Energy Ar Ion Research Articles

Silicide formation in cobalt/amorphous silicon, amorphous Co [sbnd]Si and bias-induced Co [sbnd]Si films

The silicide formation in cobalt/amorphous silicon multilayer films, amorphous cobalt-silicon films, and bias-induced cobalt-silicon films has been examined by differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy. For amorphous cobalt-silicon and bias-induced cobalt-silicon films, Co 2Si forms as a firstsilicide phase, followed by the formation of CoSi and CoSi 2. For a Co/a-Si multilayer film with the atomic concentration ratio of the cobalt to silicon layer being 1:2, CoSi is found to be formed as the first silicide phase. It is confirmed that CoSi, Co 2Si, CoSi, and CoSi 2 form sequentially as the scanning temperature increases. The observed phase sequence is analyzed by the effective heat of formation. A structure factor in addition to the effective heat of formation is used to explain the difference in the formation of the firstphase between cobalt/amorphous silicon multilayer films, amorphous cobalt-silicon alloy films, and bias-induced cobalt-silicon films. For the case of bias-induced cobalt-silicon films prepared at various substrate temperatures and bias conditions, the phase sequence and crystallinity of cobalt silicide have a stronger dependence on the substrate bias voltage than on the substrate temperature due to the effects of collisional cascade mixing, in-situ cleaning, and an increase in the number of nucleation sites by ion bombardment on the growing surface. Also, bias-induced epitaxial CoSi 2 layer is grown at 200 °C,a much lower temperature than molecular beam epitaxy. In order to quantitatively explain low-temperature epitaxial growth of the CoSi 2 layer, the Ar ion energy transferred to Co and Si atomsand the resputtering yield as a function of substrate bias voltage are calculated.

Dual ion-beam deposition of metallic thin films

The influence of argon ion-beam bombardment of growing Al, Mo and Ti thin films deposited by ion-beam sputtering on their composition and optical properties was studied. The Ar ion energy and ion-to-atom arrival ratio were 100–600 eV and 0.15–1.75 respectively. The concentration of Mo (A1) in the thin films decreased (increased) with ion energy as the Ar content increased (decreased). The Ti content was below 35% for all ion energies. The ratio O/Ti was close to the stoichiometric value of two for all ion energies up to 400 eV. Higher ion-beam energies and doses led to higher values of the index of refraction for Al and Ti thin films. Furthermore, an increase in the energy of the ions caused a decrease in the deposition rates of all films due to resputtering of the thin film atoms and, in the case of Al thin films, intensified the amorphization process in the Al/Si structure.

Resonance charge-exchange in ion scattering and sputtering at the SrTiO 3 surface

Experimental studies of inelastic interaction of low-energy Ar + ions (200–1400 eV) with SrTiO 3(100) surface are presented. The studies were performed by means of Auger spectroscopy, secondary ion mass spectroscopy and ion surface scattering. The oscillating dependence of the Sr ion yield on the incident Ar ion energy was found. The Sr ion yield and the scattered Ar ion intensity were oscillated in antiphase. The results are interpreted in terms of the quasi-resonant charge-exchange model. The performed simulation of the ion charge-exchange confirms the validity of the model used.

Synthesis of Ti-Al alloys by ion-beam-enhanced deposition

Titanium aluminide (Ti-Al) thin films were synthesized by ion-beam-enhanced deposition (IBED), where the films were prepared by depositing Ti and Al metal vapour under simultaneous bombardment with Ar ions in the energy range 2–20 keV. Experiments were undertaken using a compact IBED system with a bucket-type 2.45 GHz electron cyclotron resonance ion source and an electron beam evaporation source. Results of Rutherford backscattering spectrometry have suggested the presence of effective mixing between Al substrate and Ti film deposited under simultaneous bombardment with Ar ions. Glancing angle X-ray diffraction patterns showed that the phase structure of Ti-Al films was determined by both the Ar ion energy and the Ar/(Ti + Al) transport ratio.

Low energy ion bombardment and surface spin pinning in yttrium iron garnet films

Surface spin pinning and physical and chemical changes on the surface of yttrium iron garnet crystalline films were investigated. The magnetic properties of these films as determined by magnetostatic surface waves and ferromagnetic resonance measurements were studied as functions of Ar ion energy E/sub i/=200-1000 eV and ion dose D/sub i/=10/sup 14/-10/sup 18/ ions/cm/sup 2/. The surface spin pinning appears in a mildly damaged, non-stoichiometric layer with oxygen depletion. An alternative mechanism for the surface spin pinning effect based on an anisotropy associated with the oxygen vacancies and iron ion valence changes is proposed. >

Planarization Mechanism of RF‐Biased Al Sputtering

The planarization mechanism of Al bias sputtering is clarified by evaluating the effects of the incident angle range of Al deposition and resputtering independently. Although narrowing the range of Al incident angles increases the amount of Al deposited on the via bottom to improve step coverage, the effect is limited due to the self‐shadowing effect. When the substrate bias voltage (Ar ion energy) is high, most of the resputtered Al from the via upper peripherals redeposits only on opposite side of via upper peripherals, resulting in void and damage formation in the via. When the substrate bias voltage is reduced, resputtered Al redeposits efficiently inside the vias, and sufficient via filling and surface planarization are achieved. A new deposition method, i.e., the combination of deposition and resputtering by Ar ions both with a range of incident angles, is also proposed. The new method showed sufficient filling effect although little planarization was observed.

Radiation induced diffusion of Xe to a polymer film

Abstract In the present work we have studied the most important parameters which can influence the radiation induced diffusion mechanism of Xe ions implanted into photoresist films. With this aim we have Ar post-bombarded the Xe implanted samples at a fixed Ar ion energy, covering a wide range of fluences. In addition the implantation fluences as well as the ion species used in the bombardment were changed. The results show that the radiation induced diffusion process undergoes a trapping-detrapping mechanism. The trapping probability is proportional to the implanted fluence, and the detrapping one depends on the kind of ion used in the bombarding experiment. Finally it is shown that the nuclear energy transfer plays an important role in the radiation induced diffusion mechanism.

Ion radiation induced diffusion of Xe implanted into a polymer film

In the present work, we have studied the most important parameters which can influence the radiation induced diffusion mechanism of Xe ions implanted into a photoresist film. With this aim, we have Ar post-bombarded the Xe implanted samples at a fixed Ar ion energy, covering a wide range of fluences. In addition, the implantation fluences, as well as the ion species used in the bombardment, were changed. The results show that the radiation induced diffusion process undergoes a trapping-detrapping mechanism. The trapping probability is proportional to the implanted fluence, and the detrapping one depends on the kind of ion used in the bombarding experiment. Finally, it is shown that the nuclear energy transfer plays an important role in the radiation induced diffusion mechanism.

Formation of Copper Thin Films by a Low Kinetic Energy Particle Process

Low kinetic energy particle bombardment of a growing film surface has been employed to grow high‐quality copper thin films on silicon and with ideal metal/substrate interface characteristics. It is shown that the energy of Ar ions concurrently bombarding a growing film surface determines the crystal structure of the film. Under relatively low‐energy ion bombardment conditions, (100)‐ or (111)‐oriented Cu films are grown epitaxially on (100) Si or (111) Si surfaces, respectively. On the other hand, completely (111)‐oriented films are obtained either on (100) Si, (111) Si, or surfaces when large ion bombardment energies are employed. It has been found that (111)‐oriented films thus created on are metastable and easily transform by thermal annealing into completely (100)‐oriented films with large grains of about 100 μm. This unique transformation phenomenon has been successfully applied to the formation of almost single‐crystal (100)‐oriented Cu islands on . In situ substrate surface cleaning by extremely low energy Ar ion bombardment has enabled the formation of ideal metal/silicon contacts without any postmetallization alloying heat cycles. Excellent adhesion of Cu thin films on has also been demonstrated by the employment of the in situ substrate surface cleaning.

TOF-ICISS study of surface damage formed by Ar ion bombardment on Si(100)

The surface damage formed on a clean Si(100)-2 × 1 surface by low-energy Ar ion bombardment has been studied in situ using the impact collision ion scattering spectroscopy (ICISS) method and the time-of-flight (TOF) technique. The Ar ion energy was 1 keV and the ion doses were in the range of 10 14-10 15ions/cm 2. Channeling and focusing effects were observed very clearly on a clean and well-ordered surface. With the increase of the Ar ion dose, such channeling and focusing effects gradually disappear. The annealing process of the surface damage was also investigated.

Sputtering Angular Distributions of Individual Elements for Low-Energy Ar Ion Irradiation of PtCu Alloy

The dynamic Monte Carlo program including a bombardment-induced Gibbsian segregation process was used to calculate angular distributions of individual elements from sputtered Cu0.5Pt0.5 alloy in the Ar ion energy range between 0.2 and 1.5ke V. Calculated results show that for each investigated incident energy, the angular distribution of the Pt element is more forward-pointed than that of the Cu one; the reason may be that different percentage of sputtered atoms (37 similar 45% of Pt and 12 similar 19% of Cu) come from beneath the topmost layer.

Ion-irradiation-induced suppression of three-dimensional island formation during InAs growth on Si(100)

Nucleation and growth of InAs on Si(100) substrates during ion-assisted deposition has been investigated. Reflection high-energy electron diffraction studies showed that InAs films nucleated by the Stranski–Krastanov (SK) mechanism. Ar ion irradiation with energies E near 30 eV and a flux of 4 ions per deposited atom prolonged the layer-by-layer stage of SK nucleation. The transition from layer-by-layer to island growth was at 2–3 monolayers (ML) for growth temperature Ts=380 °C and E=13 eV. With Ts=380 °C and E=28 eV, on the other hand, layer-by-layer growth was maintained up to ∼10 ML. A further increase in E to 38 eV reduced the transition coverage to ∼7 ML. In addition, epitaxial temperatures were reduced from >345 to <250 °C by increasing the Ar ion energy E from 13 to 38 eV. Cross-sectional transmission electron microscopy studies of 500 nm thick films showed that increasing E from 13 to 28 eV during the nucleation stage smoothened the surface and improved the crystalline perfection. The effect of ion bombardment on the nucleation mechanism is explained as being due to ion-induced dissociation of three-dimensional islands and ion-enhanced surface diffusion.

Synchrotron radiation photoionization of sputtered neutrals

A photoionization effect of sputtered neutrals by synchrotron radiation (SR) is observed for the first time. Synchrotron radiation from a bending magnet is irradiated 5 mm ‘‘above’’ the Ar ion sputtered area of the sample surfaces, and photoionized ions and secondary ions are detected with a quadrupole mass spectrometer with and without this SR irradiation. A large ratio of photoionized ions to secondary ions is obtained when Au and Pb are sputtered with a low primary Ar ion energy. On the contrary, no detectable photoionization effect is observed from Al, Si, or GaAs. These results are explained qualitatively by the photoionization process where the number of generated ions can be calculated based on the photon flux density, photoionization cross sections, and duration in which sputtered neutrals pass through the SR beam.

Crystal structure analysis of epitaxial silicon films formed by a low kinetic energy particle process

Formation of high quality epitaxial silicon films at 350 °C by a low kinetic energy particle process has been verified by a series of crystal structure analyses performed on these films. It was found that the crystallinity of a grown film is drastically changed by the energy of Ar ions concurrently bombarding the growing silicon film surface. The epitaxially grown film with an optimum ion bombardment energy is defect-free both at the interface and in the bulk of the film as revealed by high-resolution transmission electron microscopy.

Studies of Ion-Assisted Growth and Properties of PbTe Epilayers Deposited by Rf Magnetron Sputtering

ABSTRACT(111) PbTe // (111) BaF2 epilayers have been prepared by rf magnetron sputtering. A small negative substrate bias voltage (-10 V) enhances the (111) growth habit at reduced substrate temperatures (180 °C) and increased deposition rates (2.5 μ/h–1). Langmuir probe diagnostics is used to determine the energy and flux density of Ar ions incident on the growing film. Hall effect measurements are made to determine the carrier type and mobility as a function of the growth temperature.

On Energy and Dose Effects During Ion-Assisted Epitaxial Growth of InAs on Si(100)

ABSTRACTEpitaxial InAs films have been grown on Si(100) substrates using triode ion-assisted deposition (TRIAD). The ratio r of the impinging Ar ion flux J to the deposited InAs flux was varied from 2.5 to 8.5 for Ar ion energies E from 5 to 55 eV. The growth temperature T was 350°C while the growth rate R was fixed at 0.6 μm/h. Two types of experiments were carried out. First, in order to investigate ion damage effects, X-ray diffraction rocking curve full-widths at half-maximum (FWHM) were measured as a function of E and r. In these experiments, the first 50 nm of InAs was always grown under the same conditions, r = 5 and E = 25 eV, in order to eliminate possible complicating effects caused by ion irradiation during InAs nucleation on Si, followed by 550 nm of growth at different E and r values. FWHM values increased with increasing E and r from 2800 arcsec, a value limited by defects arising from the 11% mismatch between InAs and Si, to 8900 arcsec as a result of ion damage. The FWHM value was found to be dependent on the total number of atomic displacements due to ion irradiation, estimated using a modified Kinchin-Pease expression. In the second set of experiments, E during the first 50 nm of growth was varied while ion irradiation damage in the remaining 5500 nm was minimized. Increasing E from 15 to 40 eV resulted in a decrease in the FWHM from 5500 to 2600 arcsec, followed by a gradual increase when E was increased above 40 eV. Ion irradiation at the onset of film growth thus reduced the propagation of defects from the InAs/Si interface into the film.

Selective resputtering-induced anisotropy in amorphous films

Resputtering effect on the uniaxial magnetic anisotropy in amorphous GdCo films has been investigated. A sputtering apparatus has been constructed which is able to change the energy and the accommodation rate of the resputtering Ar ions independently of each other. The energy of Ar ions bombarding the substrate electrode or the film has been measured by means of a Faraday cup and has been found to be smaller than the bias voltage applied to the substrate electrode. The deposition rate of the film has been found to decrease linearly with an increase in the accommodation rate of the resputtering Ar ions. The product of the uniaxial anisotropy constant and the deposition rate has been found to be proportional to the accommodation rate of Ar ions with constant energy. This result agrees with the selective resputtering-induced anisotropy model.

Dependence on Sputtering Conditions for a Tb-Co Magneto-Optical Thin Film

TbCo films were prepared by simultaneous magnetron Co-sputtering. The influences of the sputtering conditions on the density and magneto-optical properties were studied. Sputtering conditions such as substrate rotating speed, substrate bias voltage, Ar pressure, and film deposition rate were studied. Increasing the bias voltage or Ar pressure decreased the density of the TbCo film. This indicates that the incident energy and/or density of Ar ions and/or atoms affect the porosity of the film. This could be closely related to the magneto-optical properties of the film.

On specimen preparation by radio frequency planar magnetron sputtering

Sector type targets were used to fabricate a series of alloys by planar magnetron sputtering with an rf mode. From the binary Co–M system (M: Al, Si, Ti, Cr, Fe, Ni, Cu, Zr, Nb, Mo, Ag, Ta, and W) rf sputtering yield ratios were compared with dc sputtering yields by Laegreid and Wehner. It was found that rf planar magnetron sputtering was well predicted by dc plasma discharge data. The relation of the rf peak-to-peak voltage and Ar ion energy is discussed. Cosputtering of dissimilar elements caused cross contamination on the target surface and it was attributed to the seeding effect. The application to a ternary system Co–Nb–Zr known as an amorphous soft magnetic material was quite successful and suggests sector target to be a convenient way for searching new materials.

Study of Ion Implanted Copper Laser Mirrors by Spectroscopic Ellipsometry

AbstractImplantation with 400 keV Ag or Cu ions improves the near-surface microstructural quality and reflectance of diamond turned and mechanically polished flat copper laser mirrors. Spectroscopic ellipsometry is sensitive to changes in either the microscopic surface roughness, or in the nearsurface substrate void fraction, and both parameters are observed to change upon implantation. Substrate density as a function of ion fluence peaks at about 5 × 10 15cm-2. Low energy (300 eV) Ar ion implantation can cause either a reduction or increase in microscopic surface roughness, depending on fluence.