical constants calculated for the damaged layer correspond to those of unannealed thin films. The number of defects introduced per incident ion is estimated at 10 −3. According to ellipsometry complete recovery of the damaged surface takes place at 250°C. The amount of oxygen adsorbed on a completely annealed surface is small and increases with increasing damage.

Electrical characterization of metal/inas contacts

Metal contacts to InAs are especially interesting because the surface Fermi level is not stabilized within the forbidden band but is located above the conduction band minimum. The surface of InAs has been investigated by means of electron tunneling experiments which are uniquely sensitive to the surface barrier of p-InAs. The following experimental observations are discussed: the appearance of Esaki-type negative resistance in the forward characteristics of metal/p-InAs contacts; the influence of the metal on this behavior; and the effects of argon ion bombardment and surface preparation on the electrical characteristics. The conclusions are the existence of both a fully inverted surface and an intrinsic interfacial barrier, for both etched and vacuum cleaved surfaces. An estimate of the interfacial barrier properties is presented.

Effect of Argon Ion-Bombardment on Adsorption and Exchange Reaction of Hydrogen by Evaporated Nickel Films

Effect of activating treatment on the evaporated films of nickel has been investigated on hydrogen adsorption and hydrogen-deuterium exchange reaction in the pressure range of 10-6–10-3 Torr at room temperature. Adsorbed hydrogen can be distinguished into reversible and irreversible parts, the former can be removed easily by pumping at room temperature and the latter can not. Freundlich isotherm is applicable to the reversible hydrogen and the irreversible adsorption is decribed by Langmuir isotherm with dissociation. The ion-bombardment gave drastical increases of hydrogen adsorption, although surface area of nickel film measured by xenon adsorption showed no change by both bombardment and annealing. The rate of exchange reaction was found to obey the rate law, V = kP1.3 in the both cases after bombardment and annealing. It is concluded that the rate of the exchange is controlled by the reaction step, 2H(a)irr+D2(a)rev=2 HD, and that small part of the dissociative hydrogen which is adsorbed irreversibly might be effective on the exchange reaction near the room temperature.

Work function measurements on (100), (110) and (111) surfaces of aluminium

(100), (110) and (111) single crystal aluminium substrates were thoroughly outgassed by heating by electron bombardment in ultra high vacuum. Fresh single crystal surfaces were prepared by autoepitaxy on these substrates and the work functions of the surfaces were determined photoelectrically. The general effect of the deposition of an aluminium film on the substrate was to reduce the work function, but annealing the film at temperatures between 473 K and 573 K caused the work function to return to a constant value which was taken to be characteristic of the ordered surface. (100) aluminium surfaces were also prepared by epitaxy on potassium chloride crystals. The effect of argon ion bombardment on a bulk (110) aluminium surface is to increase the work function towards the polycrystalline value, but the characteristic value for the (110) face may be restored by annealing the crystal. There is a linear relationship between surface atom density and work function for the three faces investigated.

Metal Edge Coverage and Control of Charge Accumulation in RF Sputtered Insulators

The successful application of rf sputtered SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> in the passivation of silicon semiconductor devices depends in part on the proper control of ionic charge migration in the insulator during sputtering, and on the adequate coverage of metal line edges by the insulator. It is shown that an appropriate combination of target purity, substrate temperature control and phosphosilicate blocking layer thickness can be used to achieve ionic charge densities at the silicon-SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> interface of less than 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> charges per square centimeter. The effects of argon ion bombardment are shown to be acceptably low for typical operating conditions. In a conventional system, the adequate coverage of metal line edges is shown to be influenced primarily by argon pressure and magnetic field. In a special system where the substrate potential can be varied, it has been shown that adequate edge coverage can be obtained at sufficiently negative potentials. These data are consistent with a mechanism requiring some resputtering to obtain the desired film coverage.

Some electrical and chemical properties of the (111) niobium surface

The work function, the effects of argon-ion bombardment, and the adsorption of oxygen and carbon monoxide were investigated for the (111) surface of niobium. Cleaning of the sample was accomplished in an ultra-high vacuum system by the process of argonion bombardment and annealing. In terms of the photoelectric behavior and the oxygen adsorption properties of the surface, it was determined that many cycles of this process were required before the most satisfactory surface was obtained. Oxygen was adsorbed at room temperature with a sticking coefficient of about 0.6. The coefficient for carbon monoxide was slightly lower. Attempts to remove adsorbed oxygen by heating up to 1500° C in vacuum were unsuccessful and indicated that some diffusion into the lattice took place. Adsorbed species could be removed by the ion-bombardment cleaning process. Argon-ion bombardment in the 500 eV range caused the work function to decrease from the initial clean, annealed surface value of 4.66 eV to 4.09 eV after a bombardment of 10 17 ions/cm 2. Following shorter bombardments, the surface seemed to be in a transition state in which the fit of experimental points to the Fowler curve was poor. These bombardment effects are discussed in terms of the possible nature of the ion-bombardment damage.