Low-energy Mass-selected Ion Beam Research Articles

Identification of fragment ions produced by the decomposition of tetramethyltin and the production of low-energy Sn+ ion beam.

Tetramethyltin was decomposed in an ion source and the fragment ions produced were identified using a low-energy mass-selected ion beam machine. Dominant fragment ions were found to be H+, CH2+, and Sn+. Subsequently, fragment ions were mass-selected. The mass spectrum of the selected ions indicated that only a single peak appeared at the mass number of 120 u, being suggestive of the presence of 120Sn+ ions. The ion energy was set at the range of 20–100 eV. The Sn+ ion beam was irradiated to a Si substrate, and a film was then found deposited on the substrate after the ion beam irradiation. An X-ray diffraction measurement showed that the film obtained was metallic Sn. Then, the Sn+ ion beam was irradiated to a quartz crystal microbalance substrate. We found that most of the irradiated Sn+ ions were adhered to the substrate, at the ion energy levels of 25 and 58 eV, producing the Sn film, whereas a 107 eV Sn+ beam caused a significant proportion of Sn atoms in the film to detach from the substrate, probably due to sputtering.

Production of low-energy SiCH3+ and SiC2H7+ ion beams for 3C-SiC film formation by selecting fragment ions from dimethylsilane

Fragment ions produced from dimethylsilane (DMS) in a Bernas-type ion source were investigated. Dominant fragment ions were identified to be CH3+, Si+, SiH3+, SiCH3+, and SiC2H7+. We mass-selected SiCH3+ and SiC2H7+ ions and then produced low-energy SiCH3+ and SiC2H7+ ion beams. Subsequently, these ion beams were used to irradiate Si(111) substrates at 800 °C. The energies of SiCH3+ and SiC2H7+ ions were set at 100 eV. We found that the irradiation of these ions led to the deposition of silicon carbide (3C-SiC) films on the Si substrates. For comparison, SiC film formations on Si(111) substrates were also attempted by the chemical vapor deposition (CVD) method using DMS. The X-ray photoelectron spectroscopy measurements showed that atomic ratios of C to Si (C/Si ratio) of the films obtained by the irradiation of SiCH3+ and SiC2H7+ ion beams were 1.2 and 1.2, respectively. Conversely, the C/Si ratio of the film obtained by CVD was 1.9. Raman spectroscopy showed that the film obtained by CVD included diamond-like carbon. These results suggest that the low-energy mass-selected ion beam deposition technique using DMS-derived fragment ions is practicable for the 3C-SiC deposition on Si substrates.

Low-energy mass-selected ion beam deposition of silicon carbide with Bernas-type ion source using methylsilane

Methylsilane-derived fragment ions obtained from a Bernas-type ion source were investigated using a low-energy mass-selected ion beam system. Based on mass-energy analyzer measurements, these ions were determined to be H+, H2+, H3+, CH3+, Si+, and SiCH5+. The SiCH5+ ions were selected and injected into a Si(111) substrate at 750 °C. The ion energy was 40 eV. This injection led to the formation of a silicon carbide film on the Si substrate. An analysis of this film indicates that this type of ion beam deposition method can efficiently form silicon carbide film.

Identification of fragment ions produced from hexamethyldisilazane and production of low-energy mass-selected fragment ion beam

Abstract Fragment ions produced from hexamethyldisilazane (HMDS) with a hot tungsten wire in a Freeman-type ion source were assayed using a low-energy mass-selected ion beam system. The possible candidates of chemical formulae for these ions are C+, N+, CH3+, CH4+, Si+, SiCH5+, SiC2H6+, SiC3H9+, Si2NCH4+, Si2NC2H7+, Si2NC3H10+, Si2NC4H12+, and Si2NC5H16+. The ion production strongly depended on the tungsten temperature. Among the HMDS derived fragment ions, SiCH5+ ions were mass-selected. The ion energy was 100 eV. Then, the SiCH5+ ions were irradiated to a Si substrate. It was inferred from the analysis of resulting deposited film that silicon carbide films containing a small amount of nitrogen atoms were deposited following the irradiation.

Low-energy mass-selected ion beam production of fragments from tetraethylorthosilicate for the formation of silicon dioxide film

Fragment ions produced from tetraethylorthosilicate (TEOS) in a Freeman-type ion source were investigated using a low-energy mass-selected ion beam system and then, their mass numbers were identified. Although the chemical formulae of these fragments were not completely identified yet, the possible candidates of dominant fragment ions were C2+, C+, CH2+, O+, H2O+, Si+, SiC+, SiO+, SiH(OH)2+, Si(OH)3+, SiH(OH)(OC2H5)+, SiH(OCH3)2+, Si(OH)2(OC2H5)+, SiH(OC2H5)2+, Si(OH)(OC2H5)2+, Si(OCH3)2(OC2H5)+, Si(OCH3)(OC2H5)2+, and Si(OC2H5)3+. Among these fragment ions, Si(OH)3+ ions were mass-selected. The ion energy was approximately 50 eV. Then, the Si(OH)3+ ions were irradiated to a Si substrate and resulting deposited films were analyzed. Following the completion of the ion irradiation experiment, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy assays of the films demonstrated the occurrence of silicon dioxide deposition. We conclude that the irradiation of the mass-selected Si(OH)3+ ions, obtained from TEOS, to substrates is useful for the secure growth of silicon dioxide films.

Low-energy mass-selected ion beam production of fragments produced from hexamethyldisiloxane for the formation of silicon oxide film

Fragment ions produced from hexamethyldisiloxane (HMDSO) with a hot tungsten wire in a Freeman-type ion source were studied using a low-energy mass-selected ion beam system. The mass numbers of the fragment ions were identified. Although the chemical formulae of these fragments were not completely identified yet, the possible candidates of dominant fragment ions were H+, H2+, H3+, C+, CH3+, O+, Si+, C3H3+, SiO+, SiC2+, SiOCH2+, SiC3H9+, Si2OCH3+, Si2OC2H7+, Si2OC3H9+, Si2OC4H11+, and Si2OC5H15+. The rates of ion fragment production strongly depended on the tungsten temperature. Among those fragment ions, SiO+ ions were mass-selected. The ion energy was approximately 50eV. Then, the SiO+ ions were irradiated to substrates and resulting deposited films were analyzed. Following the completion of the ion irradiation experiment, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy measurements of the films demonstrated the occurrence of silicon oxide deposition. We conclude that the irradiation of the mass-selected SiO+ ions, obtained from HMDSO, to substrates is useful for the secure growth of silicon oxide films.

Low-energy mass-selected ion beam production of fragments produced from hexamethyldisilane for SiC film formation

We have proposed an experimental methodology which makes it possible to deposit silicon carbide (SiC) films on Si substrates with a low-energy mass-selected ion beam system using hexamethyldisilane (HMD) as a gas source. In this study, one of the fragment ions produced from HMD, SiCH4+, was mass-selected. The ion energy was approximately 100 eV. Then, the SiCH4+ ions were irradiated to a Si(100) substrate. When the temperature of the Si substrate was set at 800 °C during the ion irradiation, the X-ray diffraction and Raman spectroscopy of the substrate following the completion of ion irradiation experiment demonstrated the occurrence of 3C-SiC deposition.

Indium Implantation onto Zeolite for Development of Novel Catalysts with a Ion Beam System

The implantation of indium (In) onto zeolite was carried out with a low-energy mass-selected ion beam system for the possible development of novel catalysts. In ions were generated by sputtering an In2O3 target with Ar ions in a modified Freeman-type ion source. Ions generated in the ion source were extracted under high voltages to form mono-energetic 115In ion beams with the peak energy of around 500 eV. Then, the zeolite substrates were irradiated by the In ion beams. Both X-ray fluorescence and X-ray diffraction analyses revealed that the implantation of In on the zeolite surface was successful and dependent on the ion doses of In. We failed to detect the catalytic effects in the In implanted zeolite as far as at the conditions employed in the present study. However, a further study is still necessary to determine the catalytic effect of the In implanted zeolite.

ポリメタクリル酸メチル樹脂の水素プラズマ曝露と低エネルギーアルゴンイオンビームによるエッチング

Effects of hydrogen plasma exposure in polymer dry etching processes have been investigated with a low-energy mass-selected ion beam system. In the present study, we use a spin-coated polymethylmethacrylate (PMMA) film on a quartz crystal microbalance as a model polymer. The surface modification of the PMMA film by the hydrogen plasma exposure in an inverter plasma system was investigated by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. XPS results show that oxygen atoms were preferentially sputtered from the PMMA film by the hydrogen plasma exposure. Spectroscopic ellipsometry results show that depth of the modified layer of the hydrogen plasma exposed PMMA film was about 40 nm. Etching yields of the pristine PMMA film and the hydrogen plasma exposed PMMA film by 470 eV Ar+ ion beam injections were measured. It is found that the etching yield of the hydrogen plasma exposed PMMA film was about half of that of the pristine PMMA film.

Sputtering yields and surface modification of poly(methyl methacrylate) (PMMA) by low-energy Ar+/ ion bombardment with vacuum ultraviolet (VUV) photon irradiation

Sputtering yields and surface modification of poly(methyl methacrylate) (PMMA) by mono-energetic ion beams and/or vacuum ultraviolet (VUV) light are studied with the use of a low-energy mass-selected ion beam system. Sputtering yields of PMMA by Ar+ or ion beams are obtained as functions of ion incident energy below 500 eV. It is found that surface modification of PMMA due to ion incidence is limited to the region near the film surface, whereas that due to Ar+ ion incidence is seen in a relatively deeper region of the film, where PMMA is partially carbonized and diamond-like carbon (DLC) is formed. Under the conditions of incident energies and fluxes of ion and VUV light used in the experiments, the sputtering yield of PMMA by simultaneous incidence of VUV light and ions is found to be nearly equal to the sum of the yields by separate incidences of VUV light and ions. Some of the etching characteristics observed in this study (such as DLC formation by ion sputtering) may be shared by a wide range of organic polymers that have main chain structures similar to those of PMMA.

Effect of light irradiation from inductively coupled Ar plasma on etching yields of SiO2 film by CF3 ion beam injections

Effects of light irradiation on etching yields of SiO2 films by CF3 ion beams have been investigated with a low-energy mass selected ion beam system. An inductively coupled plasma (ICP) from Ar gas was used as the light source. The spectrum of light emitted from the Ar ICP was measured by vacuum ultraviolet and visible monochromators. Etching yields of SiO2 films by 470 eV CF3 ion beam injections were obtained from the ratio of the number of incident CF3 ions to that of removed SiO2 atoms during the ion beam injection process with or without simultaneous light irradiation from the Ar ICP. The incident ion number was evaluated from the integration of temporal evolution of ion beam current. The number of removed atoms can be obtained from the etched depth of SiO2 films measured by a laser interferometer. It is found that the obtained SiO2 etching yield by simultaneous irradiation of CF3 ions and photons from the light source was smaller than that by ion beam irradiation only.

Effect of ultraviolet light irradiation on etching process of poly(methyl methacrylate) by ion beam injections

Effects of ultraviolet (UV) light irradiation on polymer dry etching processes have been investigated with the use of a low-energy mass-selected ion beam injection system. Etching yields of poly(methyl methacrylate) (PMMA) by Ar or CF3 ion beam injections were evaluated from the loss of PMMA film weight measured by a quartz crystal microbalance (QCM) during the ion beam injection process with or without simultaneous UV light irradiation. Significant enhancement of the etching yield of PMMA was observed during the simultaneous irradiation with CF3 ion beam and UV light over the sum of its sputtering yields obtained from separate ion-beam or UV-light injection processes. By contrast, no significant change of etching yields was observed when the UV light was superposed on the Ar ion beam.

Effects of Ultraviolet Light Irradiation on Etching of Polymethylmethacrylate by CF3+ Ion Beam Injections

Effects of ultraviolet (UV) light irradiation on a polymer dry etching process have been investigated with the use of a low-energy mass-selected ion beam system. The effective etched depth of polymethylmethacrylate (PMMA) by CF3+ ion beam injection and/or UV light irradiation was evaluated from the decrement of PMMA film weight measured by a quartz crystal microbalance. A significant enhancement of the etched depth of PMMA was observed when a CF3+ ion beam was injected to PMMA substrate with UV light irradiation. The etched depth of PMMA during simultaneous irradiation of CF3+ ion beams and UV light was greater than the sum of those obtained from separate CF3+ ion beam or UV light irradiation processes.

Measurement of sticking probability and sputtering yield of Au by low-energy mass selected ion beams with a quartz crystal microbalance

A measurement system of sticking probability and sputtering yield in the energy range of 0–500 eV has been established with a low-energy mass selected ion beam system. The small change in mass of the substrate material by injected ions can be evaluated with the quartz crystal microbalance (QCM). In this study, sticking probabilities and self-sputtering yields of Au were measured as functions of the injection energy of Au ions.

Measurement of Au sputtering yields by Ar and He ions with a low-energy mass selected ion beam system

The Au sputtering yields by noble gas ions below 200 eV were measured with a low-energy mass selected ion beam system. Au sputtering yields by He and Ar ions were measured and found to incease monotonically with the ion injection energies. It was also found that the sputtering yields by He were much lower than those by Ar.

低エネルギー質量分離イオンビーム照射装置を用いたＳｉＯ２／Ｓｉ基板へのインジウムイオン注入

Implantation of In into SiO2 thin film substrates by mono-energetic In ion beams was examined with the use of a low-energy mass selected ion beam system. The goal of this study is to develop thin film based In-Si combined catalyzer for organic chemical reactions. In the experiments, In ions were generated by sputtering of an In2O3 target by Ar ions in a Freeman-type ion source and extracted to form, after mass selection, a mono-energetic beam with the peak energy of 470 eV. The ion beam was then injected into SiO2 thin films formed on Si substrates. By X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and atomic force microscopy (AFM) measurements, it was found that In nano particles were formed on the SiO2 thin film surface after the beam injections and the shapes of the particles varied depending on In ion dose.

光照射を重畳したＣＦ３イオンビームによるＳｉＯ２エッチング率の測定

Etching yields of SiO2 by CF3 ion beam injections with or without simultaneous light irradiation have been measured by a low-energy mass-selected ion beam system. A Xe Lamp, an L2D2 lamp, an Ar ICP (inductively coupled plasma) or a VUV (Vacuum Ultraviolet) Lamp was used separately as the light source. The etching yield is the ratio of the number of incident ions to that of removed atoms. The obtained SiO2 etching yields by simultaneous irradiation of CF3 ions and photons from the light source were smaller than those by ion beam irradiation only. This difference in etching yields may be caused by modification of CFx polymer formation on the substrate surface during the beam etching process.

Incident-energy dependence of crystalline structures of ion beam deposited Au thin films

The energy dependence of crystalline structures in Au thin-film deposition processes was investigated with the use of a low-energy mass-selected ion beam system. Au films deposited on Si(100) untreated wafer surfaces by the beam system at different ion energies in the range of 20–200 eV were analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD) and in-situ reflection high-energy electron diffraction (RHEED). The XRD results show that the kinetic energy provided by ion bombardment can facilitate crystal growth with specific orientations such as (100) or (110), the surfaces of which have relatively high surface energies. Our observations also suggest that each crystalline orientation appears only in a specific energy range of ion bombardment. These results indicate that Au crystalline orientations may be controlled by the ion irradiation energy during deposition processes.

Growth temperature effect on a self-assembled SiC nanostructure

Self-assembled nanostructure fabrication technology holds much potential to further the interests of nanoscience and nanotechnology. Using a low-energy mass-selected ion beam deposition system, we fabricated self-assembled silicon carbide (SiC) nanotiles. Methylsilicenium ions (SiCH 3 +) used as single precursors were generated from dimethylsilane (SiH 2(CH 3) 2). Low-energy SiCH 3 + ions (100 eV) were deposited on a Si(100) substrate at 500–600 °C. The characteristics of the self-assembled SiC nanotiles were analyzed by reflection high-energy electron diffraction (RHEED), a scanning electron microscope (SEM) and an atomic force microscope (AFM). The self-assembled SiC nanostructure displayed the properties of a zinc-blende structure (3C–SiC) and heteroepitaxial growth. The shape of the self-assembled SiC nanotiles was rectangular with an edge length of 150–200 nm and a height of 10–30 nm. Optimum temperature was found to be 600 °C due to the sensitivity of crystal quality and shape of the self-assembled SiC nanotiles to growth temperature.

Growth of carbon thin film by low-energy mass-selected ion beam deposition

Low-energy mass-selected C + ion beams have been used to deposit thin carbon films onto a Si(1 0 0) surface covered with a native oxide layer kept at various temperatures in an ultra-high vacuum (UHV) environment in order to find the optimum deposition conditions for the formation of diamond and diamond-like carbon (DLC) thin films. The deposited films were characterized by Raman spectroscopy and X-ray diffraction (XRD). Diamond and DLC films were found to be produced for C + ion energies between 80 and 120 eV at temperatures from room temperature to 200°C. For the film grown with a C + ion energy of 120 eV at room temperature, Raman spectroscopy showed clear evidence of diamond formation while XRD showed diamond crystal orientation with the (1 1 0) plane parallel to the silicon surface.